cmd/internal/obj/arm64: add assembler support for load with register offset

The patch adds support for LDR(register offset) instruction.
And add the test cases and negative tests.

Change-Id: I5b32c6a5065afc4571116d4896f7ebec3c0416d3
Reviewed-on: https://go-review.googlesource.com/87955
Reviewed-by: Cherry Zhang <cherryyz@google.com>

1 files changed, 17 insertions, 2 deletions

diff --git a/src/cmd/internal/obj/util.go b/src/cmd/internal/obj/util.go
index 3fc6113112..2d457fd503 100644
--- a/src/cmd/internal/obj/util.go
+++ b/src/cmd/internal/obj/util.go
@@ -214,7 +214,12 @@ func Dconv(p *Prog, a *Addr) string {
 	case TYPE_MEM:
 		str = Mconv(a)
 		if a.Index != REG_NONE {
-			str += fmt.Sprintf("(%v*%d)", Rconv(int(a.Index)), int(a.Scale))
+			if a.Scale == 0 {
+				// arm64 shifted or extended register offset, scale = 0.
+				str += fmt.Sprintf("(%v)", Rconv(int(a.Index)))
+			} else {
+				str += fmt.Sprintf("(%v*%d)", Rconv(int(a.Index)), int(a.Scale))
+			}
 		}
 
 	case TYPE_CONST:
@@ -294,7 +299,17 @@ func Mconv(a *Addr) string {
 		case a.Offset == 0:
 			str = fmt.Sprintf("(%v)", Rconv(int(a.Reg)))
 		case a.Offset != 0:
-			str = fmt.Sprintf("%d(%v)", a.Offset, Rconv(int(a.Reg)))
+			switch objabi.GOARCH {
+			case "arm64":
+				// the register and the extension/shift are encoded in a.Offset.
+				if a.Index != 0 {
+					str = fmt.Sprintf("(%v)", Rconv(int(a.Reg)))
+					return str
+				}
+				fallthrough
+			default:
+				str = fmt.Sprintf("%d(%v)", a.Offset, Rconv(int(a.Reg)))
+			}
 		}
 
 		// Note: a.Reg == REG_NONE encodes the default base register for the NAME_ type.