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* [Bug target/101816] New: slight missed optimization with __builtin_add_overflow with ^1
@ 2021-08-08 2:29 pinskia at gcc dot gnu.org
0 siblings, 0 replies; only message in thread
From: pinskia at gcc dot gnu.org @ 2021-08-08 2:29 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101816
Bug ID: 101816
Summary: slight missed optimization with __builtin_add_overflow
with ^1
Product: gcc
Version: 12.0
Status: UNCONFIRMED
Keywords: missed-optimization
Severity: enhancement
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: pinskia at gcc dot gnu.org
Target Milestone: ---
Target: x86_64-linux-gnu
Take:
void f(unsigned long long *x, unsigned long long y, unsigned long long z)
{
int d = __builtin_add_overflow (*x,y,x);
x[1] += z + !d;
}
Right now we produce:
xorl %eax, %eax
addq (%rdi), %rsi
setc %al
movq %rsi, (%rdi)
xorq $1, %rax
addq %rdx, %rax
addq %rax, 8(%rdi)
ret
But the setc and xor could be combined into:
setnc %al
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2021-08-08 2:29 [Bug target/101816] New: slight missed optimization with __builtin_add_overflow with ^1 pinskia at gcc dot gnu.org
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