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* [Bug c/108789] New: __builtin_(add|mul)_overflow methods generate duplicate operations if both operands are const
@ 2023-02-14 17:51 dpejesh at yahoo dot com
2023-02-14 17:53 ` [Bug middle-end/108789] " pinskia at gcc dot gnu.org
` (10 more replies)
0 siblings, 11 replies; 12+ messages in thread
From: dpejesh at yahoo dot com @ 2023-02-14 17:51 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108789
Bug ID: 108789
Summary: __builtin_(add|mul)_overflow methods generate
duplicate operations if both operands are const
Product: gcc
Version: 12.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: dpejesh at yahoo dot com
Target Milestone: ---
#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>
bool add(uint8_t *r, const uint8_t *a, const uint8_t *b) {
return __builtin_add_overflow(*a, *b, r);
}
bool mul(uint8_t *r, const uint8_t *a, const uint8_t *b) {
return __builtin_mul_overflow(*a, *b, r);
}
int main() {
uint8_t x;
/* 64 + 64 should not overflow */
x = 64;
if (add(&x, &x, &x))
printf("false positive: x=%i\n", x);
/* 4 * 4 should not overflow */
x = 4;
if (mul(&x, &x, &x))
printf("false positive: x=%i\n", x);
/* 128 + 128 should overflow */
x = 128;
if (!add(&x, &x, &x))
printf("false negative: x=%i\n", x);
/* 16 * 16 should overflow */
x = 16;
if (!mul(&x, &x, &x))
printf("false negative: x=%i\n", x);
return 0;
}
$ gcc -g3 -O1 -o test test.c; ./test
false positive: x=128
false positive: x=16
false negative: x=0
false negative: x=0
The generated assembly correctly adds a with b and stores in r but
then it does the operation again before testing for carry and
returning. If r is also one of the operands then the erroneous
second operation will use the computed value of r in place of the
original operand leading to an incorrect overflow result.
0000000000400895 <add>:
; return __builtin_add_overflow(*a, *b, r);
400895: 0f b6 02 movzbl (%rdx), %eax
400898: 02 06 addb (%rsi), %al
40089a: 88 07 movb %al, (%rdi)
40089c: 0f b6 02 movzbl (%rdx), %eax <<
40089f: 02 06 addb (%rsi), %al <<
4008a1: 0f 92 c0 setb %al
; }
4008a4: c3 retq
00000000004008a5 <mul>:
; return __builtin_mul_overflow(*a, *b, r);
4008a5: 0f b6 06 movzbl (%rsi), %eax
4008a8: f6 22 mulb (%rdx)
4008aa: 88 07 movb %al, (%rdi)
4008ac: 0f b6 06 movzbl (%rsi), %eax <<
4008af: f6 22 mulb (%rdx) <<
4008b1: 0f 90 c0 seto %al
; }
4008b4: c3 retq
This only seems to be triggered when both a *and* b are const.
Removing const from either or both operands generates the correct
assembly.
0000000000400855 <add>:
; return __builtin_add_overflow(*a, *b, r);
400855: 0f b6 02 movzbl (%rdx), %eax
400858: 02 06 addb (%rsi), %al
40085a: 88 07 movb %al, (%rdi)
40085c: 0f 92 c0 setb %al
; }
40085f: c3 retq
0000000000400860 <mul>:
; return __builtin_mul_overflow(*a, *b, r);
400860: 0f b6 06 movzbl (%rsi), %eax
400863: f6 22 mulb (%rdx)
400865: 88 07 movb %al, (%rdi)
400867: 0f 90 c0 seto %al
; }
40086a: c3 retq
Tested on the following systems:
$ uname -srm; gcc12 --version
FreeBSD 13.1-RELEASE-p2 amd64
gcc12 (FreeBSD Ports Collection) 12.2.0
$ uname -smr; gcc --version
Linux 6.1.2-1-MANJARO-ARM aarch64
gcc (GCC) 12.1.0
$ uname -srm; gcc --version
MINGW64_NT-10.0-22000 3.4.5.x86_64 x86_64
gcc.exe (Rev10, Built by MSYS2 project) 12.2.0
Poking around godbolt indicates this was likely introduced in 9.4.
