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[tcb] Value Range Propagation
- From: Diego Novillo <dnovillo at redhat dot com>
- To: gcc-patches at gcc dot gnu dot org
- Date: Thu, 3 Feb 2005 13:41:46 -0500
- Subject: [tcb] Value Range Propagation
- Organization: Red Hat Canada
This pass is essentially the same as constant propagation, except
that instead of propagating single values, we propagate value
ranges.
The basic implementation is based on the ideas described in
``Accurate Static Branch Prediction by Value Range Propagation,''
in SIGPLAN Conference on Programming Language Design and
Implementation, pp. 67-78, 1995. Also available at
http://citeseer.ist.psu.edu/patterson95accurate.html
It works in three main stages:
1- We insert ASSERT_EXPRs after every statement that provides
hints about value ranges for an SSA name. For instance,
if (x_3 > 10)
...
is converted to
if (x_3 > 10)
x_4 = ASSERT_EXPR <x_3, x_3 > 10>;
...
So now we know that x_4 is greater than 10. Uses of x_4 that
test for its range may be folded to a known value.
2- Using the SSA propagation engine, we propagate value ranges
using vrp_visit_stmt, vrp_visit_phi_node and vrp_meet. The
actions of each are documented in the source. They're all
pretty much straightforward in what they need to reason about.
3- After ranges have been propagated, the ASSERT_EXPRs are
turned into copies. The advantage is that other passes need
not deal with assertions, but we also lose range information.
I'm not too sure what to do about this ATM.
This is the initial implementation. I think we now have enough
to start replacing the unified DOM pass with separate passes.
I'll see how far that gets me.
Bootstrapped and tested on x86, x86-64, ppc, alpha and ia64.
Diego.
Value Range Propagation
* Makefile.in (tree-vrp.o): Depend on
tree-ssa-propagate.h, $(FLAGS_H) and $(TREE_DUMP_H).
* common.opt (ftree-vrp): Define.
* opts.c (decode_options): Set flag_tree_vrp at -O2.
* timevar.def (TV_TREE_INSERT_ASSERT): Remove.
(TV_TREE_VRP): Define.
* tree-flow.h (enum value_range_type): Define.
(struct value_range_def): Define.
(count_uses_and_derefs): Declare.
(get_value_range): Declare.
(dump_value_range): Declare.
(debug_value_range): Declare.
(dump_all_value_ranges): Declare.
(debug_all_value_ranges): Declare.
* tree-optimize.c (init_tree_optimization_passes): Remove
pass_insert_range_assertions and pass_remove_range_assertions.
Add pass_vrp.
* tree-pass.h (pass_insert_range_assertions): Remove.
(pass_remove_range_assertions): Remove.
(pass_vrp): Define.
* tree-ssa-alias.c (count_ptr_derefs): Make extern.
* tree.h (SSA_NAME_VALUE_RANGE): Define.
(struct value_range_def): Forward declare.
(struct tree_ssa_name): Add field value_range.
* tree-vrp.c: Include flags.h, tree-dump.h and
tree-ssa-propagate.h.
(new_ssa_names): Declare.
(old_ssa_names): Declare.
(found): Declare.
(get_opposite_operand): New.
(opposite_comparison): New.
(copy_value_range): New.
(set_value_range): New.
(update_value_range): New.
(get_value_range): New.
(symbolic_range_p): New.
(expr_computes_nonnull): New.
(range_is_nonnull): New.
(range_is_null): New.
(set_value_range_to_nonnull): New.
(set_value_range_to_null): New.
(compare_values): New.
(extract_range_from_assert): New.
(extract_range_from_binary_expr): New.
(extract_range_from_unary_expr): New.
(extract_range_from_expr): New.
(compare_ranges): New.
(compare_range_with_value): New.
(value_inside_range): New.
(value_ranges_intersect_p): New.
(dump_value_range): New.
(debug_value_range): New.
(dump_all_value_ranges): New.
(debug_all_value_ranges): New.
(build_assert_expr_for): Create a new SSA name for every
assertion.
If the conditional is an equality, create a regular
assignment.
Push the new name into NEW_SSA_NAMES. Push the operand into
OLD_SSA_NAMES.
(infer_value_range): New.
(has_assert_expr): New.
(maybe_add_assert_expr): Add ASSERT_EXPR after pointer
dereferences.
Handle cases that require inserting after the last statement
of a block.
Call has_assert_expr and infer_value_range.
(insert_range_assertions): Rename from
execute_insert_range_assertions.
Initialize new_ssa_names and old_ssa_names.
Do not use BB_VISITED to mark visited blocks.
(pass_insert_range_assertions): Remove.
(remove_range_assertions): Rename from
execute_remove_range_assertions.
(pass_remove_range_assertions): Remove.
(stmt_interesting_for_vrp): New.
(need_imm_uses_for): New.
(vrp_initialize): New.
(vrp_visit_assignment): New.
(vrp_evaluate_conditional): New.
(vrp_visit_cond_stmt): New.
(vrp_visit_stmt): New.
(vrp_meet): New.
(vrp_visit_phi_node): New.
(vrp_finalize): New.
(execute_vrp): New.
(gate_vrp): New.
(pass_vrp): Declare.
Index: Makefile.in
===================================================================
RCS file: /cvs/gcc/gcc/gcc/Makefile.in,v
retrieving revision 1.1396.2.16
diff -d -u -p -r1.1396.2.16 Makefile.in
--- Makefile.in 2 Feb 2005 02:41:41 -0000 1.1396.2.16
+++ Makefile.in 2 Feb 2005 22:10:26 -0000
@@ -1669,7 +1669,7 @@ tree-vn.o : tree-vn.c $(CONFIG_H) $(SYST
$(TREE_DUMP_H) diagnostic.h
tree-vrp.o : tree-vrp.c $(CONFIG_H) $(SYSTEM_H) coretypes.h $(TM_H) $(TREE_H) \
$(TREE_FLOW_H) tree-pass.h $(TREE_DUMP_H) diagnostic.h $(GGC_H) \
- $(BASIC_BLOCK_H)
+ $(BASIC_BLOCK_H) tree-ssa-propagate.h $(FLAGS_H) $(TREE_DUMP_H)
tree-cfg.o : tree-cfg.c $(TREE_FLOW_H) $(CONFIG_H) $(SYSTEM_H) \
$(RTL_H) $(TREE_H) $(TM_P_H) $(EXPR_H) $(GGC_H) $(FLAGS_H) output.h \
diagnostic.h errors.h function.h $(TIMEVAR_H) $(TM_H) coretypes.h \
Index: common.opt
===================================================================
RCS file: /cvs/gcc/gcc/gcc/common.opt,v
retrieving revision 1.55.2.8
diff -d -u -p -r1.55.2.8 common.opt
--- common.opt 2 Feb 2005 02:42:18 -0000 1.55.2.8
+++ common.opt 2 Feb 2005 22:10:26 -0000
@@ -892,6 +892,10 @@ ftree-lrs
Common Report Var(flag_tree_live_range_split)
Perform live range splitting during the SSA->normal pass.
+ftree-vrp
+Common Report Var(flag_tree_vrp) Init(0)
+Perform Value Range Propagation on trees
+
funit-at-a-time
Common Report Var(flag_unit_at_a_time)
Compile whole compilation unit at a time
Index: opts.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/opts.c,v
retrieving revision 1.82.2.8
diff -d -u -p -r1.82.2.8 opts.c
--- opts.c 2 Feb 2005 02:43:20 -0000 1.82.2.8
+++ opts.c 2 Feb 2005 22:10:27 -0000
@@ -540,6 +540,7 @@ decode_options (unsigned int argc, const
flag_unit_at_a_time = 1;
flag_tree_store_ccp = 1;
flag_tree_store_copy_prop = 1;
+ flag_tree_vrp = 1;
if (!optimize_size)
{
Index: timevar.def
===================================================================
RCS file: /cvs/gcc/gcc/gcc/timevar.def,v
retrieving revision 1.36.2.8
diff -d -u -p -r1.36.2.8 timevar.def
--- timevar.def 2 Feb 2005 02:43:44 -0000 1.36.2.8
+++ timevar.def 2 Feb 2005 22:10:27 -0000
@@ -65,7 +65,7 @@ DEFTIMEVAR (TV_TREE_GIMPLIFY , "tre
DEFTIMEVAR (TV_TREE_EH , "tree eh")
DEFTIMEVAR (TV_TREE_CFG , "tree CFG construction")
DEFTIMEVAR (TV_TREE_CLEANUP_CFG , "tree CFG cleanup")
-DEFTIMEVAR (TV_TREE_INSERT_ASSERT , "tree insert assertions")
+DEFTIMEVAR (TV_TREE_VRP , "tree VRP")
DEFTIMEVAR (TV_TREE_COPY_PROP , "tree copy propagation")
DEFTIMEVAR (TV_TREE_STORE_COPY_PROP , "tree store copy propagation")
DEFTIMEVAR (TV_FIND_REFERENCED_VARS , "tree find referenced vars")
Index: tree-flow.h
===================================================================
RCS file: /cvs/gcc/gcc/gcc/tree-flow.h,v
retrieving revision 2.46.2.13
diff -d -u -p -r2.46.2.13 tree-flow.h
--- tree-flow.h 2 Feb 2005 02:43:53 -0000 2.46.2.13
+++ tree-flow.h 2 Feb 2005 22:10:28 -0000
@@ -80,6 +80,34 @@ struct ptr_info_def GTY(())
};
+/* Types of value ranges. */
+enum value_range_type { VR_UNDEFINED, VR_RANGE, VR_ANTI_RANGE, VR_VARYING };
+
+
+/* Ranges of values that can be associated with an SSA_NAME after VRP
+ has executed. */
+struct value_range_def GTY(())
+{
+ /* Lattice value represented by this range. */
+ enum value_range_type type;
+
+ /* Minimum and maximum values represented by this range. These
+ values are _CST nodes that should be interpreted as follows:
+
+ - If TYPE == VR_UNDEFINED then MIN and MAX must be NULL.
+
+ - If TYPE == VR_RANGE then MIN holds the minimum value and
+ MAX holds the maximum value of the range [MIN, MAX].
