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diff src/cpu/x86/vm/assembler_x86.cpp @ 7474:00af3a3a8df4

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8005522: use fast-string instructions on x86 for zeroing Summary: use 'rep stosb' instead of 'rep stosq' when fast-string operations are available. Reviewed-by: twisti, roland
author kvn
date Thu, 03 Jan 2013 15:09:55 -0800
parents d02120b7a34f
children e2e6bf86682c
line wrap: on
line diff
--- a/src/cpu/x86/vm/assembler_x86.cpp	Sun Dec 23 17:08:22 2012 +0100
+++ b/src/cpu/x86/vm/assembler_x86.cpp	Thu Jan 03 15:09:55 2013 -0800
@@ -2544,12 +2544,18 @@
   emit_int8((unsigned char)0xA5);
 }
 
+// sets rcx bytes with rax, value at [edi]
+void Assembler::rep_stosb() {
+  emit_int8((unsigned char)0xF3); // REP
+  LP64_ONLY(prefix(REX_W));
+  emit_int8((unsigned char)0xAA); // STOSB
+}
+
 // sets rcx pointer sized words with rax, value at [edi]
 // generic
-void Assembler::rep_set() { // rep_set
-  emit_int8((unsigned char)0xF3);
-  // STOSQ
-  LP64_ONLY(prefix(REX_W));
+void Assembler::rep_stos() {
+  emit_int8((unsigned char)0xF3); // REP
+  LP64_ONLY(prefix(REX_W));       // LP64:STOSQ, LP32:STOSD
   emit_int8((unsigned char)0xAB);
 }