^ permalink raw reply [flat|nested] 12+ messages in thread
* [Bug middle-end/108789] __builtin_(add|mul)_overflow methods generate duplicate operations if both operands are const
2023-02-14 17:51 [Bug c/108789] New: __builtin_(add|mul)_overflow methods generate duplicate operations if both operands are const dpejesh at yahoo dot com
@ 2023-02-14 17:53 ` pinskia at gcc dot gnu.org
2023-11-09 6:29 ` [Bug middle-end/108789] __builtin_(add|mul)_overflow methods generate duplicate operations if both operands are const which in turn causes wrong code due to overlapping arguments pinskia at gcc dot gnu.org
` (9 subsequent siblings)
10 siblings, 0 replies; 12+ messages in thread
From: pinskia at gcc dot gnu.org @ 2023-02-14 17:53 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108789
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Component|c |middle-end
--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
The middle-end is not adding a SAVE_EXPR in the const case which causes the
duplication which is not optimized back.
^ permalink raw reply [flat|nested] 12+ messages in thread
* [Bug middle-end/108789] __builtin_(add|mul)_overflow methods generate duplicate operations if both operands are const which in turn causes wrong code due to overlapping arguments
2023-02-14 17:51 [Bug c/108789] New: __builtin_(add|mul)_overflow methods generate duplicate operations if both operands are const dpejesh at yahoo dot com
2023-02-14 17:53 ` [Bug middle-end/108789] " pinskia at gcc dot gnu.org
@ 2023-11-09 6:29 ` pinskia at gcc dot gnu.org
2024-06-03 13:56 ` pinskia at gcc dot gnu.org
` (8 subsequent siblings)
10 siblings, 0 replies; 12+ messages in thread
From: pinskia at gcc dot gnu.org @ 2023-11-09 6:29 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108789
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Summary|__builtin_(add|mul)_overflo |__builtin_(add|mul)_overflo
|w methods generate |w methods generate
|duplicate operations if |duplicate operations if
|both operands are const |both operands are const
| |which in turn causes wrong
| |code due to overlapping
| |arguments
Ever confirmed|0 |1
Status|UNCONFIRMED |NEW
Last reconfirmed| |2023-11-09
--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Confirmed.
The obvious workaround is to use a temporary variables for the arguments of
__builtin_add_overflow .
^ permalink raw reply [flat|nested] 12+ messages in thread
* [Bug middle-end/108789] __builtin_(add|mul)_overflow methods generate duplicate operations if both operands are const which in turn causes wrong code due to overlapping arguments
2023-02-14 17:51 [Bug c/108789] New: __builtin_(add|mul)_overflow methods generate duplicate operations if both operands are const dpejesh at yahoo dot com
2023-02-14 17:53 ` [Bug middle-end/108789] " pinskia at gcc dot gnu.org
2023-11-09 6:29 ` [Bug middle-end/108789] __builtin_(add|mul)_overflow methods generate duplicate operations if both operands are const which in turn causes wrong code due to overlapping arguments pinskia at gcc dot gnu.org
@ 2024-06-03 13:56 ` pinskia at gcc dot gnu.org
2024-06-03 13:59 ` [Bug middle-end/108789] __builtin_(add|mul|sub)_overflow " pinskia at gcc dot gnu.org
` (7 subsequent siblings)
10 siblings, 0 replies; 12+ messages in thread
From: pinskia at gcc dot gnu.org @ 2024-06-03 13:56 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108789
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |cody at tapscott dot me
--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
*** Bug 115326 has been marked as a duplicate of this bug. ***
^ permalink raw reply [flat|nested] 12+ messages in thread
* [Bug middle-end/108789] __builtin_(add|mul|sub)_overflow methods generate duplicate operations if both operands are const which in turn causes wrong code due to overlapping arguments
2023-02-14 17:51 [Bug c/108789] New: __builtin_(add|mul)_overflow methods generate duplicate operations if both operands are const dpejesh at yahoo dot com
` (2 preceding siblings ...)
2024-06-03 13:56 ` pinskia at gcc dot gnu.org
@ 2024-06-03 13:59 ` pinskia at gcc dot gnu.org
2024-06-03 15:35 ` jakub at gcc dot gnu.org
` (6 subsequent siblings)
10 siblings, 0 replies; 12+ messages in thread
From: pinskia at gcc dot gnu.org @ 2024-06-03 13:59 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108789
--- Comment #4 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Note the missing SAVE_EXPR issue is similar to PR 52339 (which has a patch
attached to it that would fix the issue here too I think).