+
+ - If TYPE == ANTI_RANGE the variable is known to NOT
+ take any values in the range [MIN, MAX]. */
+ tree min;
+ tree max;
+};
+
+typedef struct value_range_def value_range;
+
+
/*---------------------------------------------------------------------------
Tree annotations stored in tree_common.ann
---------------------------------------------------------------------------*/
@@ -567,6 +595,7 @@ extern void debug_points_to_info_for (tr
extern bool may_be_aliased (tree);
extern struct ptr_info_def *get_ptr_info (tree);
extern void add_type_alias (tree, tree);
+extern void count_uses_and_derefs (tree, tree, unsigned *, unsigned *, bool *);
/* Call-back function for walk_use_def_chains(). At each reaching
definition, a function with this prototype is called. */
@@ -605,6 +634,13 @@ void execute_ssa_ccp (bool);
bool fold_stmt (tree *);
tree widen_bitfield (tree, tree, tree);
+/* In tree-vrp.c */
+value_range *get_value_range (tree);
+void dump_value_range (FILE *, value_range *);
+void debug_value_range (value_range *);
+void dump_all_value_ranges (FILE *);
+void debug_all_value_ranges (void);
+
/* FIXME. Move these to tree-ssa-propagate.[ch]. */
struct prop_value_d {
Index: tree-inline.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/tree-inline.c,v
retrieving revision 1.142.2.11
diff -d -u -p -r1.142.2.11 tree-inline.c
--- tree-inline.c 2 Feb 2005 02:43:54 -0000 1.142.2.11
+++ tree-inline.c 2 Feb 2005 22:10:28 -0000
@@ -1250,7 +1250,6 @@ estimate_num_insns_1 (tree *tp, int *wal
x = TREE_OPERAND (x, 0);
/* FALLTHRU */
case TARGET_EXPR:
- case ASSERT_EXPR:
case CONSTRUCTOR:
{
HOST_WIDE_INT size;
Index: tree-optimize.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/tree-optimize.c,v
retrieving revision 2.47.2.16
diff -d -u -p -r2.47.2.16 tree-optimize.c
--- tree-optimize.c 2 Feb 2005 02:43:56 -0000 2.47.2.16
+++ tree-optimize.c 2 Feb 2005 22:10:29 -0000
@@ -346,7 +346,6 @@ init_tree_optimization_passes (void)
p = &pass_all_optimizations.sub;
NEXT_PASS (pass_referenced_vars);
NEXT_PASS (pass_maybe_create_global_var);
- NEXT_PASS (pass_insert_range_assertions);
NEXT_PASS (pass_build_ssa);
NEXT_PASS (pass_may_alias);
NEXT_PASS (pass_rename_ssa_copies);
@@ -355,6 +354,7 @@ init_tree_optimization_passes (void)
NEXT_PASS (pass_copy_prop);
NEXT_PASS (pass_fre);
NEXT_PASS (pass_dce);
+ NEXT_PASS (pass_vrp);
NEXT_PASS (pass_dominator);
NEXT_PASS (pass_dce);
NEXT_PASS (pass_merge_phi);
@@ -404,7 +404,6 @@ init_tree_optimization_passes (void)
needs to be put in SSA form and scanned for aliases. */
NEXT_PASS (pass_may_alias);
NEXT_PASS (pass_tail_calls);
- NEXT_PASS (pass_remove_range_assertions);
NEXT_PASS (pass_rename_ssa_copies);
NEXT_PASS (pass_del_ssa);
NEXT_PASS (pass_nrv);
Index: tree-pass.h
===================================================================
RCS file: /cvs/gcc/gcc/gcc/tree-pass.h,v
retrieving revision 2.15.2.11
diff -d -u -p -r2.15.2.11 tree-pass.h
--- tree-pass.h 2 Feb 2005 02:43:57 -0000 2.15.2.11
+++ tree-pass.h 2 Feb 2005 22:10:29 -0000
@@ -164,13 +164,12 @@ extern struct tree_opt_pass pass_mark_us
extern struct tree_opt_pass pass_rename_ssa_copies;
extern struct tree_opt_pass pass_expand;
extern struct tree_opt_pass pass_rest_of_compilation;
-extern struct tree_opt_pass pass_insert_range_assertions;
-extern struct tree_opt_pass pass_remove_range_assertions;
extern struct tree_opt_pass pass_fre;
extern struct tree_opt_pass pass_linear_transform;
extern struct tree_opt_pass pass_maybe_create_global_var;
extern struct tree_opt_pass pass_copy_prop;
extern struct tree_opt_pass pass_store_ccp;
extern struct tree_opt_pass pass_store_copy_prop;
+extern struct tree_opt_pass pass_vrp;
#endif /* GCC_TREE_PASS_H */
Index: tree-ssa-alias.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/tree-ssa-alias.c,v
retrieving revision 2.39.2.11
diff -d -u -p -r2.39.2.11 tree-ssa-alias.c
--- tree-ssa-alias.c 2 Feb 2005 02:43:59 -0000 2.39.2.11
+++ tree-ssa-alias.c 2 Feb 2005 22:10:30 -0000
@@ -388,7 +388,7 @@ count_ptr_derefs (tree *tp, int *walk_su
*NUM_DEREFS_P respectively. *IS_STORE_P is set to 'true' if at
least one of those dereferences is a store operation. */
-static void
+void
count_uses_and_derefs (tree ptr, tree stmt, unsigned *num_uses_p,
unsigned *num_derefs_p, bool *is_store)
{
Index: tree-ssa-ccp.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/tree-ssa-ccp.c,v
retrieving revision 2.41.2.11
diff -d -u -p -r2.41.2.11 tree-ssa-ccp.c
--- tree-ssa-ccp.c 2 Feb 2005 02:43:59 -0000 2.41.2.11
+++ tree-ssa-ccp.c 2 Feb 2005 22:10:30 -0000
@@ -474,11 +474,6 @@ likely_value (tree stmt)
&& TREE_CODE (stmt) != SWITCH_EXPR)
return VARYING;
- /* FIXME, ASSERT_EXPRs can convey useful constants. */
- if (TREE_CODE (stmt) == MODIFY_EXPR
- && TREE_CODE (TREE_OPERAND (stmt, 1)) == ASSERT_EXPR)
- return VARYING;
-
get_stmt_operands (stmt);
found_constant = false;
@@ -599,7 +594,8 @@ ccp_initialize (void)
}
/* Compute immediate uses for variables we care about. */
- compute_immediate_uses (TDFA_USE_OPS | TDFA_USE_VOPS, need_imm_uses_for);
+ compute_immediate_uses (TDFA_USE_OPS | ((do_store_ccp) ? TDFA_USE_VOPS : 0),
+ need_imm_uses_for);
}
Index: tree-ssa-dom.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/tree-ssa-dom.c,v
retrieving revision 2.44.2.12
diff -d -u -p -r2.44.2.12 tree-ssa-dom.c
--- tree-ssa-dom.c 2 Feb 2005 02:44:01 -0000 2.44.2.12
+++ tree-ssa-dom.c 2 Feb 2005 22:10:31 -0000
@@ -2684,20 +2684,6 @@ record_equivalences_from_stmt (tree stmt
|| is_gimple_min_invariant (rhs)))
SSA_NAME_VALUE (lhs) = rhs;
- /* If the RHS is ASSERT_EXPR <X, COND>, record the conditional
- COND as being true. */
- if (may_optimize_p && TREE_CODE (rhs) == ASSERT_EXPR)
- {
- tree op = TREE_OPERAND (rhs, 0);
- tree cond = fold (TREE_OPERAND (rhs, 1));
- /* If STMT is inside a basic block that will never be
- executed, the predicate of this ASSERT_EXPR will be
- false. We need to handle this contradiction gracefully
- because the CFG is not cleaned up while DOM runs. */
- if (cond != boolean_false_node)
- record_const_or_copy (lhs, op);
- }
-
/* alloca never returns zero and the address of a non-weak symbol
is never zero. NOP_EXPRs and CONVERT_EXPRs can be completely
stripped as they do not affect this equivalence. */
Index: tree-vrp.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/Attic/tree-vrp.c,v
retrieving revision 1.1.2.2
diff -d -u -p -r1.1.2.2 tree-vrp.c
--- tree-vrp.c 6 Jan 2005 21:23:23 -0000 1.1.2.2
+++ tree-vrp.c 3 Feb 2005 17:03:45 -0000
@@ -23,45 +23,1008 @@ Boston, MA 02111-1307, USA. */
#include "coretypes.h"
#include "tm.h"
#include "ggc.h"
+#include "flags.h"
#include "tree.h"
#include "basic-block.h"
#include "tree-flow.h"
#include "tree-pass.h"
+#include "tree-dump.h"
#include "timevar.h"
#include "diagnostic.h"
+#include "tree-ssa-propagate.h"
-/* Given a COND_EXPR COND of the form 'V OP W', and a symbol V, return
- the assertion assignment 'V = ASSERT_EXPR <V, V OP W>'. */
+/* Mapping between old and new SSA names created when inserting
+ ASSERT_EXPRs. Each assertion creates a new name that replaces all
+ the uses of the first operand of the ASSERT_EXPR. The mapping is
+ represented so that for every I, NEW_SSA_NAMES[I] replaces all uses
+ of OLD_SSA_NAMES[I]. */
+static VEC(tree_on_heap) *new_ssa_names;
+static VEC(tree_on_heap) *old_ssa_names;
+
+/* Set of SSA names found during the dominator traversal of a
+ sub-graph in maybe_add_assert_expr_on_edges. */
+static sbitmap found;
+
+/* Given a conditional predicate COND that has WHICH as one of its
+ operands, return the other operand. No error checking is done.
+ This helper assumes that COND is a comparison and WHICH is one of
+ its operands. */
+
+static inline tree
+get_opposite_operand (tree cond, tree which)
+{
+ if (TREE_OPERAND (cond, 0) == which)
+ return TREE_OPERAND (cond, 1);
+ else
+ return TREE_OPERAND (cond, 0);
+}
+
+
+/* Given a comparison code, return its opposite. Note that this is *not*
+ the same as inverting its truth value (invert_tree_comparison). Here we
+ just want to literally flip the comparison around.
