cmd/internal/obj/riscv: improve large branch/call/jump tests

Rework these tests such that they are built on all architectures and
actually executed when run on riscv64. This increases the likelihood
of catching code generation issues, especially those that impact
relocations. Also ensure that the generated assembly includes the
instruction sequence that is expected for the large branch/call/jump.

Change-Id: I15c40a439dd1d0d4ed189ab81697e93d82c4ef4d
Reviewed-on: https://go-review.googlesource.com/c/go/+/721621
Reviewed-by: Mark Ryan <markdryan@rivosinc.com>
Reviewed-by: Mark Freeman <markfreeman@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Junyang Shao <shaojunyang@google.com>

src/cmd/internal/obj/riscv/asm_test.go

@@ -17,7 +17,8 @@ import (
 )
 
 // TestLargeBranch generates a large function with a very far conditional
-// branch, in order to ensure that it assembles successfully.
+// branch, in order to ensure that it assembles correctly. This requires
+// inverting the branch and using a jump to reach the target.
 func TestLargeBranch(t *testing.T) {
 	if testing.Short() {
 		t.Skip("Skipping test in short mode")
@@ -26,6 +27,23 @@ func TestLargeBranch(t *testing.T) {
 
 	dir := t.TempDir()
 
+	if err := os.WriteFile(filepath.Join(dir, "go.mod"), []byte("module largecall"), 0644); err != nil {
+		t.Fatalf("Failed to write file: %v\n", err)
+	}
+	main := `package main
+
+import "fmt"
+
+func main() {
+        fmt.Print(x())
+}
+
+func x() uint64
+`
+	if err := os.WriteFile(filepath.Join(dir, "x.go"), []byte(main), 0644); err != nil {
+		t.Fatalf("failed to write main: %v\n", err)
+	}
+
 	// Generate a very large function.
 	buf := bytes.NewBuffer(make([]byte, 0, 7000000))
 	genLargeBranch(buf)
@@ -36,27 +54,62 @@ func TestLargeBranch(t *testing.T) {
 	}
 
 	// Assemble generated file.
-	cmd := testenv.Command(t, testenv.GoToolPath(t), "tool", "asm", "-o", filepath.Join(dir, "x.o"), tmpfile)
+	cmd := exec.Command(testenv.GoToolPath(t), "tool", "asm", "-o", filepath.Join(dir, "x.o"), "-S", tmpfile)
 	cmd.Env = append(os.Environ(), "GOARCH=riscv64", "GOOS=linux")
 	out, err := cmd.CombinedOutput()
+	if err != nil {
+		t.Errorf("Failed to assemble: %v\n%s", err, out)
+	}
+
+	// The expected instruction sequence for the long branch is:
+	//	BNEZ
+	//	AUIPC	$..., X31
+	//	JALR	X0, $..., X31
+	want := regexp.MustCompile(`\sBNEZ\s.*\s.*\n.*\n.*AUIPC\s\$\d+, X31.*\n.*JALR\sX0, \$\d+, ?X31`)
+	if !want.Match(out) {
+		t.Error("Missing assembly instructions")
+	}
+
+	// Build generated files.
+	cmd = testenv.Command(t, testenv.GoToolPath(t), "build", "-o", "x.exe", "-ldflags=-linkmode=internal")
+	cmd.Dir = dir
+	cmd.Env = append(os.Environ(), "GOARCH=riscv64", "GOOS=linux")
+	out, err = cmd.CombinedOutput()
 	if err != nil {
 		t.Errorf("Build failed: %v, output: %s", err, out)
 	}
+
+	if runtime.GOARCH == "riscv64" && runtime.GOOS == "linux" {
+		cmd = testenv.Command(t, filepath.Join(dir, "x.exe"))
+		out, err = cmd.CombinedOutput()
+		if err != nil {
+			t.Errorf("Failed to run test binary: %v", err)
+		}
+		if string(out) != "1" {
+			t.Errorf(`Got test output %q, want "2"`, string(out))
+		}
+	}
 }
 
 func genLargeBranch(buf *bytes.Buffer) {
-	fmt.Fprintln(buf, "TEXT f(SB),0,$0-0")
+	fmt.Fprintln(buf, "TEXT ·x(SB),0,$0-8")
-	fmt.Fprintln(buf, "BEQ X0, X0, label")
+	fmt.Fprintln(buf, "MOV X0, X10")
-	for i := 0; i < 1<<19; i++ {
+	fmt.Fprintln(buf, "BEQZ X10, label")
+	for i := 0; i < 1<<18; i++ {
+		// Use a non-compressable instruction.
 		fmt.Fprintln(buf, "ADD $0, X5, X0")
 	}
+	fmt.Fprintln(buf, "ADD $1, X10, X10")
 	fmt.Fprintln(buf, "label:")
-	fmt.Fprintln(buf, "ADD $0, X5, X0")
+	fmt.Fprintln(buf, "ADD $1, X10, X10")
+	fmt.Fprintln(buf, "MOV X10, r+0(FP)")
+	fmt.Fprintln(buf, "RET")
 }
 