^ permalink raw reply [flat|nested] 12+ messages in thread
* [Bug middle-end/108789] __builtin_(add|mul|sub)_overflow methods generate duplicate operations if both operands are const which in turn causes wrong code due to overlapping arguments
2023-02-14 17:51 [Bug c/108789] New: __builtin_(add|mul)_overflow methods generate duplicate operations if both operands are const dpejesh at yahoo dot com
` (3 preceding siblings ...)
2024-06-03 13:59 ` [Bug middle-end/108789] __builtin_(add|mul|sub)_overflow " pinskia at gcc dot gnu.org
@ 2024-06-03 15:35 ` jakub at gcc dot gnu.org
2024-06-04 10:28 ` cvs-commit at gcc dot gnu.org
` (5 subsequent siblings)
10 siblings, 0 replies; 12+ messages in thread
From: jakub at gcc dot gnu.org @ 2024-06-03 15:35 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108789
Jakub Jelinek <jakub at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |jakub at gcc dot gnu.org
--- Comment #5 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Created attachment 58336
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=58336&action=edit
gcc15-pr108789.patch
Untested fix.
^ permalink raw reply [flat|nested] 12+ messages in thread
* [Bug middle-end/108789] __builtin_(add|mul|sub)_overflow methods generate duplicate operations if both operands are const which in turn causes wrong code due to overlapping arguments
2023-02-14 17:51 [Bug c/108789] New: __builtin_(add|mul)_overflow methods generate duplicate operations if both operands are const dpejesh at yahoo dot com
` (4 preceding siblings ...)
2024-06-03 15:35 ` jakub at gcc dot gnu.org
@ 2024-06-04 10:28 ` cvs-commit at gcc dot gnu.org
2024-06-04 10:33 ` jakub at gcc dot gnu.org
` (4 subsequent siblings)
10 siblings, 0 replies; 12+ messages in thread
From: cvs-commit at gcc dot gnu.org @ 2024-06-04 10:28 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108789
--- Comment #6 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Jakub Jelinek <jakub@gcc.gnu.org>:
https://gcc.gnu.org/g:b8e28381cb5c0cddfe5201faf799d8b27f5d7d6c
commit r15-1009-gb8e28381cb5c0cddfe5201faf799d8b27f5d7d6c
Author: Jakub Jelinek <jakub@redhat.com>
Date: Tue Jun 4 12:28:01 2024 +0200
builtins: Force SAVE_EXPR for __builtin_{add,sub,mul}_overflow and
__builtin{add,sub}c [PR108789]
The following testcase is miscompiled, because we use save_expr
on the .{ADD,SUB,MUL}_OVERFLOW call we are creating, but if the first
two operands are not INTEGER_CSTs (in that case we just fold it right away)
but are TREE_READONLY/!TREE_SIDE_EFFECTS, save_expr doesn't actually
create a SAVE_EXPR at all and so we lower it to
*arg2 = REALPART_EXPR (.ADD_OVERFLOW (arg0, arg1)), \
IMAGPART_EXPR (.ADD_OVERFLOW (arg0, arg1))
which evaluates the ifn twice and just hope it will be CSEd back.
As *arg2 aliases *arg0, that is not the case.
The builtins are really never const/pure as they store into what
the third arguments points to, so after handling the
INTEGER_CST+INTEGER_CST
case, I think we should just always use SAVE_EXPR. Just building SAVE_EXPR
by hand and setting TREE_SIDE_EFFECTS on it doesn't work, because
c_fully_fold optimizes it away again, so the following patch marks the
ifn calls as TREE_SIDE_EFFECTS (but doesn't do it for the
__builtin_{add,sub,mul}_overflow_p case which were designed for use
especially in constant expressions and don't really evaluate the
realpart side, so we don't really need a SAVE_EXPR in that case).
2024-06-04 Jakub Jelinek <jakub@redhat.com>
PR middle-end/108789
* builtins.cc (fold_builtin_arith_overflow): For ovf_only,
don't call save_expr and don't build REALPART_EXPR, otherwise
set TREE_SIDE_EFFECTS on call before calling save_expr.
