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-//===------ CFIInstrInserter.cpp - Insert additional CFI instructions -----===//
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-//
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-// The LLVM Compiler Infrastructure
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-//
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-// This file is distributed under the University of Illinois Open Source
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-// License. See LICENSE.TXT for details.
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-//
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-//===----------------------------------------------------------------------===//
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-//
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-/// \file This pass verifies incoming and outgoing CFA information of basic
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-/// blocks. CFA information is information about offset and register set by CFI
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-/// directives, valid at the start and end of a basic block. This pass checks
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-/// that outgoing information of predecessors matches incoming information of
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-/// their successors. Then it checks if blocks have correct CFA calculation rule
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-/// set and inserts additional CFI instruction at their beginnings if they
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-/// don't. CFI instructions are inserted if basic blocks have incorrect offset
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-/// or register set by previous blocks, as a result of a non-linear layout of
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-/// blocks in a function.
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-//===----------------------------------------------------------------------===//
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-
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-#include "llvm/CodeGen/MachineFunctionPass.h"
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-#include "llvm/CodeGen/MachineInstrBuilder.h"
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-#include "llvm/CodeGen/MachineModuleInfo.h"
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-#include "llvm/CodeGen/Passes.h"
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-#include "llvm/CodeGen/TargetFrameLowering.h"
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-#include "llvm/CodeGen/TargetInstrInfo.h"
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-#include "llvm/Target/TargetMachine.h"
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-#include "llvm/Target/TargetSubtargetInfo.h"
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-using namespace llvm;
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-
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-namespace {
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-class CFIInstrInserter : public MachineFunctionPass {
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- public:
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- static char ID;
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-
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- CFIInstrInserter() : MachineFunctionPass(ID) {
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- initializeCFIInstrInserterPass(*PassRegistry::getPassRegistry());
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- }
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-
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- void getAnalysisUsage(AnalysisUsage &AU) const override {
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- AU.setPreservesAll();
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- MachineFunctionPass::getAnalysisUsage(AU);
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- }
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-
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- bool runOnMachineFunction(MachineFunction &MF) override {
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-
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- if (!MF.getMMI().hasDebugInfo() &&
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- !MF.getFunction()->needsUnwindTableEntry())
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- return false;
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-
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- MBBVector.resize(MF.getNumBlockIDs());
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- calculateCFAInfo(MF);
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-#ifndef NDEBUG
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- unsigned ErrorNum = verify(MF);
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- if (ErrorNum)
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- report_fatal_error("Found " + Twine(ErrorNum) +
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- " in/out CFI information errors.");
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-#endif
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- bool insertedCFI = insertCFIInstrs(MF);
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- MBBVector.clear();
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- return insertedCFI;
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- }
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-
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- private:
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- struct MBBCFAInfo {
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- MachineBasicBlock *MBB;
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- /// Value of cfa offset valid at basic block entry.
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- int IncomingCFAOffset = -1;
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- /// Value of cfa offset valid at basic block exit.
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- int OutgoingCFAOffset = -1;
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- /// Value of cfa register valid at basic block entry.
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- unsigned IncomingCFARegister = 0;
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- /// Value of cfa register valid at basic block exit.
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- unsigned OutgoingCFARegister = 0;
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- /// If in/out cfa offset and register values for this block have already
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- /// been set or not.
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- bool Processed = false;
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- };
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-
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- /// Contains cfa offset and register values valid at entry and exit of basic
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- /// blocks.
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- SmallVector<struct MBBCFAInfo, 4> MBBVector;
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-
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- /// Calculate cfa offset and register values valid at entry and exit for all
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- /// basic blocks in a function.
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- void calculateCFAInfo(MachineFunction &MF);
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- /// Calculate cfa offset and register values valid at basic block exit by
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- /// checking the block for CFI instructions. Block's incoming CFA info remains
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- /// the same.
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- void calculateOutgoingCFAInfo(struct MBBCFAInfo &MBBInfo);
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- /// Update in/out cfa offset and register values for successors of the basic
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- /// block.
