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detect AVX-512 FMA count #125

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merged 12 commits into from
Sep 22, 2020
Merged

detect AVX-512 FMA count #125

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b4b09c7
add Ice Lake Server and Sapphire Rapids models
jeffhammond Jun 26, 2020
9c29640
Tiger Lake; Ice Lake NNP-I; SPR string
Jun 26, 2020
8e7bb52
second FMA features - incomplete and wrong
Jun 26, 2020
5f31c8a
oops: use T/F not 2/1
Jun 26, 2020
9fd9181
implement SKX lookup
Jun 26, 2020
8fe0b8e
add Intel copyright
Jun 26, 2020
a77e174
cleanup AVX512 second FMA code
Jun 30, 2020
a4d0a41
fix CPX detection
Aug 15, 2020
c036903
Merge branch 'master' into avx512_fma_count
jeffhammond Sep 21, 2020
fc89ead
remove elses
Sep 21, 2020
8ff90a6
remove curly braces from single-line conditional bodies
Sep 21, 2020
fac4ede
apply clang-format
Sep 21, 2020
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remove curly braces from single-line conditional bodies 
Signed-off-by: Hammond, Jeff R <jeff.r.hammond@intel.com>
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Hammond, Jeff R committed Sep 21, 2020
commit 8ff90a69fc8a95f895c2618a05096d728e675ebb
15 changes: 5 additions & 10 deletions src/cpuinfo_x86.c
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Expand Up @@ -133,22 +133,17 @@ static bool HasSecondFMA(uint32_t model) {
// detect Xeon
if (proc_name[9]=='X') {
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Is testing individual character the official way? It feels like upcoming names could match and trigger false positives.

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All of this code is within the model==0x55 conditional so it is not vulnerable to future branding changes unless they were based on the Skylake Server microarchitecture, which seems exceedingly unlikely.

In C++ implementations of this code, I do substring matching but in the C versions I just test single characters since I believe I have complete knowledge of the relevant processor names (including off-roadmap ones), in which case it should be sufficient.

Would you prefer I test multiple characters directly (test for 'X', 'e', 'o', 'n' not just 'X'), use strncmp, or use strstr? I generally avoid the latter since it doesn't have an n version.

// detect Silver or Bronze
if (proc_name[17]=='S' || proc_name[17]=='B') {
if (proc_name[17]=='S' || proc_name[17]=='B')
return false;
}
// detect Gold 5_20 and below, except for Gold 53__
if (proc_name[17]=='G' && proc_name[22]=='5') {
return ((proc_name[23]=='3') ||
(proc_name[24]=='2' && proc_name[25]=='2'));
}
if (proc_name[17]=='G' && proc_name[22]=='5')
return ((proc_name[23]=='3') || (proc_name[24]=='2' && proc_name[25]=='2'));
// detect Xeon W 210x
if (proc_name[17]=='W' && proc_name[21]=='0') {
if (proc_name[17]=='W' && proc_name[21]=='0')
return false;
}
// detect Xeon D 2xxx
if (proc_name[17]=='D' && proc_name[19]=='2' && proc_name[20]=='1') {
if (proc_name[17]=='D' && proc_name[19]=='2' && proc_name[20]=='1')
return false;
}
}
return true;
}
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