+
+ So, '<' gets '>', '<=' gets '>='. Both '==' and '!=' are returned
+ unchanged. */
+
+static enum tree_code
+opposite_comparison (enum tree_code code)
+{
+ switch (code)
+ {
+ case EQ_EXPR:
+ case NE_EXPR:
+ case ORDERED_EXPR:
+ case UNORDERED_EXPR:
+ case LTGT_EXPR:
+ case UNEQ_EXPR:
+ return code;
+ case GT_EXPR:
+ return LT_EXPR;
+ case GE_EXPR:
+ return LE_EXPR;
+ case LT_EXPR:
+ return GT_EXPR;
+ case LE_EXPR:
+ return GE_EXPR;
+ case UNGT_EXPR:
+ return UNLT_EXPR;
+ case UNGE_EXPR:
+ return UNLE_EXPR;
+ case UNLT_EXPR:
+ return UNGT_EXPR;
+ case UNLE_EXPR:
+ return UNGE_EXPR;
+ default:
+ gcc_unreachable ();
+ }
+}
+
+
+/* Copy value range FROM to TO. */
+
+static inline void
+copy_value_range (value_range *to, value_range *from)
+{
+ *to = *from;
+}
+
+
+/* Set value range VR to {T, MIN, MAX}. */
+
+static inline void
+set_value_range (value_range *vr, enum value_range_type t, tree min, tree max)
+{
+ vr->type = t;
+ vr->min = min;
+ vr->max = max;
+}
+
+
+/* Similar to set_value_range but return true if any field of VR
+ changed from its previous value. */
+
+static inline bool
+update_value_range (value_range *vr, enum value_range_type t, tree min,
+ tree max)
+{
+ bool is_new = vr->type != t || vr->min != min || vr->max != max;
+ if (is_new)
+ set_value_range (vr, t, min, max);
+
+ return is_new;
+}
+
+
+/* Return value range information for VAR. Create an empty range if
+ none existed. */
+
+value_range *
+get_value_range (tree var)
+{
+ value_range *vr;
+ tree sym;
+
+ vr = SSA_NAME_VALUE_RANGE (var);
+ if (vr)
+ return vr;
+
+ /* Create a default value range. */
+ vr = ggc_alloc (sizeof (*vr));
+ memset ((void *) vr, 0, sizeof (*vr));
+ SSA_NAME_VALUE_RANGE (var) = vr;
+
+ /* If VAR is a default definition for a PARM_DECL, then we have to
+ assume a VARYING range for it. */
+ sym = SSA_NAME_VAR (var);
+ if (TREE_CODE (sym) == PARM_DECL && var == var_ann (sym)->default_def)
+ set_value_range (vr, VR_VARYING, NULL_TREE, NULL_TREE);
+
+ return vr;
+}
+
+
+/* Return true if value range VR involves at least one symbol. */
+
+static inline bool
+symbolic_range_p (value_range *vr)
+{
+ return (!is_gimple_min_invariant (vr->min)
+ || !is_gimple_min_invariant (vr->max));
+}
+
+
+/* Return true if EXPR computes a non-NULL pointer value. */
+
+static inline bool
+expr_computes_nonnull (tree expr)
+{
+ /* Type casts won't change anything, so just strip it. */
+ STRIP_NOPS (expr);
+
+ /* Taking the address of a non-weak symbol or calling alloca,
+ guarantees that the value is non-NULL. */
+ return (alloca_call_p (expr)
+ || (TREE_CODE (expr) == ADDR_EXPR
+ && DECL_P (TREE_OPERAND (expr, 0))
+ && !DECL_WEAK (TREE_OPERAND (expr, 0))));
+}
+
+
+/* Return true if VR is ~[0, 0]. */
+
+static inline bool
+range_is_nonnull (value_range *vr)
+{
+ return vr->type == VR_ANTI_RANGE
+ && integer_zerop (vr->min)
+ && integer_zerop (vr->max);
+}
+
+
+/* Return true if VR is [0, 0]. */
+
+static inline bool
+range_is_null (value_range *vr)
+{
+ return vr->type == VR_RANGE
+ && integer_zerop (vr->min)
+ && integer_zerop (vr->max);
+}
+
+
+/* Set value range VR to a non-NULL range of type TYPE. */
+
+static void
+set_value_range_to_nonnull (value_range *vr, tree type)
+{
+ tree zero = build_int_cst (type, 0);
+ set_value_range (vr, VR_ANTI_RANGE, zero, zero);
+}
+
+
+/* Set value range VR to a NULL range of type TYPE. */
+
+static void
+set_value_range_to_null (value_range *vr, tree type)
+{
+ tree zero = build_int_cst (type, 0);
+ set_value_range (vr, VR_RANGE, zero, zero);
+}
+
+
+/* Compare two values VAL1 and VAL2. Return
+
+ -2 if VAL1 and VAL2 cannot be compared at compile-time,
+ -1 if VAL1 < VAL2,
+ 0 if VAL1 == VAL2,
+ +1 if VAL1 > VAL2, and
+ +2 if VAL1 != VAL2
+
+ This is similar to tree_int_cst_compare but supports pointer values
+ and values that cannot be compared at compile time. */
+
+static int
+compare_values (tree val1, tree val2)
+{
+ /* We cannot compare non-constants. */
+ if (!is_gimple_min_invariant (val1) || !is_gimple_min_invariant (val2))
+ return -2;
+
+ if (!POINTER_TYPE_P (TREE_TYPE (val1)))
+ return tree_int_cst_compare (val1, val2);
+ else
+ {
+ tree t;
+
+ /* First see if VAL1 and VAL2 are not the same. */
+ if (val1 == val2 || operand_equal_p (val1, val2, 0))
+ return 0;
+
+ /* If VAL1 is a lower address than VAL2, return -1. */
+ t = fold (build2 (LT_EXPR, TREE_TYPE (val1), val1, val2));
+ if (t == boolean_true_node)
+ return -1;
+
+ /* If VAL1 is a higher address than VAL2, return +1. */
+ t = fold (build2 (GT_EXPR, TREE_TYPE (val1), val1, val2));
+ if (t == boolean_true_node)
+ return 1;
+
+ /* If VAL1 is different than VAL2, return +2. */
+ t = fold (build2 (NE_EXPR, TREE_TYPE (val1), val1, val2));
+ if (t == boolean_true_node)
+ return 2;
+
+ return -2;
+ }
+}
+
+
+/* Extract value range information from an ASSERT_EXPR EXPR and store
+ it in *VR_P. */
+
+static void
+extract_range_from_assert (value_range *vr_p, tree expr)
+{
+ tree var, cond, limit, one, type;
+
+ var = ASSERT_EXPR_VAR (expr);
+ cond = ASSERT_EXPR_COND (expr);
+
+ gcc_assert (TREE_CODE_CLASS (TREE_CODE (cond)) == tcc_comparison);
+
+ /* Find VAR in the ASSERT_EXPR conditional. */
+ limit = get_opposite_operand (cond, var);
+ type = TREE_TYPE (limit);
+ one = build_int_cst (type, 1);
+
+ gcc_assert (limit != var);
+
+ /* For pointer arithmetic, we only keep track of anti-ranges
+ (NE_EXPR). Notice that we don't need to handle EQ_EXPR in these
+ cases because assertions with equalities are never generated.
+ The assert pass generates straight assignments in those cases. */
+ if (POINTER_TYPE_P (TREE_TYPE (expr)) && TREE_CODE (cond) != NE_EXPR)
+ {
+ set_value_range (vr_p, VR_VARYING, NULL_TREE, NULL_TREE);
+ return;
+ }
+
+ if (TREE_CODE (cond) == NE_EXPR)
+ set_value_range (vr_p, VR_ANTI_RANGE, limit, limit);
+ else if (TREE_CODE (cond) == LE_EXPR)
+ set_value_range (vr_p, VR_RANGE, TYPE_MIN_VALUE (type), limit);
+ else if (TREE_CODE (cond) == LT_EXPR)
+ set_value_range (vr_p, VR_RANGE, TYPE_MIN_VALUE (type),
+ fold (build (MINUS_EXPR, type, limit, one)));
+ else if (TREE_CODE (cond) == GE_EXPR)
+ set_value_range (vr_p, VR_RANGE, limit, TYPE_MAX_VALUE (type));
+ else if (TREE_CODE (cond) == GT_EXPR)
+ set_value_range (vr_p, VR_RANGE,
+ fold (build (PLUS_EXPR, type, limit, one)),
+ TYPE_MAX_VALUE (type));
+ else
+ gcc_unreachable ();
+}
+
+
+/* Extract range information from a binary expression EXPR based on
+ the ranges of each of its operands and the expression code. */
+
+static void
+extract_range_from_binary_expr (value_range *vr, tree expr)
+{
+ enum tree_code code = TREE_CODE (expr);
+ tree op0, op1;
+ value_range vr0, vr1;
+
+ /* Not all binary expressions can be applied to ranges in a
+ meaningful way. Handle only arithmetic operations. */
+ if (code != PLUS_EXPR
+ && code != MINUS_EXPR
+ && code != MULT_EXPR
+ && code != TRUNC_DIV_EXPR
+ && code != FLOOR_DIV_EXPR
+ && code != CEIL_DIV_EXPR
+ && code != EXACT_DIV_EXPR
+ && code != ROUND_DIV_EXPR
+ && code != MIN_EXPR
+ && code != MAX_EXPR)
+ {
+ set_value_range (vr, VR_VARYING, NULL_TREE, NULL_TREE);
+ return;
+ }
+
+ /* Get value ranges for each operand. For constant operands, create
+ a new value range with the operand to simplify processing. */
+ op0 = TREE_OPERAND (expr, 0);
+ if (TREE_CODE (op0) == SSA_NAME)
+ vr0 = *(get_value_range (op0));
+ else
+ {
+ if (is_gimple_min_invariant (op0))
+ set_value_range (&vr0, VR_RANGE, op0, op0);
+ else
+ set_value_range (&vr0, VR_VARYING, 0, 0);
+ }
+
+ op1 = TREE_OPERAND (expr, 1);
+ if (TREE_CODE (op1) == SSA_NAME)
+ vr1 = *(get_value_range (op1));
+ else
+ {
+ if (is_gimple_min_invariant (op1))
+ set_value_range (&vr1, VR_RANGE, op1, op1);
+ else
+ set_value_range (&vr1, VR_VARYING, 0, 0);
+ }
+
+ /* If either range is UNDEFINED, so is the result. */
+ if (vr0.type == VR_UNDEFINED || vr1.type == VR_UNDEFINED)
+ {
+ set_value_range (vr, VR_UNDEFINED, NULL_TREE, NULL_TREE);
+ return;
+ }
+
+ /* If either range is VARYING, so is the result. */
+ if (vr0.type == VR_VARYING || vr1.type == VR_VARYING)
+ {
+ set_value_range (vr, VR_VARYING, NULL_TREE, NULL_TREE);
+ return;
+ }
+
+ /* If the ranges are of different types, the result is VARYING. */
+ if (vr0.type != vr1.type)
+ {
+ set_value_range (vr, VR_VARYING, NULL_TREE, NULL_TREE);
+ return;
+ }
+
+ /* TODO. Refuse to do any symbolic range operations for now. */
+ if (symbolic_range_p (&vr0) || symbolic_range_p (&vr1))
+ {
+ set_value_range (vr, VR_VARYING, NULL_TREE, NULL_TREE);
+ return;
+ }
+
+ /* Now evaluate the expression to determine the new range. */
+ if (POINTER_TYPE_P (TREE_TYPE (expr))
+ || POINTER_TYPE_P (TREE_TYPE (op0))
+ || POINTER_TYPE_P (TREE_TYPE (op1)))
+ {
+ /* For pointer types, we are really only interested in asserting
+ whether the expression evaluates to non-NULL. */
+ gcc_assert (code == PLUS_EXPR || code == MINUS_EXPR);
+
+ if (code == PLUS_EXPR)
+ {
+ /* Assume that pointers can never wrap around. FIXME, Is
+ this always safe? */
+ tree zero = build_int_cst (TREE_TYPE (expr), 0);
+ set_value_range (vr, VR_ANTI_RANGE, zero, zero);
+ }
+ else
+ {
+ /* Subtracting from a pointer, may yield 0, so just drop the
+ resulting range to varying. */
+ set_value_range (vr, VR_VARYING, NULL_TREE, NULL_TREE);
+ }
+
+ return;
+ }
+
+ /* For integer ranges, apply the operation to each end of the
+ range and see what we end up with. */
+ vr->type = vr0.type;
+ if (code == PLUS_EXPR
+ || code == MULT_EXPR
+ || code == MIN_EXPR
+ || code == MAX_EXPR)
+ {
+ /* For operations that make the resulting range directly
+ proportional to the original ranges, apply the operation to
+ the same end of each range. */
+ vr->min = int_const_binop (code, vr0.min, vr1.min, 0);
+ vr->max = int_const_binop (code, vr0.max, vr1.max, 0);
+ }
+ else
+ {
+ /* For operations that make the resulting range inversely
