[X86] Test the right bit to detect BMI2

[atdt]

Summary

BMI2 support is indicated in bit eight of EBX, not nine.
See Intel SDM, Vol 2A, Table 3-8:
https://www.intel.com/content/dam/www/public/us/en/documents/manuals/64-ia-32-architectures-software-developer-vol-2a-manual.pdf#page=296

[echristo]

This is fine. Can you add a link to the actual documentation in the commit message?

[craig.topper]

@atdt can you fix the copy of this code in llvm/lib/Support/Host.cpp as well?

[atdt]

Fixed this in llvm/lib/Support/Host.cpp as well.

[craig.topper]

LGTM

[xbolva00]

Should be fixed in 9.0 too?

@hans

[hans]

In D65766#1615458, @xbolva00 wrote:

Should be fixed in 9.0 too?

@hans

Merged to release_90 in r367996.

compiler-rt/lib/builtins/cpu_model.c

#define setFeature(F)                                                          \
 
   bool HasLeaf7 =
       MaxLeaf >= 0x7 && !getX86CpuIDAndInfoEx(0x7, 0x0, &EAX, &EBX, &ECX, &EDX);
 
   if (HasLeaf7 && ((EBX >> 3) & 1))
     setFeature(FEATURE_BMI);
   if (HasLeaf7 && ((EBX >> 5) & 1) && HasAVX)
     setFeature(FEATURE_AVX2);
-  if (HasLeaf7 && ((EBX >> 9) & 1))
+  if (HasLeaf7 && ((EBX >> 8) & 1))
     setFeature(FEATURE_BMI2);
   if (HasLeaf7 && ((EBX >> 16) & 1) && HasAVX512Save)
     setFeature(FEATURE_AVX512F);
   if (HasLeaf7 && ((EBX >> 17) & 1) && HasAVX512Save)
     setFeature(FEATURE_AVX512DQ);
   if (HasLeaf7 && ((EBX >> 21) & 1) && HasAVX512Save)
     setFeature(FEATURE_AVX512IFMA);
   if (HasLeaf7 && ((EBX >> 26) & 1) && HasAVX512Save)

llvm/lib/Support/Host.cpp

static void getAvailableFeatures(unsigned ECX, unsigned EDX, unsigned MaxLeaf,
 
   bool HasLeaf7 =
       MaxLeaf >= 0x7 && !getX86CpuIDAndInfoEx(0x7, 0x0, &EAX, &EBX, &ECX, &EDX);
 
   if (HasLeaf7 && ((EBX >> 3) & 1))
     setFeature(X86::FEATURE_BMI);
   if (HasLeaf7 && ((EBX >> 5) & 1) && HasAVX)
     setFeature(X86::FEATURE_AVX2);
-  if (HasLeaf7 && ((EBX >> 9) & 1))
+  if (HasLeaf7 && ((EBX >> 8) & 1))
     setFeature(X86::FEATURE_BMI2);
   if (HasLeaf7 && ((EBX >> 16) & 1) && HasAVX512Save)
     setFeature(X86::FEATURE_AVX512F);
   if (HasLeaf7 && ((EBX >> 17) & 1) && HasAVX512Save)
     setFeature(X86::FEATURE_AVX512DQ);
   if (HasLeaf7 && ((EBX >> 19) & 1))
     setFeature(X86::FEATURE_ADX);
   if (HasLeaf7 && ((EBX >> 21) & 1) && HasAVX512Save)