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authorWill Newton <will.newton@linaro.org>2013-08-07 14:15:52 +0100
committerWill Newton <will.newton@linaro.org>2013-09-16 17:55:28 +0100
commitcd90698b541046c22544c2c057a4676368fd1d7f (patch)
tree152f00ad520b5c8e106f821044f3b589da2a7872
parentf06dd27b0c61ea8905103c9391f0900fa896bd74 (diff)
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ARM: Improve armv7 memcpy performance.
Only enter the aligned copy loop with buffers that can be 8-byte
aligned. This improves performance slightly on Cortex-A9 and
Cortex-A15 cores for large copies with buffers that are 4-byte
aligned but not 8-byte aligned.

ports/ChangeLog.arm:

2013-09-16  Will Newton  <will.newton@linaro.org>

	* sysdeps/arm/armv7/multiarch/memcpy_impl.S: Tighten check
	on entry to aligned copy loop to improve performance.
-rw-r--r--ports/ChangeLog.arm5
-rw-r--r--ports/sysdeps/arm/armv7/multiarch/memcpy_impl.S11
2 files changed, 10 insertions, 6 deletions
diff --git a/ports/ChangeLog.arm b/ports/ChangeLog.arm
index 8ef09b1161..35f6f7765c 100644
--- a/ports/ChangeLog.arm
+++ b/ports/ChangeLog.arm
@@ -1,3 +1,8 @@
+2013-09-16  Will Newton  <will.newton@linaro.org>
+
+	* sysdeps/arm/armv7/multiarch/memcpy_impl.S: Tighten check
+	on entry to aligned copy loop to improve performance.
+
 2013-08-30  Roland McGrath  <roland@hack.frob.com>
 
 	* sysdeps/arm/armv6t2/strlen.S: Use sfi_pld and sfi_breg macros.
diff --git a/ports/sysdeps/arm/armv7/multiarch/memcpy_impl.S b/ports/sysdeps/arm/armv7/multiarch/memcpy_impl.S
index 3decad60bc..ad43a3db5a 100644
--- a/ports/sysdeps/arm/armv7/multiarch/memcpy_impl.S
+++ b/ports/sysdeps/arm/armv7/multiarch/memcpy_impl.S
@@ -24,7 +24,6 @@
     ARMv6 (ARMv7-a if using Neon)
     ARM state
     Unaligned accesses
-    LDRD/STRD support unaligned word accesses
 
  */
 
@@ -369,8 +368,8 @@ ENTRY(memcpy)
 	cfi_adjust_cfa_offset (FRAME_SIZE)
 	cfi_rel_offset (tmp2, 0)
 	cfi_remember_state
-	and	tmp2, src, #3
-	and	tmp1, dst, #3
+	and	tmp2, src, #7
+	and	tmp1, dst, #7
 	cmp	tmp1, tmp2
 	bne	.Lcpy_notaligned
 
@@ -381,9 +380,9 @@ ENTRY(memcpy)
 	vmov.f32	s0, s0
 #endif
 
-	/* SRC and DST have the same mutual 32-bit alignment, but we may
+	/* SRC and DST have the same mutual 64-bit alignment, but we may
 	   still need to pre-copy some bytes to get to natural alignment.
-	   We bring DST into full 64-bit alignment.  */
+	   We bring SRC and DST into full 64-bit alignment.  */
 	lsls	tmp2, dst, #29
 	beq	1f
 	rsbs	tmp2, tmp2, #0
@@ -515,7 +514,7 @@ ENTRY(memcpy)
 
 .Ltail63aligned:			/* Count in tmp2.  */
 	/* Copy up to 7 d-words of data.  Similar to Ltail63unaligned, but
-	   we know that the src and dest are 32-bit aligned so we can use
+	   we know that the src and dest are 64-bit aligned so we can use
 	   LDRD/STRD to improve efficiency.  */
 	/* TMP2 is now negative, but we don't care about that.  The bottom
 	   six bits still tell us how many bytes are left to copy.  */