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Fix PR23942
- From: Sebastian Pop <sebastian dot pop at cri dot ensmp dot fr>
- To: GCC Patches <gcc-patches at gcc dot gnu dot org>
- Date: Mon, 26 Sep 2005 20:47:20 +0200
- Subject: Fix PR23942
Hi,
This patch limits to PARAM_SCEV_MAX_EXPR_SIZE the size of trees that
are walked for detecting an updating path from a loop phi node to
itself. Bootstrapped and tested on {i686,amd64}-linux. Committed to
mainline.
Sebastian
PR tree-optimization/23942
* Makefile.in (SCEV_H): Depends on PARAMS_H.
* tree-scalar-evolution.c: Include params.h.
(t_bool): New enum.
(follow_ssa_edge, follow_ssa_edge_in_rhs,
follow_ssa_edge_in_condition_phi_branch,
follow_ssa_edge_in_condition_phi, follow_ssa_edge_inner_loop_phi):
Change return type to t_bool. Use a parameter to limit the size of
trees that are walked before stopping
(analyze_evolution_in_loop): Initialize the limit to 0.
(follow_ssa_edge): Give up by returning t_dont_know if the limit
exceeds PARAM_SCEV_MAX_EXPR_SIZE.
Index: Makefile.in
===================================================================
RCS file: /cvs/gcc/gcc/gcc/Makefile.in,v
retrieving revision 1.1541
diff -d -u -p -r1.1541 Makefile.in
--- Makefile.in 14 Sep 2005 09:26:41 -0000 1.1541
+++ Makefile.in 26 Sep 2005 18:29:49 -0000
@@ -767,7 +767,7 @@ TREE_SSA_LIVE_H = tree-ssa-live.h $(PART
PRETTY_PRINT_H = pretty-print.h input.h $(OBSTACK_H)
DIAGNOSTIC_H = diagnostic.h diagnostic.def $(PRETTY_PRINT_H)
C_PRETTY_PRINT_H = c-pretty-print.h $(PRETTY_PRINT_H) $(C_COMMON_H) $(TREE_H)
-SCEV_H = tree-scalar-evolution.h $(GGC_H) tree-chrec.h
+SCEV_H = tree-scalar-evolution.h $(GGC_H) tree-chrec.h $(PARAMS_H)
LAMBDA_H = lambda.h tree.h vec.h $(GGC_H)
TREE_DATA_REF_H = tree-data-ref.h $(LAMBDA_H)
VARRAY_H = varray.h $(MACHMODE_H) $(SYSTEM_H) coretypes.h $(TM_H)
Index: tree-scalar-evolution.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/tree-scalar-evolution.c,v
retrieving revision 2.38
diff -d -u -p -r2.38 tree-scalar-evolution.c
--- tree-scalar-evolution.c 20 Sep 2005 07:09:20 -0000 2.38
+++ tree-scalar-evolution.c 26 Sep 2005 18:29:49 -0000
@@ -251,6 +251,7 @@ Software Foundation, 51 Franklin Street,
#include "tree-scalar-evolution.h"
#include "tree-pass.h"
#include "flags.h"
+#include "params.h"
static tree analyze_scalar_evolution_1 (struct loop *, tree, tree);
static tree resolve_mixers (struct loop *, tree);
@@ -1022,19 +1023,23 @@ select_loops_exit_conditions (struct loo
/* Depth first search algorithm. */
-static bool follow_ssa_edge (struct loop *loop, tree, tree, tree *);
+typedef enum t_bool {
+ t_false,
+ t_true,
+ t_dont_know
+} t_bool;
+
+
+static t_bool follow_ssa_edge (struct loop *loop, tree, tree, tree *, int);
/* Follow the ssa edge into the right hand side RHS of an assignment.
