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* [Bug tree-optimization/108419] New: [13 Regression] Dead Code Elimination Regression at -O2 since r13-440-g98e475a8f58
@ 2023-01-16 15:18 yann at ywg dot ch
2023-01-17 1:58 ` [Bug tree-optimization/108419] " pinskia at gcc dot gnu.org
` (7 more replies)
0 siblings, 8 replies; 9+ messages in thread
From: yann at ywg dot ch @ 2023-01-16 15:18 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108419
Bug ID: 108419
Summary: [13 Regression] Dead Code Elimination Regression at
-O2 since r13-440-g98e475a8f58
Product: gcc
Version: 13.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: yann at ywg dot ch
Target Milestone: ---
Created attachment 54281
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=54281&action=edit
case as file
cat case.c #1565
static int b = 6, c;
long d;
short h;
short i;
short j;
char k;
void foo();
short(a)(short l, short m) { return l + m; }
short f();
short g(unsigned short, int, char, long);
static signed char e() {
unsigned n = -10;
for (; n >= 14; n = a(n, 8)) {
i = g(b, 0, c, b);
j = f(i, b, d < j, 5, 7, 9, 5);
k = 200 + n;
h = k % 5;
if (h)
;
else
foo();
}
return n;
}
int main() {
b || e();
b = 1;
}
`gcc-f99d7d669eaa2830eb5878df4da67e77ec791522 (trunk) -O2` can not eliminate
`foo` but `gcc-releases/gcc-12.2.0 -O2` can.
`gcc-f99d7d669eaa2830eb5878df4da67e77ec791522 (trunk) -O2 -S -o /dev/stdout
case.c`
--------- OUTPUT ---------
main:
.LFB2:
.cfi_startproc
movl b(%rip), %esi
testl %esi, %esi
je .L12
movl $1, b(%rip)
xorl %eax, %eax
ret
.L12:
pushq %r12
.cfi_def_cfa_offset 16
.cfi_offset 12, -16
movl $-10, %r12d
pushq %rbp
.cfi_def_cfa_offset 24
.cfi_offset 6, -24
movl $2, %ebp
pushq %rbx
.cfi_def_cfa_offset 32
.cfi_offset 3, -32
movl $5, %ebx
.L6:
movslq b(%rip), %rcx
xorl %edx, %edx
xorl %esi, %esi
movzwl %cx, %edi
call g
movl b(%rip), %esi
movl $5, %ecx
movswq j(%rip), %rdx
movw %ax, i(%rip)
cmpq d(%rip), %rdx
movswl %ax, %edi
movl $9, %r9d
pushq %rax
.cfi_def_cfa_offset 40
setg %dl
movl $7, %r8d
xorl %eax, %eax
pushq $5
.cfi_def_cfa_offset 48
movzbl %dl, %edx
call f
movw %ax, j(%rip)
leal -56(%r12), %eax
movb %al, k(%rip)
cbtw
idivb %bl
movl %eax, %edx
sarw $8, %dx
shrw $8, %ax
movw %dx, h(%rip)
popq %rdx
.cfi_def_cfa_offset 40
popq %rcx
.cfi_def_cfa_offset 32
je .L13
.L5:
addl $8, %r12d
subl $1, %ebp
movswl %r12w, %r12d
je .L14
movl $1, %ebp
jmp .L6
.L14:
movl $1, b(%rip)
popq %rbx
.cfi_remember_state
.cfi_def_cfa_offset 24
xorl %eax, %eax
popq %rbp
.cfi_def_cfa_offset 16
popq %r12
.cfi_def_cfa_offset 8
ret
.L13:
.cfi_restore_state
xorl %eax, %eax
call foo
jmp .L5
---------- END OUTPUT ---------
`gcc-releases/gcc-12.2.0 -O2 -S -o /dev/stdout case.c`
--------- OUTPUT ---------
main:
.LFB2:
.cfi_startproc
movl b(%rip), %r9d
testl %r9d, %r9d
je .L11
movl $1, b(%rip)
xorl %eax, %eax
ret
.L11:
pushq %rbp
.cfi_def_cfa_offset 16
.cfi_offset 6, -16
movl $-66, %ebp
pushq %rbx
.cfi_def_cfa_offset 24
.cfi_offset 3, -24
movl $5, %ebx
pushq %r8
.cfi_def_cfa_offset 32
.L5:
movslq b(%rip), %rcx
xorl %edx, %edx
xorl %esi, %esi
movzwl %cx, %edi
call g
movswq j(%rip), %rdx
cmpq d(%rip), %rdx
movl $9, %r9d
pushq %rcx
.cfi_def_cfa_offset 40
setg %dl
movl b(%rip), %esi
movswl %ax, %edi
pushq $5
.cfi_def_cfa_offset 48
movzbl %dl, %edx
movl $7, %r8d
movl $5, %ecx
movw %ax, i(%rip)
xorl %eax, %eax
call f
popq %rsi
.cfi_def_cfa_offset 40
popq %rdi
.cfi_def_cfa_offset 32
movb %bpl, k(%rip)
movw %ax, j(%rip)
movsbw %bpl, %ax
idivb %bl
sarw $8, %ax
movw %ax, h(%rip)
cmpb $-58, %bpl
je .L12
movl $-58, %ebp
jmp .L5
.L12:
movl $1, b(%rip)
xorl %eax, %eax
popq %rdx
.cfi_def_cfa_offset 24
popq %rbx
.cfi_def_cfa_offset 16
popq %rbp
.cfi_def_cfa_offset 8
ret
---------- END OUTPUT ---------
Bisects to: r13-440-g98e475a8f58
commit 98e475a8f58ca3ba6e9bd5c9276efce4236f5d26
Author: Andrew MacLeod <amacleod@redhat.com>
Date: Fri Mar 18 11:50:33 2022 -0400
Fix return value in ranger_cache::get_global_range.