 // TestLargeCall generates a large function (>1MB of text) with a call to
 // a following function, in order to ensure that it assembles and links
-// correctly.
+// correctly. This requires the use of AUIPC+JALR instruction sequences,
+// which are fixed up by the linker.
 func TestLargeCall(t *testing.T) {
 	if testing.Short() {
 		t.Skip("Skipping test in short mode")
@@ -69,12 +122,15 @@ func TestLargeCall(t *testing.T) {
 		t.Fatalf("Failed to write file: %v\n", err)
 	}
 	main := `package main
+
+import "fmt"
+
 func main() {
-        x()
+        fmt.Print(x())
 }
 
-func x()
+func x() uint64
-func y()
+func y() uint64
 `
 	if err := os.WriteFile(filepath.Join(dir, "x.go"), []byte(main), 0644); err != nil {
 		t.Fatalf("failed to write main: %v\n", err)
@@ -84,51 +140,94 @@ func y()
 	buf := bytes.NewBuffer(make([]byte, 0, 7000000))
 	genLargeCall(buf)
 
-	if err := os.WriteFile(filepath.Join(dir, "x.s"), buf.Bytes(), 0644); err != nil {
+	tmpfile := filepath.Join(dir, "x.s")
+	if err := os.WriteFile(tmpfile, buf.Bytes(), 0644); err != nil {
 		t.Fatalf("Failed to write file: %v\n", err)
 	}
 
-	// Build generated files.
+	// Assemble generated file.
-	cmd := testenv.Command(t, testenv.GoToolPath(t), "build", "-ldflags=-linkmode=internal")
+	cmd := exec.Command(testenv.GoToolPath(t), "tool", "asm", "-o", filepath.Join(dir, "x.o"), "-S", tmpfile)
-	cmd.Dir = dir
 	cmd.Env = append(os.Environ(), "GOARCH=riscv64", "GOOS=linux")
 	out, err := cmd.CombinedOutput()
+	if err != nil {
+		t.Errorf("Failed to assemble: %v\n%s", err, out)
+	}
+
+	// The expected instruction sequence for the long call is:
+	//	AUIPC	$0, $0, X31
+	//	JALR	X.., X31
+	want := regexp.MustCompile(`\sAUIPC\s\$0, \$0, X31.*\n.*\sJALR\sX.*, X31`)
+	if !want.Match(out) {
+		t.Error("Missing assembly instructions")
+	}
+
+	// Build generated files.
+	cmd = testenv.Command(t, testenv.GoToolPath(t), "build", "-o", "x.exe", "-ldflags=-linkmode=internal")
+	cmd.Dir = dir
+	cmd.Env = append(os.Environ(), "GOARCH=riscv64", "GOOS=linux")
+	out, err = cmd.CombinedOutput()
 	if err != nil {
 		t.Errorf("Build failed: %v, output: %s", err, out)
 	}
 
+	if runtime.GOARCH == "riscv64" && runtime.GOOS == "linux" {
+		cmd = testenv.Command(t, filepath.Join(dir, "x.exe"))
+		out, err = cmd.CombinedOutput()
+		if err != nil {
+			t.Errorf("Failed to run test binary: %v", err)
+		}
+		if string(out) != "2" {
+			t.Errorf(`Got test output %q, want "2"`, string(out))
+		}
+	}
+
 	if runtime.GOARCH == "riscv64" && testenv.HasCGO() {
-		cmd := testenv.Command(t, testenv.GoToolPath(t), "build", "-ldflags=-linkmode=external")
+		cmd := testenv.Command(t, testenv.GoToolPath(t), "build", "-o", "x.exe", "-ldflags=-linkmode=external")
 		cmd.Dir = dir
 		cmd.Env = append(os.Environ(), "GOARCH=riscv64", "GOOS=linux")
 		out, err := cmd.CombinedOutput()
 		if err != nil {
 			t.Errorf("Build failed: %v, output: %s", err, out)
 		}
+
+		if runtime.GOARCH == "riscv64" && runtime.GOOS == "linux" {
+			cmd = testenv.Command(t, filepath.Join(dir, "x.exe"))
+			out, err = cmd.CombinedOutput()
+			if err != nil {
+				t.Errorf("Failed to run test binary: %v", err)
+			}
+			if string(out) != "2" {
+				t.Errorf(`Got test output %q, want "2"`, string(out))
+			}
+		}
 	}
 }
 
