cmd/compile: enable ssacheck for tests in ssa_test.go

I thought SSA check was enabled for those tests, but in fact it
was not. Enable it. So we have SSA check on for at least some
tests on all architectures.

Updates #22499.

Change-Id: I51fcdda3af7faab5aeb33bf46c6db309285ce42c
Reviewed-on: https://go-review.googlesource.com/76024Reviewed-by: Keith Randall <khr@golang.org>

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

@@ -8,6 +8,7 @@ import (
 	"bytes"
 	"internal/testenv"
 	"io/ioutil"
+	"os"
 	"os/exec"
 	"path/filepath"
 	"runtime"
@@ -27,11 +28,38 @@ func buildTest(t *testing.T, filename string) {
 }
 func doTest(t *testing.T, filename string, kind string) {
 	testenv.MustHaveGoBuild(t)
+	gotool := testenv.GoToolPath(t)
+	tmpdir, ok := ioutil.TempDir("", "ssatest")
+	if ok != nil {
+		t.Fatalf("Failed to create temporary directory")
+	}
+	defer os.RemoveAll(tmpdir)
+
+	// Execute compile+link+run instead of "go run" to avoid applying -gcflags=-d=ssa/check/on
+	// to the runtime (especially over and over and over).
+	// compile
 	var stdout, stderr bytes.Buffer
-	cmd := exec.Command(testenv.GoToolPath(t), kind, filepath.Join("testdata", filename))
+	cmd := exec.Command(gotool, "tool", "compile", "-d=ssa/check/on", "-o", filepath.Join(tmpdir, "run.a"), filepath.Join("testdata", filename))
 	cmd.Stdout = &stdout
 	cmd.Stderr = &stderr
-	if err := cmd.Run(); err != nil {
+	err := cmd.Run()
+	if kind == "run" {
+		if err == nil {
+			// link
+			cmd = exec.Command(gotool, "tool", "link", "-o", filepath.Join(tmpdir, "run.exe"), filepath.Join(tmpdir, "run.a"))
+			cmd.Stdout = &stdout
+			cmd.Stderr = &stderr
+			err = cmd.Run()
+		}
+		if err == nil {
+			// run
+			cmd = exec.Command(filepath.Join(tmpdir, "run.exe"))
+			cmd.Stdout = &stdout
+			cmd.Stderr = &stderr
+			err = cmd.Run()
+		}
+	}
+	if err != nil {
 		t.Fatalf("Failed: %v:\nOut: %s\nStderr: %s\n", err, &stdout, &stderr)
 	}
 	if s := stdout.String(); s != "" {