go/ssa: fix crash when building map[*struct{}]bool{{}: true}

Since Go 1.5, if a key expression in a map literal is itself a composite
literal, the type may be omitted.  An & operation may be implied,
but was not generated, resulting in a type mismatch crash.

Added regression test.
Also, added missing intrinsic math.hasSSE4 to interpreter.

Fixes issue 13341

Change-Id: I6a5e560460cdcac295a500a3fc3738cbe8aa5853
Reviewed-on: https://go-review.googlesource.com/17123
Reviewed-by: Robert Griesemer <gri@golang.org>

go/ssa/builder.go

@@ -1194,9 +1194,26 @@ func (b *builder) compLit(fn *Function, addr Value, e *ast.CompositeLit, isZero
 		fn.emit(m)
 		for _, e := range e.Elts {
 			e := e.(*ast.KeyValueExpr)
+
+			// If a key expression in a map literal is  itself a
+			// composite literal, the type may be omitted.
+			// For example:
+			//	map[*struct{}]bool{{}: true}
+			// An &-operation may be implied:
+			//	map[*struct{}]bool{&struct{}{}: true}
+			var key Value
+			if _, ok := unparen(e.Key).(*ast.CompositeLit); ok && isPointer(t.Key()) {
+				// A CompositeLit never evaluates to a pointer,
+				// so if the type of the location is a pointer,
+				// an &-operation is implied.
+				key = b.addr(fn, e.Key, true).address(fn)
+			} else {
+				key = b.expr(fn, e.Key)
+			}
+
 			loc := element{
 				m:   m,
-				k:   emitConv(fn, b.expr(fn, e.Key), t.Key()),
+				k:   emitConv(fn, key, t.Key()),
 				t:   t.Elem(),
 				pos: e.Colon,
 			}

go/ssa/interp/external.go

@@ -80,6 +80,7 @@ func init() {
 		"math.Ldexp":                       ext۰math۰Ldexp,
 		"math.Log":                         ext۰math۰Log,
 		"math.Min":                         ext۰math۰Min,
+		"math.hasSSE4":                     ext۰math۰hasSSE4,
 		"os.runtime_args":                  ext۰os۰runtime_args,
 		"os.runtime_beforeExit":            ext۰os۰runtime_beforeExit,
 		"reflect.New":                      ext۰reflect۰New,
@@ -220,6 +221,10 @@ func ext۰math۰Min(fr *frame, args []value) value {
 	return math.Min(args[0].(float64), args[1].(float64))
 }
 
+func ext۰math۰hasSSE4(fr *frame, args []value) value {
+	return false
+}
+
 func ext۰math۰Ldexp(fr *frame, args []value) value {
 	return math.Ldexp(args[0].(float64), args[1].(int))
 }

go/ssa/interp/testdata/complit.go

@@ -164,5 +164,21 @@ func init() {
 	}
 }
 
+// Regression test for https://github.com/golang/go/issues/13341:
+// within a map literal, if a key expression is a composite literal,
+// Go 1.5 allows its type to be omitted.  An & operation may be implied.
+func init() {
+	type S struct{ x int }
+	// same as map[*S]bool{&S{x: 1}: true}
+	m := map[*S]bool{{x: 1}: true}
+	for s := range m {
+		if s.x != 1 {
+			panic(s) // wrong key
+		}
+		return
+	}
+	panic("map is empty")
+}
+
 func main() {
 }