C PATCH to kill c_save_expr or towards delayed folding for the C FE
Marek Polacek
polacek@redhat.com
Fri May 12 19:48:00 GMT 2017
[ This patch depends on my previous patch that removes the fold call from
save_expr. ]
In the effort of reducing early folding, we should avoid calling c_fully_fold
blithely, except when needed for e.g. initializers. This is a teeny tiny step
down that path. This patch does away with c_save_expr, which always fully
folded the expression. Instead, I moved the SAVE_EXPR folding to c_fully_fold.
The new flag SAVE_EXPR_FOLDED_P ensures we only fold the contents once. Also,
if the contents of the SAVE_EXPR are tree_invariant_p, we don't have to wrap
the expression with SAVE_EXPR. I wonder if I should instead introduce a hash
map, much like C++; if we fold the contents of a SAVE_EXPR to an invariant, I
think we'll fold the expression multiple times, because in that case we cannot
check the SAVE_EXPR_FOLDED_P flag.
Comments/future directions very much appreciated.
Bootstrapped/regtested on x86_64-linux, ok for trunk once the other patch makes
it in?
2017-05-12 Marek Polacek <polacek@redhat.com>
* c-common.c (c_save_expr): Remove.
(c_common_truthvalue_conversion): Remove a call to c_save_expr.
* c-common.h (c_save_expr): Remove declaration.
* c-convert.c (convert): Replace c_save_expr with save_expr. Don't
call c_fully_fold.
* c-decl.c (grokdeclarator): Replace c_save_expr with save_expr.
* c-fold.c (c_fully_fold_internal): Handle SAVE_EXPR.
* c-parser.c (c_parser_declaration_or_fndef): Replace c_save_expr with
save_expr.
(c_parser_conditional_expression): Likewise.
* c-tree.h (SAVE_EXPR_FOLDED_P): Define.
* c-typeck.c (build_modify_expr): Replace c_save_expr with save_expr.
(process_init_element): Likewise.
(build_binary_op): Likewise.
(handle_omp_array_sections_1): Likewise.
diff --git gcc/c-family/c-common.c gcc/c-family/c-common.c
index ad686d2..f606e94 100644
--- gcc/c-family/c-common.c
+++ gcc/c-family/c-common.c
@@ -3164,24 +3164,6 @@ c_wrap_maybe_const (tree expr, bool non_const)
return expr;
}
-/* Wrap a SAVE_EXPR around EXPR, if appropriate. Like save_expr, but
- for C folds the inside expression and wraps a C_MAYBE_CONST_EXPR
- around the SAVE_EXPR if needed so that c_fully_fold does not need
- to look inside SAVE_EXPRs. */
-
-tree
-c_save_expr (tree expr)
-{
- bool maybe_const = true;
- if (c_dialect_cxx ())
- return save_expr (expr);
- expr = c_fully_fold (expr, false, &maybe_const);
- expr = save_expr (expr);
- if (!maybe_const)
- expr = c_wrap_maybe_const (expr, true);
- return expr;
-}
-
/* Return whether EXPR is a declaration whose address can never be
NULL. */
@@ -3436,7 +3418,7 @@ c_common_truthvalue_conversion (location_t location, tree expr)
if (TREE_CODE (TREE_TYPE (expr)) == COMPLEX_TYPE)
{
- tree t = (in_late_binary_op ? save_expr (expr) : c_save_expr (expr));
+ tree t = save_expr (expr);
expr = (build_binary_op
(EXPR_LOCATION (expr),
(TREE_SIDE_EFFECTS (expr)
diff --git gcc/c-family/c-common.h gcc/c-family/c-common.h
index 9e3982d..3981544 100644
--- gcc/c-family/c-common.h
+++ gcc/c-family/c-common.h
@@ -836,7 +836,6 @@ extern enum conversion_safety unsafe_conversion_p (location_t, tree, tree,
extern bool decl_with_nonnull_addr_p (const_tree);
extern tree c_fully_fold (tree, bool, bool *);
extern tree c_wrap_maybe_const (tree, bool);
-extern tree c_save_expr (tree);
extern tree c_common_truthvalue_conversion (location_t, tree);
extern void c_apply_type_quals_to_decl (int, tree);
extern tree c_sizeof_or_alignof_type (location_t, tree, bool, bool, int);
diff --git gcc/c/c-convert.c gcc/c/c-convert.c
index 163feff..a7764f0 100644
--- gcc/c/c-convert.c
+++ gcc/c/c-convert.c
@@ -111,13 +111,7 @@ convert (tree type, tree expr)
