@@ -1119,6 +1119,10 @@ https://www.intel.com/content/www/us/en/support/articles/000059422/processors.ht
if (CPU_FEATURES_CPU_P (cpu_features, CMOV))
cpu_features->preferred[index_arch_I686] |= bit_arch_I686;
+ /* No ERMS, we want to avoid stosb for memset. */
+ if (!CPU_FEATURE_USABLE_P (cpu_features, ERMS))
+ cpu_features->preferred[index_arch_Avoid_STOSB] |= bit_arch_Avoid_STOSB;
+
#if !HAS_CPUID
no_cpuid:
#endif
@@ -193,6 +193,8 @@ TUNABLE_CALLBACK (set_hwcaps) (tunable_val_t *valp)
11);
CHECK_GLIBC_IFUNC_PREFERRED_BOTH (n, cpu_features, Prefer_FSRM,
11);
+ CHECK_GLIBC_IFUNC_PREFERRED_BOTH (n, cpu_features, Avoid_STOSB,
+ 11);
CHECK_GLIBC_IFUNC_PREFERRED_NEED_BOTH (n, cpu_features,
Slow_SSE4_2,
SSE4_2,
@@ -1041,18 +1041,42 @@ dl_init_cacheinfo (struct cpu_features *cpu_features)
slightly better than ERMS. */
rep_stosb_threshold = SIZE_MAX;
+ /*
+ For memset, the non-temporal implementation is only accessed through the
+ stosb code. ie:
+ ```
+ if (size >= rep_stosb_thresh)
+ {
+ if (size >= non_temporal_thresh)
+ {
+ do_non_temporal ();
+ }
+ do_stosb ();
+ }
+ do_normal_vec_loop ();
+ ```
+ So if we prefer non-temporal, set `rep_stosb_thresh = non_temporal_thresh`
+ to enable the implementation. If `rep_stosb_thresh = non_temporal_thresh`,
+ `rep stosb` will never be used.
+ */
+ TUNABLE_SET_WITH_BOUNDS (x86_memset_non_temporal_threshold,
+ memset_non_temporal_threshold,
+ minimum_non_temporal_threshold, SIZE_MAX);
+ /* Do `rep_stosb_thresh = non_temporal_thresh` after setting/getting the
+ final value of `x86_memset_non_temporal_threshold`. In some cases this can
+ be a matter of correctness. */
+ if (CPU_FEATURES_ARCH_P (cpu_features, Avoid_STOSB))
+ rep_stosb_threshold
+ = TUNABLE_GET (x86_memset_non_temporal_threshold, long int, NULL);
+ TUNABLE_SET_WITH_BOUNDS (x86_rep_stosb_threshold, rep_stosb_threshold, 1,
+ SIZE_MAX);
TUNABLE_SET_WITH_BOUNDS (x86_data_cache_size, data, 0, SIZE_MAX);
TUNABLE_SET_WITH_BOUNDS (x86_shared_cache_size, shared, 0, SIZE_MAX);
TUNABLE_SET_WITH_BOUNDS (x86_non_temporal_threshold, non_temporal_threshold,
minimum_non_temporal_threshold,
maximum_non_temporal_threshold);
- TUNABLE_SET_WITH_BOUNDS (x86_memset_non_temporal_threshold,
- memset_non_temporal_threshold,
- minimum_non_temporal_threshold, SIZE_MAX);
TUNABLE_SET_WITH_BOUNDS (x86_rep_movsb_threshold, rep_movsb_threshold,
minimum_rep_movsb_threshold, SIZE_MAX);
- TUNABLE_SET_WITH_BOUNDS (x86_rep_stosb_threshold, rep_stosb_threshold, 1,
- SIZE_MAX);
unsigned long int rep_movsb_stop_threshold;
/* Setting the upper bound of ERMS to the computed value of
@@ -34,3 +34,4 @@ BIT (MathVec_Prefer_No_AVX512)
BIT (Prefer_FSRM)
BIT (Avoid_Short_Distance_REP_MOVSB)
BIT (Avoid_Non_Temporal_Memset)
+BIT (Avoid_STOSB)
@@ -60,7 +60,8 @@ static const struct test_t
/* Disable everything. */
"-Prefer_ERMS,-Prefer_FSRM,-AVX,-AVX2,-AVX512F,-AVX512VL,"
"-SSE4_1,-SSE4_2,-SSSE3,-Fast_Unaligned_Load,-ERMS,"
- "-AVX_Fast_Unaligned_Load,-Avoid_Non_Temporal_Memset",
+ "-AVX_Fast_Unaligned_Load,-Avoid_Non_Temporal_Memset,"
+ "-Avoid_STOSB",
test_1,
array_length (test_1)
},
