Merge branch 'master' into net-url-testparseerrors-fix-again

src/cmd/compile/internal/gc/const.go

@@ -6,6 +6,8 @@ package gc
 
 import (
 	"cmd/compile/internal/types"
+	"cmd/internal/src"
+	"fmt"
 	"math/big"
 	"strings"
 )
@@ -1397,28 +1399,30 @@ func hascallchan(n *Node) bool {
 
 // A constSet represents a set of Go constant expressions.
 type constSet struct {
-	m map[constSetKey]*Node
+	m map[constSetKey]src.XPos
 }
 
 type constSetKey struct {
 	typ *types.Type
 	val interface{}
 }
 
-// add adds constant expressions to s. If a constant expression of
-// equal value and identical type has already been added, then that
-// type expression is returned. Otherwise, add returns nil.
+// add adds constant expression n to s. If a constant expression of
+// equal value and identical type has already been added, then add
+// reports an error about the duplicate value.
 //
-// add also returns nil if n is not a Go constant expression.
+// pos provides position information for where expression n occured
+// (in case n does not have its own position information). what and
+// where are used in the error message.
 //
 // n must not be an untyped constant.
-func (s *constSet) add(n *Node) *Node {
+func (s *constSet) add(pos src.XPos, n *Node, what, where string) {
 	if n.Op == OCONVIFACE && n.Implicit() {
 		n = n.Left
 	}
 
 	if !n.isGoConst() {
-		return nil
+		return
 	}
 	if n.Type.IsUntyped() {
 		Fatalf("%v is untyped", n)
@@ -1448,12 +1452,32 @@ func (s *constSet) add(n *Node) *Node {
 	}
 	k := constSetKey{typ, n.Val().Interface()}
 
+	if hasUniquePos(n) {
+		pos = n.Pos
+	}
+
 	if s.m == nil {
-		s.m = make(map[constSetKey]*Node)
+		s.m = make(map[constSetKey]src.XPos)
 	}
-	old, dup := s.m[k]
-	if !dup {
-		s.m[k] = n
+
+	if prevPos, isDup := s.m[k]; isDup {
+		yyerrorl(pos, "duplicate %s %s in %s\n\tprevious %s at %v",
+			what, nodeAndVal(n), where,
+			what, linestr(prevPos))
+	} else {
+		s.m[k] = pos
 	}
-	return old
+}
+
+// nodeAndVal reports both an expression and its constant value, if
+// the latter is non-obvious.
+//
+// TODO(mdempsky): This could probably be a fmt.go flag.
+func nodeAndVal(n *Node) string {
+	show := n.String()
+	val := n.Val().Interface()
+	if s := fmt.Sprintf("%#v", val); show != s {
+		show += " (value " + s + ")"
+	}
+	return show
 }

src/cmd/compile/internal/gc/subr.go

@@ -194,30 +194,37 @@ func Fatalf(fmt_ string, args ...interface{}) {
 	errorexit()
 }
 
-func setlineno(n *Node) src.XPos {
-	lno := lineno
-	if n != nil {
-		switch n.Op {
-		case ONAME, OPACK:
-			break
-
-		case OLITERAL, OTYPE:
-			if n.Sym != nil {
-				break
-			}
-			fallthrough
+// hasUniquePos reports whether n has a unique position that can be
+// used for reporting error messages.
+//
+// It's primarily used to distinguish references to named objects,
+// whose Pos will point back to their declaration position rather than
+// their usage position.
+func hasUniquePos(n *Node) bool {
+	switch n.Op {
+	case ONAME, OPACK:
+		return false
+	case OLITERAL, OTYPE:
+		if n.Sym != nil {
+			return false
+		}
+	}
 
-		default:
-			lineno = n.Pos
-			if !lineno.IsKnown() {
-				if Debug['K'] != 0 {
-					Warn("setlineno: unknown position (line 0)")
-				}
-				lineno = lno
-			}
+	if !n.Pos.IsKnown() {
+		if Debug['K'] != 0 {
+			Warn("setlineno: unknown position (line 0)")
 		}
+		return false
 	}
 
+	return true
+}
+
+func setlineno(n *Node) src.XPos {
+	lno := lineno
+	if n != nil && hasUniquePos(n) {
+		lineno = n.Pos
+	}
 	return lno
 }
 

src/cmd/compile/internal/gc/swt.go

@@ -6,7 +6,6 @@ package gc
 
 import (
 	"cmd/compile/internal/types"
-	"fmt"
 	"sort"
 )
 
@@ -641,23 +640,11 @@ func checkDupExprCases(exprname *Node, clauses []*Node) {
 				continue
 			}
 
-			if prev := cs.add(n); prev != nil {
-				yyerrorl(ncase.Pos, "duplicate case %s in switch\n\tprevious case at %v",
-					nodeAndVal(n), prev.Line())
-			}
+			cs.add(ncase.Pos, n, "case", "switch")
 		}
 	}
 }
 
-func nodeAndVal(n *Node) string {
-	show := n.String()
-	val := n.Val().Interface()
-	if s := fmt.Sprintf("%#v", val); show != s {
-		show += " (value " + s + ")"
-	}
-	return show
-}
-
 // walk generates an AST that implements sw,
 // where sw is a type switch.
 // The AST is generally of the form of a linear

src/cmd/compile/internal/gc/typecheck.go

@@ -2911,9 +2911,7 @@ func typecheckcomplit(n *Node) (res *Node) {
 			r = typecheck(r, ctxExpr)
 			r = defaultlit(r, t.Key())
 			l.Left = assignconv(r, t.Key(), "map key")
-			if cs.add(l.Left) != nil {
-				yyerror("duplicate key %v in map literal", l.Left)
-			}
+			cs.add(lineno, l.Left, "key", "map literal")
 
 			r = l.Right
 			pushtype(r, t.Elem())

src/cmd/compile/internal/ssa/gen/generic.rules

@@ -1733,6 +1733,12 @@
 (Eq(8|16|32|64)  s:(Sub(8|16|32|64) x y) (Const(8|16|32|64) [0])) && s.Uses == 1 -> (Eq(8|16|32|64)  x y)
 (Neq(8|16|32|64) s:(Sub(8|16|32|64) x y) (Const(8|16|32|64) [0])) && s.Uses == 1 -> (Neq(8|16|32|64) x y)
 
+// Optimize bitsets
+(Eq(8|16|32|64) (And(8|16|32|64) <t> x (Const(8|16|32|64) <t> [y])) (Const(8|16|32|64) <t> [y])) && isPowerOfTwo(y)
+  -> (Neq(8|16|32|64) (And(8|16|32|64) <t> x (Const(8|16|32|64) <t> [y])) (Const(8|16|32|64) <t> [0]))
+(Neq(8|16|32|64) (And(8|16|32|64) <t> x (Const(8|16|32|64) <t> [y])) (Const(8|16|32|64) <t> [y])) && isPowerOfTwo(y)
+  -> (Eq(8|16|32|64) (And(8|16|32|64) <t> x (Const(8|16|32|64) <t> [y])) (Const(8|16|32|64) <t> [0]))
+
 // Reassociate expressions involving
 // constants such that constants come first,
 // exposing obvious constant-folding opportunities.