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m68k: tear down frames on external conditional branches
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Irmen de Jong committed
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@@ -28,40 +28,46 @@ import prog8.intermediate.requireSrcB
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import prog8.intermediate.requireTarget
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internal fun AsmGen.translateBranch(insn: IRInstruction) {
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val label: String = when (val target = insn.requireTarget()) {
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val target = insn.requireTarget()
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val label: String = when (target) {
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is CodeReference.Label -> fixNameSymbols(target.name)
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is CodeReference.Absolute -> target.address.toHex()
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is CodeReference.Indirect -> error("branch needs a static target")
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}
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val leavesSubroutine = when (target) {
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is CodeReference.Label -> labelIsOutsideCurrentSub(target.name)
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is CodeReference.Absolute -> true
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is CodeReference.Indirect -> false
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}
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when (insn.opcode) {
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Opcode.BSTCC -> emitBranch("bcc", label)
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Opcode.BSTCS -> emitBranch("bcs", label)
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Opcode.BSTEQ -> emitBranch("beq", label)
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Opcode.BSTNE -> emitBranch("bne", label)
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Opcode.BSTNEG -> emitBranch("bmi", label)
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Opcode.BSTPOS -> emitBranch("bpl", label)
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Opcode.BSTVC -> emitBranch("bvc", label)
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Opcode.BSTVS -> emitBranch("bvs", label)
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Opcode.BSTCC -> emitBranch("bcc", label, leavesSubroutine)
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Opcode.BSTCS -> emitBranch("bcs", label, leavesSubroutine)
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Opcode.BSTEQ -> emitBranch("beq", label, leavesSubroutine)
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Opcode.BSTNE -> emitBranch("bne", label, leavesSubroutine)
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Opcode.BSTNEG -> emitBranch("bmi", label, leavesSubroutine)
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Opcode.BSTPOS -> emitBranch("bpl", label, leavesSubroutine)
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Opcode.BSTVC -> emitBranch("bvc", label, leavesSubroutine)
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Opcode.BSTVS -> emitBranch("bvs", label, leavesSubroutine)
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// Unsigned integer comparison branches
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Opcode.BGT -> cmpBranchUnsignedImm(insn, label, "bhi")
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Opcode.BGE -> cmpBranchUnsignedImm(insn, label, "bhs")
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Opcode.BLT -> cmpBranchUnsignedImm(insn, label, "blo")
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Opcode.BLE -> cmpBranchUnsignedImm(insn, label, "bls")
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Opcode.BGT -> cmpBranchUnsignedImm(insn, label, "bhi", leavesSubroutine)
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Opcode.BGE -> cmpBranchUnsignedImm(insn, label, "bhs", leavesSubroutine)
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Opcode.BLT -> cmpBranchUnsignedImm(insn, label, "blo", leavesSubroutine)
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Opcode.BLE -> cmpBranchUnsignedImm(insn, label, "bls", leavesSubroutine)
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Opcode.BGTR -> cmpBranchUnsignedReg(insn, label, "bhi")
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Opcode.BGER -> cmpBranchUnsignedReg(insn, label, "bhs")
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Opcode.BGTR -> cmpBranchUnsignedReg(insn, label, "bhi", leavesSubroutine)
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Opcode.BGER -> cmpBranchUnsignedReg(insn, label, "bhs", leavesSubroutine)
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// BLTR doesn't exist in IR — uses BGTR with swapped operands
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// Signed integer comparison branches
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Opcode.BGTS -> cmpBranchSignedImm(insn, label, "bgt")
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Opcode.BGES -> cmpBranchSignedImm(insn, label, "bge")
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Opcode.BLTS -> cmpBranchSignedImm(insn, label, "blt")
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Opcode.BLES -> cmpBranchSignedImm(insn, label, "ble")
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Opcode.BGTS -> cmpBranchSignedImm(insn, label, "bgt", leavesSubroutine)
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Opcode.BGES -> cmpBranchSignedImm(insn, label, "bge", leavesSubroutine)
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Opcode.BLTS -> cmpBranchSignedImm(insn, label, "blt", leavesSubroutine)
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Opcode.BLES -> cmpBranchSignedImm(insn, label, "ble", leavesSubroutine)
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Opcode.BGTSR -> cmpBranchSignedReg(insn, label, "bgt")
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Opcode.BGESR -> cmpBranchSignedReg(insn, label, "bge")
