exp/ssa: fixed bug (typo) in findPromotedField.

By appending to the wrong (always empty) list, only the last
anonymous field was being considered for promotion.

Also:
- eliminated "function-local NamedTypes" TODO; nothing to do.
- fixed Function.DumpTo: printing of anon receivers was "( T)",
  now "(T)"; extracted writeSignature into own function.
- eliminated blockNames function;
  thanks to BasicBlock.String, "%s" of []*BasicBlock is fine.
- extracted buildReferrers into own function.

exp/ssa can now build its own transitive closure.

R=gri
CC=golang-dev
https://golang.org/cl/7384054

src/pkg/exp/ssa/builder.go

@@ -33,8 +33,6 @@ package ssa
 // TODO(adonovan): fix the following:
 // - support f(g()) where g has multiple result parameters.
 // - concurrent SSA code generation of multiple packages.
-// - consider function-local NamedTypes.
-//   They can have nonempty method-sets due to promotion.  Test.
 
 import (
 	"fmt"

src/pkg/exp/ssa/func.go

@@ -265,6 +265,25 @@ func numberRegisters(f *Function) {
 	}
 }
 
+// buildReferrers populates the def/use information in all non-nil
+// Value.Referrers slice.
+// Precondition: all such slices are initially empty.
+func buildReferrers(f *Function) {
+	var rands []*Value
+	for _, b := range f.Blocks {
+		for _, instr := range b.Instrs {
+			rands = instr.Operands(rands[:0]) // recycle storage
+			for _, rand := range rands {
+				if r := *rand; r != nil {
+					if ref := r.Referrers(); ref != nil {
+						*ref = append(*ref, instr)
+					}
+				}
+			}
+		}
+	}
+}
+
 // finish() finalizes the function after SSA code generation of its body.
 func (f *Function) finish() {
 	f.objects = nil
@@ -289,20 +308,7 @@ func (f *Function) finish() {
 
 	optimizeBlocks(f)
 
-	// Build immediate-use (referrers) graph.
-	var rands []*Value
-	for _, b := range f.Blocks {
-		for _, instr := range b.Instrs {
-			rands = instr.Operands(rands[:0]) // recycle storage
-			for _, rand := range rands {
-				if r := *rand; r != nil {
-					if ref := r.Referrers(); ref != nil {
-						*ref = append(*ref, instr)
-					}
-				}
-			}
-		}
-	}
+	buildReferrers(f)
 
 	if f.Prog.mode&NaiveForm == 0 {
 		// For debugging pre-state of lifting pass:
@@ -460,6 +466,47 @@ func (f *Function) fullName(from *Package) string {
 	return f.Name_
 }
 
+// writeSignature writes to w the signature sig in declaration syntax.
+// Derived from types.Signature.String().
+//
+func writeSignature(w io.Writer, name string, sig *types.Signature, params []*Parameter) {
+	io.WriteString(w, "func ")
+	if sig.Recv != nil {
+		io.WriteString(w, "(")
+		if n := params[0].Name(); n != "" {
+			io.WriteString(w, n)
+			io.WriteString(w, " ")
+		}
+		io.WriteString(w, params[0].Type().String())
+		io.WriteString(w, ") ")
+		params = params[1:]
+	}
+	io.WriteString(w, name)
+	io.WriteString(w, "(")
+	for i, v := range params {
+		if i > 0 {
+			io.WriteString(w, ", ")
+		}
+		io.WriteString(w, v.Name())
+		io.WriteString(w, " ")
+		if sig.IsVariadic && i == len(params)-1 {
+			io.WriteString(w, "...")
+		}
+		io.WriteString(w, v.Type().String())
+	}
+	io.WriteString(w, ")")
+	if res := sig.Results; res != nil {
+		io.WriteString(w, " ")
+		var t types.Type
+		if len(res) == 1 && res[0].Name == "" {
+			t = res[0].Type
+		} else {
+			t = &types.Result{Values: res}
+		}
+		io.WriteString(w, t.String())
+	}
+}
+
 // DumpTo prints to w a human readable "disassembly" of the SSA code of
 // all basic blocks of function f.
 //
@@ -485,37 +532,7 @@ func (f *Function) DumpTo(w io.Writer) {
 		}
 	}
 
