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Show First 20 Lines • Show All 194 Lines • ▼ Show 20 Lines	bool llvm::isTriviallyDead(const MachineInstr &MI,
const MachineRegisterInfo &MRI) {		const MachineRegisterInfo &MRI) {
// FIXME: This logical is mostly duplicated with		// FIXME: This logical is mostly duplicated with
// DeadMachineInstructionElim::isDead. Why is LOCAL_ESCAPE not considered in		// DeadMachineInstructionElim::isDead. Why is LOCAL_ESCAPE not considered in
// MachineInstr::isLabel?		// MachineInstr::isLabel?

// Don't delete frame allocation labels.		// Don't delete frame allocation labels.
if (MI.getOpcode() == TargetOpcode::LOCAL_ESCAPE)		if (MI.getOpcode() == TargetOpcode::LOCAL_ESCAPE)
return false;		return false;
		// LIFETIME markers should be preserved even if they seem dead.
		if (MI.getOpcode() == TargetOpcode::LIFETIME_START \|\|
		MI.getOpcode() == TargetOpcode::LIFETIME_END)
		return false;

// If we can move an instruction, we can remove it. Otherwise, it has		// If we can move an instruction, we can remove it. Otherwise, it has
// a side-effect of some sort.		// a side-effect of some sort.
bool SawStore = false;		bool SawStore = false;
if (!MI.isSafeToMove(/AA=/nullptr, SawStore) && !MI.isPHI())		if (!MI.isSafeToMove(/AA=/nullptr, SawStore) && !MI.isPHI())
return false;		return false;

// Instructions without side-effects are dead iff they only define dead vregs.		// Instructions without side-effects are dead iff they only define dead vregs.
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llvm/test/CodeGen/AArch64/GlobalISel/lifetime-marker-no-dce.mir

				# NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py
				# RUN: llc -mtriple aarch64 -run-pass=aarch64-prelegalizer-combiner -global-isel -verify-machineinstrs %s -o - \| FileCheck %s
				# Check that we don't DCE the lifetime markers even though they don't have any users.
				---
				name: test_lifetime_no_dce
				alignment: 4
				tracksRegLiveness: true
				frameInfo:
				maxAlignment: 4
				stack:
				- { id: 0, size: 4, alignment: 4 }
				machineFunctionInfo: {}
				body: \|
				bb.1:
				;%0:_(p0) = G_FRAME_INDEX %stack.0.slot
				; CHECK-LABEL: name: test_lifetime_no_dce
				; CHECK: LIFETIME_START %stack.0
				; CHECK: LIFETIME_END %stack.0
				; CHECK: RET_ReallyLR
				arsenmUnsubmitted Not Done Reply Inline Actions Don't need the IR section arsenm: Don't need the IR section
				aemersonAuthorUnsubmitted Done Reply Inline Actions We do because we need the stack slot defined by the alloca. aemerson: We do because we need the stack slot defined by the alloca.
				arsenmUnsubmitted Not Done Reply Inline Actions You don't need it, you just need to drop the name arsenm: You don't need it, you just need to drop the name
				LIFETIME_START %stack.0
				LIFETIME_END %stack.0
				RET_ReallyLR

				...