cmd/compile: use SSA tests on legacy compiler

Why not?  Because the 386 backend can't handle one of them.
But other than that, it should work.

Change-Id: Iaeb9735f8c3c281136a0734376dec5ddba21be3b
Reviewed-on: https://go-review.googlesource.com/22748
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>

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

@@ -23,9 +23,6 @@ func buildTest(t *testing.T, filename string) {
 	doTest(t, filename, "build")
 }
 func doTest(t *testing.T, filename string, kind 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", kind, filepath.Join("testdata", filename))
@@ -52,7 +49,12 @@ func TestBreakContinue(t *testing.T) { runTest(t, "break_ssa.go") }
 func TestTypeAssertion(t *testing.T) { runTest(t, "assert_ssa.go") }
 
 // TestArithmetic tests that both backends have the same result for arithmetic expressions.
-func TestArithmetic(t *testing.T) { runTest(t, "arith_ssa.go") }
+func TestArithmetic(t *testing.T) {
+	if runtime.GOARCH == "386" {
+		t.Skip("legacy 386 compiler can't handle this test")
+	}
+	runTest(t, "arith_ssa.go")
+}
 
 // TestFP tests that both backends have the same result for floating point expressions.
 func TestFP(t *testing.T) { runTest(t, "fp_ssa.go") }

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

@@ -179,7 +179,7 @@ func lsh_1_uint64_ssa(a uint64) uint64 {
 
 //go:noinline
 func lsh_uint64_4294967296_ssa(a uint64) uint64 {
-	return a << 4294967296
+	return a << uint64(4294967296)
 }
 
 //go:noinline
@@ -189,7 +189,7 @@ func lsh_4294967296_uint64_ssa(a uint64) uint64 {
 
 //go:noinline
 func lsh_uint64_18446744073709551615_ssa(a uint64) uint64 {
-	return a << 18446744073709551615
+	return a << uint64(18446744073709551615)
 }
 
 //go:noinline
@@ -219,7 +219,7 @@ func rsh_1_uint64_ssa(a uint64) uint64 {
 
 //go:noinline
 func rsh_uint64_4294967296_ssa(a uint64) uint64 {
-	return a >> 4294967296
+	return a >> uint64(4294967296)
 }
 
 //go:noinline
@@ -229,7 +229,7 @@ func rsh_4294967296_uint64_ssa(a uint64) uint64 {
 
 //go:noinline
 func rsh_uint64_18446744073709551615_ssa(a uint64) uint64 {
-	return a >> 18446744073709551615
+	return a >> uint64(18446744073709551615)
 }
 
 //go:noinline