go.tools/ssa: avoid redundant uint64 conversion of right operand of <<, >>.

Also: add sanity check that no Instruction yields a Value of 'untyped' type.

R=golang-dev, gri
CC=golang-dev
https://golang.org/cl/11011043

ssa/emit.go

@@ -38,7 +38,6 @@ func emitArith(f *Function, op token.Token, x, y Value, t types.Type, pos token.
 	switch op {
 	case token.SHL, token.SHR:
 		x = emitConv(f, x, t)
-		y = emitConv(f, y, types.Typ[types.Uint64])
 
 	case token.ADD, token.SUB, token.MUL, token.QUO, token.REM, token.AND, token.OR, token.XOR, token.AND_NOT:
 		x = emitConv(f, x, t)

ssa/interp/ops.go

@@ -130,26 +130,6 @@ func asInt(x value) int {
 	panic(fmt.Sprintf("cannot convert %T to int", x))
 }
 
-// asUint64 converts x, which must be an unsigned integer, to a uint64
-// suitable for use as a bitwise shift count.
-func asUint64(x value) uint64 {
-	switch x := x.(type) {
-	case uint:
-		return uint64(x)
-	case uint8:
-		return uint64(x)
-	case uint16:
-		return uint64(x)
-	case uint32:
-		return uint64(x)
-	case uint64:
-		return x
-	case uintptr:
-		return uint64(x)
-	}
-	panic(fmt.Sprintf("cannot convert %T to uint64", x))
-}
-
 // zero returns a new "zero" value of the specified type.
 func zero(t types.Type) value {
 	switch t := t.(type) {
@@ -563,7 +543,7 @@ func binop(op token.Token, x, y value) value {
 		}
 
 	case token.SHL:
-		y := asUint64(y)
+		y := uint64(asInt(y))
 		switch x.(type) {
 		case int:
 			return x.(int) << y
@@ -590,7 +570,7 @@ func binop(op token.Token, x, y value) value {
 		}
 
 	case token.SHR:
-		y := asUint64(y)
+		y := uint64(asInt(y))
 		switch x.(type) {
 		case int:
 			return x.(int) >> y

ssa/interp/testdata/coverage.go

@@ -270,6 +270,16 @@ func main() {
 	}
 }
 
+type mybool bool
+
+func (mybool) f() {}
+
+func init() {
+	var x, y int
+	var b mybool = x == y // x==y is an untyped bool
+	b.f()
+}
+
 // Simple closures.
 func init() {
 	b := 3

ssa/sanity.go

@@ -160,11 +160,23 @@ func (s *sanity) checkInstr(idx int, instr Instruction) {
 		panic(fmt.Sprintf("Unknown instruction type: %T", instr))
 	}
 
+	// Check that value-defining instructions have valid types.
 	if v, ok := instr.(Value); ok {
-		if v.Type() == nil {
+		t := v.Type()
+		if t == nil {
 			s.errorf("no type: %s = %s", v.Name(), v)
+		} else if t == tRangeIter {
+			// not a proper type; ignore.
+		} else if b, ok := t.Underlying().(*types.Basic); ok && b.Info()&types.IsUntyped != 0 {
+			s.errorf("instruction has 'untyped' result: %s = %s : %s", v.Name(), v, t)
 		}
 	}
+
+	// TODO(adonovan): sanity-check Literals used as instruction Operands(),
+	// e.g. reject Literals with "untyped" types.
+	//
+	// All other non-Instruction Values can be found via their
+	// enclosing Function or Package.
 }
 
 func (s *sanity) checkFinalInstr(idx int, instr Instruction) {