https://gcc.gnu.org/bugzilla/show_bug.cgi?id=124093
Bug ID: 124093
Summary: [missed optimization] wrapped value range with <= is
not optimized
Product: gcc
Version: 16.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: nsz at gcc dot gnu.org
Target Milestone: ---
at -O2 i expected the same code gen for foo*:
char foo1(unsigned char *p)
{
return (unsigned)*p-2 <= 999;
}
char foo2(unsigned char *p)
{
return (unsigned)*p-2 <= 253;
}
char foo3(unsigned char *p)
{
return (unsigned)*p-2 <= -3u;
}
char foo4(unsigned char *p)
{
return *p >= 2;
}
note: (unsigned)*p-2 is in [0,253] U [-2u,-1u],
with -O2 or -O3 on x86_64 i get
foo1:
movzbl (%rdi), %eax
subl $2, %eax
cmpl $999, %eax
setbe %al
ret
foo2:
movzbl (%rdi), %eax
subl $2, %eax
cmpl $253, %eax
setbe %al
ret
foo3:
cmpb $1, (%rdi)
seta %al
ret
foo4:
cmpb $1, (%rdi)
seta %al
ret
