Don't access leaf 7 subleaf 1 unless subleaf 0 says it is
supported via EAX.
Intel documentation says invalid subleaves return 0. We had been
relying on that behavior instead of checking the max sublef number.
It appears that some Sandy Bridge CPUs return at least the subleaf 0
EDX value for subleaf 1. Best guess is that this is a bug in a
microcode patch since all of the bits we're seeing set in EDX were
introduced after Sandy Bridge was originally released.
This is causing avxvnniint16 to be incorrectly enabled with
-march=native on these CPUs.
BTW: Thanks for reminder from llvm forks Phoebe and Craig.
Bootstrapped and regtested on x86_64-pc-linux-gnu{-m32,}.
Ok for trunk and backport?
gcc/ChangeLog:
* common/config/i386/cpuinfo.h (get_available_features): Check
EAX for valid subleaf before use CPUID.
---
gcc/common/config/i386/cpuinfo.h | 84 +++++++++++++++++---------------
1 file changed, 46 insertions(+), 38 deletions(-)
diff --git a/gcc/common/config/i386/cpuinfo.h b/gcc/common/config/i386/cpuinfo.h
index 30ef0d334ca..24ab2252eb0 100644
--- a/gcc/common/config/i386/cpuinfo.h
+++ b/gcc/common/config/i386/cpuinfo.h
@@ -874,45 +874,53 @@ get_available_features (struct __processor_model
*cpu_model,
set_feature (FEATURE_AVX512FP16);
}
- __cpuid_count (7, 1, eax, ebx, ecx, edx);
- if (eax & bit_HRESET)
- set_feature (FEATURE_HRESET);
- if (eax & bit_CMPCCXADD)
- set_feature(FEATURE_CMPCCXADD);
- if (edx & bit_PREFETCHI)
- set_feature (FEATURE_PREFETCHI);
- if (eax & bit_RAOINT)
- set_feature (FEATURE_RAOINT);
- if (avx_usable)
- {
- if (eax & bit_AVXVNNI)
- set_feature (FEATURE_AVXVNNI);
- if (eax & bit_AVXIFMA)
- set_feature (FEATURE_AVXIFMA);
- if (edx & bit_AVXVNNIINT8)
- set_feature (FEATURE_AVXVNNIINT8);
- if (edx & bit_AVXNECONVERT)
- set_feature (FEATURE_AVXNECONVERT);
- if (edx & bit_AVXVNNIINT16)
- set_feature (FEATURE_AVXVNNIINT16);
- if (eax & bit_SM3)
- set_feature (FEATURE_SM3);
- if (eax & bit_SHA512)
- set_feature (FEATURE_SHA512);
- if (eax & bit_SM4)
- set_feature (FEATURE_SM4);
- }
- if (avx512_usable)
- {
- if (eax & bit_AVX512BF16)
- set_feature (FEATURE_AVX512BF16);
- }
- if (amx_usable)
+ /* According to document, when subleaf is invliad, EAX,EBX,ECX,EDX should
+ return 0 for CPUID (7, 1, EAX, EBX, ECX, EDX).
+ But looks like it doesn't satisfy the document on some CPU, refer to
+ https://reviews.llvm.org/D155145.
+ Manually check valid subleaf here. */
+ if (eax)
{
- if (eax & bit_AMX_FP16)
- set_feature (FEATURE_AMX_FP16);
- if (edx & bit_AMX_COMPLEX)
- set_feature (FEATURE_AMX_COMPLEX);
+ __cpuid_count (7, 1, eax, ebx, ecx, edx);
+ if (eax & bit_HRESET)
+ set_feature (FEATURE_HRESET);
+ if (eax & bit_CMPCCXADD)
+ set_feature(FEATURE_CMPCCXADD);
+ if (edx & bit_PREFETCHI)
+ set_feature (FEATURE_PREFETCHI);
+ if (eax & bit_RAOINT)
+ set_feature (FEATURE_RAOINT);
+ if (avx_usable)
+ {
+ if (eax & bit_AVXVNNI)
+ set_feature (FEATURE_AVXVNNI);
+ if (eax & bit_AVXIFMA)
+ set_feature (FEATURE_AVXIFMA);
+ if (edx & bit_AVXVNNIINT8)
+ set_feature (FEATURE_AVXVNNIINT8);
+ if (edx & bit_AVXNECONVERT)
+ set_feature (FEATURE_AVXNECONVERT);
+ if (edx & bit_AVXVNNIINT16)
+ set_feature (FEATURE_AVXVNNIINT16);
+ if (eax & bit_SM3)
+ set_feature (FEATURE_SM3);
+ if (eax & bit_SHA512)
+ set_feature (FEATURE_SHA512);
+ if (eax & bit_SM4)
+ set_feature (FEATURE_SM4);
+ }
+ if (avx512_usable)
+ {
+ if (eax & bit_AVX512BF16)
+ set_feature (FEATURE_AVX512BF16);
+ }
+ if (amx_usable)
+ {
+ if (eax & bit_AMX_FP16)
+ set_feature (FEATURE_AMX_FP16);
+ if (edx & bit_AMX_COMPLEX)
+ set_feature (FEATURE_AMX_COMPLEX);
+ }
}
}
--
2.31.1
