[dev.ssa] cmd/compile: implement control flow handling

Add label and goto checks and improve test coverage.

Implement OSWITCH and OSELECT.

Implement OBREAK and OCONTINUE.

Allow generation of code in dead blocks.

Change-Id: Ibebb7c98b4b2344f46d38db7c9dce058c56beaac
Reviewed-on: https://go-review.googlesource.com/12445Reviewed-by: Keith Randall <khr@golang.org>

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

@@ -141,6 +141,8 @@ func newlab(n *Node) *Label {
 	return lab
 }
 
+// There is a copy of checkgoto in the new SSA backend.
+// Please keep them in sync.
 func checkgoto(from *Node, to *Node) {
 	if from.Sym == to.Sym {
 		return

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

@@ -8,23 +8,24 @@ import (
 	"bytes"
 	"internal/testenv"
 	"os/exec"
+	"path/filepath"
 	"runtime"
 	"strings"
 	"testing"
 )
 
-// Tests OANDAND and OOROR expressions and short circuiting.
-// TODO: move these tests elsewhere? perhaps teach test/run.go how to run them
-// with a new action verb.
-func TestShortCircuit(t *testing.T) {
+// TODO: move all these tests elsewhere?
+// Perhaps teach test/run.go how to run them with a new action verb.
+func runTest(t *testing.T, filename string) {
 	if runtime.GOARCH != "amd64" {
 		t.Skipf("skipping SSA tests on %s for now", runtime.GOARCH)
 	}
 	testenv.MustHaveGoBuild(t)
 	var stdout, stderr bytes.Buffer
-	cmd := exec.Command("go", "run", "testdata/short_ssa.go")
+	cmd := exec.Command("go", "run", filepath.Join("testdata", filename))
 	cmd.Stdout = &stdout
 	cmd.Stderr = &stderr
+	// TODO: set GOGC=off until we have stackmaps
 	if err := cmd.Run(); err != nil {
 		t.Fatalf("Failed: %v:\nOut: %s\nStderr: %s\n", err, &stdout, &stderr)
 	}
@@ -35,3 +36,9 @@ func TestShortCircuit(t *testing.T) {
 		t.Errorf("Unimplemented message found in stderr:\n%s", s)
 	}
 }
+
+// TestShortCircuit tests OANDAND and OOROR expressions and short circuiting.
+func TestShortCircuit(t *testing.T) { runTest(t, "short_ssa.go") }
+
+// TestBreakContinue tests that continue and break statements do what they say.
+func TestBreakContinue(t *testing.T) { runTest(t, "break_ssa.go") }