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- void updateSuccCFAInfo(struct MBBCFAInfo &MBBInfo);
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-
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- /// Check if incoming CFA information of a basic block matches outgoing CFA
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- /// information of the previous block. If it doesn't, insert CFI instruction
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- /// at the beginning of the block that corrects the CFA calculation rule for
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- /// that block.
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- bool insertCFIInstrs(MachineFunction &MF);
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- /// Return the cfa offset value that should be set at the beginning of a MBB
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- /// if needed. The negated value is needed when creating CFI instructions that
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- /// set absolute offset.
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- int getCorrectCFAOffset(MachineBasicBlock *MBB) {
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- return -MBBVector[MBB->getNumber()].IncomingCFAOffset;
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- }
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-
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- void report(const char *msg, MachineBasicBlock &MBB);
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- /// Go through each MBB in a function and check that outgoing offset and
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- /// register of its predecessors match incoming offset and register of that
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- /// MBB, as well as that incoming offset and register of its successors match
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- /// outgoing offset and register of the MBB.
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- unsigned verify(MachineFunction &MF);
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-};
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-}
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-
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-char CFIInstrInserter::ID = 0;
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-INITIALIZE_PASS(CFIInstrInserter, "cfi-instr-inserter",
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- "Check CFA info and insert CFI instructions if needed", false,
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- false)
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-FunctionPass *llvm::createCFIInstrInserter() { return new CFIInstrInserter(); }
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-
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-void CFIInstrInserter::calculateCFAInfo(MachineFunction &MF) {
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- // Initial CFA offset value i.e. the one valid at the beginning of the
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- // function.
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- int InitialOffset =
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- MF.getSubtarget().getFrameLowering()->getInitialCFAOffset(MF);
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- // Initial CFA register value i.e. the one valid at the beginning of the
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- // function.
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- unsigned InitialRegister =
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- MF.getSubtarget().getFrameLowering()->getInitialCFARegister(MF);
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-
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- // Initialize MBBMap.
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- for (MachineBasicBlock &MBB : MF) {
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- struct MBBCFAInfo MBBInfo;
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- MBBInfo.MBB = &MBB;
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- MBBInfo.IncomingCFAOffset = InitialOffset;
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- MBBInfo.OutgoingCFAOffset = InitialOffset;
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- MBBInfo.IncomingCFARegister = InitialRegister;
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- MBBInfo.OutgoingCFARegister = InitialRegister;
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- MBBVector[MBB.getNumber()] = MBBInfo;
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- }
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-
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- // Set in/out cfa info for all blocks in the function. This traversal is based
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- // on the assumption that the first block in the function is the entry block
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- // i.e. that it has initial cfa offset and register values as incoming CFA
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- // information.
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- for (MachineBasicBlock &MBB : MF) {
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- if (MBBVector[MBB.getNumber()].Processed) continue;
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- calculateOutgoingCFAInfo(MBBVector[MBB.getNumber()]);
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- updateSuccCFAInfo(MBBVector[MBB.getNumber()]);
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- }
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-}
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-
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-void CFIInstrInserter::calculateOutgoingCFAInfo(struct MBBCFAInfo &MBBInfo) {
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- // Outgoing cfa offset set by the block.
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- int SetOffset = MBBInfo.IncomingCFAOffset;
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- // Outgoing cfa register set by the block.
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- unsigned SetRegister = MBBInfo.IncomingCFARegister;
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- const std::vector<MCCFIInstruction> &Instrs =
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- MBBInfo.MBB->getParent()->getFrameInstructions();
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-
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- // Determine cfa offset and register set by the block.
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- for (MachineInstr &MI :
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- make_range(MBBInfo.MBB->instr_begin(), MBBInfo.MBB->instr_end())) {
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- if (MI.isCFIInstruction()) {
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- unsigned CFIIndex = MI.getOperand(0).getCFIIndex();
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- const MCCFIInstruction &CFI = Instrs[CFIIndex];
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- if (CFI.getOperation() == MCCFIInstruction::OpDefCfaRegister) {
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- SetRegister = CFI.getRegister();
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- } else if (CFI.getOperation() == MCCFIInstruction::OpDefCfaOffset) {
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- SetOffset = CFI.getOffset();
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- } else if (CFI.getOperation() == MCCFIInstruction::OpAdjustCfaOffset) {
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- SetOffset += CFI.getOffset();
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- } else if (CFI.getOperation() == MCCFIInstruction::OpDefCfa) {
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- SetRegister = CFI.getRegister();
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- SetOffset = CFI.getOffset();
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- }
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- }
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- }
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-
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- MBBInfo.Processed = true;
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-
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- // Update outgoing CFA info.
