https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90044
Bug ID: 90044
Summary: extraneous setne after asm statement with flag output
operands
Product: gcc
Version: 9.0
Status: UNCONFIRMED
Keywords: missed-optimization
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: zsojka at seznam dot cz
Target Milestone: ---
Host: x86_64-pc-linux-gnu
Created attachment 46140
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=46140&action=edit
reduced testcase
For the attached code, gcc -O3 generates (simplified):
$ x86_64-pc-linux-gnu-gcc -O3 tste.c -masm=intel -S -o-
...
foo:
xor eax, eax
# SETNE
setne al
je .L2
xor eax, eax
# TRUE
ret
.L2:
# FALSE
ret
which is way too complex; "setne" is useless there, and it even only modifies
the value 0 already in eax; this one would be better:
foo:
xor eax, eax
# SETNE
je .L2
# TRUE
ret
.L2:
# FALSE
ret
