https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99419
Bug ID: 99419
Summary: possible missed optimization for dead code elimination
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: ipa
Assignee: unassigned at gcc dot gnu.org
Reporter: zhendong.su at inf dot ethz.ch
CC: marxin at gcc dot gnu.org
Target Milestone: ---
[552] % 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 20210305 (experimental) [master revision
9ee91079fd5:70357716fd6:3d9577c254003f2d18185015b75ce6e3e4af9ca2] (GCC)
[553] %
[553] % gcctk -O3 -S small.c
[554] %
[554] % cat small.c
extern void foo(void);
int a;
static int b[2] = {0,0};
int main() {
if (b[a])
foo();
return 0;
}
[555] %
[555] % cat small.s
.file "small.c"
.text
.section .text.startup,"ax",@progbits
.p2align 4
.globl main
.type main, @function
main:
.LFB0:
.cfi_startproc
movslq a(%rip), %rax
movl b(,%rax,4), %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
.section .rodata
.align 8
.type b, @object
.size b, 8
b:
.zero 8
.globl a
.bss
.align 4
.type a, @object
.size a, 4
a:
.zero 4
.ident "GCC: (GNU) 11.0.1 20210305 (experimental) [master revision
9ee91079fd5:70357716fd6:3d9577c254003f2d18185015b75ce6e3e4af9ca2]"
.section .note.GNU-stack,"",@progbits
