http://llvm.org/bugs/show_bug.cgi?id=19431
Bug ID: 19431
Summary: BMI intrinsic not recognized?
Product: clang
Version: trunk
Hardware: PC
OS: All
Status: NEW
Severity: normal
Priority: P
Component: Headers
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected]
Classification: Unclassified
Using:
$ ./clang -v
clang version 3.5.0 (trunk 206222) (llvm/trunk 206220)
Target: x86_64-apple-darwin13.1.0
Thread model: posix
I tried to generate an x86 bit manipulation instruction (BMI) via its C
intrinsic:
$ cat bmi.c
#include <x86intrin.h>
int foo(int a) { return _blsmsk_u32(a); }
$ ./clang bmi.c -mbmi -S -o -
bmi.c:2:25: warning: implicit declaration of function '_blsmsk_u32' is invalid
in C99 [-Wimplicit-function-declaration]
The generated asm shows:
callq __blsmsk_u32
I confirmed the same behavior with clang 3.2 on Ubuntu 13.04. However, gcc
4.8.2 generates the expected instruction from the same source file and compiler
flags:
blsmsk %edi, %eax
I also confirmed that a BMI2 instruction is generated using the same kind of C
instrinsic (I tested '_bzhi_u32') and "-mbmi2" with both clang versions and
gcc.
Is "-mbmi" no longer the correct feature flag for the BMI ISA?
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