Return true if the strongly connected component has been found. */
-static bool
-follow_ssa_edge_in_rhs (struct loop *loop,
- tree at_stmt,
- tree rhs,
- tree halting_phi,
- tree *evolution_of_loop)
+static t_bool
+follow_ssa_edge_in_rhs (struct loop *loop, tree at_stmt, tree rhs,
+ tree halting_phi, tree *evolution_of_loop, int limit)
{
- bool res = false;
+ t_bool res = t_false;
tree rhs0, rhs1;
tree type_rhs = TREE_TYPE (rhs);
@@ -1050,20 +1055,20 @@ follow_ssa_edge_in_rhs (struct loop *loo
case NOP_EXPR:
/* This assignment is under the form "a_1 = (cast) rhs. */
res = follow_ssa_edge_in_rhs (loop, at_stmt, TREE_OPERAND (rhs, 0),
- halting_phi, evolution_of_loop);
+ halting_phi, evolution_of_loop, limit);
*evolution_of_loop = chrec_convert (TREE_TYPE (rhs),
*evolution_of_loop, at_stmt);
break;
case INTEGER_CST:
/* This assignment is under the form "a_1 = 7". */
- res = false;
+ res = t_false;
break;
case SSA_NAME:
/* This assignment is under the form: "a_1 = b_2". */
res = follow_ssa_edge
- (loop, SSA_NAME_DEF_STMT (rhs), halting_phi, evolution_of_loop);
+ (loop, SSA_NAME_DEF_STMT (rhs), halting_phi, evolution_of_loop, limit);
break;
case PLUS_EXPR:
@@ -1081,26 +1086,32 @@ follow_ssa_edge_in_rhs (struct loop *loo
"a = b + c". */
res = follow_ssa_edge
(loop, SSA_NAME_DEF_STMT (rhs0), halting_phi,
- evolution_of_loop);
+ evolution_of_loop, limit);
- if (res)
+ if (res == t_true)
*evolution_of_loop = add_to_evolution
(loop->num,
chrec_convert (type_rhs, *evolution_of_loop, at_stmt),
PLUS_EXPR, rhs1);
- else
+ else if (res == t_false)
{
res = follow_ssa_edge
(loop, SSA_NAME_DEF_STMT (rhs1), halting_phi,
- evolution_of_loop);
+ evolution_of_loop, limit);
- if (res)
+ if (res == t_true)
*evolution_of_loop = add_to_evolution
(loop->num,
chrec_convert (type_rhs, *evolution_of_loop, at_stmt),
PLUS_EXPR, rhs0);
+
+ else if (res == t_dont_know)
+ *evolution_of_loop = chrec_dont_know;
}
+
+ else if (res == t_dont_know)
+ *evolution_of_loop = chrec_dont_know;
}
else
@@ -1109,12 +1120,15 @@ follow_ssa_edge_in_rhs (struct loop *loo
"a = b + ...". */
res = follow_ssa_edge
(loop, SSA_NAME_DEF_STMT (rhs0), halting_phi,
- evolution_of_loop);
- if (res)
+ evolution_of_loop, limit);
+ if (res == t_true)
*evolution_of_loop = add_to_evolution
(loop->num, chrec_convert (type_rhs, *evolution_of_loop,
at_stmt),
PLUS_EXPR, rhs1);
+
+ else if (res == t_dont_know)
+ *evolution_of_loop = chrec_dont_know;
}
}
@@ -1124,19 +1138,22 @@ follow_ssa_edge_in_rhs (struct loop *loo
"a = ... + c". */
res = follow_ssa_edge
(loop, SSA_NAME_DEF_STMT (rhs1), halting_phi,
- evolution_of_loop);
- if (res)
+ evolution_of_loop, limit);
+ if (res == t_true)
*evolution_of_loop = add_to_evolution
(loop->num, chrec_convert (type_rhs, *evolution_of_loop,
at_stmt),
PLUS_EXPR, rhs0);
+
+ else if (res == t_dont_know)
+ *evolution_of_loop = chrec_dont_know;
}
else
/* Otherwise, match an assignment under the form:
"a = ... + ...". */
/* And there is nothing to do. */
- res = false;
+ res = t_false;
break;
@@ -1152,18 +1169,20 @@ follow_ssa_edge_in_rhs (struct loop *loo
/* Match an assignment under the form:
"a = b - ...". */
res = follow_ssa_edge (loop, SSA_NAME_DEF_STMT (rhs0), halting_phi,
- evolution_of_loop);
- if (res)
+ evolution_of_loop, limit);
+ if (res == t_true)
*evolution_of_loop = add_to_evolution
- (loop->num, chrec_convert (type_rhs, *evolution_of_loop,
- at_stmt),
- MINUS_EXPR, rhs1);
+ (loop->num, chrec_convert (type_rhs, *evolution_of_loop, at_stmt),
+ MINUS_EXPR, rhs1);
+
+ else if (res == t_dont_know)
+ *evolution_of_loop = chrec_dont_know;
}
else
/* Otherwise, match an assignment under the form:
"a = ... - ...". */
/* And there is nothing to do. */
- res = false;
+ res = t_false;
break;
@@ -1182,18 +1201,18 @@ follow_ssa_edge_in_rhs (struct loop *loo
"a = b * c". */
res = follow_ssa_edge
(loop, SSA_NAME_DEF_STMT (rhs0), halting_phi,
- evolution_of_loop);
+ evolution_of_loop, limit);
- if (res)
+ if (res == t_true || res == t_dont_know)