&& COMPLETE_TYPE_P (type)
&& do_ubsan_in_current_function ())
{
- if (in_late_binary_op)
- expr = save_expr (expr);
- else
- {
- expr = c_save_expr (expr);
- expr = c_fully_fold (expr, false, NULL);
- }
+ expr = save_expr (expr);
tree check = ubsan_instrument_float_cast (loc, type, expr);
expr = fold_build1 (FIX_TRUNC_EXPR, type, expr);
if (check == NULL_TREE)
@@ -146,8 +140,7 @@ convert (tree type, tree expr)
case COMPLEX_TYPE:
/* If converting from COMPLEX_TYPE to a different COMPLEX_TYPE
- and e is not COMPLEX_EXPR, convert_to_complex uses save_expr,
- but for the C FE c_save_expr needs to be called instead. */
+ and E is not COMPLEX_EXPR, convert_to_complex uses save_expr. */
if (TREE_CODE (TREE_TYPE (e)) == COMPLEX_TYPE)
{
if (TREE_CODE (e) != COMPLEX_EXPR)
@@ -155,10 +148,7 @@ convert (tree type, tree expr)
tree subtype = TREE_TYPE (type);
tree elt_type = TREE_TYPE (TREE_TYPE (e));
- if (in_late_binary_op)
- e = save_expr (e);
- else
- e = c_save_expr (e);
+ e = save_expr (e);
ret
= fold_build2_loc (loc, COMPLEX_EXPR, type,
convert (subtype,
diff --git gcc/c/c-decl.c gcc/c/c-decl.c
index b779d37..8ae09c4 100644
--- gcc/c/c-decl.c
+++ gcc/c/c-decl.c
@@ -6076,7 +6076,7 @@ grokdeclarator (const struct c_declarator *declarator,
&& do_ubsan_in_current_function ())
{
/* Evaluate the array size only once. */
- size = c_save_expr (size);
+ size = save_expr (size);
size = c_fully_fold (size, false, NULL);
size = fold_build2 (COMPOUND_EXPR, TREE_TYPE (size),
ubsan_instrument_vla (loc, size),
diff --git gcc/c/c-fold.c gcc/c/c-fold.c
index b060d76..1baee44 100644
--- gcc/c/c-fold.c
+++ gcc/c/c-fold.c
@@ -120,12 +120,11 @@ c_fully_fold_internal (tree expr, bool in_init, bool *maybe_const_operands,
bool unused_p;
source_range old_range;
- /* Constants, declarations, statements, errors, SAVE_EXPRs and
- anything else not counted as an expression cannot usefully be
- folded further at this point. */
+ /* Constants, declarations, statements, errors, and anything else not
+ counted as an expression cannot usefully be folded further at this
+ point. */
if (!IS_EXPR_CODE_CLASS (kind)
- || kind == tcc_statement
- || code == SAVE_EXPR)
+ || kind == tcc_statement)
return expr;
if (IS_EXPR_CODE_CLASS (kind))
@@ -565,6 +564,25 @@ c_fully_fold_internal (tree expr, bool in_init, bool *maybe_const_operands,
appropriate in any particular case. */
gcc_unreachable ();
+ case SAVE_EXPR:
+ /* Make sure to fold the contents of a SAVE_EXPR exactly once. */
+ if (!SAVE_EXPR_FOLDED_P (expr))
+ {
+ op0 = TREE_OPERAND (expr, 0);
+ op0 = c_fully_fold_internal (op0, in_init, maybe_const_operands,
+ maybe_const_itself, for_int_const);
+ /* Don't wrap the folded tree in a SAVE_EXPR if we don't
+ have to. */
+ if (tree_invariant_p (op0))
+ ret = op0;
+ else
+ {
+ TREE_OPERAND (expr, 0) = op0;
+ SAVE_EXPR_FOLDED_P (expr) = true;
+ }
+ }
+ goto out;
+
default:
/* Various codes may appear through folding built-in functions
and their arguments. */
diff --git gcc/c/c-parser.c gcc/c/c-parser.c
index 90d2d17..96c0749 100644
--- gcc/c/c-parser.c
+++ gcc/c/c-parser.c
@@ -1880,7 +1880,7 @@ c_parser_declaration_or_fndef (c_parser *parser, bool fndef_ok,
bool vm_type = variably_modified_type_p (init_type,
NULL_TREE);
if (vm_type)
- init.value = c_save_expr (init.value);
+ init.value = save_expr (init.value);
finish_init ();
specs->typespec_kind = ctsk_typeof;
specs->locations[cdw_typedef] = init_loc;
@@ -6500,7 +6500,7 @@ c_parser_conditional_expression (c_parser *parser, struct c_expr *after,
e = TREE_OPERAND (e, 1);
warn_for_omitted_condop (middle_loc, e);
/* Make sure first operand is calculated only once. */
- exp1.value = c_save_expr (default_conversion (cond.value));
+ exp1.value = save_expr (default_conversion (cond.value));
if (eptype)