(fold_builtin_addc_subc): Set TREE_SIDE_EFFECTS on call before
calling save_expr.
* gcc.c-torture/execute/pr108789.c: New test.
^ permalink raw reply [flat|nested] 12+ messages in thread
* [Bug middle-end/108789] __builtin_(add|mul|sub)_overflow methods generate duplicate operations if both operands are const which in turn causes wrong code due to overlapping arguments
2023-02-14 17:51 [Bug c/108789] New: __builtin_(add|mul)_overflow methods generate duplicate operations if both operands are const dpejesh at yahoo dot com
` (5 preceding siblings ...)
2024-06-04 10:28 ` cvs-commit at gcc dot gnu.org
@ 2024-06-04 10:33 ` jakub at gcc dot gnu.org
2024-06-04 14:26 ` cvs-commit at gcc dot gnu.org
` (3 subsequent siblings)
10 siblings, 0 replies; 12+ messages in thread
From: jakub at gcc dot gnu.org @ 2024-06-04 10:33 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108789
Jakub Jelinek <jakub at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Assignee|unassigned at gcc dot gnu.org |jakub at gcc dot gnu.org
Status|NEW |ASSIGNED
--- Comment #7 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Fixed for 15.1+ so far.
^ permalink raw reply [flat|nested] 12+ messages in thread
* [Bug middle-end/108789] __builtin_(add|mul|sub)_overflow methods generate duplicate operations if both operands are const which in turn causes wrong code due to overlapping arguments
2023-02-14 17:51 [Bug c/108789] New: __builtin_(add|mul)_overflow methods generate duplicate operations if both operands are const dpejesh at yahoo dot com
` (6 preceding siblings ...)
2024-06-04 10:33 ` jakub at gcc dot gnu.org
@ 2024-06-04 14:26 ` cvs-commit at gcc dot gnu.org
2024-06-11 6:17 ` cvs-commit at gcc dot gnu.org
` (2 subsequent siblings)
10 siblings, 0 replies; 12+ messages in thread
From: cvs-commit at gcc dot gnu.org @ 2024-06-04 14:26 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108789
--- Comment #8 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-14 branch has been updated by Jakub Jelinek
<jakub@gcc.gnu.org>:
https://gcc.gnu.org/g:f9af4a05e027a8b797628f1a2c39ef0b28dc36d9
commit r14-10279-gf9af4a05e027a8b797628f1a2c39ef0b28dc36d9
Author: Jakub Jelinek <jakub@redhat.com>
Date: Tue Jun 4 12:28:01 2024 +0200
builtins: Force SAVE_EXPR for __builtin_{add,sub,mul}_overflow and
__builtin{add,sub}c [PR108789]
The following testcase is miscompiled, because we use save_expr
on the .{ADD,SUB,MUL}_OVERFLOW call we are creating, but if the first
two operands are not INTEGER_CSTs (in that case we just fold it right away)
but are TREE_READONLY/!TREE_SIDE_EFFECTS, save_expr doesn't actually
create a SAVE_EXPR at all and so we lower it to
*arg2 = REALPART_EXPR (.ADD_OVERFLOW (arg0, arg1)), \
IMAGPART_EXPR (.ADD_OVERFLOW (arg0, arg1))
which evaluates the ifn twice and just hope it will be CSEd back.
As *arg2 aliases *arg0, that is not the case.
The builtins are really never const/pure as they store into what
the third arguments points to, so after handling the
INTEGER_CST+INTEGER_CST
case, I think we should just always use SAVE_EXPR. Just building SAVE_EXPR
by hand and setting TREE_SIDE_EFFECTS on it doesn't work, because
c_fully_fold optimizes it away again, so the following patch marks the
ifn calls as TREE_SIDE_EFFECTS (but doesn't do it for the
__builtin_{add,sub,mul}_overflow_p case which were designed for use
especially in constant expressions and don't really evaluate the
realpart side, so we don't really need a SAVE_EXPR in that case).
2024-06-04 Jakub Jelinek <jakub@redhat.com>
PR middle-end/108789
* builtins.cc (fold_builtin_arith_overflow): For ovf_only,
don't call save_expr and don't build REALPART_EXPR, otherwise
set TREE_SIDE_EFFECTS on call before calling save_expr.
