Use AVX unaligned memcpy only if AVX2 is available

memcpy with unaligned 256-bit AVX register loads/stores are slow on older
processorsl like Sandy Bridge.  This patch adds bit_AVX_Fast_Unaligned_Load
and sets it only when AVX2 is available.

	[BZ #17801]
	* sysdeps/x86_64/multiarch/init-arch.c (__init_cpu_features):
	Set the bit_AVX_Fast_Unaligned_Load bit for AVX2.
	* sysdeps/x86_64/multiarch/init-arch.h (bit_AVX_Fast_Unaligned_Load):
	New.
	(index_AVX_Fast_Unaligned_Load): Likewise.
	(HAS_AVX_FAST_UNALIGNED_LOAD): Likewise.
	* sysdeps/x86_64/multiarch/memcpy.S (__new_memcpy): Check the
	bit_AVX_Fast_Unaligned_Load bit instead of the bit_AVX_Usable bit.
	* sysdeps/x86_64/multiarch/memcpy_chk.S (__memcpy_chk): Likewise.
	* sysdeps/x86_64/multiarch/mempcpy.S (__mempcpy): Likewise.
	* sysdeps/x86_64/multiarch/mempcpy_chk.S (__mempcpy_chk): Likewise.
	* sysdeps/x86_64/multiarch/memmove.c (__libc_memmove): Replace
	HAS_AVX with HAS_AVX_FAST_UNALIGNED_LOAD.
	* sysdeps/x86_64/multiarch/memmove_chk.c (__memmove_chk): Likewise.

8 files changed, 17 insertions, 8 deletions

diff --git a/sysdeps/x86_64/multiarch/init-arch.c b/sysdeps/x86_64/multiarch/init-arch.c
index 9299360..7dec218 100644
--- a/sysdeps/x86_64/multiarch/init-arch.c
+++ b/sysdeps/x86_64/multiarch/init-arch.c
@@ -171,9 +171,14 @@ __init_cpu_features (void)
 	  /* Determine if AVX is usable.  */
 	  if (CPUID_AVX)
 	    __cpu_features.feature[index_AVX_Usable] |= bit_AVX_Usable;
-	  /* Determine if AVX2 is usable.  */
+#if index_AVX2_Usable != index_AVX_Fast_Unaligned_Load
+# error index_AVX2_Usable != index_AVX_Fast_Unaligned_Load
+#endif
+	  /* Determine if AVX2 is usable.  Unaligned load with 256-bit
+	     AVX registers are faster on processors with AVX2.  */
 	  if (CPUID_AVX2)
-	    __cpu_features.feature[index_AVX2_Usable] |= bit_AVX2_Usable;
+	    __cpu_features.feature[index_AVX2_Usable]
+	      |= bit_AVX2_Usable | bit_AVX_Fast_Unaligned_Load;
 	  /* Determine if FMA is usable.  */
 	  if (CPUID_FMA)
 	    __cpu_features.feature[index_FMA_Usable] |= bit_FMA_Usable;
diff --git a/sysdeps/x86_64/multiarch/init-arch.h b/sysdeps/x86_64/multiarch/init-arch.h
index 55f1c5b..e6b5ba5 100644
--- a/sysdeps/x86_64/multiarch/init-arch.h
+++ b/sysdeps/x86_64/multiarch/init-arch.h
@@ -25,6 +25,7 @@
 #define bit_FMA4_Usable			(1 << 8)
 #define bit_Slow_SSE4_2			(1 << 9)
 #define bit_AVX2_Usable			(1 << 10)
+#define bit_AVX_Fast_Unaligned_Load	(1 << 11)
 
 /* CPUID Feature flags.  */
 
@@ -74,6 +75,7 @@
 # define index_FMA4_Usable		FEATURE_INDEX_1*FEATURE_SIZE
 # define index_Slow_SSE4_2		FEATURE_INDEX_1*FEATURE_SIZE
 # define index_AVX2_Usable		FEATURE_INDEX_1*FEATURE_SIZE
+# define index_AVX_Fast_Unaligned_Load	FEATURE_INDEX_1*FEATURE_SIZE
 
 #else	/* __ASSEMBLER__ */
 
@@ -169,6 +171,7 @@ extern const struct cpu_features *__get_cpu_features (void)
 # define index_FMA4_Usable		FEATURE_INDEX_1
 # define index_Slow_SSE4_2		FEATURE_INDEX_1
 # define index_AVX2_Usable		FEATURE_INDEX_1
+# define index_AVX_Fast_Unaligned_Load	FEATURE_INDEX_1
 
 # define HAS_ARCH_FEATURE(name) \
   ((__get_cpu_features ()->feature[index_##name] & (bit_##name)) != 0)
@@ -181,5 +184,6 @@ extern const struct cpu_features *__get_cpu_features (void)
 # define HAS_AVX2			HAS_ARCH_FEATURE (AVX2_Usable)
 # define HAS_FMA			HAS_ARCH_FEATURE (FMA_Usable)
 # define HAS_FMA4			HAS_ARCH_FEATURE (FMA4_Usable)
+# define HAS_AVX_FAST_UNALIGNED_LOAD	HAS_ARCH_FEATURE (AVX_Fast_Unaligned_Load)
 