 func genLargeCall(buf *bytes.Buffer) {
-	fmt.Fprintln(buf, "TEXT ·x(SB),0,$0-0")
+	fmt.Fprintln(buf, "TEXT ·x(SB),0,$0-8")
+	fmt.Fprintln(buf, "MOV  X0, X10")
 	fmt.Fprintln(buf, "CALL ·y(SB)")
-	for i := 0; i < 1<<19; i++ {
+	fmt.Fprintln(buf, "ADD $1, X10, X10")
+	fmt.Fprintln(buf, "MOV X10, r+0(FP)")
+	fmt.Fprintln(buf, "RET")
+	for i := 0; i < 1<<18; i++ {
+		// Use a non-compressable instruction.
 		fmt.Fprintln(buf, "ADD $0, X5, X0")
 	}
+	fmt.Fprintln(buf, "ADD $1, X10, X10")
 	fmt.Fprintln(buf, "RET")
 	fmt.Fprintln(buf, "TEXT ·y(SB),0,$0-0")
-	fmt.Fprintln(buf, "ADD $0, X5, X0")
+	fmt.Fprintln(buf, "ADD $1, X10, X10")
 	fmt.Fprintln(buf, "RET")
 }
 
 // TestLargeJump generates a large jump (>1MB of text) with a JMP to the
 // end of the function, in order to ensure that it assembles correctly.
+// This requires the use of AUIPC+JALR instruction sequences.
 func TestLargeJump(t *testing.T) {
 	if testing.Short() {
 		t.Skip("Skipping test in short mode")
 	}
-	if runtime.GOARCH != "riscv64" {
-		t.Skip("Require riscv64 to run")
-	}
 	testenv.MustHaveGoBuild(t)
 
 	dir := t.TempDir()
@@ -154,22 +253,46 @@ func x() uint64
 	buf := bytes.NewBuffer(make([]byte, 0, 7000000))
 	genLargeJump(buf)
 
-	if err := os.WriteFile(filepath.Join(dir, "x.s"), buf.Bytes(), 0644); err != nil {
+	tmpfile := filepath.Join(dir, "x.s")
+	if err := os.WriteFile(tmpfile, buf.Bytes(), 0644); err != nil {
 		t.Fatalf("Failed to write file: %v\n", err)
 	}
 
-	// Build generated files.
+	// Assemble generated file.
-	cmd := testenv.Command(t, testenv.GoToolPath(t), "build", "-o", "x.exe")
+	cmd := exec.Command(testenv.GoToolPath(t), "tool", "asm", "-o", filepath.Join(dir, "x.o"), "-S", tmpfile)
-	cmd.Dir = dir
+	cmd.Env = append(os.Environ(), "GOARCH=riscv64", "GOOS=linux")
 	out, err := cmd.CombinedOutput()
+	if err != nil {
+		t.Errorf("Failed to assemble: %v\n%s", err, out)
+	}
+
+	// The expected instruction sequence for the long call is:
+	//	AUIPC	$..., X31
+	//	JALR	X0, $.., X31
+	want := regexp.MustCompile(`\sAUIPC\s\$\d+, X31.*\n.*\sJALR\sX0, \$\d+, ?X31`)
+	if !want.Match(out) {
+		t.Error("Missing assembly instructions")
+		t.Errorf("%s", out)
+	}
+
+	// Build generated files.
+	cmd = testenv.Command(t, testenv.GoToolPath(t), "build", "-o", "x.exe")
+	cmd.Dir = dir
+	cmd.Env = append(os.Environ(), "GOARCH=riscv64", "GOOS=linux")
+	out, err = cmd.CombinedOutput()
 	if err != nil {
 		t.Errorf("Build failed: %v, output: %s", err, out)
 	}
 
-	cmd = testenv.Command(t, filepath.Join(dir, "x.exe"))
+	if runtime.GOARCH == "riscv64" && runtime.GOOS == "linux" {
-	out, err = cmd.CombinedOutput()
+		cmd = testenv.Command(t, filepath.Join(dir, "x.exe"))
-	if string(out) != "1" {
+		out, err = cmd.CombinedOutput()
-		t.Errorf(`Got test output %q, want "1"`, string(out))
+		if err != nil {
+			t.Errorf("Failed to run test binary: %v", err)
+		}
+		if string(out) != "1" {
+			t.Errorf(`Got test output %q, want "1"`, string(out))
+		}
 	}
 }
 
@@ -178,8 +301,10 @@ func genLargeJump(buf *bytes.Buffer) {
 	fmt.Fprintln(buf, "MOV  X0, X10")
 	fmt.Fprintln(buf, "JMP end")
 	for i := 0; i < 1<<18; i++ {
-		fmt.Fprintln(buf, "ADD $1, X10, X10")
+		// Use a non-compressable instruction.
+		fmt.Fprintln(buf, "ADD $0, X5, X0")
 	}
+	fmt.Fprintln(buf, "ADD $1, X10, X10")
 	fmt.Fprintln(buf, "end:")
 	fmt.Fprintln(buf, "ADD $1, X10, X10")
 	fmt.Fprintln(buf, "MOV X10, r+0(FP)")