cmd/internal/obj/arm64: fix return with register

ARM64 allows for a register to be specified with a return instruction. While the assembler parsing and encoding currently supports this, the preprocess function uses LR unconditionally. Correct this such that if a register is specified, the register is used. Change-Id: I708f6c7e910d141559b60d2d5ee76ae2e1dc3a0e Reviewed-on: https://go-review.googlesource.com/c/go/+/592796 Reviewed-by: Cherry Mui <[email protected]> Reviewed-by: David Chase <[email protected]> LUCI-TryBot-Result: Go LUCI <[email protected]>
golang · Jun 25, 2024 · b1fd047 · b1fd047
1 parent b3b4556
commit b1fd047
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Showing 2 changed files with 12 additions and 6 deletions.
diff --git a/src/cmd/asm/internal/asm/testdata/arm64.s b/src/cmd/asm/internal/asm/testdata/arm64.s
@@ -961,7 +961,11 @@ again:
 	CASPD	(R2, R3), (R2), (R8, R9)             // 487c2248
 
 // RET
-	RET
+	RET                                        // c0035fd6
+	RET R0					   // 00005fd6
+	RET R6					   // c0005fd6
+	RET R27					   // 60035fd6
+	RET R30					   // c0035fd6
 	RET	foo(SB)
 
 // B/BL/B.cond cases, and canonical names JMP, CALL.

diff --git a/src/cmd/internal/obj/arm64/obj7.go b/src/cmd/internal/obj/arm64/obj7.go
@@ -552,7 +552,6 @@ func preprocess(ctxt *obj.Link, cursym *obj.LSym, newprog obj.ProgAlloc) {
 
 	var q *obj.Prog
 	var q1 *obj.Prog
-	var retjmp *obj.LSym
 	for p := c.cursym.Func().Text; p != nil; p = p.Link {
 		o := p.As
 		switch o {
@@ -846,7 +845,10 @@ func preprocess(ctxt *obj.Link, cursym *obj.LSym, newprog obj.ProgAlloc) {
 				break
 			}
 
-			retjmp = p.To.Sym
+			retJMP, retReg := p.To.Sym, p.To.Reg
+			if retReg == 0 {
+				retReg = REGLINK
+			}
 			p.To = obj.Addr{}
 			if c.cursym.Func().Text.Mark&LEAF != 0 {
 				if c.autosize != 0 {
@@ -924,18 +926,18 @@ func preprocess(ctxt *obj.Link, cursym *obj.LSym, newprog obj.ProgAlloc) {
 				p = q
 			}
 
-			if retjmp != nil { // retjmp
+			if retJMP != nil {
 				p.As = AB
 				p.To.Type = obj.TYPE_BRANCH
-				p.To.Sym = retjmp
+				p.To.Sym = retJMP
 				p.Spadj = +c.autosize
 				break
 			}
 
 			p.As = obj.ARET
 			p.To.Type = obj.TYPE_MEM
 			p.To.Offset = 0
-			p.To.Reg = REGLINK
+			p.To.Reg = retReg
 			p.Spadj = +c.autosize
 
 		case AADD, ASUB: