[dev.ssa] cmd/compile/internal/ssa/gen: move variable reset code into a function

Shaves about 3 lines per generated rule.

Change-Id: I94adc94ab79f90ac5fd033f896ece3b1eddf0f3d
Reviewed-on: https://go-review.googlesource.com/19197
Reviewed-by: Keith Randall <khr@golang.org>

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

@@ -122,10 +122,7 @@ func decomposeStringPhi(v *Value) {
 		ptr.AddArg(a.Block.NewValue1(v.Line, OpStringPtr, ptrType, a))
 		len.AddArg(a.Block.NewValue1(v.Line, OpStringLen, lenType, a))
 	}
-	v.Op = OpStringMake
-	v.AuxInt = 0
-	v.Aux = nil
-	v.resetArgs()
+	v.reset(OpStringMake)
 	v.AddArg(ptr)
 	v.AddArg(len)
 }
@@ -143,10 +140,7 @@ func decomposeSlicePhi(v *Value) {
 		len.AddArg(a.Block.NewValue1(v.Line, OpSliceLen, lenType, a))
 		cap.AddArg(a.Block.NewValue1(v.Line, OpSliceCap, lenType, a))
 	}
-	v.Op = OpSliceMake
-	v.AuxInt = 0
-	v.Aux = nil
-	v.resetArgs()
+	v.reset(OpSliceMake)
 	v.AddArg(ptr)
 	v.AddArg(len)
 	v.AddArg(cap)
@@ -170,10 +164,7 @@ func decomposeComplexPhi(v *Value) {
 		real.AddArg(a.Block.NewValue1(v.Line, OpComplexReal, partType, a))
 		imag.AddArg(a.Block.NewValue1(v.Line, OpComplexImag, partType, a))
 	}
-	v.Op = OpComplexMake
-	v.AuxInt = 0
-	v.Aux = nil
-	v.resetArgs()
+	v.reset(OpComplexMake)
 	v.AddArg(real)
 	v.AddArg(imag)
 }
@@ -187,10 +178,7 @@ func decomposeInterfacePhi(v *Value) {
 		itab.AddArg(a.Block.NewValue1(v.Line, OpITab, ptrType, a))
 		data.AddArg(a.Block.NewValue1(v.Line, OpIData, ptrType, a))
 	}
-	v.Op = OpIMake
-	v.AuxInt = 0
-	v.Aux = nil
-	v.resetArgs()
+	v.reset(OpIMake)
 	v.AddArg(itab)
 	v.AddArg(data)
 }
@@ -206,10 +194,7 @@ func decomposeStructPhi(v *Value) {
 			fields[i].AddArg(a.Block.NewValue1I(v.Line, OpStructSelect, t.FieldType(i), i, a))
 		}
 	}
-	v.Op = StructMakeOp(n)
-	v.AuxInt = 0
-	v.Aux = nil
-	v.resetArgs()
+	v.reset(StructMakeOp(n))
 	v.AddArgs(fields[:n]...)
 
 	// Recursively decompose phis for each field.

src/cmd/compile/internal/ssa/gen/rulegen.go

@@ -435,10 +435,7 @@ func genResult0(w io.Writer, arch arch, result string, alloc *int, top bool, loc
 			// It in not safe in general to move a variable between blocks
 			// (and particularly not a phi node).
 			// Introduce a copy.
-			fmt.Fprintf(w, "v.Op = OpCopy\n")
-			fmt.Fprintf(w, "v.AuxInt = 0\n")
-			fmt.Fprintf(w, "v.Aux = nil\n")
-			fmt.Fprintf(w, "v.resetArgs()\n")
+			fmt.Fprintf(w, "v.reset(OpCopy)\n")
 			fmt.Fprintf(w, "v.Type = %s.Type\n", result)
 			fmt.Fprintf(w, "v.AddArg(%s)\n", result)
 		}
@@ -478,13 +475,10 @@ func genResult0(w io.Writer, arch arch, result string, alloc *int, top bool, loc
 	var v string
 	if top && loc == "b" {
 		v = "v"
+		fmt.Fprintf(w, "v.reset(%s)\n", opName(s[0], arch))
 		if typeOverride {
 			fmt.Fprintf(w, "v.Type = %s\n", opType)
 		}
-		fmt.Fprintf(w, "v.Op = %s\n", opName(s[0], arch))
-		fmt.Fprintf(w, "v.AuxInt = 0\n")
-		fmt.Fprintf(w, "v.Aux = nil\n")
-		fmt.Fprintf(w, "v.resetArgs()\n")
 	} else {
 		if opType == "" {
 			log.Fatalf("sub-expression %s (op=%s) must have a type", result, s[0])
@@ -494,10 +488,7 @@ func genResult0(w io.Writer, arch arch, result string, alloc *int, top bool, loc
 		fmt.Fprintf(w, "%s := %s.NewValue0(v.Line, %s, %s)\n", v, loc, opName(s[0], arch), opType)
 		if top {
 			// Rewrite original into a copy
-			fmt.Fprintf(w, "v.Op = OpCopy\n")
-			fmt.Fprintf(w, "v.AuxInt = 0\n")
-			fmt.Fprintf(w, "v.Aux = nil\n")
-			fmt.Fprintf(w, "v.resetArgs()\n")
+			fmt.Fprintf(w, "v.reset(OpCopy)\n")
 			fmt.Fprintf(w, "v.AddArg(%s)\n", v)
 		}
 	}

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

@@ -170,6 +170,13 @@ func (v *Value) resetArgs() {
 	v.Args = v.argstorage[:0]
 }
 
+func (v *Value) reset(op Op) {
+	v.Op = op
+	v.resetArgs()
+	v.AuxInt = 0
+	v.Aux = nil
+}
+
 // copyInto makes a new value identical to v and adds it to the end of b.
 func (v *Value) copyInto(b *Block) *Value {
 	c := b.NewValue0(v.Line, v.Op, v.Type)