cmd/internal/ssa: utility functions to make Funcs

Adds a more convenient way to define Funcs for testing.
For instance,

  b1:
    v1 = Arg <mem> [.mem]
    Plain -> b2
  b2:
    Exit v1
  b3:
    v2 = Const <bool> [true]
    If v2 -> b3 b2

can be defined as

	 fun :=Fun("entry",
		Bloc("entry",
			Valu("mem", OpArg, TypeMem, ".mem"),
			Goto("exit")),
		Bloc("exit",
			Exit("mem")),
		Bloc("deadblock",
			Valu("deadval", OpConst, TypeBool, true),
			If("deadval", "deadblock", "exit")))

Also add an Equiv function to test two Funcs for equivalence.

Change-Id: If1633865aeefb8e765e772b6dad19250d93a413a
Reviewed-on: https://go-review.googlesource.com/9992Reviewed-by: Keith Randall <khr@golang.org>

src/cmd/internal/ssa/deadcode_test.go

@@ -2,44 +2,35 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// TODO: these tests are pretty verbose.  Is there a way to simplify
-// building a small Func for testing?
-
-package ssa_test
+package ssa
 
 import (
-	. "cmd/internal/ssa"
 	"testing"
 )
 
 func TestDeadLoop(t *testing.T) {
-	f := new(Func)
-	entry := f.NewBlock(BlockPlain)
-	exit := f.NewBlock(BlockExit)
-	f.Entry = entry
-	addEdge(entry, exit)
-	mem := entry.NewValue(OpArg, TypeMem, ".mem")
-	exit.Control = mem
-
+	fun := Fun("entry",
+		Bloc("entry",
+			Valu("mem", OpArg, TypeMem, ".mem"),
+			Goto("exit")),
+		Bloc("exit",
+			Exit("mem")),
 		// dead loop
-	deadblock := f.NewBlock(BlockIf)
-	addEdge(deadblock, deadblock)
-	addEdge(deadblock, exit)
-
+		Bloc("deadblock",
 			// dead value in dead block
-	deadval := deadblock.NewValue(OpConst, TypeBool, true)
-	deadblock.Control = deadval
+			Valu("deadval", OpConst, TypeBool, true),
+			If("deadval", "deadblock", "exit")))
 
-	CheckFunc(f)
-	Deadcode(f)
-	CheckFunc(f)
+	CheckFunc(fun.f)
+	Deadcode(fun.f)
+	CheckFunc(fun.f)
 
-	for _, b := range f.Blocks {
-		if b == deadblock {
+	for _, b := range fun.f.Blocks {
+		if b == fun.blocks["deadblock"] {
 			t.Errorf("dead block not removed")
 		}
 		for _, v := range b.Values {
-			if v == deadval {
+			if v == fun.values["deadval"] {
 				t.Errorf("control value of dead block not removed")
 			}
 		}
@@ -47,23 +38,21 @@ func TestDeadLoop(t *testing.T) {
 }
 
 func TestDeadValue(t *testing.T) {
-	f := new(Func)
-	entry := f.NewBlock(BlockPlain)
-	exit := f.NewBlock(BlockExit)
-	f.Entry = entry
-	addEdge(entry, exit)
-	mem := entry.NewValue(OpArg, TypeMem, ".mem")
-	exit.Control = mem
-
-	deadval := entry.NewValue(OpConst, TypeInt64, int64(37))
-
-	CheckFunc(f)
-	Deadcode(f)
-	CheckFunc(f)
-
-	for _, b := range f.Blocks {
+	fun := Fun("entry",
+		Bloc("entry",
+			Valu("mem", OpArg, TypeMem, ".mem"),
+			Valu("deadval", OpConst, TypeInt64, int64(37)),
+			Goto("exit")),
+		Bloc("exit",
+			Exit("mem")))
+
+	CheckFunc(fun.f)
+	Deadcode(fun.f)
+	CheckFunc(fun.f)
+
+	for _, b := range fun.f.Blocks {
 		for _, v := range b.Values {
-			if v == deadval {
+			if v == fun.values["deadval"] {
 				t.Errorf("dead value not removed")
 			}
 		}
@@ -71,42 +60,34 @@ func TestDeadValue(t *testing.T) {
 }
 
 func TestNeverTaken(t *testing.T) {
-	f := new(Func)
-	entry := f.NewBlock(BlockIf)
-	exit := f.NewBlock(BlockExit)
-	then := f.NewBlock(BlockPlain)
-	else_ := f.NewBlock(BlockPlain)
-	f.Entry = entry
-	addEdge(entry, then)
-	addEdge(entry, else_)
-	addEdge(then, exit)
-	addEdge(else_, exit)
-	mem := entry.NewValue(OpArg, TypeMem, ".mem")
-	exit.Control = mem
-
-	cond := entry.NewValue(OpConst, TypeBool, false)
-	entry.Control = cond
-
-	CheckFunc(f)
-	Deadcode(f)
-	CheckFunc(f)
-
-	if entry.Kind != BlockPlain {
+	fun := Fun("entry",
+		Bloc("entry",
+			Valu("cond", OpConst, TypeBool, false),
+			Valu("mem", OpArg, TypeMem, ".mem"),
+			If("cond", "then", "else")),
+		Bloc("then",
+			Goto("exit")),
+		Bloc("else",
+			Goto("exit")),
+		Bloc("exit",
+			Exit("mem")))
+
+	CheckFunc(fun.f)
+	Deadcode(fun.f)
+	CheckFunc(fun.f)
+
+	if fun.blocks["entry"].Kind != BlockPlain {
 		t.Errorf("if(false) not simplified")
 	}
-	for _, b := range f.Blocks {
-		if b == then {
+	for _, b := range fun.f.Blocks {
+		if b == fun.blocks["then"] {
 			t.Errorf("then block still present")
 		}
 		for _, v := range b.Values {
-			if v == cond {
+			if v == fun.values["cond"] {
 				t.Errorf("constant condition still present")
 			}
 		}
 	}
-}
 
-func addEdge(b, c *Block) {
-	b.Succs = append(b.Succs, c)
-	c.Preds = append(c.Preds, b)
 }