 #endif	/* __ASSEMBLER__ */
diff --git a/sysdeps/x86_64/multiarch/memcpy.S b/sysdeps/x86_64/multiarch/memcpy.S
index 992e40d..4e18cd3 100644
--- a/sysdeps/x86_64/multiarch/memcpy.S
+++ b/sysdeps/x86_64/multiarch/memcpy.S
@@ -33,7 +33,7 @@ ENTRY(__new_memcpy)
 	jne	1f
 	call	__init_cpu_features
 1:	leaq	__memcpy_avx_unaligned(%rip), %rax
-	testl	$bit_AVX_Usable, __cpu_features+FEATURE_OFFSET+index_AVX_Usable(%rip)
+	testl	$bit_AVX_Fast_Unaligned_Load, __cpu_features+FEATURE_OFFSET+index_AVX_Fast_Unaligned_Load(%rip)
 	jz 1f
 	ret
 1:	leaq	__memcpy_sse2(%rip), %rax
diff --git a/sysdeps/x86_64/multiarch/memcpy_chk.S b/sysdeps/x86_64/multiarch/memcpy_chk.S
index 5e9cf00..1e756ea 100644
--- a/sysdeps/x86_64/multiarch/memcpy_chk.S
+++ b/sysdeps/x86_64/multiarch/memcpy_chk.S
@@ -39,7 +39,7 @@ ENTRY(__memcpy_chk)
 	testl	$bit_Fast_Copy_Backward, __cpu_features+FEATURE_OFFSET+index_Fast_Copy_Backward(%rip)
 	jz	2f
 	leaq	__memcpy_chk_ssse3_back(%rip), %rax
-	testl   $bit_AVX_Usable, __cpu_features+FEATURE_OFFSET+index_AVX_Usable(%rip)
+	testl   $bit_AVX_Fast_Unaligned_Load, __cpu_features+FEATURE_OFFSET+index_AVX_Fast_Unaligned_Load(%rip)
 	jz  2f
 	leaq    __memcpy_chk_avx_unaligned(%rip), %rax
 2:	ret
diff --git a/sysdeps/x86_64/multiarch/memmove.c b/sysdeps/x86_64/multiarch/memmove.c
index d93bfd0..dd153a3 100644
--- a/sysdeps/x86_64/multiarch/memmove.c
+++ b/sysdeps/x86_64/multiarch/memmove.c
@@ -49,7 +49,7 @@ extern __typeof (__redirect_memmove) __memmove_avx_unaligned attribute_hidden;
    ifunc symbol properly.  */
 extern __typeof (__redirect_memmove) __libc_memmove;
 libc_ifunc (__libc_memmove,
-	    HAS_AVX
+	    HAS_AVX_FAST_UNALIGNED_LOAD
 	    ? __memmove_avx_unaligned
 	    : (HAS_SSSE3
 	       ? (HAS_FAST_COPY_BACKWARD
diff --git a/sysdeps/x86_64/multiarch/memmove_chk.c b/sysdeps/x86_64/multiarch/memmove_chk.c
index 743ca2a..8b12d00 100644
--- a/sysdeps/x86_64/multiarch/memmove_chk.c
+++ b/sysdeps/x86_64/multiarch/memmove_chk.c
@@ -30,7 +30,7 @@ extern __typeof (__memmove_chk) __memmove_chk_avx_unaligned attribute_hidden;
 #include "debug/memmove_chk.c"
 
 libc_ifunc (__memmove_chk,
-	    HAS_AVX ? __memmove_chk_avx_unaligned :
+	    HAS_AVX_FAST_UNALIGNED_LOAD ? __memmove_chk_avx_unaligned :
 	    (HAS_SSSE3
 	    ? (HAS_FAST_COPY_BACKWARD
 	       ? __memmove_chk_ssse3_back : __memmove_chk_ssse3)
diff --git a/sysdeps/x86_64/multiarch/mempcpy.S b/sysdeps/x86_64/multiarch/mempcpy.S
index cdf1dab..2eaacdf 100644
--- a/sysdeps/x86_64/multiarch/mempcpy.S
+++ b/sysdeps/x86_64/multiarch/mempcpy.S
@@ -37,7 +37,7 @@ ENTRY(__mempcpy)
 	testl	$bit_Fast_Copy_Backward, __cpu_features+FEATURE_OFFSET+index_Fast_Copy_Backward(%rip)
 	jz	2f
 	leaq	__mempcpy_ssse3_back(%rip), %rax
-	testl	$bit_AVX_Usable, __cpu_features+FEATURE_OFFSET+index_AVX_Usable(%rip)
+	testl	$bit_AVX_Fast_Unaligned_Load, __cpu_features+FEATURE_OFFSET+index_AVX_Fast_Unaligned_Load(%rip)
 	jz	2f
 	leaq	__mempcpy_avx_unaligned(%rip), %rax
 2:	ret
diff --git a/sysdeps/x86_64/multiarch/mempcpy_chk.S b/sysdeps/x86_64/multiarch/mempcpy_chk.S
index b7f9e89..17b8470 100644
--- a/sysdeps/x86_64/multiarch/mempcpy_chk.S
+++ b/sysdeps/x86_64/multiarch/mempcpy_chk.S
@@ -39,7 +39,7 @@ ENTRY(__mempcpy_chk)
 	testl	$bit_Fast_Copy_Backward, __cpu_features+FEATURE_OFFSET+index_Fast_Copy_Backward(%rip)
 	jz	2f
 	leaq	__mempcpy_chk_ssse3_back(%rip), %rax
-	testl	$bit_AVX_Usable, __cpu_features+FEATURE_OFFSET+index_AVX_Usable(%rip)
+	testl	$bit_AVX_Fast_Unaligned_Load, __cpu_features+FEATURE_OFFSET+index_AVX_Fast_Unaligned_Load(%rip)
 	jz	2f
 	leaq	__mempcpy_chk_avx_unaligned(%rip), %rax
 2:	ret