+ proportional to the original ranges (-, /), apply the
+ operation to the opposite ends of each range. */
+ vr->min = int_const_binop (code, vr0.min, vr1.max, 0);
+ vr->max = int_const_binop (code, vr0.max, vr1.min, 0);
+ }
+
+ if (vr->min == TYPE_MIN_VALUE (TREE_TYPE (vr->min))
+ && vr->max == TYPE_MAX_VALUE (TREE_TYPE (vr->max)))
+ {
+ /* If the new range covers the whole range of values for the type,
+ mark it VARYING. */
+ set_value_range (vr, VR_VARYING, NULL_TREE, NULL_TREE);
+ }
+ else
+ {
+ int cmp = compare_values (vr->min, vr->max);
+ if (cmp == -2 || cmp == 1)
+ {
+ /* If the new range has its limits swapped around (MIN >
+ MAX), then the operation caused one of them to wrap
+ around, mark the new range VARYING. */
+ set_value_range (vr, VR_VARYING, NULL_TREE, NULL_TREE);
+ }
+ }
+}
+
+
+/* Extract range information from a unary expression EXPR based on
+ the range of its operand and the expression code. */
+
+static void
+extract_range_from_unary_expr (value_range *vr, tree expr)
+{
+ enum tree_code code = TREE_CODE (expr);
+ tree op0 = TREE_OPERAND (expr, 0);
+ value_range vr0;
+
+ /* Get value ranges for the operand. For constant operands, create
+ a new value range with the operand to simplify processing. */
+ op0 = TREE_OPERAND (expr, 0);
+ if (TREE_CODE (op0) == SSA_NAME)
+ vr0 = *(get_value_range (op0));
+ else
+ {
+ if (is_gimple_min_invariant (op0))
+ set_value_range (&vr0, VR_RANGE, op0, op0);
+ else
+ set_value_range (&vr0, VR_VARYING, 0, 0);
+ }
+
+ /* If VR0 is UNDEFINED, so is the result. */
+ if (vr0.type == VR_UNDEFINED)
+ {
+ set_value_range (vr, VR_UNDEFINED, NULL_TREE, NULL_TREE);
+ return;
+ }
+
+ /* If VR0 is VARYING, so is the result. */
+ if (vr0.type == VR_VARYING)
+ {
+ set_value_range (vr, VR_VARYING, NULL_TREE, NULL_TREE);
+ return;
+ }
+
+ /* TODO. Refuse to do any symbolic range operations for now. */
+ if (symbolic_range_p (&vr0))
+ {
+ set_value_range (vr, VR_VARYING, NULL_TREE, NULL_TREE);
+ return;
+ }
+
+ /* If the operand is neither a pointer nor an integral type, set the
+ range to VARYING. TODO, we may set the range to non-zero. */
+ if (!INTEGRAL_TYPE_P (TREE_TYPE (op0))
+ && !POINTER_TYPE_P (TREE_TYPE (op0)))
+ {
+ set_value_range (vr, VR_VARYING, NULL_TREE, NULL_TREE);
+ return;
+ }
+
+ /* If the expression involves pointers, we are only interested in
+ determining if it evaluates to NULL [0, 0] or non-NULL (~[0, 0]). */
+ if (POINTER_TYPE_P (TREE_TYPE (expr)) || POINTER_TYPE_P (TREE_TYPE (op0)))
+ {
+ if (range_is_nonnull (&vr0) || expr_computes_nonnull (expr))
+ set_value_range_to_nonnull (vr, TREE_TYPE (expr));
+ else if (range_is_null (&vr0))
+ set_value_range_to_null (vr, TREE_TYPE (expr));
+ else
+ set_value_range (vr, VR_VARYING, NULL_TREE, NULL_TREE);
+
+ return;
+ }
+
+ /* Handle unary expressions on integer ranges. */
+ if (TREE_CODE (expr) == ABS_EXPR)
+ {
+ /* ABS_EXPR always compute a positive value. If VR0.MIN is
+ greater than 0, use it as the lower end of the new VR. */
+ tree zero = build_int_cst (TREE_TYPE (expr), 0);
+ if (compare_values (vr0.min, zero) == 1)
+ set_value_range (vr, VR_RANGE, vr0.min, vr0.max);
+ else
+ set_value_range (vr, VR_RANGE, zero, vr0.max);
+ }
+ else if (TREE_CODE (expr) == NOP_EXPR || TREE_CODE (expr) == CONVERT_EXPR)
+ {
+ /* If this is a cast operation and either limit in VR0 is set to
+ VR0's type min/max values, set the corresponding limits in VR
+ to EXPR's type min/max values. */
+ vr->type = vr0.type;
+
+ if (vr0.min == TYPE_MIN_VALUE (TREE_TYPE (vr0.min)))
+ vr->min = TYPE_MIN_VALUE (TREE_TYPE (expr));
+ else
+ {
+ /* If VR0.MIN is smaller than the minimum value for EXPR's
+ type, then set it to that value. */
+ int cmp = compare_values (vr0.min, TYPE_MIN_VALUE (TREE_TYPE (expr)));
+ if (cmp == -1)
+ vr->min = TYPE_MIN_VALUE (TREE_TYPE (expr));
+ else
+ vr->min = fold_unary_to_constant (code, TREE_TYPE (expr), vr0.min);
+ }
+
+ if (vr0.max == TYPE_MAX_VALUE (TREE_TYPE (vr0.max)))
+ vr->max = TYPE_MAX_VALUE (TREE_TYPE (expr));
+ else
+ {
+ /* Similarly, if VR0.MAX is larger than the maximum value
+ for EXPR's type, set it to that value. */
+ int cmp = compare_values (vr0.max, TYPE_MAX_VALUE (TREE_TYPE (expr)));
+ if (cmp == 1)
+ vr->max = TYPE_MAX_VALUE (TREE_TYPE (expr));
+ else
+ vr->max = fold_unary_to_constant (code, TREE_TYPE (expr), vr0.max);
+ }
+ }
+ else
+ {
+ /* Apply the operation to each end of the range and see what we end
+ up with. */
+ vr->type = vr0.type;
+ vr->min = fold_unary_to_constant (code, TREE_TYPE (expr), vr0.min);
+ vr->max = fold_unary_to_constant (code, TREE_TYPE (expr), vr0.max);
+ }
+
+ /* If the new range covers the whole range of values for the type,
+ mark it VARYING. */
+ if (vr->min == TYPE_MIN_VALUE (TREE_TYPE (expr))
+ && vr->max == TYPE_MAX_VALUE (TREE_TYPE (expr)))
+ set_value_range (vr, VR_VARYING, NULL_TREE, NULL_TREE);
+}
+
+
+/* Try to compute a useful range out of expression EXPR and store it
+ in *VR_P. */
+
+static void
+extract_range_from_expr (value_range *vr, tree expr)
+{
+ enum tree_code code = TREE_CODE (expr);
+
+ if (code == ASSERT_EXPR)
+ extract_range_from_assert (vr, expr);
+ else if (code == SSA_NAME)
+ copy_value_range (vr, get_value_range (expr));
+ else if (TREE_CODE_CLASS (code) == tcc_binary)
+ extract_range_from_binary_expr (vr, expr);
+ else if (TREE_CODE_CLASS (code) == tcc_unary)
+ extract_range_from_unary_expr (vr, expr);
+ else if (expr_computes_nonnull (expr))
+ set_value_range_to_nonnull (vr, TREE_TYPE (expr));
+ else
+ set_value_range (vr, VR_VARYING, NULL_TREE, NULL_TREE);
+}
+
+
+/* Given two numeric value ranges VR0, VR1 and a comparison code COMP:
+
+ - Return BOOLEAN_TRUE_NODE if VR0 COMP VR1 always returns true for all the
+ values in the ranges.
+
+ - Return BOOLEAN_FALSE_NODE if the comparison always returns false.
+
+ - Return NULL_TREE if it is not always possible to determine the value of
+ the comparison. */
+
+static tree
+compare_ranges (enum tree_code comp, value_range *vr0, value_range *vr1)
+{
+ /* VARYING or UNDEFINED ranges cannot be compared. */
+ if (vr0->type == VR_VARYING
+ || vr0->type == VR_UNDEFINED
+ || vr1->type == VR_VARYING
+ || vr1->type == VR_UNDEFINED)
+ return NULL_TREE;
+
+ /* TODO. Refuse to compare symbolic ranges for now. */
+ if (symbolic_range_p (vr0) || symbolic_range_p (vr1))
+ return NULL_TREE;
+
+ /* Anti-ranges need to be handled separately. */
+ if (vr0->type == VR_ANTI_RANGE || vr1->type == VR_ANTI_RANGE)
+ {
+ /* If both are anti-ranges, then we cannot compute any
+ comparison. */
+ if (vr0->type == VR_ANTI_RANGE && vr1->type == VR_ANTI_RANGE)
+ return NULL_TREE;
+
+ /* These comparisons are never statically computable. */
+ if (comp == GT_EXPR
+ || comp == GE_EXPR
+ || comp == LT_EXPR
+ || comp == LE_EXPR)
+ return NULL_TREE;
+
+ /* Equality can be computed only between a range and an
+ anti-range. ~[VAL1, VAL2] == [VAL1, VAL2] is always false. */
+ if (vr0->type == VR_RANGE)
+ {
+ /* To simplify processing, make VR0 the anti-range. */
+ value_range *tmp = vr0;
+ vr0 = vr1;
+ vr1 = tmp;
+ }
+
+ gcc_assert (comp == NE_EXPR || comp == EQ_EXPR);
+
+ if (compare_values (vr0->min, vr1->min) == 0
+ && compare_values (vr0->max, vr1->max) == 0)
+ return (comp == NE_EXPR) ? boolean_true_node : boolean_false_node;
+
+ return NULL_TREE;
+ }
+
+ /* Simplify processing. If COMP is GT_EXPR or GE_EXPR, switch the
+ operands around and change the comparison code. */
+ if (comp == GT_EXPR || comp == GE_EXPR)
+ {
+ value_range *tmp;
+ comp = (comp == GT_EXPR) ? LT_EXPR : LE_EXPR;
+ tmp = vr0;
+ vr0 = vr1;
+ vr1 = tmp;
+ }
+
+ if (comp == EQ_EXPR)
+ {
+ /* Equality may only be computed if both ranges represent
+ exactly one value. */
+ if (compare_values (vr0->min, vr0->max) == 0
+ && compare_values (vr1->min, vr1->max) == 0)
+ {
+ if (compare_values (vr0->min, vr1->min) == 0
+ && compare_values (vr0->max, vr1->max) == 0)
+ return boolean_true_node;
+ else
+ return boolean_false_node;
+ }
+
+ return NULL_TREE;
+ }
+ else if (comp == NE_EXPR)
+ {
+ int cmp1, cmp2;
+
+ /* If VR0 is completely to the left or completely to the right
+ of VR1, they are always different. Notice that we need to
+ make sure that both comparisons yield similar results to
+ avoid comparing values that cannot be compared at
+ compile-time. */
+ cmp1 = compare_values (vr0->max, vr1->min);
+ cmp2 = compare_values (vr0->min, vr1->max);
+ if ((cmp1 == -1 && cmp2 == -1) || (cmp1 == 1 && cmp2 == 1))
+ return boolean_true_node;
+
+ /* If VR0 and VR1 represent a single value and are identical,
+ return false. */
+ else if (compare_values (vr0->min, vr0->max) == 0
+ && compare_values (vr1->min, vr1->max) == 0
+ && compare_values (vr0->min, vr1->min) == 0
+ && compare_values (vr0->max, vr1->max) == 0)
+ return boolean_false_node;
+
+ /* Otherwise, they may or may not be different. */
+ else
+ return NULL_TREE;
+ }
+ else if (comp == LT_EXPR || comp == LE_EXPR)
+ {
+ int tst;
+
+ /* If VR0 is to the left of VR1, return true. */
+ tst = compare_values (vr0->max, vr1->min);
+ if ((comp == LT_EXPR && tst == -1)
+ || (comp == LE_EXPR && (tst == -1 || tst == 0)))
+ return boolean_true_node;
+
+ /* If VR0 is to the right of VR1, return false. */
+ tst = compare_values (vr0->min, vr1->max);
+ if ((comp == LT_EXPR && (tst == 0 || tst == 1))
+ || (comp == LE_EXPR && tst == 1))
+ return boolean_false_node;
+
+ /* Otherwise, we don't know. */
+ return NULL_TREE;
+ }
+
+ gcc_unreachable ();
+}
+
+
+/* Given a value range VR, a value VAL and a comparison code COMP, return
+ BOOLEAN_TRUE_NODE if VR COMP VR1 always returns true for all the
+ values in VR. Return BOOLEAN_FALSE_NODE if the comparison
+ always returns false. Return NULL_TREE if it is not always
+ possible to determine the value of the comparison. */
+
+static tree
+compare_range_with_value (enum tree_code comp, value_range *vr, tree val)