(fold_builtin_addc_subc): Set TREE_SIDE_EFFECTS on call before
calling save_expr.
* gcc.c-torture/execute/pr108789.c: New test.
(cherry picked from commit b8e28381cb5c0cddfe5201faf799d8b27f5d7d6c)
^ permalink raw reply [flat|nested] 12+ messages in thread
* [Bug middle-end/108789] __builtin_(add|mul|sub)_overflow methods generate duplicate operations if both operands are const which in turn causes wrong code due to overlapping arguments
2023-02-14 17:51 [Bug c/108789] New: __builtin_(add|mul)_overflow methods generate duplicate operations if both operands are const dpejesh at yahoo dot com
` (7 preceding siblings ...)
2024-06-04 14:26 ` cvs-commit at gcc dot gnu.org
@ 2024-06-11 6:17 ` cvs-commit at gcc dot gnu.org
2024-06-11 10:39 ` cvs-commit at gcc dot gnu.org
2024-06-11 10:56 ` jakub at gcc dot gnu.org
10 siblings, 0 replies; 12+ messages in thread
From: cvs-commit at gcc dot gnu.org @ 2024-06-11 6:17 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108789
--- Comment #9 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-13 branch has been updated by Jakub Jelinek
<jakub@gcc.gnu.org>:
https://gcc.gnu.org/g:f9db8b0571348adfcc98204ea7be787058af85cd
commit r13-8836-gf9db8b0571348adfcc98204ea7be787058af85cd
Author: Jakub Jelinek <jakub@redhat.com>
Date: Tue Jun 4 12:28:01 2024 +0200
builtins: Force SAVE_EXPR for __builtin_{add,sub,mul}_overflow [PR108789]
The following testcase is miscompiled, because we use save_expr
on the .{ADD,SUB,MUL}_OVERFLOW call we are creating, but if the first
two operands are not INTEGER_CSTs (in that case we just fold it right away)
but are TREE_READONLY/!TREE_SIDE_EFFECTS, save_expr doesn't actually
create a SAVE_EXPR at all and so we lower it to
*arg2 = REALPART_EXPR (.ADD_OVERFLOW (arg0, arg1)), \
IMAGPART_EXPR (.ADD_OVERFLOW (arg0, arg1))
which evaluates the ifn twice and just hope it will be CSEd back.
As *arg2 aliases *arg0, that is not the case.
The builtins are really never const/pure as they store into what
the third arguments points to, so after handling the
INTEGER_CST+INTEGER_CST
case, I think we should just always use SAVE_EXPR. Just building SAVE_EXPR
by hand and setting TREE_SIDE_EFFECTS on it doesn't work, because
c_fully_fold optimizes it away again, so the following patch marks the
ifn calls as TREE_SIDE_EFFECTS (but doesn't do it for the
__builtin_{add,sub,mul}_overflow_p case which were designed for use
especially in constant expressions and don't really evaluate the
realpart side, so we don't really need a SAVE_EXPR in that case).
2024-06-04 Jakub Jelinek <jakub@redhat.com>
PR middle-end/108789
* builtins.cc (fold_builtin_arith_overflow): For ovf_only,
don't call save_expr and don't build REALPART_EXPR, otherwise
set TREE_SIDE_EFFECTS on call before calling save_expr.
* gcc.c-torture/execute/pr108789.c: New test.
(cherry picked from commit b8e28381cb5c0cddfe5201faf799d8b27f5d7d6c)
^ permalink raw reply [flat|nested] 12+ messages in thread
* [Bug middle-end/108789] __builtin_(add|mul|sub)_overflow methods generate duplicate operations if both operands are const which in turn causes wrong code due to overlapping arguments
2023-02-14 17:51 [Bug c/108789] New: __builtin_(add|mul)_overflow methods generate duplicate operations if both operands are const dpejesh at yahoo dot com
` (8 preceding siblings ...)