The "is_current" status is returned by parameter, but was being returned by
the
function as well instead of true if NAME had a global range, and FALSE
if it did not.
* gimple-range-cache.cc (ranger_cache::get_global_range): Return
the
had_global value instead.
^ permalink raw reply [flat|nested] 9+ messages in thread
* [Bug tree-optimization/108419] [13 Regression] Dead Code Elimination Regression at -O2 since r13-440-g98e475a8f58
2023-01-16 15:18 [Bug tree-optimization/108419] New: [13 Regression] Dead Code Elimination Regression at -O2 since r13-440-g98e475a8f58 yann at ywg dot ch
@ 2023-01-17 1:58 ` pinskia at gcc dot gnu.org
2023-01-17 13:26 ` marxin at gcc dot gnu.org
` (6 subsequent siblings)
7 siblings, 0 replies; 9+ messages in thread
From: pinskia at gcc dot gnu.org @ 2023-01-17 1:58 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108419
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Keywords| |missed-optimization
Target Milestone|--- |13.0
^ permalink raw reply [flat|nested] 9+ messages in thread
* [Bug tree-optimization/108419] [13 Regression] Dead Code Elimination Regression at -O2 since r13-440-g98e475a8f58
2023-01-16 15:18 [Bug tree-optimization/108419] New: [13 Regression] Dead Code Elimination Regression at -O2 since r13-440-g98e475a8f58 yann at ywg dot ch
2023-01-17 1:58 ` [Bug tree-optimization/108419] " pinskia at gcc dot gnu.org
@ 2023-01-17 13:26 ` marxin at gcc dot gnu.org
2023-02-21 13:09 ` rguenth at gcc dot gnu.org
` (5 subsequent siblings)
7 siblings, 0 replies; 9+ messages in thread
From: marxin at gcc dot gnu.org @ 2023-01-17 13:26 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108419
Martin Liška <marxin at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Last reconfirmed| |2023-01-17
Status|UNCONFIRMED |NEW
CC| |marxin at gcc dot gnu.org
Ever confirmed|0 |1
^ permalink raw reply [flat|nested] 9+ messages in thread
* [Bug tree-optimization/108419] [13 Regression] Dead Code Elimination Regression at -O2 since r13-440-g98e475a8f58
2023-01-16 15:18 [Bug tree-optimization/108419] New: [13 Regression] Dead Code Elimination Regression at -O2 since r13-440-g98e475a8f58 yann at ywg dot ch
2023-01-17 1:58 ` [Bug tree-optimization/108419] " pinskia at gcc dot gnu.org
2023-01-17 13:26 ` marxin at gcc dot gnu.org
@ 2023-02-21 13:09 ` rguenth at gcc dot gnu.org
2023-02-21 22:11 ` pinskia at gcc dot gnu.org
` (4 subsequent siblings)
7 siblings, 0 replies; 9+ messages in thread
From: rguenth at gcc dot gnu.org @ 2023-02-21 13:09 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108419
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Last reconfirmed|2023-01-17 00:00:00 |2023-2-21
--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
Re-confirmed but still without analysis.
^ permalink raw reply [flat|nested] 9+ messages in thread
* [Bug tree-optimization/108419] [13 Regression] Dead Code Elimination Regression at -O2 since r13-440-g98e475a8f58
2023-01-16 15:18 [Bug tree-optimization/108419] New: [13 Regression] Dead Code Elimination Regression at -O2 since r13-440-g98e475a8f58 yann at ywg dot ch
` (2 preceding siblings ...)