exp1.value = build1 (EXCESS_PRECISION_EXPR, eptype, exp1.value);
exp1.original_type = NULL;
diff --git gcc/c/c-tree.h gcc/c/c-tree.h
index 8d232a4..a27a2c7 100644
--- gcc/c/c-tree.h
+++ gcc/c/c-tree.h
@@ -113,6 +113,10 @@ along with GCC; see the file COPYING3. If not see
subexpression meaning it is not a constant expression. */
#define CONSTRUCTOR_NON_CONST(EXPR) TREE_LANG_FLAG_1 (CONSTRUCTOR_CHECK (EXPR))
+/* For a SAVE_EXPR, nonzero if the contents of the SAVE_EXPR have already
+ been folded. */
+#define SAVE_EXPR_FOLDED_P(EXP) TREE_LANG_FLAG_1 (SAVE_EXPR_CHECK (EXP))
+
/* Record parser information about an expression that is irrelevant
for code generation alongside a tree representing its value. */
struct c_expr
diff --git gcc/c/c-typeck.c gcc/c/c-typeck.c
index 6f9909c..1edf521 100644
--- gcc/c/c-typeck.c
+++ gcc/c/c-typeck.c
@@ -5777,7 +5777,7 @@ build_modify_expr (location_t location, tree lhs, tree lhs_origtype,
that modify LHS. */
if (TREE_SIDE_EFFECTS (rhs))
{
- newrhs = in_late_binary_op ? save_expr (rhs) : c_save_expr (rhs);
+ newrhs = save_expr (rhs);
rhseval = newrhs;
}
newrhs = build_binary_op (location,
@@ -9301,7 +9301,7 @@ process_init_element (location_t loc, struct c_expr value, bool implicit,
semantic_type = TREE_TYPE (value.value);
value.value = TREE_OPERAND (value.value, 0);
}
- value.value = c_save_expr (value.value);
+ value.value = save_expr (value.value);
if (semantic_type)
value.value = build1 (EXCESS_PRECISION_EXPR, semantic_type,
value.value);
@@ -11621,7 +11621,7 @@ build_binary_op (location_t location, enum tree_code code,
return error_mark_node;
if (first_complex)
{
- op0 = c_save_expr (op0);
+ op0 = save_expr (op0);
real = build_unary_op (EXPR_LOCATION (orig_op0), REALPART_EXPR,
op0, true);
imag = build_unary_op (EXPR_LOCATION (orig_op0), IMAGPART_EXPR,
@@ -11630,7 +11630,7 @@ build_binary_op (location_t location, enum tree_code code,
{
case MULT_EXPR:
case TRUNC_DIV_EXPR:
- op1 = c_save_expr (op1);
+ op1 = save_expr (op1);
imag = build2 (resultcode, real_type, imag, op1);
/* Fall through. */
case PLUS_EXPR:
@@ -11643,7 +11643,7 @@ build_binary_op (location_t location, enum tree_code code,
}
else
{
- op1 = c_save_expr (op1);
+ op1 = save_expr (op1);
real = build_unary_op (EXPR_LOCATION (orig_op1), REALPART_EXPR,
op1, true);
imag = build_unary_op (EXPR_LOCATION (orig_op1), IMAGPART_EXPR,
@@ -11651,7 +11651,7 @@ build_binary_op (location_t location, enum tree_code code,
switch (code)
{
case MULT_EXPR:
- op0 = c_save_expr (op0);
+ op0 = save_expr (op0);
imag = build2 (resultcode, real_type, op0, imag);
/* Fall through. */
case PLUS_EXPR:
@@ -11835,8 +11835,8 @@ build_binary_op (location_t location, enum tree_code code,
&& !require_constant_value)
{
/* OP0 and/or OP1 might have side-effects. */
- op0 = c_save_expr (op0);
- op1 = c_save_expr (op1);
+ op0 = save_expr (op0);
+ op1 = save_expr (op1);
op0 = c_fully_fold (op0, false, NULL);
op1 = c_fully_fold (op1, false, NULL);
if (doing_div_or_mod && (flag_sanitize & (SANITIZE_DIVIDE
@@ -12435,7 +12435,7 @@ handle_omp_array_sections_1 (tree c, tree t, vec<tree> &types,
/* For [lb:] we will need to evaluate lb more than once. */
if (length == NULL_TREE && OMP_CLAUSE_CODE (c) != OMP_CLAUSE_DEPEND)
{
- tree lb = c_save_expr (low_bound);
+ tree lb = save_expr (low_bound);
if (lb != low_bound)
{
TREE_PURPOSE (t) = lb;
@@ -12480,7 +12480,7 @@ handle_omp_array_sections_1 (tree c, tree t, vec<tree> &types,
if (OMP_CLAUSE_CODE (c) != OMP_CLAUSE_DEPEND)
types.safe_push (TREE_TYPE (ret));
/* We will need to evaluate lb more than once. */
- tree lb = c_save_expr (low_bound);
+ tree lb = save_expr (low_bound);
if (lb != low_bound)
{
TREE_PURPOSE (t) = lb;
Marek
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