-	// Function Signature in declaration syntax; derived from types.Signature.String().
-	io.WriteString(w, "func ")
-	params := f.Params
-	if f.Signature.Recv != nil {
-		fmt.Fprintf(w, "(%s %s) ", params[0].Name(), params[0].Type())
-		params = params[1:]
-	}
-	io.WriteString(w, f.Name())
-	io.WriteString(w, "(")
-	for i, v := range params {
-		if i > 0 {
-			io.WriteString(w, ", ")
-		}
-		io.WriteString(w, v.Name())
-		io.WriteString(w, " ")
-		if f.Signature.IsVariadic && i == len(params)-1 {
-			io.WriteString(w, "...")
-		}
-		io.WriteString(w, v.Type().String())
-	}
-	io.WriteString(w, ")")
-	if res := f.Signature.Results; res != nil {
-		io.WriteString(w, " ")
-		var t types.Type
-		if len(res) == 1 && res[0].Name == "" {
-			t = res[0].Type
-		} else {
-			t = &types.Result{Values: res}
-		}
-		io.WriteString(w, t.String())
-	}
+	writeSignature(w, f.Name(), f.Signature, f.Params)
 	io.WriteString(w, ":\n")
 
 	if f.Blocks == nil {
@@ -530,7 +547,7 @@ func (f *Function) DumpTo(w io.Writer) {
 		}
 		fmt.Fprintf(w, ".%s:\t\t\t\t\t\t\t       P:%d S:%d\n", b, len(b.Preds), len(b.Succs))
 		if false { // CFG debugging
-			fmt.Fprintf(w, "\t# CFG: %s --> %s --> %s\n", blockNames(b.Preds), b, blockNames(b.Succs))
+			fmt.Fprintf(w, "\t# CFG: %s --> %s --> %s\n", b.Preds, b, b.Succs)
 		}
 		for _, instr := range b.Instrs {
 			io.WriteString(w, "\t")

src/pkg/exp/ssa/promote.go

@@ -408,7 +408,7 @@ func findPromotedField(st *types.Struct, id Id) (*anonFieldPath, int) {
 	var list, next []*anonFieldPath
 	for i, f := range st.Fields {
 		if f.IsAnonymous {
-			list = append(next, &anonFieldPath{nil, i, f})
+			list = append(list, &anonFieldPath{nil, i, f})
 		}
 	}
 

src/pkg/exp/ssa/sanity.go

@@ -4,7 +4,6 @@ package ssa
 // Currently it checks CFG invariants but little at the instruction level.
 
 import (
-	"bytes"
 	"fmt"
 	"io"
 	"os"
@@ -41,20 +40,6 @@ func MustSanityCheck(fn *Function, reporter io.Writer) {
 	}
 }
 
-// blockNames returns the names of the specified blocks as a
-// human-readable string.
-//
-func blockNames(blocks []*BasicBlock) string {
-	var buf bytes.Buffer
-	for i, b := range blocks {
-		if i > 0 {
-			io.WriteString(&buf, ", ")
-		}
-		io.WriteString(&buf, b.String())
-	}
-	return buf.String()
-}
-
 func (s *sanity) diagnostic(prefix, format string, args ...interface{}) {
 	fmt.Fprintf(s.reporter, "%s: function %s", prefix, s.fn.FullName())
 	if s.block != nil {
@@ -236,7 +221,7 @@ func (s *sanity) checkBlock(b *BasicBlock, index int) {
 			}
 		}
 		if !found {
-			s.errorf("expected successor edge in predecessor %s; found only: %s", a, blockNames(a.Succs))
+			s.errorf("expected successor edge in predecessor %s; found only: %s", a, a.Succs)
 		}
 		if a.Func != s.fn {
 			s.errorf("predecessor %s belongs to different function %s", a, a.Func.FullName())
@@ -251,7 +236,7 @@ func (s *sanity) checkBlock(b *BasicBlock, index int) {
 			}
 		}
 		if !found {
-			s.errorf("expected predecessor edge in successor %s; found only: %s", c, blockNames(c.Preds))
+			s.errorf("expected predecessor edge in successor %s; found only: %s", c, c.Preds)
 		}
 		if c.Func != s.fn {
 			s.errorf("successor %s belongs to different function %s", c, c.Func.FullName())