+{
+ if (vr->type == VR_VARYING || vr->type == VR_UNDEFINED)
+ return NULL_TREE;
+
+ /* TODO. Refuse to compare symbolic ranges for now. */
+ if (symbolic_range_p (vr))
+ return NULL_TREE;
+
+ /* Anti-ranges need to be handled separately. */
+ if (vr->type == VR_ANTI_RANGE)
+ {
+ /* For anti-ranges, the only predicates that we can compute at
+ compile time are equality and inequality. */
+ if (comp == GT_EXPR
+ || comp == GE_EXPR
+ || comp == LT_EXPR
+ || comp == LE_EXPR)
+ return NULL_TREE;
+
+ /* ~[VAL, VAL] == VAL is always false. */
+ if (compare_values (vr->min, val) == 0
+ && compare_values (vr->max, val) == 0)
+ return (comp == NE_EXPR) ? boolean_true_node : boolean_false_node;
+
+ return NULL_TREE;
+ }
+
+ if (comp == EQ_EXPR)
+ {
+ /* EQ_EXPR may only be computed if VR represents exactly
+ one value. */
+ if (compare_values (vr->min, vr->max) == 0)
+ {
+ if (compare_values (vr->min, val) == 0)
+ return boolean_true_node;
+ else
+ return boolean_false_node;
+ }
+
+ return NULL_TREE;
+ }
+ else if (comp == NE_EXPR)
+ {
+ /* If VAL is not inside VR, then they are always different. */
+ if (compare_values (vr->max, val) == -1
+ || compare_values (vr->min, val) == 1)
+ return boolean_true_node;
+
+ /* If VR represents exactly one value equal to VAL, then return
+ false. */
+ if (compare_values (vr->min, vr->max) == 0
+ && compare_values (vr->min, val) == 0)
+ return boolean_false_node;
+
+ /* Otherwise, they may or may not be different. */
+ return NULL_TREE;
+ }
+ else if (comp == LT_EXPR || comp == LE_EXPR)
+ {
+ int tst;
+
+ /* If VR is to the left of VAL, return true. */
+ tst = compare_values (vr->max, val);
+ if ((comp == LT_EXPR && tst == -1)
+ || (comp == LE_EXPR && (tst == -1 || tst == 0)))
+ return boolean_true_node;
+
+ /* If VR is to the right of VAL, return false. */
+ tst = compare_values (vr->min, val);
+ if ((comp == LT_EXPR && (tst == 0 || tst == 1))
+ || (comp == LE_EXPR && tst == 1))
+ return boolean_false_node;
+
+ /* Otherwise, we don't know. */
+ return NULL_TREE;
+ }
+ else if (comp == GT_EXPR || comp == GE_EXPR)
+ {
+ int tst;
+
+ /* If VR is to the right of VAL, return true. */
+ tst = compare_values (vr->min, val);
+ if ((comp == GT_EXPR && tst == 1)
+ || (comp == GE_EXPR && (tst == 0 || tst == 1)))
+ return boolean_true_node;
+
+ /* If VR is to the left of VAL, return false. */
+ tst = compare_values (vr->max, val);
+ if ((comp == GT_EXPR && (tst == -1 || tst == 0))
+ || (comp == GE_EXPR && tst == -1))
+ return boolean_false_node;
+
+ /* Otherwise, we don't know. */
+ return NULL_TREE;
+ }
+
+ gcc_unreachable ();
+}
+
+
+/* Return 1 if VAL is inside value range VR (VR->MIN <= VAL <= VR->MAX),
+ 0 if VAL is not inside VR,
+ -2 if we cannot tell either way. */
+
+static inline int
+value_inside_range (tree val, value_range *vr)
+{
+ int cmp1, cmp2;
+
+ cmp1 = compare_values (vr->min, val);
+ if (cmp1 == -2 || cmp1 == 2)
+ return cmp1;
+
+ cmp2 = compare_values (val, vr->max);
+ if (cmp2 == -2 || cmp2 == 2)
+ return cmp2;
+
+ return (cmp1 == 0 || cmp1 == 1) && (cmp2 == -1 || cmp2 == 0);
+}
+
+
+/* Return true if value ranges VR0 and VR1 have a non-empty
+ intersection. */
+
+static inline bool
+value_ranges_intersect_p (value_range *vr0, value_range *vr1)
+{
+ return (value_inside_range (vr1->min, vr0) == 1
+ || value_inside_range (vr1->max, vr0) == 1
+ || value_inside_range (vr0->min, vr1) == 1
+ || value_inside_range (vr0->max, vr1) == 1);
+}
+
+
+/* Debugging dumps. */
+
+void
+dump_value_range (FILE *file, value_range *vr)
+{
+ if (vr == NULL)
+ fprintf (file, "[]");
+ else if (vr->type == VR_UNDEFINED)
+ fprintf (file, "UNDEFINED");
+ else if (vr->type == VR_RANGE || vr->type == VR_ANTI_RANGE)
+ {
+ fprintf (file, "%s[", (vr->type == VR_ANTI_RANGE) ? "~" : "");
+ print_generic_expr (file, vr->min, 0);
+ fprintf (file, ", ");
+ print_generic_expr (file, vr->max, 0);
+ fprintf (file, "]");
+ }
+ else if (vr->type == VR_VARYING)
+ fprintf (file, "VARYING");
+ else
+ fprintf (file, "INVALID RANGE");
+}
+
+
+/* Dump value range VR to stderr. */
+
+void
+debug_value_range (value_range *vr)
+{
+ dump_value_range (stderr, vr);
+}
+
+
+/* Dump value ranges of all SSA_NAMEs to FILE. */
+
+void
+dump_all_value_ranges (FILE *file)
+{
+ size_t i;
+
+ for (i = 0; i < num_ssa_names; i++)
+ {
+ tree var = ssa_name (i);
+ if (var && SSA_NAME_VALUE_RANGE (var))
+ {
+ print_generic_expr (file, var, 0);
+ fprintf (file, ": ");
+ dump_value_range (file, SSA_NAME_VALUE_RANGE (var));
+ fprintf (file, "\n");
+ }
+ }
+
+ fprintf (file, "\n");
+}
+
+
+/* Dump all value ranges to stderr. */
+
+void
+debug_all_value_ranges (void)
+{
+ dump_all_value_ranges (stderr);
+}
+
+
+/*---------------------------------------------------------------------------
+ Value Range Propagation
+---------------------------------------------------------------------------*/
+
+/* Given a COND_EXPR COND of the form 'V OP W', and an SSA name V,
+ create a new SSA name N and return the assertion assignment
+ 'V = ASSERT_EXPR <V, V OP W>'. */
static tree
build_assert_expr_for (tree cond, tree v)
{
- tree assertion = NULL_TREE;
+ tree n, assertion;
- gcc_assert (DECL_P (v));
+ gcc_assert (TREE_CODE (v) == SSA_NAME);
+ n = make_ssa_name (SSA_NAME_VAR (v), NULL_TREE);
if (TREE_CODE_CLASS (TREE_CODE (cond)) == tcc_comparison)
{
- /* Build V = ASSERT_EXPR <V, COND>. */
- assertion = build (MODIFY_EXPR, TREE_TYPE (v), v,
- build (ASSERT_EXPR, TREE_TYPE (v), v, cond));
+ /* Build N = ASSERT_EXPR <V, COND>. As a special case, if the
+ conditional is an EQ_EXPR (V == Z), just build the assignment
+ N = Z. */
+ if (TREE_CODE (cond) == EQ_EXPR)
+ {
+ tree other = get_opposite_operand (cond, v);
+ assertion = build (MODIFY_EXPR, TREE_TYPE (v), n, other);
+ }
+ else
+ assertion = build (MODIFY_EXPR, TREE_TYPE (v), n,
+ build (ASSERT_EXPR, TREE_TYPE (v), v, cond));
}
else if (TREE_CODE (cond) == TRUTH_NOT_EXPR)
{
/* Given !V, build the assignment V = false. */
tree op0 = TREE_OPERAND (cond, 0);
gcc_assert (op0 == v);
- assertion = build (MODIFY_EXPR, TREE_TYPE (v), v, boolean_false_node);
+ assertion = build (MODIFY_EXPR, TREE_TYPE (v), n, boolean_false_node);
}
- else if (DECL_P (cond))
+ else if (TREE_CODE (cond) == SSA_NAME)
{
/* Given V, build the assignment V = true. */
gcc_assert (v == cond);
- assertion = build (MODIFY_EXPR, TREE_TYPE (v), v, boolean_true_node);
+ assertion = build (MODIFY_EXPR, TREE_TYPE (v), n, boolean_true_node);
}
else
gcc_unreachable ();
+ SSA_NAME_DEF_STMT (n) = assertion;
+
+ /* The new ASSERT_EXPR, creates a new SSA name that replaces the
+ operand of the ASSERT_EXPR. Register the new name and the old one
+ in the replacement table so that we can fix the SSA web after
+ adding all the ASSERT_EXPRs. */
+ VEC_safe_push (tree_on_heap, new_ssa_names, n);
+ VEC_safe_push (tree_on_heap, old_ssa_names, v);
return assertion;
}
@@ -77,6 +1040,86 @@ fp_predicate (tree expr)
&& FLOAT_TYPE_P (TREE_TYPE (TREE_OPERAND (expr, 0)));
}
+
+/* Return an expression predicate that represents the range of values
+ that can be taken by operand OP after STMT executes. */
+
+static tree
+infer_value_range (tree stmt, tree op)
+{
+ if (POINTER_TYPE_P (TREE_TYPE (op)))
+ {
+ bool is_store;
+ unsigned num_uses, num_derefs;
+
+ count_uses_and_derefs (op, stmt, &num_uses, &num_derefs, &is_store);
+ if (num_derefs > 0)
+ {
+ tree null = build_int_cst (TREE_TYPE (op), 0);
+ tree t = build (NE_EXPR, boolean_type_node, op, null);
+ return t;
+ }
+ }
+
+ return NULL_TREE;
+}
+
+
+/* Return true if OP is the result of an ASSERT_EXPR that tests the
+ same condition as COND. */
+
+static bool
+has_assert_expr (tree op, tree cond)
+{
+ tree def_stmt = SSA_NAME_DEF_STMT (op);
+ tree assert_expr, other_cond, other_op;
+
+ /* If OP was not generated by an ASSERT_EXPR, return false. */
+ if (TREE_CODE (def_stmt) != MODIFY_EXPR
+ || TREE_CODE (TREE_OPERAND (def_stmt, 1)) != ASSERT_EXPR)
+ return false;
+
+ assert_expr = TREE_OPERAND (def_stmt, 1);
+ other_cond = ASSERT_EXPR_COND (assert_expr);
+ other_op = ASSERT_EXPR_VAR (assert_expr);
+
+ if (TREE_CODE (cond) == TREE_CODE (other_cond))
+ {
+ tree t1, t2;
+
+ /* If COND is not a comparison predicate, something is wrong. */
+ gcc_assert (TREE_CODE_CLASS (TREE_CODE (cond)) == tcc_comparison);
+
+ /* Note that we only need to compare against one of the operands
+ of OTHER_COND.
+
+ Suppose that we are about to insert the assertion ASSERT_EXPR
+ <x_4, x_4 != 0> and the defining statement for x_4 is x_4 =
+ ASSERT_EXPR <x_3, x_3 != 0>.
+
+ In this case, we don't really want to insert a new
+ ASSERT_EXPR for x_4 because that would be redundant. We
+ already know that x_4 is not 0. So, when comparing the
+ conditionals 'x_3 != 0' and 'x_4 != 0', we don't want to
+ compare x_3 and x_4, we just want to compare the predicate's
+ code (!=) and the other operand (0). */
+ if (TREE_OPERAND (cond, 0) == op)
+ t1 = TREE_OPERAND (cond, 1);
+ else
+ t1 = TREE_OPERAND (cond, 0);
+
+ if (TREE_OPERAND (other_cond, 0) == other_op)
+ t2 = TREE_OPERAND (other_cond, 1);
+ else
+ t2 = TREE_OPERAND (other_cond, 0);
+
+ return (t1 == t2 || operand_equal_p (t1, t2, 0));
+ }
+
+ return false;
+}
+
+
/* Traverse all the statements in block BB looking for used variables.
Variables used in BB are added to bitmap FOUND. The algorithm
works in three main parts:
@@ -84,18 +1127,28 @@ fp_predicate (tree expr)
1- For every statement S in BB, all the variables used by S are
added to bitmap FOUND.
- 2- If the last statement of BB is a conditional expression, then
+ 2- If statement S uses an operand N in a way that exposes a known
+ value range for N, then if N was not already generated by an
+ ASSERT_EXPR, create a new ASSERT_EXPR for N. For instance, if N
+ is a pointer and the statement dereferences it, we can assume
+ that N is not NULL.