src/cmd/compile/internal/gc/testdata/break_ssa.go

+// run
+
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Tests continue and break.
+
+package main
+
+func continuePlain_ssa() int {
+	var n int
+	for i := 0; i < 10; i++ {
+		if i == 6 {
+			continue
+		}
+		n = i
+	}
+	return n
+}
+
+func continueLabeled_ssa() int {
+	var n int
+Next:
+	for i := 0; i < 10; i++ {
+		if i == 6 {
+			continue Next
+		}
+		n = i
+	}
+	return n
+}
+
+func continuePlainInner_ssa() int {
+	var n int
+	for j := 0; j < 30; j += 10 {
+		for i := 0; i < 10; i++ {
+			if i == 6 {
+				continue
+			}
+			n = i
+		}
+		n += j
+	}
+	return n
+}
+
+func continueLabeledInner_ssa() int {
+	var n int
+	for j := 0; j < 30; j += 10 {
+	Next:
+		for i := 0; i < 10; i++ {
+			if i == 6 {
+				continue Next
+			}
+			n = i
+		}
+		n += j
+	}
+	return n
+}
+
+func continueLabeledOuter_ssa() int {
+	var n int
+Next:
+	for j := 0; j < 30; j += 10 {
+		for i := 0; i < 10; i++ {
+			if i == 6 {
+				continue Next
+			}
+			n = i
+		}
+		n += j
+	}
+	return n
+}
+
+func breakPlain_ssa() int {
+	var n int
+	for i := 0; i < 10; i++ {
+		if i == 6 {
+			break
+		}
+		n = i
+	}
+	return n
+}
+
+func breakLabeled_ssa() int {
+	var n int
+Next:
+	for i := 0; i < 10; i++ {
+		if i == 6 {
+			break Next
+		}
+		n = i
+	}
+	return n
+}
+
+func breakPlainInner_ssa() int {
+	var n int
+	for j := 0; j < 30; j += 10 {
+		for i := 0; i < 10; i++ {
+			if i == 6 {
+				break
+			}
+			n = i
+		}
+		n += j
+	}
+	return n
+}
+
+func breakLabeledInner_ssa() int {
+	var n int
+	for j := 0; j < 30; j += 10 {
+	Next:
+		for i := 0; i < 10; i++ {
+			if i == 6 {
+				break Next
+			}
+			n = i
+		}
+		n += j
+	}
+	return n
+}
+
+func breakLabeledOuter_ssa() int {
+	var n int
+Next:
+	for j := 0; j < 30; j += 10 {
+		for i := 0; i < 10; i++ {
+			if i == 6 {
+				break Next
+			}
+			n = i
+		}
+		n += j
+	}
+	return n
+}
+
+var g, h int // globals to ensure optimizations don't collapse our switch statements
+
+func switchPlain_ssa() int {
+	var n int
+	switch g {
+	case 0:
+		n = 1
+		break
+		n = 2
+	}
+	return n
+}
+
+func switchLabeled_ssa() int {
+	var n int
+Done:
+	switch g {
+	case 0:
+		n = 1
+		break Done
+		n = 2
+	}
+	return n
+}
+
+func switchPlainInner_ssa() int {
+	var n int
+	switch g {
+	case 0:
+		n = 1
+		switch h {
+		case 0:
+			n += 10
+			break
+		}
+		n = 2
+	}
+	return n
+}
+
+func switchLabeledInner_ssa() int {
+	var n int
+	switch g {
+	case 0:
+		n = 1
+	Done:
+		switch h {
+		case 0:
+			n += 10
+			break Done
+		}
+		n = 2
+	}
+	return n
+}
+
+func switchLabeledOuter_ssa() int {
+	var n int
+Done:
+	switch g {
+	case 0:
+		n = 1
+		switch h {
+		case 0:
+			n += 10
+			break Done
+		}
+		n = 2
+	}
+	return n
+}
+
+func main() {
+	tests := [...]struct {
+		name string
+		fn   func() int
+		want int
+	}{
+		{"continuePlain_ssa", continuePlain_ssa, 9},
+		{"continueLabeled_ssa", continueLabeled_ssa, 9},
+		{"continuePlainInner_ssa", continuePlainInner_ssa, 29},
+		{"continueLabeledInner_ssa", continueLabeledInner_ssa, 29},
+		{"continueLabeledOuter_ssa", continueLabeledOuter_ssa, 5},
+
+		{"breakPlain_ssa", breakPlain_ssa, 5},
+		{"breakLabeled_ssa", breakLabeled_ssa, 5},
+		{"breakPlainInner_ssa", breakPlainInner_ssa, 25},
+		{"breakLabeledInner_ssa", breakLabeledInner_ssa, 25},
+		{"breakLabeledOuter_ssa", breakLabeledOuter_ssa, 5},
+
+		{"switchPlain_ssa", switchPlain_ssa, 1},
+		{"switchLabeled_ssa", switchLabeled_ssa, 1},
+		{"switchPlainInner_ssa", switchPlainInner_ssa, 2},
+		{"switchLabeledInner_ssa", switchLabeledInner_ssa, 2},
+		{"switchLabeledOuter_ssa", switchLabeledOuter_ssa, 11},
+
+		// no select tests; they're identical to switch
+	}
+
+	var failed bool
+	for _, test := range tests {
+		if got := test.fn(); test.fn() != test.want {
+			print(test.name, "()=", got, ", want ", test.want, "\n")
+			failed = true
+		}
+	}
+
+	if failed {
+		panic("failed")
+	}
+}

src/cmd/compile/internal/ssa/compile.go

@@ -50,6 +50,7 @@ type pass struct {
 var passes = [...]pass{
 	{"phielim", phielim},
 	{"copyelim", copyelim},
+	{"early deadcode", deadcode}, // remove generated dead code to avoid doing pointless work during opt
 	{"opt", opt},
 	{"opt deadcode", deadcode}, // remove any blocks orphaned during opt
 	{"generic cse", cse},

test/label.go

@@ -58,4 +58,8 @@ L10:
 	default:
 		break L10
 	}
+
+	goto L10
+
+	goto go2 // ERROR "label go2 not defined"
 }

test/label1.go

@@ -31,11 +31,17 @@ L2:
 			break L2
 		}
 		if x == 1 {
-			continue L2 // ERROR "invalid continue label .*L2"
+			continue L2 // ERROR "invalid continue label .*L2|continue is not in a loop"
 		}
 		goto L2
 	}
 
+	for {
+		if x == 1 {
+			continue L2 // ERROR "invalid continue label .*L2"
+		}
+	}
+
 L3:
 	switch {
 	case x > 10:
@@ -43,7 +49,7 @@ L3:
 			break L3
 		}
 		if x == 12 {
-			continue L3 // ERROR "invalid continue label .*L3"
+			continue L3 // ERROR "invalid continue label .*L3|continue is not in a loop"
 		}
 		goto L3
 	}
@@ -54,7 +60,7 @@ L4:
 			break L4 // ERROR "invalid break label .*L4"
 		}
 		if x == 14 {
-			continue L4 // ERROR "invalid continue label .*L4"
+			continue L4 // ERROR "invalid continue label .*L4|continue is not in a loop"
 		}
 		if x == 15 {
 			goto L4
@@ -67,7 +73,7 @@ L5:
 		break L5 // ERROR "invalid break label .*L5"
 	}
 	if x == 17 {
-		continue L5 // ERROR "invalid continue label .*L5"
+		continue L5 // ERROR "invalid continue label .*L5|continue is not in a loop"
 	}
 	if x == 18 {
 		goto L5
@@ -84,4 +90,21 @@ L5:
 			goto L1
 		}
 	}
+
+	continue // ERROR "continue is not in a loop"
+	for {
+		continue on // ERROR "continue label not defined: on"
+	}
+
+	break // ERROR "break is not in a loop"
+	for {
+		break dance // ERROR "break label not defined: dance"
+	}
+
+	for {
+		switch x {
+		case 1:
+			continue
+		}
+	}
 }