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C-cpuid (very small) bug? #300

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fcorbelli opened this issue Apr 20, 2023 · 1 comment
Closed

C-cpuid (very small) bug? #300

fcorbelli opened this issue Apr 20, 2023 · 1 comment

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@fcorbelli
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Hello, here

https://github.com/BLAKE3-team/BLAKE3/blob/master/c/blake3_dispatch.c

@lines 104-105

    if (*ecx & (1UL << 0))
      features |= SSSE3;

But the SSSE3 should be bit 9
https://www.felixcloutier.com/x86/cpuid

SSE3 is bit 0, just like in your code
(Intel, I really love you!)
@sneves
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sneves commented Apr 21, 2023

You're right; I can't tell whether this was a typo or a SSE3/SSSE3 mixup.

@sneves sneves closed this as completed in 9ac0a9b Apr 21, 2023
oconnor663 added a commit to oconnor663/K12 that referenced this issue Apr 21, 2023
@oconnor663
apply an upstream fix in SSSE3 detection
e7e2333 
BLAKE3-team/BLAKE3#300
@oconnor663 oconnor663 mentioned this issue Apr 21, 2023
Merged
kevingoh pushed a commit to ITS-AT-dev/BLAKE3 that referenced this issue Oct 23, 2023
@sneves
correct SSSE3 detection; fixes BLAKE3-team#300
53faeb3 
SSSE3 is indicated by bit 9 of ECX, not bit 0, which indicates the
presence of SSE3.

There are very few CPUs in use affected by this bug; SSE3 was part of
the Prescott new instructions, introduced in the later Pentium 4 chips,
whereas SSSE3 was introduced in Intel's Core 2 and AMD's Bulldozer. This
leaves a few Pentium 4 and Athlon 64 models that will potentially run an
illegal pshufb or pblendw.
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@sneves @fcorbelli