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Disable PEXT on AMD Excavator CPUs

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Excavator also supports BMI2, where it has the same microcoded performance implications as on Zen pre-3.

closes https://github.com/official-stockfish/Stockfish/pull/6868

No functional change
This commit is contained in:
Ciekce
2026-06-06 09:58:43 +02:00
committed by Joost VandeVondele
parent 91045b2ff6
commit 0c1001c93e
2 changed files with 12 additions and 9 deletions
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scripts/get_native_properties.sh
+8 -6
View File
@@ -138,17 +138,19 @@ match_sse3() {
match_any_flags sse3 pni
}
# AMD Zen1/2 exclusion logic (used for bmi2 tier).
# AMD Excavator/Zen1/2 exclusion logic (used for bmi2 tier).
# https://web.archive.org/web/20250821132355/https://en.wikichip.org/wiki/amd/cpuid
is_znver_1_2() (
# All of Bulldozer through Excavator are matched here, but pre-Excavator doesn't support bmi2 anyway
has_slow_bmi2() (
[ -r "$cpuinfo_path" ] || exit 1
vendor_id=$(awk '/^vendor_id/{print $3; exit}' "$cpuinfo_path" 2>/dev/null)
cpu_family=$(awk '/^cpu family/{print $4; exit}' "$cpuinfo_path" 2>/dev/null)
[ "$vendor_id" = "AuthenticAMD" ] && [ "$cpu_family" = "23" ]
[ "$vendor_id" = "AuthenticAMD" ] \
&& { [ "$cpu_family" = "21" ] || [ "$cpu_family" = "23" ]; }
)
match_not_znver12_and_flags() {
is_znver_1_2 && return 1
match_not_slow_bmi2_and_flags() {
has_slow_bmi2 && return 1
match_flags "$@"
}
@@ -199,7 +201,7 @@ x86-64-avx512icl|match_flags|avx512f avx512cd avx512vl avx512dq avx512bw avx512i
x86-64-vnni512|match_flags|avx512vnni avx512dq avx512f avx512bw avx512vl
x86-64-avx512|match_flags|avx512f avx512bw
x86-64-avxvnni|match_flags|avxvnni
x86-64-bmi2|match_not_znver12_and_flags|bmi2
x86-64-bmi2|match_not_slow_bmi2_and_flags|bmi2
x86-64-avx2|match_flags|avx2
x86-64-sse41-popcnt|match_flags|sse41 popcnt
x86-64-ssse3|match_flags|ssse3
src/universal/entry_x86.cpp
+4 -3
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@@ -67,16 +67,17 @@ DEFINE_BUILD(x86_64_avx512)
DEFINE_BUILD(x86_64_vnni512)
DEFINE_BUILD(x86_64_avx512icl)
// AMD Zen/Zen+/Zen2 (family 17h) implement pdep/pext via microcode.
// AMD Excavator (family 15h) and Zen/Zen+/Zen2 (family 17h) implement pdep/pext via microcode.
static bool has_slow_bmi2() {
return __builtin_cpu_is("amd") && (__builtin_cpu_is("znver1") || __builtin_cpu_is("znver2"));
return __builtin_cpu_is("amd")
&& (__builtin_cpu_is("bdver4") || __builtin_cpu_is("znver1") || __builtin_cpu_is("znver2"));
}
struct CpuFeatures {
bool sse41; // SSE4.1
bool popcnt; // POPCNT
bool avx2; // AVX2
bool bmi2; // BMI2 (may be slow on AMD Zen/Zen+/Zen2)
bool bmi2; // BMI2 (may be slow on AMD Excavator and Zen/Zen+/Zen2)
bool avx512f; // AVX-512 Foundation
bool avx512vl; // AVX-512 Vector Length extensions
bool avx512bw; // AVX-512 Byte and Word instructions