在 2022/11/30 15:23, bootmgr--- via Gcc-help 写道:
And I want to port it to Linux, so I am looking for any functions like _BitScanForward. I trying to use __builtin_ctz instead _BitScanForward, but it is undefined when x is 0 and it can't determine whether x is 0 or not. Then I found __bsfd in x86intrin.h, but it's the same as __builtin_ctz, which can't determine x is 0. So is there any solution, preferably cross-platform?
```
__attribute__((__gnu_inline__, __nothrow__, __pure__))
extern __inline__
bool
_BitScanForward(uint32_t* index, uint32_t value)
{
bool zf;
__asm__ (
"{ bsfl %2, %1 | bsf %1, %2 }"
: "=@ccz"(zf), "=r"(*index) : "rm"(value)
);
return !zf;
}
```
Godbolt: https://gcc.godbolt.org/z/vzEjGj11e
--
Best regards,
LIU Hao
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