x86-64: Skip zero length in __mem[pcpy|move|set]_erms

Message ID 20180523172853.GA1327@gmail.com
State New
Headers show
Series
  • x86-64: Skip zero length in __mem[pcpy|move|set]_erms
Related show

Commit Message

H.J. Lu May 23, 2018, 5:28 p.m.
This patch skips zero length in __mempcpy_erms, __memmove_erms and
__memset_erms.

Tested on x86-64.  I will check it in shortly.


H.J.
---
	* sysdeps/x86_64/multiarch/memmove-vec-unaligned-erms.S
	(__mempcpy_erms): Skip zero length.
	(__memmove_erms): Likewise.
	* sysdeps/x86_64/multiarch/memset-vec-unaligned-erms.S
	(__memset_erms): Likewise.
---
 sysdeps/x86_64/multiarch/memmove-vec-unaligned-erms.S | 6 ++++++
 sysdeps/x86_64/multiarch/memset-vec-unaligned-erms.S  | 5 +++++
 2 files changed, 11 insertions(+)

-- 
2.17.0

Patch

diff --git a/sysdeps/x86_64/multiarch/memmove-vec-unaligned-erms.S b/sysdeps/x86_64/multiarch/memmove-vec-unaligned-erms.S
index 1404131bb7..e2ede45e9f 100644
--- a/sysdeps/x86_64/multiarch/memmove-vec-unaligned-erms.S
+++ b/sysdeps/x86_64/multiarch/memmove-vec-unaligned-erms.S
@@ -156,6 +156,9 @@  END (__mempcpy_chk_erms)
 /* Only used to measure performance of REP MOVSB.  */
 ENTRY (__mempcpy_erms)
 	movq	%rdi, %rax
+	/* Skip zero length.  */
+	testq	%rdx, %rdx
+	jz	2f
 	addq	%rdx, %rax
 	jmp	L(start_movsb)
 END (__mempcpy_erms)
@@ -167,6 +170,9 @@  END (__memmove_chk_erms)
 
 ENTRY (__memmove_erms)
 	movq	%rdi, %rax
+	/* Skip zero length.  */
+	testq	%rdx, %rdx
+	jz	2f
 L(start_movsb):
 	movq	%rdx, %rcx
 	cmpq	%rsi, %rdi
diff --git a/sysdeps/x86_64/multiarch/memset-vec-unaligned-erms.S b/sysdeps/x86_64/multiarch/memset-vec-unaligned-erms.S
index 0a827f3e47..dc9cb88b37 100644
--- a/sysdeps/x86_64/multiarch/memset-vec-unaligned-erms.S
+++ b/sysdeps/x86_64/multiarch/memset-vec-unaligned-erms.S
@@ -128,6 +128,11 @@  END (__memset_chk_erms)
 
 /* Only used to measure performance of REP STOSB.  */
 ENTRY (__memset_erms)
+	/* Skip zero length.  */
+	testq	%rdx, %rdx
+	jnz	 L(stosb)
+	movq	%rdi, %rax
+	ret
 # else
 /* Provide a hidden symbol to debugger.  */
 	.hidden	MEMSET_SYMBOL (__memset, erms)