2023-02-21 13:09 ` rguenth at gcc dot gnu.org
@ 2023-02-21 22:11 ` pinskia at gcc dot gnu.org
2023-03-17 17:34 ` jakub at gcc dot gnu.org
` (3 subsequent siblings)
7 siblings, 0 replies; 9+ messages in thread
From: pinskia at gcc dot gnu.org @ 2023-02-21 22:11 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108419
--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Hmm, the first difference between the trunk and GCC 12.2.0 is inside IV-OPTs.
But I don't see why that would make a difference ...
^ permalink raw reply [flat|nested] 9+ messages in thread
* [Bug tree-optimization/108419] [13 Regression] Dead Code Elimination Regression at -O2 since r13-440-g98e475a8f58
2023-01-16 15:18 [Bug tree-optimization/108419] New: [13 Regression] Dead Code Elimination Regression at -O2 since r13-440-g98e475a8f58 yann at ywg dot ch
` (3 preceding siblings ...)
2023-02-21 22:11 ` pinskia at gcc dot gnu.org
@ 2023-03-17 17:34 ` jakub at gcc dot gnu.org
2023-03-17 18:17 ` amacleod at redhat dot com
` (2 subsequent siblings)
7 siblings, 0 replies; 9+ messages in thread
From: jakub at gcc dot gnu.org @ 2023-03-17 17:34 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108419
Jakub Jelinek <jakub at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |aldyh at gcc dot gnu.org,
| |jakub at gcc dot gnu.org
--- Comment #3 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Slightly cleaned up testcase:
static int b = 6, c;
long d;
short h, i, j;
signed char k;
void foo (void);
short baz (int, int, int, int, int, int, int);
short qux (unsigned short, int, char, long);
short
bar (short l, short m)
{
return l + m;
}
static signed char
corge (void)
{
unsigned n;
for (n = -10U; n >= 14; n = bar (n, 8))
{
i = qux (b, 0, c, b);
j = baz (i, b, d < j, 5, 7, 9, 5);
k = 200 + n;
h = k % 5;
if (!h)
foo ();
}
return n;
}
int
main ()
{
b || corge ();
b = 1;
}
The loop iterates twice, with n -10U and -2U, in third iteration 6U fails the
6U >= 14 condition.
In GCC 12 as well as in r13-439 and r13-440 the loop IV is
# ivtmp.30_42 = PHI <ivtmp.30_34(8), 190(7)>
and loop condition is
ivtmp.30_34 = ivtmp.30_42 + 8;
if (ivtmp.30_34 != 206)
while trunk has 2 IVs:
# RANGE [irange] unsigned int [38, 32767][4294934528, +INF] NONZERO
0xfffffffe
# n_32 = PHI <n_30(8), 4294967286(7)>
# RANGE [irange] unsigned int [1, +INF]
# ivtmp_2 = PHI <ivtmp_43(8), 2(7)>
and
# RANGE [irange] unsigned short [30, +INF] NONZERO 0xfffe
l.0_27 = (unsigned short) n_32;
# RANGE [irange] unsigned short [0, 7][38, +INF] NONZERO 0xfffe
_28 = l.0_27 + 8;
# RANGE [irange] short int [-INF, 7][38, +INF] NONZERO 0xfffe
_29 = (short int) _28;
# RANGE [irange] unsigned int [0, 7][38, 32767][4294934528, +INF] NONZERO
0xfffffffe
n_30 = (unsigned int) _29;
ivtmp_43 = ivtmp_2 - 1;
if (ivtmp_43 != 0)
The r13-440 regression is in vrp2, previously we were able to determine that
because ivtmp.30_42 is [190, 190][198, 198]
then (signed char) of that is [-66, -66][-58, -58] and that % 5 is [-3, -3][-1,
-1].
Folding statement: _24 = (signed char) ivtmp.30_42;
- Loops range found for ivtmp.30_42: unsigned char [190, 198] and calculated
range :unsigned char [190, 190][198, 205]
-Global Exported: _24 = signed char [-66, -58] ... irange was : signed char
[-66, -66][-58, -58]
+Global Exported: _24 = signed char [-66, -58]
Not folded
Folding statement: k = _24;
Not folded
Folding statement: _25 = _24 % 5;
-Global Exported: _25 = signed char [-3, -1] ... irange was : signed char [-3,
-3][-1, -1]
+Global Exported: _25 = signed char [-4, 0]
is the first difference in the vrp2 dump between r13-439 and r13-440.
