http://llvm.org/bugs/show_bug.cgi?id=17038
Bug ID: 17038
Summary: bzhi not generated
Product: libraries
Version: trunk
Hardware: PC
OS: All
Status: NEW
Severity: normal
Priority: P
Component: Backend: X86
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected]
Classification: Unclassified
$ ./clang -v
clang version 3.4 (trunk 189409)
Target: x86_64-apple-darwin11.4.2
Thread model: posix
$ cat bzhi.c
int foo(int x, unsigned char index) {
return (x & ((1 << index) - 1));
}
$ ./clang -S -O3 -march=core-avx2 bzhi.c -o /dev/stdout
.section __TEXT,__text,regular,pure_instructions
.globl _foo
.align 4, 0x90
_foo: ## @foo
.cfi_startproc
## BB#0: ## %entry
pushq %rbp
Ltmp2:
.cfi_def_cfa_offset 16
Ltmp3:
.cfi_offset %rbp, -16
movq %rsp, %rbp
Ltmp4:
.cfi_def_cfa_register %rbp
movl $1, %eax
shlxl %esi, %eax, %eax
decl %eax
andl %edi, %eax
popq %rbp
ret
...
I was expecting this code sequence to generate the BMI2 instruction 'BZHI'
rather than mov/shift/subtract/and. Something like this:
bzhi %esi, %edi, %eax
--
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