2024-06-11 6:17 ` cvs-commit at gcc dot gnu.org
@ 2024-06-11 10:39 ` cvs-commit at gcc dot gnu.org
2024-06-11 10:56 ` jakub at gcc dot gnu.org
10 siblings, 0 replies; 12+ messages in thread
From: cvs-commit at gcc dot gnu.org @ 2024-06-11 10:39 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108789
--- Comment #10 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-12 branch has been updated by Jakub Jelinek
<jakub@gcc.gnu.org>:
https://gcc.gnu.org/g:91a371254494934e191e3060ae2a86905eb4b2b2
commit r12-10532-g91a371254494934e191e3060ae2a86905eb4b2b2
Author: Jakub Jelinek <jakub@redhat.com>
Date: Tue Jun 4 12:28:01 2024 +0200
builtins: Force SAVE_EXPR for __builtin_{add,sub,mul}_overflow [PR108789]
The following testcase is miscompiled, because we use save_expr
on the .{ADD,SUB,MUL}_OVERFLOW call we are creating, but if the first
two operands are not INTEGER_CSTs (in that case we just fold it right away)
but are TREE_READONLY/!TREE_SIDE_EFFECTS, save_expr doesn't actually
create a SAVE_EXPR at all and so we lower it to
*arg2 = REALPART_EXPR (.ADD_OVERFLOW (arg0, arg1)), \
IMAGPART_EXPR (.ADD_OVERFLOW (arg0, arg1))
which evaluates the ifn twice and just hope it will be CSEd back.
As *arg2 aliases *arg0, that is not the case.
The builtins are really never const/pure as they store into what
the third arguments points to, so after handling the
INTEGER_CST+INTEGER_CST
case, I think we should just always use SAVE_EXPR. Just building SAVE_EXPR
by hand and setting TREE_SIDE_EFFECTS on it doesn't work, because
c_fully_fold optimizes it away again, so the following patch marks the
ifn calls as TREE_SIDE_EFFECTS (but doesn't do it for the
__builtin_{add,sub,mul}_overflow_p case which were designed for use
especially in constant expressions and don't really evaluate the
realpart side, so we don't really need a SAVE_EXPR in that case).
2024-06-04 Jakub Jelinek <jakub@redhat.com>
PR middle-end/108789
* builtins.cc (fold_builtin_arith_overflow): For ovf_only,
don't call save_expr and don't build REALPART_EXPR, otherwise
set TREE_SIDE_EFFECTS on call before calling save_expr.
* gcc.c-torture/execute/pr108789.c: New test.
(cherry picked from commit b8e28381cb5c0cddfe5201faf799d8b27f5d7d6c)
^ permalink raw reply [flat|nested] 12+ messages in thread
* [Bug middle-end/108789] __builtin_(add|mul|sub)_overflow methods generate duplicate operations if both operands are const which in turn causes wrong code due to overlapping arguments
2023-02-14 17:51 [Bug c/108789] New: __builtin_(add|mul)_overflow methods generate duplicate operations if both operands are const dpejesh at yahoo dot com
` (9 preceding siblings ...)
2024-06-11 10:39 ` cvs-commit at gcc dot gnu.org
@ 2024-06-11 10:56 ` jakub at gcc dot gnu.org
10 siblings, 0 replies; 12+ messages in thread
From: jakub at gcc dot gnu.org @ 2024-06-11 10:56 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108789
--- Comment #11 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Should be fixed for 12.4+, 13.4+ and 14.2+ too.
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2023-02-14 17:51 [Bug c/108789] New: __builtin_(add|mul)_overflow methods generate duplicate operations if both operands are const dpejesh at yahoo dot com
2023-02-14 17:53 ` [Bug middle-end/108789] " pinskia at gcc dot gnu.org
2023-11-09 6:29 ` [Bug middle-end/108789] __builtin_(add|mul)_overflow methods generate duplicate operations if both operands are const which in turn causes wrong code due to overlapping arguments pinskia at gcc dot gnu.org
2024-06-03 13:56 ` pinskia at gcc dot gnu.org
2024-06-03 13:59 ` [Bug middle-end/108789] __builtin_(add|mul|sub)_overflow " pinskia at gcc dot gnu.org
2024-06-03 15:35 ` jakub at gcc dot gnu.org
2024-06-04 10:28 ` cvs-commit at gcc dot gnu.org
2024-06-04 10:33 ` jakub at gcc dot gnu.org
2024-06-04 14:26 ` cvs-commit at gcc dot gnu.org
2024-06-11 6:17 ` cvs-commit at gcc dot gnu.org
2024-06-11 10:39 ` cvs-commit at gcc dot gnu.org
2024-06-11 10:56 ` jakub at gcc dot gnu.org
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