*evolution_of_loop = chrec_dont_know;
- else
+ else if (res == t_false)
{
res = follow_ssa_edge
(loop, SSA_NAME_DEF_STMT (rhs1), halting_phi,
- evolution_of_loop);
+ evolution_of_loop, limit);
- if (res)
+ if (res == t_true || res == t_dont_know)
*evolution_of_loop = chrec_dont_know;
}
}
@@ -1204,8 +1223,8 @@ follow_ssa_edge_in_rhs (struct loop *loo
"a = b * ...". */
res = follow_ssa_edge
(loop, SSA_NAME_DEF_STMT (rhs0), halting_phi,
- evolution_of_loop);
- if (res)
+ evolution_of_loop, limit);
+ if (res == t_true || res == t_dont_know)
*evolution_of_loop = chrec_dont_know;
}
}
@@ -1216,8 +1235,8 @@ follow_ssa_edge_in_rhs (struct loop *loo
"a = ... * c". */
res = follow_ssa_edge
(loop, SSA_NAME_DEF_STMT (rhs1), halting_phi,
- evolution_of_loop);
- if (res)
+ evolution_of_loop, limit);
+ if (res == t_true || res == t_dont_know)
*evolution_of_loop = chrec_dont_know;
}
@@ -1225,7 +1244,7 @@ follow_ssa_edge_in_rhs (struct loop *loo
/* Otherwise, match an assignment under the form:
"a = ... * ...". */
/* And there is nothing to do. */
- res = false;
+ res = t_false;
break;
@@ -1236,15 +1255,15 @@ follow_ssa_edge_in_rhs (struct loop *loo
tree op0 = ASSERT_EXPR_VAR (rhs);
if (TREE_CODE (op0) == SSA_NAME)
res = follow_ssa_edge (loop, SSA_NAME_DEF_STMT (op0),
- halting_phi, evolution_of_loop);
+ halting_phi, evolution_of_loop, limit);
else
- res = false;
+ res = t_false;
break;
}
default:
- res = false;
+ res = t_false;
break;
}
@@ -1271,13 +1290,13 @@ backedge_phi_arg_p (tree phi, int i)
true if the strongly connected component has been found following
this path. */
-static inline bool
+static inline t_bool
follow_ssa_edge_in_condition_phi_branch (int i,
struct loop *loop,
tree condition_phi,
tree halting_phi,
tree *evolution_of_branch,
- tree init_cond)
+ tree init_cond, int limit)
{
tree branch = PHI_ARG_DEF (condition_phi, i);
*evolution_of_branch = chrec_dont_know;
@@ -1285,13 +1304,13 @@ follow_ssa_edge_in_condition_phi_branch
/* Do not follow back edges (they must belong to an irreducible loop, which
we really do not want to worry about). */
if (backedge_phi_arg_p (condition_phi, i))
- return false;
+ return t_false;
if (TREE_CODE (branch) == SSA_NAME)
{
*evolution_of_branch = init_cond;
return follow_ssa_edge (loop, SSA_NAME_DEF_STMT (branch), halting_phi,
- evolution_of_branch);
+ evolution_of_branch, limit);
}
/* This case occurs when one of the condition branches sets
@@ -1301,27 +1320,28 @@ follow_ssa_edge_in_condition_phi_branch
FIXME: This case have to be refined correctly:
in some cases it is possible to say something better than
chrec_dont_know, for example using a wrap-around notation. */
- return false;
+ return t_false;
}
/* This function merges the branches of a condition-phi-node in a
loop. */
-static bool
+static t_bool
follow_ssa_edge_in_condition_phi (struct loop *loop,
tree condition_phi,
tree halting_phi,
- tree *evolution_of_loop)
+ tree *evolution_of_loop, int limit)
{
int i;
tree init = *evolution_of_loop;
tree evolution_of_branch;
+ t_bool res = follow_ssa_edge_in_condition_phi_branch (0, loop, condition_phi,
+ halting_phi,
+ &evolution_of_branch,
+ init, limit);
+ if (res == t_false || res == t_dont_know)
+ return res;
- if (!follow_ssa_edge_in_condition_phi_branch (0, loop, condition_phi,
- halting_phi,
- &evolution_of_branch,
- init))
- return false;
*evolution_of_loop = evolution_of_branch;
for (i = 1; i < PHI_NUM_ARGS (condition_phi); i++)
@@ -1329,19 +1349,20 @@ follow_ssa_edge_in_condition_phi (struct
/* Quickly give up when the evolution of one of the branches is
not known. */
if (*evolution_of_loop == chrec_dont_know)
- return true;
+ return t_true;
- if (!follow_ssa_edge_in_condition_phi_branch (i, loop, condition_phi,
- halting_phi,
- &evolution_of_branch,
- init))
- return false;
+ res = follow_ssa_edge_in_condition_phi_branch (i, loop, condition_phi,
+ halting_phi,
+ &evolution_of_branch,
+ init, limit);
+ if (res == t_false || res == t_dont_know)
+ return res;
