[dev.simd] simd/_gen: fix sorting ops slices

Fix sorting slices to avoid panic when there are more opsDataImm than
opsData (the problem occurs when generating only a subset of instructions
but it may be better to keep them sorted by their own names anyway).

Change-Id: Iea7fe61259e8416f16c46158d87c84b1d7a3076d
Reviewed-on: https://go-review.googlesource.com/c/go/+/716121
Reviewed-by: Junyang Shao <shaojunyang@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Auto-Submit: Junyang Shao <shaojunyang@google.com>

src/simd/_gen/simdgen/gen_simdMachineOps.go

@@ -185,13 +185,13 @@ func writeSIMDMachineOps(ops []Operation) *bytes.Buffer {
 		return compareNatural(opsData[i].OpName, opsData[j].OpName) < 0
 	})
 	sort.Slice(opsDataImm, func(i, j int) bool {
-		return compareNatural(opsData[i].OpName, opsData[j].OpName) < 0
+		return compareNatural(opsDataImm[i].OpName, opsDataImm[j].OpName) < 0
 	})
 	sort.Slice(opsDataLoad, func(i, j int) bool {
-		return compareNatural(opsData[i].OpName, opsData[j].OpName) < 0
+		return compareNatural(opsDataLoad[i].OpName, opsDataLoad[j].OpName) < 0
 	})
 	sort.Slice(opsDataImmLoad, func(i, j int) bool {
-		return compareNatural(opsData[i].OpName, opsData[j].OpName) < 0
+		return compareNatural(opsDataImmLoad[i].OpName, opsDataImmLoad[j].OpName) < 0
 	})
 	err := t.Execute(buffer, machineOpsData{opsData, opsDataImm, opsDataLoad, opsDataImmLoad})
 	if err != nil {