https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84413
Bug ID: 84413
Summary: -march=skylake-avx512 disables BT instruction
Product: gcc
Version: 8.0.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: hjl.tools at gmail dot com
CC: ubizjak at gmail dot com
Target Milestone: ---
Target: x86
[hjl@gnu-skx-1 gcc]$ cat x.c
unsigned long long bextr64_demanded(unsigned long long x)
{
return x | 0x8000000000;
}
[hjl@gnu-skx-1 gcc]$ ./xgcc -B./ -S -O2 x.c -march=skylake-avx512
[hjl@gnu-skx-1 gcc]$ cat x.s
.file "x.c"
.text
.p2align 4,,15
.globl bextr64_demanded
.type bextr64_demanded, @function
bextr64_demanded:
.LFB0:
.cfi_startproc
movabsq $549755813888, %rax
orq %rdi, %rax
xorl %edi, %edi
ret
.cfi_endproc
.LFE0:
.size bextr64_demanded, .-bextr64_demanded
.ident "GCC: (GNU) 8.0.1 20180212 (experimental)"
.section .note.GNU-stack,"",@progbits
[hjl@gnu-skx-1 gcc]$ ./xgcc -B./ -S -O2 x.c
[hjl@gnu-skx-1 gcc]$ cat x.s
.file "x.c"
.text
.p2align 4,,15
.globl bextr64_demanded
.type bextr64_demanded, @function
bextr64_demanded:
.LFB0:
.cfi_startproc
movq %rdi, %rax
xorl %edi, %edi
btsq $39, %rax
ret
.cfi_endproc
.LFE0:
.size bextr64_demanded, .-bextr64_demanded
.ident "GCC: (GNU) 8.0.1 20180212 (experimental)"
.section .note.GNU-stack,"",@progbits
[hjl@gnu-skx-1 gcc]$