The other major change is starting with r13-3486-g4c5b1160776382772 when ivopts
uses the 2 IVs rather than one
and the convoluted increment by 8. It is actually only a normal increment by 8
if n_32 is in [0, 32759][-32777U, -1U]
but that is actually the case here.
I think the ranger doesn't iterate, right? So is there any way that it would
figure out the exact range for the IV?
^ permalink raw reply [flat|nested] 9+ messages in thread
* [Bug tree-optimization/108419] [13 Regression] Dead Code Elimination Regression at -O2 since r13-440-g98e475a8f58
2023-01-16 15:18 [Bug tree-optimization/108419] New: [13 Regression] Dead Code Elimination Regression at -O2 since r13-440-g98e475a8f58 yann at ywg dot ch
` (4 preceding siblings ...)
2023-03-17 17:34 ` jakub at gcc dot gnu.org
@ 2023-03-17 18:17 ` amacleod at redhat dot com
2023-03-27 11:11 ` [Bug tree-optimization/108419] [13/14 " rguenth at gcc dot gnu.org
2024-05-07 7:40 ` [Bug tree-optimization/108419] [13/14/15/14 " rguenth at gcc dot gnu.org
7 siblings, 0 replies; 9+ messages in thread
From: amacleod at redhat dot com @ 2023-03-17 18:17 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108419
--- Comment #4 from Andrew Macleod <amacleod at redhat dot com> ---
Not easily. I have started working on a phi analyzer for ranger to assist with
various issues like this.
It will analyze phi patterns to weed out the ssa-names that are just copies,
and then allow the few remaining ssa-names that actually change the values in
the phi seqeuence to be looked at more easily.
It will help develop better initial ranges. So cases where the non-phi names
are starting value and an increment or decrement can start with something
better than VARYING. This will help with cases like
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107986
It can help identify cases where values will have restricted smallish ranges,
such as https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107822.
Cases like this one with the second IV are trickier as there isnt a relation to
dicover between the two IVs... at leats not easily.
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107639 is a case like that too I
think.
When there are 2 IVs I dont suppose there is any way to indicate there is a
connection? then if we can end up counting one, we might be able to do
something with the other.
^ permalink raw reply [flat|nested] 9+ messages in thread
* [Bug tree-optimization/108419] [13/14 Regression] Dead Code Elimination Regression at -O2 since r13-440-g98e475a8f58
2023-01-16 15:18 [Bug tree-optimization/108419] New: [13 Regression] Dead Code Elimination Regression at -O2 since r13-440-g98e475a8f58 yann at ywg dot ch
` (5 preceding siblings ...)
2023-03-17 18:17 ` amacleod at redhat dot com
@ 2023-03-27 11:11 ` rguenth at gcc dot gnu.org
2024-05-07 7:40 ` [Bug tree-optimization/108419] [13/14/15/14 " rguenth at gcc dot gnu.org
7 siblings, 0 replies; 9+ messages in thread
From: rguenth at gcc dot gnu.org @ 2023-03-27 11:11 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108419
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Priority|P3 |P2
Summary|[13 Regression] Dead Code |[13/14 Regression] Dead
|Elimination Regression at |Code Elimination Regression
|-O2 since |at -O2 since
|r13-440-g98e475a8f58 |r13-440-g98e475a8f58
Target Milestone|13.0 |14.0
--- Comment #5 from Richard Biener <rguenth at gcc dot gnu.org> ---
ranger relies on SCEV only while the old VRP pass iterated (very few times) to
derive ranges for cases SCEV cannot handle.
I've postponed a related bug to GCC 14, it's not realistic to fix this for GCC
13(.1) unfortunately.
^ permalink raw reply [flat|nested] 9+ messages in thread
* [Bug tree-optimization/108419] [13/14/15/14 Regression] Dead Code Elimination Regression at -O2 since r13-440-g98e475a8f58
2023-01-16 15:18 [Bug tree-optimization/108419] New: [13 Regression] Dead Code Elimination Regression at -O2 since r13-440-g98e475a8f58 yann at ywg dot ch
` (6 preceding siblings ...)
2023-03-27 11:11 ` [Bug tree-optimization/108419] [13/14 " rguenth at gcc dot gnu.org
@ 2024-05-07 7:40 ` rguenth at gcc dot gnu.org
7 siblings, 0 replies; 9+ messages in thread
From: rguenth at gcc dot gnu.org @ 2024-05-07 7:40 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108419
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Target Milestone|14.0 |14.2
--- Comment #6 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] 9+ messages in thread
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2023-01-17 1:58 ` [Bug tree-optimization/108419] " pinskia at gcc dot gnu.org
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