[Bug middle-end/77357] strlen of constant strings not folded
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77357 eggert at cs dot ucla.edu changed: What|Removed |Added CC||eggert at cs dot ucla.edu --- Comment #8 from eggert at cs dot ucla.edu --- (In reply to Martin Sebor from comment #7) > Committed in r262522. Unfortunately this commit apparently causes GCC to generate incorrect code when compiling Emacs. See Bug#86528.
[Bug middle-end/77357] strlen of constant strings not folded
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77357 Martin Sebor changed: What|Removed |Added Status|ASSIGNED|RESOLVED Resolution|--- |FIXED --- Comment #7 from Martin Sebor --- Committed in r262522.
[Bug middle-end/77357] strlen of constant strings not folded
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77357 --- Comment #6 from Martin Sebor --- Author: msebor Date: Mon Jul 9 20:33:48 2018 New Revision: 262522 URL: https://gcc.gnu.org/viewcvs?rev=262522=gcc=rev Log: PR middle-end/77357 - strlen of constant strings not folded gcc/ChangeLog: PR middle-end/77357 PR middle-end/86428 * builtins.c (c_strlen): Avoid out-of-bounds warnings when accessing implicitly initialized array elements. * expr.c (string_constant): Handle string initializers of character arrays within aggregates. * gimple-fold.c (fold_array_ctor_reference): Add argument. Store element offset. As a special case, handle zero size. (fold_nonarray_ctor_reference): Same. (fold_ctor_reference): Add argument. Store subobject offset. * gimple-fold.h (fold_ctor_reference): Add argument. gcc/testsuite/ChangeLog: PR middle-end/77357 * gcc.dg/strlenopt-49.c: New test. * gcc.dg/strlenopt-50.c: New test. * gcc.dg/strlenopt-51.c: New test. * gcc.dg/strlenopt-52.c: New test. Added: trunk/gcc/testsuite/gcc.dg/strlenopt-49.c trunk/gcc/testsuite/gcc.dg/strlenopt-50.c trunk/gcc/testsuite/gcc.dg/strlenopt-51.c trunk/gcc/testsuite/gcc.dg/strlenopt-52.c Modified: trunk/gcc/ChangeLog trunk/gcc/builtins.c trunk/gcc/expr.c trunk/gcc/fold-const.c trunk/gcc/fold-const.h trunk/gcc/gimple-fold.c trunk/gcc/gimple-fold.h trunk/gcc/testsuite/ChangeLog trunk/gcc/testsuite/gcc.c-torture/execute/builtins/strlen-3.c
[Bug middle-end/77357] strlen of constant strings not folded
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77357 Martin Sebor changed: What|Removed |Added Keywords||patch --- Comment #5 from Martin Sebor --- Patch: https://gcc.gnu.org/ml/gcc-patches/2018-07/msg00279.html
[Bug middle-end/77357] strlen of constant strings not folded
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77357 Martin Sebor changed: What|Removed |Added Status|NEW |ASSIGNED Assignee|unassigned at gcc dot gnu.org |msebor at gcc dot gnu.org --- Comment #4 from Martin Sebor --- Working on a patch.
[Bug middle-end/77357] strlen of constant strings not folded
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77357
--- Comment #3 from Richard Biener ---
Ok, I'm less interested in -O0 but even with -O1 we fail for global_struct
and local_struct. We can improve things by doing
Index: gcc/expr.c
===
--- gcc/expr.c (revision 239778)
+++ gcc/expr.c (working copy)
@@ -60,6 +60,7 @@ along with GCC; see the file COPYING3.
