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bmiintrin.h: Allow using the tzcnt intrinsics for non-BMI targets 

The tzcnt intrinsics are used non non-BMI targets by code (e.g. ffmpeg)
that uses it as a potentially faster BSF.

The TZCNT instruction is special in that it's encoded in a
backward-compatible way and behaves as BSF on non-BMI targets.

Differential Revision: http://reviews.llvm.org/D14748

llvm-svn: 253358
This commit is contained in:
Hans Wennborg 2015-11-17 18:46:48 +00:00
parent f09d1bfced
commit 1acf955a6a
1 changed files with 9 additions and 3 deletions
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12
clang/lib/Headers/bmiintrin.h
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@ -39,7 +39,12 @@
/* Define the default attributes for the functions in this file. */
#define __DEFAULT_FN_ATTRS __attribute__((__always_inline__, __nodebug__, __target__("bmi")))
static __inline__ unsigned short __DEFAULT_FN_ATTRS
/* Allow using the tzcnt intrinsics even for non-BMI targets. Since the TZCNT
instruction behaves as BSF on non-BMI targets, there is code that expects
to use it as a potentially faster version of BSF. */
#define __RELAXED_FN_ATTRS __attribute__((__always_inline__, __nodebug__))
static __inline__ unsigned short __RELAXED_FN_ATTRS
__tzcnt_u16(unsigned short __X)
{
return __X ? __builtin_ctzs(__X) : 16;
@ -83,7 +88,7 @@ __blsr_u32(unsigned int __X)
return __X & (__X - 1);
}
static __inline__ unsigned int __DEFAULT_FN_ATTRS
static __inline__ unsigned int __RELAXED_FN_ATTRS
__tzcnt_u32(unsigned int __X)
{
return __X ? __builtin_ctz(__X) : 32;
@ -136,7 +141,7 @@ __blsr_u64(unsigned long long __X)
return __X & (__X - 1);
}
static __inline__ unsigned long long __DEFAULT_FN_ATTRS
static __inline__ unsigned long long __RELAXED_FN_ATTRS
__tzcnt_u64(unsigned long long __X)
{
return __X ? __builtin_ctzll(__X) : 64;
@ -145,5 +150,6 @@ __tzcnt_u64(unsigned long long __X)
#endif /* __x86_64__ */
#undef __DEFAULT_FN_ATTRS
#undef __RELAXED_FN_ATTRS
#endif /* __BMIINTRIN_H */