@@ -68,7 +69,8 @@ static const struct test_t
/* Same as before, but with some empty suboptions. */
",-,-Prefer_ERMS,-Prefer_FSRM,-AVX,-AVX2,-AVX512F,-AVX512VL,"
"-SSE4_1,-SSE4_2,-SSSE3,-Fast_Unaligned_Load,,-,"
- "-ERMS,-AVX_Fast_Unaligned_Load,-Avoid_Non_Temporal_Memset,-,",
+ "-ERMS,-AVX_Fast_Unaligned_Load,-Avoid_Non_Temporal_Memset,"
+ "-Avoid_STOSB,-,",
test_1,
array_length (test_1)
}
@@ -61,7 +61,9 @@ IFUNC_SELECTOR (void)
&& X86_ISA_CPU_FEATURE_USABLE_P (cpu_features, AVX512BW)
&& X86_ISA_CPU_FEATURE_USABLE_P (cpu_features, BMI2))
{
- if (CPU_FEATURE_USABLE_P (cpu_features, ERMS))
+ if (CPU_FEATURE_USABLE_P (cpu_features, ERMS)
+ || !CPU_FEATURES_ARCH_P (cpu_features,
+ Avoid_Non_Temporal_Memset))
return OPTIMIZE (avx512_unaligned_erms);
return OPTIMIZE (avx512_unaligned);
@@ -76,7 +78,9 @@ IFUNC_SELECTOR (void)
&& X86_ISA_CPU_FEATURE_USABLE_P (cpu_features, AVX512BW)
&& X86_ISA_CPU_FEATURE_USABLE_P (cpu_features, BMI2))
{
- if (CPU_FEATURE_USABLE_P (cpu_features, ERMS))
+ if (CPU_FEATURE_USABLE_P (cpu_features, ERMS)
+ || !CPU_FEATURES_ARCH_P (cpu_features,
+ Avoid_Non_Temporal_Memset))
return OPTIMIZE (evex_unaligned_erms);
return OPTIMIZE (evex_unaligned);
@@ -84,7 +88,9 @@ IFUNC_SELECTOR (void)
if (CPU_FEATURE_USABLE_P (cpu_features, RTM))
{
- if (CPU_FEATURE_USABLE_P (cpu_features, ERMS))
+ if (CPU_FEATURE_USABLE_P (cpu_features, ERMS)
+ || !CPU_FEATURES_ARCH_P (cpu_features,
+ Avoid_Non_Temporal_Memset))
return OPTIMIZE (avx2_unaligned_erms_rtm);
return OPTIMIZE (avx2_unaligned_rtm);
@@ -93,14 +99,17 @@ IFUNC_SELECTOR (void)
if (X86_ISA_CPU_FEATURES_ARCH_P (cpu_features,
Prefer_No_VZEROUPPER, !))
{
- if (CPU_FEATURE_USABLE_P (cpu_features, ERMS))
+ if (CPU_FEATURE_USABLE_P (cpu_features, ERMS)
+ || !CPU_FEATURES_ARCH_P (cpu_features,
+ Avoid_Non_Temporal_Memset))
return OPTIMIZE (avx2_unaligned_erms);
return OPTIMIZE (avx2_unaligned);
}
}
- if (CPU_FEATURE_USABLE_P (cpu_features, ERMS))
+ if (CPU_FEATURE_USABLE_P (cpu_features, ERMS)
+ || !CPU_FEATURES_ARCH_P (cpu_features, Avoid_Non_Temporal_Memset))
return OPTIMIZE (sse2_unaligned_erms);
return OPTIMIZE (sse2_unaligned);
The goal of this flag is to allow targets which don't prefer/have ERMS to still access the non-temporal memset implementation. There are 4 cases for tuning memset: 1) `Avoid_STOSB && Avoid_Non_Temporal_Memset` - Memset with temporal stores 2) `Avoid_STOSB && !Avoid_Non_Temporal_Memset` - Memset with temporal/non-temporal stores. Non-temporal path goes through `rep stosb` path. We accomplish this by setting `x86_rep_stosb_threshold` to `x86_memset_non_temporal_threshold`. 3) `!Avoid_STOSB && Avoid_Non_Temporal_Memset` - Memset with temporal stores/`rep stosb` 3) `!Avoid_STOSB && !Avoid_Non_Temporal_Memset` - Memset with temporal stores/`rep stosb`/non-temporal stores. --- sysdeps/x86/cpu-features.c | 4 +++ sysdeps/x86/cpu-tunables.c | 2 ++ sysdeps/x86/dl-cacheinfo.h | 34 ++++++++++++++++--- ...cpu-features-preferred_feature_index_1.def | 1 + sysdeps/x86/tst-hwcap-tunables.c | 6 ++-- sysdeps/x86_64/multiarch/ifunc-memset.h | 19 ++++++++--- 6 files changed, 54 insertions(+), 12 deletions(-)