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* [Bug tree-optimization/110873] New: [14 Regression] Dead Code Elimination Regression at -O2 since r14-376-g47a76439911
@ 2023-08-02 12:34 scherrer.sv at gmail dot com
2023-08-02 13:02 ` [Bug tree-optimization/110873] " rguenth at gcc dot gnu.org
` (4 more replies)
0 siblings, 5 replies; 6+ messages in thread
From: scherrer.sv at gmail dot com @ 2023-08-02 12:34 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110873
Bug ID: 110873
Summary: [14 Regression] Dead Code Elimination Regression at
-O2 since r14-376-g47a76439911
Product: gcc
Version: 14.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: scherrer.sv at gmail dot com
Target Milestone: ---
static int b;
static short c;
static char d;
static int *e = &b;
void foo(void);
void bar110_(void);
static char(a)(char f, char g) { return f + g; }
int main() {
*e = 3;
unsigned char h;
c = 0;
i:
if (!b)
foo();
h = -25;
for (; h >= 7; h = a(h, 6))
for (; d; d--)
;
if (!(h >= 5))
bar110_();
if (c)
goto i;
}
-----------------------------------------------------------------------
gcc-68c3aa7510b (trunk) -O2 cannot eliminate the call to foo but
gcc-releases/gcc-13.1.0 -O2 can
-----------------------------------------------------------------------
gcc-68c3aa7510b2f45f44379ecd77e97c88780a84ed -O2 case.c -S -o case.s
--------- OUTPUT ---------
main:
.LFB1:
.cfi_startproc
movl $3, b(%rip)
xorl %esi, %esi
movw %si, c(%rip)
.L11:
cmpb $0, d(%rip)
je .L13
movb $0, d(%rip)
.L13:
cmpw $0, c(%rip)
je .L15
movl b(%rip), %eax
testl %eax, %eax
jne .L11
subq $8, %rsp
.cfi_def_cfa_offset 16
.L6:
call foo
.L2:
cmpb $0, d(%rip)
je .L4
movb $0, d(%rip)
.L4:
cmpw $0, c(%rip)
je .L5
movl b(%rip), %ecx
testl %ecx, %ecx
jne .L2
jmp .L6
.L15:
.cfi_def_cfa_offset 8
xorl %eax, %eax
ret
.L5:
.cfi_def_cfa_offset 16
xorl %eax, %eax
popq %rdx
.cfi_def_cfa_offset 8
ret
---------- END OUTPUT ---------
-----------------------------------------------------------------------
gcc-2b98cc24d6af0432a74f6dad1c722ce21c1f7458 -O2 case.c -S -o case.s
--------- OUTPUT ---------
main:
.LFB1:
.cfi_startproc
movl $3, b(%rip)
xorl %eax, %eax
cmpb $0, d(%rip)
movw %ax, c(%rip)
je .L3
movb $0, d(%rip)
.L3:
xorl %eax, %eax
ret
---------- END OUTPUT ---------
-----------------------------------------------------------------------
Bisects to r14-376-g47a76439911
^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug tree-optimization/110873] [14 Regression] Dead Code Elimination Regression at -O2 since r14-376-g47a76439911
2023-08-02 12:34 [Bug tree-optimization/110873] New: [14 Regression] Dead Code Elimination Regression at -O2 since r14-376-g47a76439911 scherrer.sv at gmail dot com
@ 2023-08-02 13:02 ` rguenth at gcc dot gnu.org
2023-08-03 2:59 ` pinskia at gcc dot gnu.org
` (3 subsequent siblings)
4 siblings, 0 replies; 6+ messages in thread
From: rguenth at gcc dot gnu.org @ 2023-08-02 13:02 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110873
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Keywords| |missed-optimization
Target Milestone|--- |14.0
^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug tree-optimization/110873] [14 Regression] Dead Code Elimination Regression at -O2 since r14-376-g47a76439911
2023-08-02 12:34 [Bug tree-optimization/110873] New: [14 Regression] Dead Code Elimination Regression at -O2 since r14-376-g47a76439911 scherrer.sv at gmail dot com
2023-08-02 13:02 ` [Bug tree-optimization/110873] " rguenth at gcc dot gnu.org
@ 2023-08-03 2:59 ` pinskia at gcc dot gnu.org
2023-08-03 3:00 ` pinskia at gcc dot gnu.org
` (2 subsequent siblings)
4 siblings, 0 replies; 6+ messages in thread
From: pinskia at gcc dot gnu.org @ 2023-08-03 2:59 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110873
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Last reconfirmed| |2023-08-03
Status|UNCONFIRMED |NEW
Ever confirmed|0 |1
--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
GCC 13 had:
```
Registering value_relation (h_29 == h_13) (bb10) at h_29 = PHI <h_13(9)>