*evolution_of_loop = chrec_merge (*evolution_of_loop,
evolution_of_branch);
}
- return true;
+ return t_true;
}
/* Follow an SSA edge in an inner loop. It computes the overall
@@ -1349,11 +1370,11 @@ follow_ssa_edge_in_condition_phi (struct
it follows the edges in the parent loop. The inner loop is
considered as a single statement. */
-static bool
+static t_bool
follow_ssa_edge_inner_loop_phi (struct loop *outer_loop,
tree loop_phi_node,
tree halting_phi,
- tree *evolution_of_loop)
+ tree *evolution_of_loop, int limit)
{
struct loop *loop = loop_containing_stmt (loop_phi_node);
tree ev = analyze_scalar_evolution (loop, PHI_RESULT (loop_phi_node));
@@ -1362,7 +1383,7 @@ follow_ssa_edge_inner_loop_phi (struct l
result of the analysis is a symbolic parameter. */
if (ev == PHI_RESULT (loop_phi_node))
{
- bool res = false;
+ t_bool res = t_false;
int i;
for (i = 0; i < PHI_NUM_ARGS (loop_phi_node); i++)
@@ -1373,13 +1394,15 @@ follow_ssa_edge_inner_loop_phi (struct l
/* Follow the edges that exit the inner loop. */
bb = PHI_ARG_EDGE (loop_phi_node, i)->src;
if (!flow_bb_inside_loop_p (loop, bb))
- res = res || follow_ssa_edge_in_rhs (outer_loop, loop_phi_node,
- arg, halting_phi,
- evolution_of_loop);
+ res = follow_ssa_edge_in_rhs (outer_loop, loop_phi_node,
+ arg, halting_phi,
+ evolution_of_loop, limit);
+ if (res == t_true)
+ break;
}
/* If the path crosses this loop-phi, give up. */
- if (res == true)
+ if (res == t_true)
*evolution_of_loop = chrec_dont_know;
return res;
@@ -1388,22 +1411,24 @@ follow_ssa_edge_inner_loop_phi (struct l
/* Otherwise, compute the overall effect of the inner loop. */
ev = compute_overall_effect_of_inner_loop (loop, ev);
return follow_ssa_edge_in_rhs (outer_loop, loop_phi_node, ev, halting_phi,
- evolution_of_loop);
+ evolution_of_loop, limit);
}
/* Follow an SSA edge from a loop-phi-node to itself, constructing a
path that is analyzed on the return walk. */
-static bool
-follow_ssa_edge (struct loop *loop,
- tree def,
- tree halting_phi,
- tree *evolution_of_loop)
+static t_bool
+follow_ssa_edge (struct loop *loop, tree def, tree halting_phi,
+ tree *evolution_of_loop, int limit)
{
struct loop *def_loop;
if (TREE_CODE (def) == NOP_EXPR)
- return false;
+ return t_false;
+
+ /* Give up if the path is longer than the MAX that we allow. */
+ if (limit++ > PARAM_VALUE (PARAM_SCEV_MAX_EXPR_SIZE))
+ return t_dont_know;
def_loop = loop_containing_stmt (def);
@@ -1416,39 +1441,39 @@ follow_ssa_edge (struct loop *loop,
information and set the approximation to the main
variable. */
return follow_ssa_edge_in_condition_phi
- (loop, def, halting_phi, evolution_of_loop);
+ (loop, def, halting_phi, evolution_of_loop, limit);
/* When the analyzed phi is the halting_phi, the
depth-first search is over: we have found a path from
the halting_phi to itself in the loop. */
if (def == halting_phi)
- return true;
+ return t_true;
/* Otherwise, the evolution of the HALTING_PHI depends
on the evolution of another loop-phi-node, i.e. the
evolution function is a higher degree polynomial. */
if (def_loop == loop)
- return false;
+ return t_false;
/* Inner loop. */
if (flow_loop_nested_p (loop, def_loop))
return follow_ssa_edge_inner_loop_phi
- (loop, def, halting_phi, evolution_of_loop);
+ (loop, def, halting_phi, evolution_of_loop, limit);
/* Outer loop. */
- return false;
+ return t_false;
case MODIFY_EXPR:
return follow_ssa_edge_in_rhs (loop, def,
TREE_OPERAND (def, 1),
halting_phi,
- evolution_of_loop);
+ evolution_of_loop, limit);
default:
/* At this level of abstraction, the program is just a set
of MODIFY_EXPRs and PHI_NODEs. In principle there is no
other node to be handled. */
- return false;
+ return t_false;
}
}
@@ -1491,7 +1516,7 @@ analyze_evolution_in_loop (tree loop_phi
/* Pass in the initial condition to the follow edge function. */
ev_fn = init_cond;
- res = follow_ssa_edge (loop, ssa_chain, loop_phi_node, &ev_fn);
+ res = follow_ssa_edge (loop, ssa_chain, loop_phi_node, &ev_fn, 0);
}
else
res = false;