#include "tree-chkp.h"
#include "rtl-chkp.h"
#include "ccmp.h"
+#include "tree-dfa.h"
/* If this is nonzero, we do not bother generating VOLATILE
@@ -11098,51 +11081,14 @@ string_constant (tree arg, tree *ptr_off
if (TREE_CODE (arg) == ADDR_EXPR)
{
- if (TREE_CODE (TREE_OPERAND (arg, 0)) == STRING_CST)
- {
- *ptr_offset = size_zero_node;
- return TREE_OPERAND (arg, 0);
- }
- else if (TREE_CODE (TREE_OPERAND (arg, 0)) == VAR_DECL)
- {
- array = TREE_OPERAND (arg, 0);
- offset = size_zero_node;
- }
- else if (TREE_CODE (TREE_OPERAND (arg, 0)) == ARRAY_REF)
- {
- array = TREE_OPERAND (TREE_OPERAND (arg, 0), 0);
- offset = TREE_OPERAND (TREE_OPERAND (arg, 0), 1);
- if (TREE_CODE (array) != STRING_CST
- && TREE_CODE (array) != VAR_DECL)
- return 0;
-
- /* Check if the array has a nonzero lower bound. */
- lower_bound = array_ref_low_bound (TREE_OPERAND (arg, 0));
- if (!integer_zerop (lower_bound))
- {
- /* If the offset and base aren't both constants, return 0. */
- if (TREE_CODE (lower_bound) != INTEGER_CST)
- return 0;
- if (TREE_CODE (offset) != INTEGER_CST)
- return 0;
- /* Adjust offset by the lower bound. */
- offset = size_diffop (fold_convert (sizetype, offset),
- fold_convert (sizetype, lower_bound));
- }
- }
- else if (TREE_CODE (TREE_OPERAND (arg, 0)) == MEM_REF)
- {
- array = TREE_OPERAND (TREE_OPERAND (arg, 0), 0);
- offset = TREE_OPERAND (TREE_OPERAND (arg, 0), 1);
- if (TREE_CODE (array) != ADDR_EXPR)
- return 0;
- array = TREE_OPERAND (array, 0);
- if (TREE_CODE (array) != STRING_CST
- && TREE_CODE (array) != VAR_DECL)
- return 0;
- }
- else
+ HOST_WIDE_INT off;
+ array = get_addr_base_and_unit_offset (TREE_OPERAND (arg, 0), );
+ if (! array
+ || (TREE_CODE (array) != VAR_DECL
+ && TREE_CODE (array) != CONST_DECL
+ && TREE_CODE (array) != STRING_CST))
return 0;
+ *ptr_offset = size_int (off);
}
else if (TREE_CODE (arg) == PLUS_EXPR || TREE_CODE (arg) ==
POINTER_PLUS_EXPR)
{
but then we only handle STRING_CST ctors and not {.a="abc"} we do have
some generic fold-a-ctor-reference-at-offset thing
(gimple-fold.c:fold_*ctor_reference) but that hasn't the
get-me-the-ctor-element-at-offset part factored out. Or finding the ctor
element that the offset
is within (we can then adjust offset).
So a bit of refactoring is missing here.
[Bug middle-end/77357] strlen of constant strings not folded
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77357
Martin Sebor changed:
What|Removed |Added
Status|WAITING |NEW
--- Comment #2 from Martin Sebor ---
Sorry, wrong test case. Here's the right one:
const char a[] = "abc";
const char* const s = "abc";
void global_array (void)
{
if (__builtin_strlen (a) != 3)
__builtin_abort ();
}
void local_array (void)
{
static const char a[] = "abc";
if (__builtin_strlen (a) != 3)
__builtin_abort ();
}
void global_pointer (void)
{
if (__builtin_strlen (s) != 3)
__builtin_abort ();
}
void local_pointer (void)
{
static const char* const s = "abc";
if (__builtin_strlen (s) != 3)
__builtin_abort ();
}
struct X { char a [4]; };
const struct X x = { "abc" };
void global_struct (void)
{
if (__builtin_strlen (x.a) != 3)
__builtin_abort ();
}
void local_struct (void)
{
static const struct X x = { "abc" };
if (__builtin_strlen (x.a) != 3)
__builtin_abort ();
}
[Bug middle-end/77357] strlen of constant strings not folded
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77357 Richard Biener changed: What|Removed |Added Status|UNCONFIRMED |WAITING Last reconfirmed||2016-08-24 CC||rguenth at gcc dot gnu.org Ever confirmed|0 |1 --- Comment #1 from Richard Biener --- Contents of strlen.c?
[Bug middle-end/77357] strlen of constant strings not folded
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77357 Martin Sebor changed: What|Removed |Added Keywords||missed-optimization Severity|normal |enhancement