- a) The variables involved in the conditional are removed from
- FOUND.
+ 3- COND_EXPRs are a special case of #2. We can derive range
+ information from the predicate but need to insert different
+ ASSERT_EXPRs for each of the sub-graphs rooted at the
+ conditional block. If the last statement of BB is a conditional
+ expression of the form 'X op Y', then
- b) We recurse into the sub-graph starting at the THEN_CLAUSE.
- On return, if X and/or Y are marked in FOUND, then an
- ASSERT_EXPR is added for the corresponding variable.
+ a) Remove X and Y from the set FOUND.
- c) Step (b) is repeated on the ELSE_CLAUSE.
+ b) If the conditional dominates its THEN_CLAUSE sub-graph,
+ recurse into it. On return, if X and/or Y are marked in
+ FOUND, then an ASSERT_EXPR is added for the corresponding
+ variable.
- d) X and Y are marked in FOUND.
+ c) Repeat step (b) on the ELSE_CLAUSE.
+
+ d) Mark X and Y in FOUND.
3- If BB does not end in a conditional expression, then we recurse
into BB's dominator children.
@@ -112,56 +1165,88 @@ fp_predicate (tree expr)
In this case, an assertion on the THEN clause is useful to
determine that 'a' is always 9 on that edge. However, an assertion
on the ELSE clause would be unnecessary.
-
- FIXME. This may still cause the SSA renamer to add a PHI node for
- 'a' at the 'endif' block. This creates unnecessary churn in
- the optimizers as this PHI node produces nothing new.
- TODO 1. It may be better to do some simplified life analysis to
- avoid adding ASSERT_EXPRs unnecessarily. In the example
- above, if variable 'a' is set before its first use on the
- THEN_CLAUSE, then an ASSERT_EXPR would just be killed by
- the first DCE run.
-
- TODO 2. Handle SWITCH_EXPR. */
+ On exit from this function, all the names created by the newly
+ inserted ASSERT_EXPRs need to be added to the SSA web by rewriting
+ the SSA names that they replace. The vectors NEW_SSA_NAMES and
+ OLD_SSA_NAMES contain that information.
+
+ TODO. Handle SWITCH_EXPR. */
static bool
-maybe_add_assert_expr_on_edges (basic_block bb, sbitmap found)
+maybe_add_assert_expr (basic_block bb)
{
block_stmt_iterator si;
tree last;
- size_t i;
bool added;
- /* This is not a true dominator traversal, so we have to avoid
- duplicate visits. See the logic for COND_EXPRs in 'Step 2'
- below. */
- if (bb->flags & BB_VISITED)
- return false;
-
- bb->flags |= BB_VISITED;
-
- /* Step 1. Mark all the variables used in BB in bitmap FOUND. */
+ /* Step 1. Mark all the SSA names used in BB in bitmap FOUND. */
added = false;
last = NULL_TREE;
for (si = bsi_start (bb); !bsi_end_p (si); bsi_next (&si))
{
- tree stmt;
- use_optype uses;
+ tree stmt, op;
+ ssa_op_iter i;
stmt = bsi_stmt (si);
get_stmt_operands (stmt);
- uses = STMT_USE_OPS (stmt);
- /* Mark all the variables used by STMT in bitmap FOUND. */
- for (i = 0; i < NUM_USES (uses); i++)
- SET_BIT (found, var_ann (USE_OP (uses, i))->uid);
+ /* Mark all the SSA names used by STMT in bitmap FOUND. If STMT
+ is inside the sub-graph of a conditional block, when we
+ return from this recursive walk, our parent will use the
+ FOUND bitset to determine if one of the operands it was
+ looking for was present in the sub-graph. */
+ FOR_EACH_SSA_TREE_OPERAND (op, stmt, i, SSA_OP_USE)
+ {
+ tree cond;
+
+ SET_BIT (found, SSA_NAME_VERSION (op));
+
+ cond = infer_value_range (stmt, op);
+ if (!cond)
+ continue;
+
+ /* Step 3. If OP is used in such a way that we can infer a
+ value range for it, create a new ASSERT_EXPR for OP
+ (unless OP already has an ASSERT_EXPR). */
+ gcc_assert (!is_ctrl_stmt (stmt));
+
+ if (has_assert_expr (op, cond))
+ continue;
+
+ if (!stmt_ends_bb_p (stmt))
+ {
+ /* If STMT does not end the block, we can insert the new
+ assertion right after it. */
+ tree t = build_assert_expr_for (cond, op);
+ bsi_insert_after (&si, t, BSI_NEW_STMT);
+ added = true;
+ }
+ else
+ {
+ /* STMT must be the last statement in BB. We can only
+ insert new assertions on the non-abnormal edge out of
+ BB. Note that since STMT is not control flow, there
+ may only be one non-abnormal edge out of BB. */
+ edge_iterator ei;
+ edge e;
+
+ FOR_EACH_EDGE (e, ei, bb->succs)
+ if (!(e->flags & EDGE_ABNORMAL))
+ {
+ tree t = build_assert_expr_for (cond, op);
+ bsi_insert_on_edge (e, t);
+ added = true;
+ break;
+ }
+ }
+ }
/* Remember the last statement of the block. */
last = stmt;
}
- /* Step 2. If BB's last statement is a conditional expression
+ /* Step 3. If BB's last statement is a conditional expression
involving integer operands, recurse into each of the sub-graphs
rooted at BB to determine if we need to add ASSERT_EXPRs. */
if (last
@@ -170,18 +1255,18 @@ maybe_add_assert_expr_on_edges (basic_bl
{
edge e;
edge_iterator ei;
- size_t nuses;
- tree cond = COND_EXPR_COND (last);
- use_optype uses = STMT_USE_OPS (last);
+ ssa_op_iter i;
+ tree op, cond;
+
+ cond = COND_EXPR_COND (last);
/* Remove the COND_EXPR operands from the FOUND bitmap.
Otherwise, when we finish traversing each of the sub-graphs,
we won't know whether the variables were found in the
sub-graphs or if they had been found in a block upstream from
BB. */
- nuses = NUM_USES (uses);
- for (i = 0; i < nuses; i++)
- RESET_BIT (found, var_ann (USE_OP (uses, i))->uid);
+ FOR_EACH_SSA_TREE_OPERAND (op, last, i, SSA_OP_USE)
+ RESET_BIT (found, SSA_NAME_VERSION (op));
/* Look for uses of the operands in each of the sub-graphs
rooted at BB. We need to check each of the outgoing edges
@@ -189,28 +1274,18 @@ maybe_add_assert_expr_on_edges (basic_bl
insert. */
FOR_EACH_EDGE (e, ei, bb->succs)
{
- /* Notice that by traversing the sub-graphs directly, we may
- be breaking the dominator traversal we have been doing.
- This happens if BB does not dominate one of its clauses:
-
- 1 if (y <= 10)
- 2 {
- 3 y = x + 1
- 4 if (y > 10)
- 5 y--;
- 6 }
- 7 z = y + x;
-
- The COND_EXPR at line 4 does not dominate its ELSE_CLAUSE
- at line 7, but we still want to add an ASSERT_EXPR at
- line 6 as it may still be useful. */
- added |= maybe_add_assert_expr_on_edges (e->dest, found);
+ /* If BB strictly dominates the sub-graph at E->DEST,
+ recurse into it. */
+ if (e->dest != bb
+ && dominated_by_p (CDI_DOMINATORS, e->dest, bb))
+ added |= maybe_add_assert_expr (e->dest);
- for (i = 0; i < nuses; i++)
+ /* Once we traversed the sub-graph, check if any block inside
+ used either of the predicate's operands. If so, add the
+ appropriate ASSERT_EXPR. */
+ FOR_EACH_SSA_TREE_OPERAND (op, last, i, SSA_OP_USE)
{
- tree op = USE_OP (uses, i);
-
- if (TEST_BIT (found, var_ann (op)->uid))
+ if (TEST_BIT (found, SSA_NAME_VERSION (op)))
{
/* We found a use of OP in the sub-graph rooted at
E->DEST. Add an ASSERT_EXPR according to whether
@@ -232,8 +1307,8 @@ maybe_add_assert_expr_on_edges (basic_bl
}
/* Finally, mark all the COND_EXPR operands as found. */
- for (i = 0; i < nuses; i++)
- SET_BIT (found, var_ann (USE_OP (uses, i))->uid);
+ FOR_EACH_SSA_TREE_OPERAND (op, last, i, SSA_OP_USE)
+ SET_BIT (found, SSA_NAME_VERSION (op));
}
else
{
@@ -243,7 +1318,7 @@ maybe_add_assert_expr_on_edges (basic_bl
for (son = first_dom_son (CDI_DOMINATORS, bb);
son;
son = next_dom_son (CDI_DOMINATORS, son))
- added |= maybe_add_assert_expr_on_edges (son, found);
+ added |= maybe_add_assert_expr (son);
}
return added;
@@ -283,58 +1358,47 @@ maybe_add_assert_expr_on_edges (basic_bl
definition of 'x'. */
static void
-execute_insert_range_assertions (void)
+insert_range_assertions (void)
{
- basic_block bb;
edge e;
edge_iterator ei;
- sbitmap found;
+ bool update_ssa_p;
- found = sbitmap_alloc (num_referenced_vars);
- sbitmap_zero (found);
+ new_ssa_names = VEC_alloc (tree_on_heap, 20);
+ old_ssa_names = VEC_alloc (tree_on_heap, 20);
- /* FIXME. Passes are free to assume that BB_VISITED will always be
- clear. This is error-prone. We now have to assert that it is
- indeed clear to avoid hard-to-find bugs. */
-#if defined ENABLE_CHECKING
- FOR_ALL_BB (bb)
- gcc_assert (!(bb->flags & BB_VISITED));
-#endif
+ found = sbitmap_alloc (num_ssa_names);
+ sbitmap_zero (found);
calculate_dominance_info (CDI_DOMINATORS);
+ update_ssa_p = false;
FOR_EACH_EDGE (e, ei, ENTRY_BLOCK_PTR->succs)
- if (maybe_add_assert_expr_on_edges (e->dest, found))
+ if (maybe_add_assert_expr (e->dest))
+ update_ssa_p = true;
+
+ if (update_ssa_p)
+ {
bsi_commit_edge_inserts ();
+ update_ssa (new_ssa_names, old_ssa_names);
+ }
- FOR_ALL_BB (bb)
- bb->flags &= ~BB_VISITED;
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ {
+ fprintf (dump_file, "\nSSA form after inserting ASSERT_EXPRs\n");
+ dump_function_to_file (current_function_decl, dump_file, dump_flags);
+ }
+ VEC_free (tree_on_heap, new_ssa_names);
+ VEC_free (tree_on_heap, old_ssa_names);
sbitmap_free (found);
}
-struct tree_opt_pass pass_insert_range_assertions =
-{
- "add_assert", /* name */
- NULL, /* gate */
- execute_insert_range_assertions, /* execute */
- NULL, /* sub */
- NULL, /* next */
- 0, /* static_pass_number */
- TV_TREE_INSERT_ASSERT, /* tv_id */
- PROP_cfg | PROP_gimple_leh, /* properties_required */
- 0, /* properties_provided */
- 0, /* properties_destroyed */
