Added B instruction

Author: RealA10N

instructions/b.go

@@ -0,0 +1,25 @@
+package instructions
+
+import (
+	"fmt"
+
+	"alon.kr/x/aarch64codegen/immediates"
+)
+
+type Branch uint32
+
+func B(offset immediates.Offset26Align4) Branch {
+	return Branch(0b101<<26 | offset.Binary())
+}
+
+func (i Branch) Offset() immediates.Offset26Align4 {
+	return immediates.Offset26Align4(i & 0x3FFFFFF)
+}
+
+func (i Branch) String() string {
+	return fmt.Sprintf("B %s", i.Offset())
+}
+
+func (i Branch) Binary() uint32 {
+	return uint32(i)
+}

instructions/b_test.go

@@ -0,0 +1,36 @@
+package instructions_test
+
+import (
+	"testing"
+
+	"alon.kr/x/aarch64codegen/immediates"
+	"alon.kr/x/aarch64codegen/instructions"
+	"github.com/stretchr/testify/assert"
+)
+
+func AssertExpectedBranchInstruction(t *testing.T, expected string, offset int32) {
+	off26, err := immediates.NewOffset26Align4(offset)
+	assert.NoError(t, err)
+	instruction := instructions.B(off26)
+	AssertExpectedInstruction(t, expected, instruction)
+}
+
+func TestBranch0(t *testing.T) {
+	AssertExpectedBranchInstruction(t, "B #0", 0)
+}
+
+func TestBranch1(t *testing.T) {
+	AssertExpectedBranchInstruction(t, "B #4", 4)
+}
+
+func TestBranchMinus1(t *testing.T) {
+	AssertExpectedBranchInstruction(t, "B #-4", -4)
+}
+
+func TestBranchMax(t *testing.T) {
+	AssertExpectedBranchInstruction(t, "B #134217724", 0x7FFFFFC)
+}
+
+func TestBranchMin(t *testing.T) {
+	AssertExpectedBranchInstruction(t, "B #-134217728", -0x8000000)
+}