8305690: [X86] Do not emit two REX prefixes in Assembler::prefix

lgxbslgx · DamonFool · commit 6a8497437ad1 · 2023-05-09T07:33:34.000Z
Backport-of: 49726ee3a95023a912aacad0e3714eae146eed21
diff --git a/src/hotspot/cpu/x86/assembler_x86.cpp b/src/hotspot/cpu/x86/assembler_x86.cpp
@@ -9683,7 +9683,7 @@ void Assembler::prefix(Register dst, Address adr, Prefix p) {
     if (adr.index_needs_rex()) {
       assert(false, "prefix(Register dst, Address adr, Prefix p) does not support handling of an X");
     } else {
-      prefix(REX_B);
+      p = (Prefix)(p | REX_B);
     }
   } else {
     if (adr.index_needs_rex()) {

Original file line number	Diff line number	Diff line change
`@@ -9683,7 +9683,7 @@ void Assembler::prefix(Register dst, Address adr, Prefix p) {`
`9683`	`9683`	`if (adr.index_needs_rex()) {`
`9684`	`9684`	`assert(false, "prefix(Register dst, Address adr, Prefix p) does not support handling of an X");`
`9685`	`9685`	`} else {`
`9686`		`- prefix(REX_B);`
	`9686`	`+ p = (Prefix)(p \| REX_B);`
`9687`	`9687`	`}`
`9688`	`9688`	`} else {`
`9689`	`9689`	`if (adr.index_needs_rex()) {`