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Opcode.BGTSR -> cmpBranchSignedReg(insn, label, "bgt", leavesSubroutine)
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Opcode.BGESR -> cmpBranchSignedReg(insn, label, "bge", leavesSubroutine)
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// BLTSR doesn't exist in IR — uses BGTSR with swapped operands
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else -> error("Unknown branch opcode: ${insn.opcode}")
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@@ -70,7 +76,7 @@ internal fun AsmGen.translateBranch(insn: IRInstruction) {
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// === Unsigned comparisons: register vs immediate ===
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private fun AsmGen.cmpBranchUnsignedImm(insn: IRInstruction, label: String, branchOp: String) {
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private fun AsmGen.cmpBranchUnsignedImm(insn: IRInstruction, label: String, branchOp: String, leavesSubroutine: Boolean) {
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val type = insn.type ?: IRDataType.BYTE
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val reg = insn.requireSrcA().intNumber
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val imm = insn.requireImmediateInt()
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@@ -81,24 +87,24 @@ private fun AsmGen.cmpBranchUnsignedImm(insn: IRInstruction, label: String, bran
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emitLine("tst$s ${regAddr(reg)}")
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else
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emitLine("cmpi$s #$imm, ${regAddr(reg)}")
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emitBranch(branchOp, label)
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emitBranch(branchOp, label, leavesSubroutine)
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}
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// === Unsigned comparisons: register vs register ===
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private fun AsmGen.cmpBranchUnsignedReg(insn: IRInstruction, label: String, branchOp: String) {
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private fun AsmGen.cmpBranchUnsignedReg(insn: IRInstruction, label: String, branchOp: String, leavesSubroutine: Boolean) {
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val type = insn.type ?: IRDataType.BYTE
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val left = insn.requireSrcA().intNumber
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val right = insn.requireSrcB().intNumber
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val s = dtSuffix(type)
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emitLoadD0(left, type)
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emitLine("cmp$s ${regAddr(right)}, d0")
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emitBranch(branchOp, label)
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emitBranch(branchOp, label, leavesSubroutine)
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}
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// === Signed comparisons: register vs immediate ===
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private fun AsmGen.cmpBranchSignedImm(insn: IRInstruction, label: String, branchOp: String) {
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private fun AsmGen.cmpBranchSignedImm(insn: IRInstruction, label: String, branchOp: String, leavesSubroutine: Boolean) {
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val type = insn.type ?: IRDataType.BYTE
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val reg = insn.requireSrcA().intNumber
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val imm = insn.requireImmediateInt()
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@@ -109,22 +115,41 @@ private fun AsmGen.cmpBranchSignedImm(insn: IRInstruction, label: String, branch
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emitLine("tst$s ${regAddr(reg)}")
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else
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emitLine("cmpi$s #$imm, ${regAddr(reg)}")
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emitBranch(branchOp, label)
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emitBranch(branchOp, label, leavesSubroutine)
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}
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// === Signed comparisons: register vs register ===
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private fun AsmGen.cmpBranchSignedReg(insn: IRInstruction, label: String, branchOp: String) {
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private fun AsmGen.cmpBranchSignedReg(insn: IRInstruction, label: String, branchOp: String, leavesSubroutine: Boolean) {
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val type = insn.type ?: IRDataType.BYTE
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val left = insn.requireSrcA().intNumber
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val right = insn.requireSrcB().intNumber
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val s = dtSuffix(type)
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emitLoadD0(left, type)
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emitLine("cmp$s ${regAddr(right)}, d0")
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emitBranch(branchOp, label)
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emitBranch(branchOp, label, leavesSubroutine)
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}
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private fun AsmGen.emitBranch(branchOp: String, label: String) {
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private val inverseBranchOps = mapOf(
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"bcc" to "bcs", "bcs" to "bcc",
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"beq" to "bne", "bne" to "beq",
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"bmi" to "bpl", "bpl" to "bmi",
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"bvc" to "bvs", "bvs" to "bvc",
