https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84527
Bug ID: 84527
Summary: missed optimization for special ternary operation
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: rtl-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: ktietz at gcc dot gnu.org
Target Milestone: ---
The following sample:
int foo(int a, int b)
{
return a < b ? -1 : 1;
}
gets translated to
...
xorl %eax, %eax
cmpl %edx, %ecx
setge %al
leal -1(%rax,%rax), %eax
ret
...
There would be instead a better representation for such kind of patterns as
... cmpl %ecx, %edx
sbb %eax, %eax
orb $1, %al
ret
The missed patterns are 'result = COND ? -1 : VAL' and its permutations.
The same applies to the pattern 'result = COND ? VAL : 0' and its permuations,
which can be expressed as 'CMP a, b; SBB reg, reg; AND $VAL, reg;'
