cpu.test: add test cases for add, ebreak, assembling fragments with llvm

cpu_test.go

@@ -1,17 +1,91 @@
 package riscvemu
 
 import (
+	"bytes"
+	"errors"
+	"fmt"
+	"os/exec"
+	"strings"
 	"testing"
 )
 
-func TestCPU(t *testing.T) {
+// assemble_llvm assembles RISC-V source code with the installed system LLVM
+// compiler and returns the raw bytes from the resulting .text section.
+func assemble_llvm(source string) ([]byte, error) {
+	// echo 'nop' | clang --target=riscv32 -march=rv32i -x assembler - -c -o - | llvm-objcopy - /dev/null --dump-section .text=/dev/stdout | xxd
 
+	cmd := exec.Command(`/bin/bash`, `-c`, `/usr/bin/clang --target=riscv32 -march=rv32i -x assembler - -c -o - | /usr/bin/llvm-objcopy - /dev/null --dump-section .text=/dev/stdout`)
+	cmd.Stdin = strings.NewReader(source)
+
+	so_buff := bytes.Buffer{}
+	cmd.Stdout = &so_buff
+
+	err := cmd.Wait()
+	if err != nil {
+		return nil, err
+	}
+
+	return so_buff.Bytes(), nil
+}
+
+func runUntilEbreak(c *CPUState, expect_insns int) error {
+	for i := 0; i < expect_insns-1; i++ {
+		err := c.Step()
+		if err != nil {
+			return err
+		}
+	}
+
+	err := c.Step()
+	if err != nil {
+		if eb := (ErrBreak{}); errors.As(err, &eb) {
+			return nil // Successfully got EBREAK precisely when wanted
+		}
+		return err // Some other real error
+	}
+
+	return fmt.Errorf("Expected EBREAK at instruction count %d, but got %v", expect_insns, err)
+}
+
+func TestBreak(t *testing.T) {
 	env := NewVirtualEEI()
-	_ = env.Write32(0, 0b00000000000100000000000001110011) // EBREAK
+
+	// ebreak
+	_, err := env.WriteAt([]byte{0x73, 0x00, 0x10, 0x00}, 0)
+	if err != nil {
+		t.Fatal(err)
+	}
 
 	c := NewCPU(&env)
 
-	err := c.Step()
-	panic(err)
-
+	err = c.Step()
+	if err == nil {
+		t.Fatal("expected ErrBreak, got <nil>")
+	}
+	if eb := (ErrBreak{}); !errors.As(err, &eb) {
+		t.Fatalf("expected ErrBreak, got %#v", err)
+	}
+}
+
+func TestAdd(t *testing.T) {
+	env := NewVirtualEEI()
+
+	// li a0, 0xffff
+	// ebreak
+	_, err := env.WriteAt([]byte{0x37, 0xc5, 0xad, 0xde, 0x13, 0x05, 0xf5, 0xee, 0x73, 0x00, 0x10, 0x00}, 0)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	c := NewCPU(&env)
+
+	err = runUntilEbreak(&c, 3)
+	if err != nil {
+		t.Error(err)
+	}
+
+	// Check that we managed to load into the register
+	if c.Registers[10] != 0xdeadbeef {
+		t.Errorf("expected register a0 (x10) to contain 0xdeadbeef, got %#v", c.Registers[10])
+	}
 }