https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99428
Bug ID: 99428
Summary: possible missed optimization for dead code elimination
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: zhendong.su at inf dot ethz.ch
Target Milestone: ---
[604] % gcctk -v
Using built-in specs.
COLLECT_GCC=gcctk
COLLECT_LTO_WRAPPER=/local/suz-local/software/local/gcc-trunk/libexec/gcc/x86_64-pc-linux-gnu/11.0.1/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: ../gcc-trunk/configure --disable-bootstrap
--prefix=/local/suz-local/software/local/gcc-trunk --enable-languages=c,c++
--disable-werror --enable-multilib --with-system-zlib
Thread model: posix
Supported LTO compression algorithms: zlib
gcc version 11.0.1 20210306 (experimental) [master revision
02a35548790:4487c1830cf:ceae9533826aabaf4c78d173c60e3bedeffc6955] (GCC)
[605] %
[605] % gcctk -O3 -S small.c
[606] %
[606] % cat small.c
extern void foo(void);
static int a;
static int *b = &a;
int main() {
if (*b)
foo();
return 0;
}
[607] %
[607] % cat small.s
.file "small.c"
.text
.section .text.startup,"ax",@progbits
.p2align 4
.globl main
.type main, @function
main:
.LFB0:
.cfi_startproc
movl a(%rip), %ecx
testl %ecx, %ecx
jne .L8
xorl %eax, %eax
ret
.L8:
pushq %rax
.cfi_def_cfa_offset 16
call foo
xorl %eax, %eax
popq %rdx
.cfi_def_cfa_offset 8
ret
.cfi_endproc
.LFE0:
.size main, .-main
.local a
.comm a,4,4
.ident "GCC: (GNU) 11.0.1 20210306 (experimental) [master revision
02a35548790:4487c1830cf:ceae9533826aabaf4c78d173c60e3bedeffc6955]"
.section .note.GNU-stack,"",@progbits
