[dev.simd] cmd/compile: remove VPADDD4

It is from my sample SIMD compilation, not used in the real thing.
The actual operation is VPADDD128.

Also clean up some of my XXX comments.

Change-Id: Ic20a9dd3c8531e25d88ba045ccef70cb856790d8
Reviewed-on: https://go-review.googlesource.com/c/go/+/698475
Reviewed-by: David Chase <drchase@google.com>
Reviewed-by: Junyang Shao <shaojunyang@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

src/cmd/compile/internal/amd64/ssa.go

@@ -1708,19 +1708,11 @@ func ssaGenValue(s *ssagen.State, v *ssa.Value) {
 		p.To.Type = obj.TYPE_REG
 		p.To.Reg = v.Reg()
 
-	// XXX SIMD
+	// SIMD ops
-	// XXX may change depending on how we handle aliased registers
 	case ssa.OpAMD64VZEROUPPER, ssa.OpAMD64VZEROALL:
 		s.Prog(v.Op.Asm())
 	case ssa.OpAMD64Zero128, ssa.OpAMD64Zero256, ssa.OpAMD64Zero512:
 		// zero-width, no instruction generated
-	case ssa.OpAMD64VPADDD4:
-		p := s.Prog(v.Op.Asm())
-		p.From.Type = obj.TYPE_REG
-		p.From.Reg = simdReg(v.Args[0])
-		p.AddRestSourceReg(simdReg(v.Args[1]))
-		p.To.Type = obj.TYPE_REG
-		p.To.Reg = simdReg(v)
 	case ssa.OpAMD64VMOVDQUload128, ssa.OpAMD64VMOVDQUload256, ssa.OpAMD64VMOVDQUload512, ssa.OpAMD64KMOVQload:
 		p := s.Prog(v.Op.Asm())
 		p.From.Type = obj.TYPE_MEM

src/cmd/compile/internal/ssa/_gen/AMD64.rules

@@ -1639,7 +1639,7 @@
 // If we don't use the flags any more, just use the standard op.
 (Select0 a:(ADD(Q|L)constflags [c] x)) && a.Uses == 1 => (ADD(Q|L)const [c] x)
 
-// XXX SIMD
+// SIMD lowering rules
 
 // Mask loads
 (LoadMask8x16 <t> ptr mem) => (VPMOVMToVec8x16 <types.TypeVec128> (KMOVQload <t> ptr mem))

src/cmd/compile/internal/ssa/_gen/AMD64Ops.go

@@ -1315,9 +1315,7 @@ func init() {
 		// output[i] = (input[i] >> 7) & 1
 		{name: "PMOVMSKB", argLength: 1, reg: fpgp, asm: "PMOVMSKB"},
 
-		// XXX SIMD
+		// SIMD ops
-		{name: "VPADDD4", argLength: 2, reg: fp21, asm: "VPADDD", commutative: true}, // arg0 + arg1
-
 		{name: "VMOVDQUload128", argLength: 2, reg: fpload, asm: "VMOVDQU", aux: "SymOff", faultOnNilArg0: true, symEffect: "Read"},    // load from arg0+auxint+aux, arg1 = mem
 		{name: "VMOVDQUstore128", argLength: 3, reg: fpstore, asm: "VMOVDQU", aux: "SymOff", faultOnNilArg0: true, symEffect: "Write"}, // store, *(arg0+auxint+aux) = arg1, arg2 = mem
 

src/cmd/compile/internal/ssa/opGen.go

@@ -1165,7 +1165,6 @@ const (
 	OpAMD64PSIGNB
 	OpAMD64PCMPEQB
 	OpAMD64PMOVMSKB
-	OpAMD64VPADDD4
 	OpAMD64VMOVDQUload128
 	OpAMD64VMOVDQUstore128
 	OpAMD64VMOVDQUload256
@@ -18179,21 +18178,6 @@ var opcodeTable = [...]opInfo{
 			},
 		},
 	},
-	{
-		name:        "VPADDD4",
-		argLen:      2,
-		commutative: true,
-		asm:         x86.AVPADDD,
-		reg: regInfo{
-			inputs: []inputInfo{
-				{0, 2147418112}, // X0 X1 X2 X3 X4 X5 X6 X7 X8 X9 X10 X11 X12 X13 X14
-				{1, 2147418112}, // X0 X1 X2 X3 X4 X5 X6 X7 X8 X9 X10 X11 X12 X13 X14
-			},
-			outputs: []outputInfo{
-				{0, 2147418112}, // X0 X1 X2 X3 X4 X5 X6 X7 X8 X9 X10 X11 X12 X13 X14
-			},
-		},
-	},
 	{
 		name:           "VMOVDQUload128",
 		auxType:        auxSymOff,