- TODO_cleanup_cfg, /* todo_flags_start */
- TODO_dump_func | TODO_ggc_collect, /* todo_flags_finish */
- 0 /* letter */
-};
-
/* Convert range assertion expressions into copies. FIXME, explain why. */
static void
-execute_remove_range_assertions (void)
+remove_range_assertions (void)
{
basic_block bb;
block_stmt_iterator si;
@@ -348,28 +1412,619 @@ execute_remove_range_assertions (void)
&& TREE_CODE (TREE_OPERAND (stmt, 1)) == ASSERT_EXPR)
{
tree rhs = TREE_OPERAND (stmt, 1);
- tree cond = fold (TREE_OPERAND (rhs, 1));
+ tree cond = fold (ASSERT_EXPR_COND (rhs));
gcc_assert (cond != boolean_false_node);
- TREE_OPERAND (stmt, 1) = TREE_OPERAND (rhs, 0);
+ TREE_OPERAND (stmt, 1) = ASSERT_EXPR_VAR (rhs);
modify_stmt (stmt);
}
}
}
-struct tree_opt_pass pass_remove_range_assertions =
+/* Return true if STMT is interesting for VRP. */
+
+static bool
+stmt_interesting_for_vrp (tree stmt)
{
- "remove_assert", /* name */
- NULL, /* gate */
- execute_remove_range_assertions, /* execute */
+ if (TREE_CODE (stmt) == PHI_NODE
+ && is_gimple_reg (PHI_RESULT (stmt))
+ && (INTEGRAL_TYPE_P (TREE_TYPE (PHI_RESULT (stmt)))
+ || POINTER_TYPE_P (TREE_TYPE (PHI_RESULT (stmt)))))
+ return true;
+ else if (TREE_CODE (stmt) == MODIFY_EXPR)
+ {
+ tree lhs = TREE_OPERAND (stmt, 0);
+ stmt_ann_t ann = stmt_ann (stmt);
+
+ if (TREE_CODE (lhs) == SSA_NAME
+ && (INTEGRAL_TYPE_P (TREE_TYPE (lhs))
+ || POINTER_TYPE_P (TREE_TYPE (lhs)))
+ && NUM_V_MAY_DEFS (V_MAY_DEF_OPS (ann)) == 0
+ && NUM_VUSES (VUSE_OPS (ann)) == 0
+ && NUM_V_MUST_DEFS (V_MUST_DEF_OPS (ann)) == 0)
+ return true;
+ }
+ else if (TREE_CODE (stmt) == COND_EXPR || TREE_CODE (stmt) == SWITCH_EXPR)
+ return true;
+
+ return false;
+}
+
+
+/* Function indicating whether we ought to include information for VAR
+ when calculating immediate uses. */
+
+static bool
+need_imm_uses_for (tree var)
+{
+ tree def_stmt = SSA_NAME_DEF_STMT (var);
+ return stmt_interesting_for_vrp (def_stmt);
+}
+
+
+/* Initialize local data structures for VRP. Return true if VRP
+ is worth running (i.e. if we found any statements that could
+ benefit from range information). */
+
+static bool
+vrp_initialize (void)
+{
+ basic_block bb;
+ bool do_vrp;
+
+ /* If we don't find any ASSERT_EXPRs in the code, there's no point
+ running VRP. */
+ do_vrp = false;
+
+ FOR_EACH_BB (bb)
+ {
+ block_stmt_iterator si;
+ tree phi;
+
+ for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi))
+ {
+ if (!stmt_interesting_for_vrp (phi))
+ {
+ tree lhs = PHI_RESULT (phi);
+ set_value_range (get_value_range (lhs), VR_VARYING, 0, 0);
+ DONT_SIMULATE_AGAIN (phi) = true;
+ }
+ else
+ DONT_SIMULATE_AGAIN (phi) = false;
+ }
+
+ for (si = bsi_start (bb); !bsi_end_p (si); bsi_next (&si))
+ {
+ tree stmt = bsi_stmt (si);
+
+ if (!stmt_interesting_for_vrp (stmt))
+ {
+ ssa_op_iter i;
+ tree def;
+ FOR_EACH_SSA_TREE_OPERAND (def, stmt, i, SSA_OP_DEF)
+ set_value_range (get_value_range (def), VR_VARYING, 0, 0);
+ DONT_SIMULATE_AGAIN (stmt) = true;
+ }
+ else
+ {
+ if (TREE_CODE (stmt) == MODIFY_EXPR
+ && TREE_CODE (TREE_OPERAND (stmt, 1)) == ASSERT_EXPR)
+ do_vrp = true;
+
+ DONT_SIMULATE_AGAIN (stmt) = false;
+ }
+ }
+ }
+
+ /* Compute immediate uses for variables we care about. */
+ if (do_vrp)
+ compute_immediate_uses (TDFA_USE_OPS | TDFA_USE_VOPS, need_imm_uses_for);
+
+ return do_vrp;
+}
+
+
+/* Visit assignment STMT. If it produces an interesting range, record
+ the SSA name in *OUTPUT_P. */
+
+static enum ssa_prop_result
+vrp_visit_assignment (tree stmt, tree *output_p)
+{
+ tree lhs, rhs, def;
+ ssa_op_iter iter;
+
+ lhs = TREE_OPERAND (stmt, 0);
+ rhs = TREE_OPERAND (stmt, 1);
+
+ /* We only keep track of ranges in integral and pointer types. */
+ if (TREE_CODE (lhs) == SSA_NAME
+ && (INTEGRAL_TYPE_P (TREE_TYPE (lhs))
+ || POINTER_TYPE_P (TREE_TYPE (lhs))))
+ {
+ value_range *vr, new_vr;
+
+ vr = get_value_range (lhs);
+ extract_range_from_expr (&new_vr, rhs);
+
+ if (update_value_range (vr, new_vr.type, new_vr.min, new_vr.max))
+ {
+ *output_p = lhs;
+
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ {
+ fprintf (dump_file, "Found new range ");
+ dump_value_range (dump_file, &new_vr);
+ fprintf (dump_file, " for ");
+ print_generic_expr (dump_file, lhs, 0);
+ fprintf (dump_file, "\n\n");
+ }
+
+ if (new_vr.type == VR_VARYING)
+ return SSA_PROP_VARYING;
+
+ return SSA_PROP_INTERESTING;
+ }
+
+ return SSA_PROP_NOT_INTERESTING;
+ }
+
+ /* Every other statements produces no useful ranges. */
+ FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter, SSA_OP_DEF)
+ set_value_range (get_value_range (def), VR_VARYING, 0, 0);
+
+ return SSA_PROP_VARYING;
+}
+
+
+/* Given a conditional predicate COND, try to determine if COND yields
+ true or false based on the value ranges of its operands. */
+
+static tree
+vrp_evaluate_conditional (tree cond)
+{
+ gcc_assert (TREE_CODE (cond) == SSA_NAME
+ || TREE_CODE_CLASS (TREE_CODE (cond)) == tcc_comparison);
+
+ if (TREE_CODE (cond) == SSA_NAME)
+ {
+ /* For SSA names, only return a truth value if the range is
+ known and contains exactly one value. */
+ value_range *vr = SSA_NAME_VALUE_RANGE (cond);
+ if (vr && vr->type == VR_RANGE && vr->min == vr->max)
+ return vr->min;
+ }
+ else
+ {
+ /* For comparisons, evaluate each operand and compare their
+ ranges. */
+ tree op0, op1;
+ value_range *vr0, *vr1;
+
+ op0 = TREE_OPERAND (cond, 0);
+ vr0 = (TREE_CODE (op0) == SSA_NAME) ? get_value_range (op0) : NULL;
+
+ op1 = TREE_OPERAND (cond, 1);
+ vr1 = (TREE_CODE (op1) == SSA_NAME) ? get_value_range (op1) : NULL;
+
+ if (vr0 && vr1)
+ return compare_ranges (TREE_CODE (cond), vr0, vr1);
+ else if (vr0 && vr1 == NULL)
+ return compare_range_with_value (TREE_CODE (cond), vr0, op1);
+ else if (vr0 == NULL && vr1)
+ return compare_range_with_value (opposite_comparison (TREE_CODE (cond)),
+ vr1, op0);
+ }
+
+ /* Anything else cannot be computed statically. */
+ return NULL_TREE;
+}
+
+
+/* Visit conditional statement STMT. If we can determine which edge
+ will be taken out of STMT's basic block, record it in
+ *TAKEN_EDGE_P and return SSA_PROP_INTERESTING. Otherwise, return
+ SSA_PROP_VARYING. */
+
+static enum ssa_prop_result
+vrp_visit_cond_stmt (tree stmt, edge *taken_edge_p)
+{
+ tree cond, val;
+
+ *taken_edge_p = NULL;
+
+ /* FIXME. Handle SWITCH_EXPRs. But first, the assert pass needs to
+ add ASSERT_EXPRs for them. */
+ if (TREE_CODE (stmt) == SWITCH_EXPR)
+ return SSA_PROP_VARYING;
+
+ cond = COND_EXPR_COND (stmt);
+
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ {
+ tree use;
+ ssa_op_iter i;
+
+ fprintf (dump_file, "\nVisiting conditional with predicate: ");
+ print_generic_expr (dump_file, cond, 0);
+ fprintf (dump_file, "\nWith known ranges\n");
+
+ FOR_EACH_SSA_TREE_OPERAND (use, stmt, i, SSA_OP_USE)
+ {
+ fprintf (dump_file, "\t");
+ print_generic_expr (dump_file, use, 0);
+ fprintf (dump_file, ": ");
+ dump_value_range (dump_file, SSA_NAME_VALUE_RANGE (use));
+ }
+
+ fprintf (dump_file, "\n");
+ }
+
+ /* Compute the value of the predicate COND by checking the known
+ ranges of each of its operands. */
+ val = vrp_evaluate_conditional (cond);
+ if (val)
+ *taken_edge_p = find_taken_edge (bb_for_stmt (stmt), val);
+
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ {
+ fprintf (dump_file, "\nPredicate evaluates to: ");
+ if (val == NULL_TREE)
+ fprintf (dump_file, "DON'T KNOW\n");
+ else
+ print_generic_stmt (dump_file, val, 0);
+ }
+
+ return (*taken_edge_p) ? SSA_PROP_INTERESTING : SSA_PROP_VARYING;
+}
+
+
+/* Evaluate statement STMT. If the statement produces a useful range,
+ return SSA_PROP_INTERESTING and record the SSA name with the
+ interesting range into *OUTPUT_P.
+
+ If STMT is a conditional branch and we can determine its truth
+ value, the taken edge is recorded in *TAKEN_EDGE_P.
+
+ If STMT produces a varying value, return SSA_PROP_VARYING. */
+
+static enum ssa_prop_result
+vrp_visit_stmt (tree stmt, edge *taken_edge_p, tree *output_p)
+{
+ tree def;
+ ssa_op_iter iter;
+ stmt_ann_t ann;
+
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ {
+ fprintf (dump_file, "\nVisiting statement:\n");
+ print_generic_stmt (dump_file, stmt, dump_flags);
+ fprintf (dump_file, "\n");
+ }
+
+ ann = stmt_ann (stmt);
+ if (TREE_CODE (stmt) == MODIFY_EXPR
+ && NUM_V_MAY_DEFS (V_MAY_DEF_OPS (ann)) == 0
+ && NUM_VUSES (VUSE_OPS (ann)) == 0
+ && NUM_V_MUST_DEFS (V_MUST_DEF_OPS (ann)) == 0)
+ return vrp_visit_assignment (stmt, output_p);
+ else if (TREE_CODE (stmt) == COND_EXPR || TREE_CODE (stmt) == SWITCH_EXPR)
+ return vrp_visit_cond_stmt (stmt, taken_edge_p);
+
+ /* All other statements produce nothing of interest for VRP, so mark
+ their outputs varying and prevent further simulation. */
+ FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter, SSA_OP_DEF)
+ set_value_range (get_value_range (def), VR_VARYING, 0, 0);
+
+ return SSA_PROP_VARYING;
+}
+
+
+/* Meet operation for value ranges. Given two value ranges VR0 and
+ VR1, store in VR0 the result of meeting VR0 and VR1.
+
+ The meeting rules are as follows:
+
+ 1- If VR0 and VR1 have an empty intersection, set VR0 to VR_VARYING.