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"bhi" to "bls", "bls" to "bhi",
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"bhs" to "blo", "blo" to "bhs",
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"bgt" to "ble", "ble" to "bgt",
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"bge" to "blt", "blt" to "bge")
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private fun AsmGen.emitBranch(branchOp: String, label: String, leavesSubroutine: Boolean) {
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invalidateD0Cache()
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emitLine("$branchOp $label")
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if (!leavesSubroutine || !frameActive) {
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emitLine("$branchOp $label")
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return
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}
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val skipLabel = makeLabel("branch_keep_frame")
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emitLine("${inverseBranchOps.getValue(branchOp)} $skipLabel")
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emitFrameUnlk()
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emitLine("jmp $label")
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emitLabel(skipLabel)
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}
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@@ -377,6 +377,51 @@ class TestStackFrameEmission : FunSpec({
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lines.none { it.startsWith("unlk") } shouldBe true
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}
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test("conditional branch to an absolute address tears down only the taken path") {
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val lines = generateAsm(16, listOf(
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IRInstructions.branch(Opcode.BSTEQ, codeAddress(0x1234u)),
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IRInstructions.simple(Opcode.RETURN)
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))
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val branchIdx = lines.indexOfFirst { it.startsWith("bne") }
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val jmpIdx = lines.indexOfFirst { it.startsWith("jmp") && "$1234" in it }
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(branchIdx >= 0) shouldBe true
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(jmpIdx > branchIdx) shouldBe true
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lines[jmpIdx - 1] shouldBe "unlk a5"
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lines.count { it == "unlk a5" } shouldBe 2
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}
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test("conditional branch to an external non-entry label tears down only the taken path") {
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val outsideInner = IRCodeChunk("test.outside.inner", null).also {
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it.instructions.add(IRInstructions.simple(Opcode.RETURN))
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}
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val lines = generateAsmForSubs(
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sub("test.start", frameSize = 16, instructions = listOf(
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IRInstructions.branch(Opcode.BSTEQ, CodeReference.Label("test.outside.inner")),
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IRInstructions.simple(Opcode.RETURN)
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)),
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sub("test.outside", frameSize = 0, instructions = listOf(IRInstructions.simple(Opcode.RETURN)),
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extraChunks = listOf(outsideInner))
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)
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val jmpIdx = lines.indexOfFirst { it.startsWith("jmp") && "outside.inner" in it }
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(jmpIdx > 0) shouldBe true
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lines[jmpIdx - 1] shouldBe "unlk a5"
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lines.any { it.startsWith("bne") } shouldBe true
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}
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test("signed comparison branch to an absolute address tears down only the taken path") {
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val lines = generateAsm(16, listOf(
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IRInstructions.branchImmediate(Opcode.BGTS, IRDataType.WORD, 1, 1, codeAddress(0x1234u)),
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IRInstructions.simple(Opcode.RETURN)
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))
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lines.any { it.startsWith("cmpi.w") } shouldBe true
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val branchIdx = lines.indexOfFirst { it.startsWith("ble") }
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val jmpIdx = lines.indexOfFirst { it.startsWith("jmp") && "$1234" in it }
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(branchIdx >= 0) shouldBe true
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(jmpIdx > branchIdx) shouldBe true
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lines[jmpIdx - 1] shouldBe "unlk a5"
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lines.count { it == "unlk a5" } shouldBe 2
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}
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test("jump to a label in another subroutine pops the frame before jumping") {
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// jumping out of the subroutine is a documented way to end it, so our frame must not be
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// left behind for whatever runs next (and its eventual rts) to trip over
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