Loops range found for h_29: [irange] unsigned char [5, 5] NONZERO 0x5 and
calculated range :[irange] unsigned char [0, 5] NONZERO 0x7
Global Exported: h_29 = [irange] unsigned char [5, 5] NONZERO 0x5
Folding PHI node: h_29 = PHI <h_13(9)>
Queued PHI for removal. Folds to: 5
Folding statement: if (h_29 <= 4)
gimple_simplified to if (0 != 0)
gimple_simplified to if (0 != 0)
Folded into: if (0 != 0)
``
While trunk does:
```
redicate evaluates to: DON'T KNOW
Not folded
Registering value_relation (h_29 == h_13) (bb10) at h_29 = PHI <h_13(9)>
Global Exported: h_29 = [irange] unsigned char [0, 5] MASK 0xfe VALUE 0xe7
Folding PHI node: h_29 = PHI <h_13(9)>
No folding possible
Folding statement: if (h_29 <= 4)
Visiting conditional with predicate: if (h_29 <= 4)
With known ranges
h_29: [irange] unsigned char [0, 5] MASK 0xfe VALUE 0xe7
Predicate evaluates to: DON'T KNOW
Simplified relational if (h_29 <= 4)
into if (h_29 != 5)
Folded into: if (h_29 != 5)
```
Which totally misses that h_29 was just 5.
^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug tree-optimization/110873] [14 Regression] Dead Code Elimination Regression at -O2 since r14-376-g47a76439911
2023-08-02 12:34 [Bug tree-optimization/110873] New: [14 Regression] Dead Code Elimination Regression at -O2 since r14-376-g47a76439911 scherrer.sv at gmail dot com
2023-08-02 13:02 ` [Bug tree-optimization/110873] " rguenth at gcc dot gnu.org
2023-08-03 2:59 ` pinskia at gcc dot gnu.org
@ 2023-08-03 3:00 ` pinskia at gcc dot gnu.org
2024-03-07 23:27 ` law at gcc dot gnu.org
2024-05-07 7:41 ` [Bug tree-optimization/110873] [14/15 " rguenth at gcc dot gnu.org
4 siblings, 0 replies; 6+ messages in thread
From: pinskia at gcc dot gnu.org @ 2023-08-03 3:00 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110873
--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Note there are other missed optimizations later on too even in GCC 13.
^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug tree-optimization/110873] [14 Regression] Dead Code Elimination Regression at -O2 since r14-376-g47a76439911
2023-08-02 12:34 [Bug tree-optimization/110873] New: [14 Regression] Dead Code Elimination Regression at -O2 since r14-376-g47a76439911 scherrer.sv at gmail dot com
` (2 preceding siblings ...)
2023-08-03 3:00 ` pinskia at gcc dot gnu.org
@ 2024-03-07 23:27 ` law at gcc dot gnu.org
2024-05-07 7:41 ` [Bug tree-optimization/110873] [14/15 " rguenth at gcc dot gnu.org
4 siblings, 0 replies; 6+ messages in thread
From: law at gcc dot gnu.org @ 2024-03-07 23:27 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110873
Jeffrey A. Law <law at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |law at gcc dot gnu.org
Priority|P3 |P2
^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug tree-optimization/110873] [14/15 Regression] Dead Code Elimination Regression at -O2 since r14-376-g47a76439911
2023-08-02 12:34 [Bug tree-optimization/110873] New: [14 Regression] Dead Code Elimination Regression at -O2 since r14-376-g47a76439911 scherrer.sv at gmail dot com
` (3 preceding siblings ...)
2024-03-07 23:27 ` law at gcc dot gnu.org
@ 2024-05-07 7:41 ` rguenth at gcc dot gnu.org
4 siblings, 0 replies; 6+ messages in thread
From: rguenth at gcc dot gnu.org @ 2024-05-07 7:41 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110873
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Target Milestone|14.0 |14.2
--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
GCC 14.1 is being released, retargeting bugs to GCC 14.2.
^ permalink raw reply [flat|nested] 6+ messages in thread
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2023-08-02 12:34 [Bug tree-optimization/110873] New: [14 Regression] Dead Code Elimination Regression at -O2 since r14-376-g47a76439911 scherrer.sv at gmail dot com
2023-08-02 13:02 ` [Bug tree-optimization/110873] " rguenth at gcc dot gnu.org
2023-08-03 2:59 ` pinskia at gcc dot gnu.org
2023-08-03 3:00 ` pinskia at gcc dot gnu.org
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