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libgo: use inline assembly in favor of call to _xgetbv() 

Use inline assembly in the implementation of internal_cpu.xgetbv as
    opposed to a call to the intrinsic _xgetbv(), since non-gcc compilers
    (e.g. clang) may or may not have support for it.
    
    Reviewed-on: https://go-review.googlesource.com/c/140137

From-SVN: r264882
This commit is contained in:
Ian Lance Taylor 2018-10-05 17:51:57 +00:00
parent d5a9895595
commit 7fc9c2e52f
2 changed files with 11 additions and 5 deletions
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2
gcc/go/gofrontend/MERGE
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@ -1,4 +1,4 @@
9f4cf23e716bcf65e071260afa032a64acd3fdde
d0739c13ca3686df1f8d0fae7c6c5caaed058503
The first line of this file holds the git revision number of the last
merge done from the gofrontend repository.

14
libgo/go/internal/cpu/cpu_gccgo.c
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@ -52,12 +52,18 @@ struct xgetbv_ret xgetbv(void)
#pragma GCC target("xsave")
struct xgetbv_ret xgetbv(void) {
long long r;
struct xgetbv_ret ret;
r = _xgetbv(0);
ret.eax = r & 0xffffffff;
ret.edx = r >> 32;
// At some point, use call to _xgetbv() instead:
//
// long long r = _xgetbv(0);
// ret.eax = r & 0xffffffff;
// ret.edx = r >> 32;
//
unsigned int __eax, __edx, __xcr_no = 0;
__asm__ ("xgetbv" : "=a" (__eax), "=d" (__edx) : "c" (__xcr_no));
ret.eax = __eax;
ret.edx = __edx;
return ret;
}