arm64/instgen: make addr the last op in SVE stores

This CL generates CL 772520.

Change-Id: Ieff3ed502325d5bf20adf5ffc0f2cc915ead8506
Reviewed-on: https://go-review.googlesource.com/c/arch/+/772500
Auto-Submit: Junyang Shao <shaojunyang@google.com>
LUCI-TryBot-Result: golang-scoped@luci-project-accounts.iam.gserviceaccount.com <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: David Chase <drchase@google.com>

arm64/instgen/generator.go

diff --git a/arm64/instgen/generator.go b/arm64/instgen/generator.go
index 98d223f..1950d87 100644
--- a/arm64/instgen/generator.go
+++ b/arm64/instgen/generator.go
@@ -1525,6 +1525,12 @@
 			}
 		}
 		// Try to assemble the GNU version.
+		// Stores are not reversed in Go, so we reverse them back.
+		if strings.HasPrefix(name, "ST") {
+			for i, j := 0, len(gnuAsmOps)-1; i < j; i, j = i+1, j-1 {
+				gnuAsmOps[i], gnuAsmOps[j] = gnuAsmOps[j], gnuAsmOps[i]
+			}
+		}
 		gnuAsm := fmt.Sprintf(".arch_extension sve2p1\n%s %s", name, strings.Join(gnuAsmOps, ", "))
 		hex, err := assembleGNU(gnuAsm)
 		goAsmStr := fmt.Sprintf("%s %s", enc.GoOp[1:], strings.Join(goAsmOps, ", "))

arm64/instgen/xmlspec/parser.go

diff --git a/arm64/instgen/xmlspec/parser.go b/arm64/instgen/xmlspec/parser.go
index a285698..5258413 100644
--- a/arm64/instgen/xmlspec/parser.go
+++ b/arm64/instgen/xmlspec/parser.go
@@ -751,6 +751,11 @@
 
 // sortOperands reorders the operands of an encoding according to Go assembly syntax.
 func (enc *EncodingParsed) sortOperands() {
+	// For stores, we need to make sure the memory is the destination.
+	// The original order fits just naturally, so no-op.
+	if strings.HasPrefix(enc.Operands[0].Name, "ST") {
+		return
+	}
 	// Reverse args, placing dest last.
 	for i, j := 1, len(enc.Operands)-1; i < j; i, j = i+1, j-1 {
 		enc.Operands[i], enc.Operands[j] = enc.Operands[j], enc.Operands[i]