summaryrefslogtreecommitdiff
path: root/tools/arch/x86/lib/memcpy_64.S
diff options
context:
space:
mode:
Diffstat (limited to 'tools/arch/x86/lib/memcpy_64.S')
-rw-r--r--tools/arch/x86/lib/memcpy_64.S34
1 files changed, 10 insertions, 24 deletions
diff --git a/tools/arch/x86/lib/memcpy_64.S b/tools/arch/x86/lib/memcpy_64.S
index a91ac666f758..d055b82d22cc 100644
--- a/tools/arch/x86/lib/memcpy_64.S
+++ b/tools/arch/x86/lib/memcpy_64.S
@@ -10,13 +10,6 @@
.section .noinstr.text, "ax"
/*
- * We build a jump to memcpy_orig by default which gets NOPped out on
- * the majority of x86 CPUs which set REP_GOOD. In addition, CPUs which
- * have the enhanced REP MOVSB/STOSB feature (ERMS), change those NOPs
- * to a jmp to memcpy_erms which does the REP; MOVSB mem copy.
- */
-
-/*
* memcpy - Copy a memory block.
*
* Input:
@@ -26,17 +19,21 @@
*
* Output:
* rax original destination
+ *
+ * The FSRM alternative should be done inline (avoiding the call and
+ * the disgusting return handling), but that would require some help
+ * from the compiler for better calling conventions.
+ *
+ * The 'rep movsb' itself is small enough to replace the call, but the
+ * two register moves blow up the code. And one of them is "needed"
+ * only for the return value that is the same as the source input,
+ * which the compiler could/should do much better anyway.
*/
SYM_TYPED_FUNC_START(__memcpy)
- ALTERNATIVE_2 "jmp memcpy_orig", "", X86_FEATURE_REP_GOOD, \
- "jmp memcpy_erms", X86_FEATURE_ERMS
+ ALTERNATIVE "jmp memcpy_orig", "", X86_FEATURE_FSRM
movq %rdi, %rax
movq %rdx, %rcx
- shrq $3, %rcx
- andl $7, %edx
- rep movsq
- movl %edx, %ecx
rep movsb
RET
SYM_FUNC_END(__memcpy)
@@ -45,17 +42,6 @@ EXPORT_SYMBOL(__memcpy)
SYM_FUNC_ALIAS(memcpy, __memcpy)
EXPORT_SYMBOL(memcpy)
-/*
- * memcpy_erms() - enhanced fast string memcpy. This is faster and
- * simpler than memcpy. Use memcpy_erms when possible.
- */
-SYM_FUNC_START_LOCAL(memcpy_erms)
- movq %rdi, %rax
- movq %rdx, %rcx
- rep movsb
- RET
-SYM_FUNC_END(memcpy_erms)
-
SYM_FUNC_START_LOCAL(memcpy_orig)
movq %rdi, %rax