+
+ 2- If VR0 and VR1 have a non-empty intersection, set VR0 to the
+ union of VR0 and VR1. */
+
+static void
+vrp_meet (value_range *vr0, value_range *vr1)
+{
+ if (vr0->type == VR_UNDEFINED)
+ {
+ *vr0 = *vr1;
+ return;
+ }
+
+ if (vr1->type == VR_UNDEFINED)
+ {
+ /* Nothing to do. VR0 already has the resulting range. */
+ return;
+ }
+
+ if (vr0->type == VR_VARYING)
+ {
+ /* Nothing to do. VR0 already has the resulting range. */
+ return;
+ }
+
+ if (vr1->type == VR_VARYING)
+ {
+ *vr0 = *vr1;
+ return;
+ }
+
+ /* If either is a symbolic range, drop to VARYING. */
+ if (symbolic_range_p (vr0) || symbolic_range_p (vr1))
+ {
+ set_value_range (vr0, VR_VARYING, NULL_TREE, NULL_TREE);
+ return;
+ }
+
+ if (vr0->type == VR_RANGE && vr1->type == VR_RANGE)
+ {
+ /* If VR0 and VR1 have a non-empty intersection, compute the
+ union of both ranges. */
+ if (value_ranges_intersect_p (vr0, vr1))
+ {
+ /* The lower limit of the new range is the minimum of the
+ two ranges. */
+ if (compare_values (vr0->min, vr1->min) == 1)
+ vr0->min = vr1->min;
+
+ /* The upper limit of the new range is the maximium of the
+ two ranges. */
+ if (compare_values (vr0->max, vr1->max) == -1)
+ vr0->max = vr1->max;
+
+ /* If the new range is (-INF, +INF), set it to VR_VARYING as
+ it is not a useful range. */
+ if (!POINTER_TYPE_P (TREE_TYPE (vr0->min))
+ && vr0->min == TYPE_MIN_VALUE (TREE_TYPE (vr0->min))
+ && vr0->max == TYPE_MAX_VALUE (TREE_TYPE (vr0->max)))
+ set_value_range (vr0, VR_VARYING, NULL_TREE, NULL_TREE);
+ }
+ else
+ {
+ /* The two ranges don't intersect, set the result to VR_VARYING. */
+ set_value_range (vr0, VR_VARYING, NULL_TREE, NULL_TREE);
+ }
+ }
+ else if (vr0->type == VR_ANTI_RANGE && vr1->type == VR_ANTI_RANGE)
+ {
+ /* Two anti-ranges meet only if they are both identical. */
+ if (compare_values (vr0->min, vr1->min) == 0
+ && compare_values (vr0->max, vr1->max) == 0
+ && compare_values (vr0->min, vr0->max) == 0)
+ /* Nothing to do. */ ;
+ else
+ set_value_range (vr0, VR_VARYING, NULL_TREE, NULL_TREE);
+ }
+ else if (vr0->type == VR_ANTI_RANGE || vr1->type == VR_ANTI_RANGE)
+ {
+ /* A range [VAL1, VAL2] and an anti-range ~[VAL3, VAL4] meet
+ only if the ranges have an empty intersection. The result of
+ the meet operation is the anti-range. */
+ if (!value_ranges_intersect_p (vr0, vr1))
+ {
+ if (vr1->type == VR_ANTI_RANGE)
+ *vr0 = *vr1;
+ }
+ else
+ set_value_range (vr0, VR_VARYING, NULL_TREE, NULL_TREE);
+ }
+ else
+ gcc_unreachable ();
+}
+
+
+/* Visit all arguments for PHI node PHI that flow through executable
+ edges. If a valid value range can be derived from all the incoming
+ value ranges, set a new range for the LHS of PHI.
+
+ FIXME Using the derivation techniques mentioned in Patterson's
+ paper we should be able to get better ranges when one of the
+ edges of the PHI is a back-edge. */
+
+static enum ssa_prop_result
+vrp_visit_phi_node (tree phi)
+{
+ int i;
+ tree lhs = PHI_RESULT (phi);
+ value_range *lhs_vr = get_value_range (lhs);
+ value_range vr_result = *lhs_vr;
+
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ {
+ fprintf (dump_file, "\nVisiting PHI node: ");
+ print_generic_expr (dump_file, phi, dump_flags);
+ }
+
+ for (i = 0; i < PHI_NUM_ARGS (phi); i++)
+ {
+ edge e = PHI_ARG_EDGE (phi, i);
+
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ {
+ fprintf (dump_file,
+ "\n Argument #%d (%d -> %d %sexecutable)\n",
+ i, e->src->index, e->dest->index,
+ (e->flags & EDGE_EXECUTABLE) ? "" : "not ");
+ }
+
+ if (e->flags & EDGE_EXECUTABLE)
+ {
+ tree arg = PHI_ARG_DEF (phi, i);
+ value_range vr_arg;
+
+ if (TREE_CODE (arg) == SSA_NAME)
+ vr_arg = *(get_value_range (arg));
+ else
+ {
+ vr_arg.type = VR_RANGE;
+ vr_arg.min = arg;
+ vr_arg.max = arg;
+ }
+
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ {
+ fprintf (dump_file, "\t");
+ print_generic_expr (dump_file, arg, dump_flags);
+ fprintf (dump_file, "\n\tValue: ");
+ dump_value_range (dump_file, &vr_arg);
+ fprintf (dump_file, "\n");
+ }
+
+ vrp_meet (&vr_result, &vr_arg);
+
+ if (vr_result.type == VR_VARYING)
+ break;
+ }
+ }
+
+ if (vr_result.type == VR_VARYING)
+ {
+ set_value_range (lhs_vr, VR_VARYING, 0, 0);
+ return SSA_PROP_VARYING;
+ }
+
+ /* To prevent infinite iterations in the algorithm, derive ranges
+ when the new value is slightly bigger or smaller than the
+ previous one. */
+ if (lhs_vr->type == VR_RANGE)
+ {
+ if (!POINTER_TYPE_P (TREE_TYPE (lhs)))
+ {
+ int cmp_min = compare_values (lhs_vr->min, vr_result.min);
+ int cmp_max = compare_values (lhs_vr->max, vr_result.max);
+
+ /* If the new minimum is smaller or larger than the previous
+ one, go all the way to -INF. In the first case, to avoid
+ iterating millions of times to reach -INF, and in the
+ other case to avoid infinite bouncing between different
+ minimums. */
+ if (cmp_min > 0 || cmp_min < 0)
+ vr_result.min = TYPE_MIN_VALUE (TREE_TYPE (vr_result.min));
+
+ /* Similarly, if the new maximum is smaller or larger than
+ the previous one, go all the way to +INF. */
+ if (cmp_max < 0 || cmp_max > 0)
+ vr_result.max = TYPE_MAX_VALUE (TREE_TYPE (vr_result.max));
+
+ /* If we ended up with a (-INF, +INF) range, set it to
+ VARYING. */
+ if (vr_result.min == TYPE_MIN_VALUE (TREE_TYPE (vr_result.min))
+ && vr_result.max == TYPE_MAX_VALUE (TREE_TYPE (vr_result.max)))
+ {
+ set_value_range (lhs_vr, VR_VARYING, 0, 0);
+ return SSA_PROP_VARYING;
+ }
+ }
+ }
+
+ /* If the new range is different than the previous value, keep
+ iterating. */
+ if (update_value_range (lhs_vr, vr_result.type, vr_result.min, vr_result.max))
+ return SSA_PROP_INTERESTING;
+
+ /* Nothing changed, don't add outgoing edges. */
+ return SSA_PROP_NOT_INTERESTING;
+}
+
+
+/* Traverse all the blocks folding conditionals with known ranges. */
+
+static void
+vrp_finalize (void)
+{
+ basic_block bb;
+
+ if (dump_file)
+ {
+ fprintf (dump_file, "\nValue ranges after VRP:\n\n");
+ dump_all_value_ranges (dump_file);
+ fprintf (dump_file, "\n");
+ }
+
+ FOR_EACH_BB (bb)
+ {
+ tree last = last_stmt (bb);
+ if (last && TREE_CODE (last) == COND_EXPR)
+ {
+ tree val = vrp_evaluate_conditional (COND_EXPR_COND (last));
+ if (val)
+ {
+ if (dump_file)
+ {
+ fprintf (dump_file, "Folding predicate ");
+ print_generic_expr (dump_file, COND_EXPR_COND (last), 0);
+ fprintf (dump_file, " to ");
+ print_generic_expr (dump_file, val, 0);
+ fprintf (dump_file, "\n");
+ }
+
+ COND_EXPR_COND (last) = val;
+ }
+ }
+ }
+}
+
+
+/* Main entry point to VRP (Value Range Propagation). This pass is
+ loosely based on J. R. C. Patterson, ``Accurate Static Branch
+ Prediction by Value Range Propagation,'' in SIGPLAN Conference on
+ Programming Language Design and Implementation, pp. 67-78, 1995.
+ Also available at http://citeseer.ist.psu.edu/patterson95accurate.html
+
+ This is essentially an SSA-CCP pass modified to deal with ranges
+ instead of constants.
+
+ TODO, the main difference between this pass and Patterson's is that
+ we do not propagate edge probabilities. We only compute whether
+ edges can be taken or not. That is, instead of having a spectrum
+ of jump probabilities between 0 and 1, we only deal with 0, 1 and
+ DON'T KNOW. In the future, it may be worthwhile to propagate
+ probabilities to aid branch prediction. */
+
+static void
+execute_vrp (void)
+{
+ insert_range_assertions ();
+
+ if (vrp_initialize ())
+ {
+ ssa_propagate (vrp_visit_stmt, vrp_visit_phi_node);
+ vrp_finalize ();
+ }
+
+ remove_range_assertions ();
+}
+
+static bool
+gate_vrp (void)
+{
+ return flag_tree_vrp != 0;
+}
+
+struct tree_opt_pass pass_vrp =
+{
+ "vrp", /* name */
+ gate_vrp, /* gate */
+ execute_vrp, /* execute */
NULL, /* sub */
NULL, /* next */
0, /* static_pass_number */
- 0, /* tv_id */
- PROP_ssa, /* properties_required */
+ TV_TREE_VRP, /* tv_id */
+ PROP_ssa | PROP_alias, /* properties_required */
0, /* properties_provided */
0, /* properties_destroyed */
0, /* todo_flags_start */
- TODO_dump_func | TODO_ggc_collect, /* todo_flags_finish */
+ TODO_cleanup_cfg
+ | TODO_ggc_collect
+ | TODO_verify_ssa
+ | TODO_dump_func
+ | TODO_rename_vars, /* todo_flags_finish */
0 /* letter */
};
Index: tree.h
===================================================================
RCS file: /cvs/gcc/gcc/gcc/tree.h,v
retrieving revision 1.625.2.12
diff -d -u -p -r1.625.2.12 tree.h
--- tree.h 2 Feb 2005 02:44:12 -0000 1.625.2.12
+++ tree.h 2 Feb 2005 22:10:32 -0000
@@ -1331,12 +1335,17 @@ struct tree_exp GTY(())
#define SSA_NAME_VALUE(N) \
SSA_NAME_CHECK (N)->ssa_name.value_handle
+/* Range information for SSA_NAMEs. */
+#define SSA_NAME_VALUE_RANGE(N) \
+ SSA_NAME_CHECK (N)->ssa_name.value_range
+
/* Auxiliary pass-specific data. */
#define SSA_NAME_AUX(N) \
SSA_NAME_CHECK (N)->ssa_name.aux
#ifndef _TREE_FLOW_H
struct ptr_info_def;
+struct value_range_def;
#endif
struct tree_ssa_name GTY(())
@@ -1359,6 +1368,9 @@ struct tree_ssa_name GTY(())
as well. */
tree value_handle;
+ /* Value range information. */
+ struct value_range_def *value_range;
+
/* Auxiliary information stored with the ssa name. */
PTR GTY((skip)) aux;
};