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- MBBInfo.OutgoingCFAOffset = SetOffset;
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- MBBInfo.OutgoingCFARegister = SetRegister;
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-}
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-
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-void CFIInstrInserter::updateSuccCFAInfo(struct MBBCFAInfo &MBBInfo) {
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-
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- for (MachineBasicBlock *Succ : MBBInfo.MBB->successors()) {
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- struct MBBCFAInfo &SuccInfo = MBBVector[Succ->getNumber()];
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- if (SuccInfo.Processed) continue;
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- SuccInfo.IncomingCFAOffset = MBBInfo.OutgoingCFAOffset;
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- SuccInfo.IncomingCFARegister = MBBInfo.OutgoingCFARegister;
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- calculateOutgoingCFAInfo(SuccInfo);
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- updateSuccCFAInfo(SuccInfo);
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- }
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-}
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-
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-bool CFIInstrInserter::insertCFIInstrs(MachineFunction &MF) {
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-
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- const struct MBBCFAInfo *PrevMBBInfo = &MBBVector[MF.front().getNumber()];
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- const TargetInstrInfo *TII = MF.getSubtarget().getInstrInfo();
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- bool InsertedCFIInstr = false;
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-
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- for (MachineBasicBlock &MBB : MF) {
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- // Skip the first MBB in a function
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- if (MBB.getNumber() == MF.front().getNumber()) continue;
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-
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- const struct MBBCFAInfo& MBBInfo = MBBVector[MBB.getNumber()];
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- auto MBBI = MBBInfo.MBB->begin();
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- DebugLoc DL = MBBInfo.MBB->findDebugLoc(MBBI);
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-
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- if (PrevMBBInfo->OutgoingCFAOffset != MBBInfo.IncomingCFAOffset) {
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- // If both outgoing offset and register of a previous block don't match
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- // incoming offset and register of this block, add a def_cfa instruction
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- // with the correct offset and register for this block.
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- if (PrevMBBInfo->OutgoingCFARegister != MBBInfo.IncomingCFARegister) {
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- unsigned CFIIndex = MF.addFrameInst(MCCFIInstruction::createDefCfa(
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- nullptr, MBBInfo.IncomingCFARegister, getCorrectCFAOffset(&MBB)));
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- BuildMI(*MBBInfo.MBB, MBBI, DL, TII->get(TargetOpcode::CFI_INSTRUCTION))
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- .addCFIIndex(CFIIndex);
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- // If outgoing offset of a previous block doesn't match incoming offset
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- // of this block, add a def_cfa_offset instruction with the correct
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- // offset for this block.
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- } else {
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- unsigned CFIIndex =
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- MF.addFrameInst(MCCFIInstruction::createDefCfaOffset(
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- nullptr, getCorrectCFAOffset(&MBB)));
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- BuildMI(*MBBInfo.MBB, MBBI, DL, TII->get(TargetOpcode::CFI_INSTRUCTION))
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- .addCFIIndex(CFIIndex);
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- }
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- InsertedCFIInstr = true;
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- // If outgoing register of a previous block doesn't match incoming
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- // register of this block, add a def_cfa_register instruction with the
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- // correct register for this block.
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- } else if (PrevMBBInfo->OutgoingCFARegister != MBBInfo.IncomingCFARegister) {
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- unsigned CFIIndex =
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- MF.addFrameInst(MCCFIInstruction::createDefCfaRegister(
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- nullptr, MBBInfo.IncomingCFARegister));
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- BuildMI(*MBBInfo.MBB, MBBI, DL, TII->get(TargetOpcode::CFI_INSTRUCTION))
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- .addCFIIndex(CFIIndex);
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- InsertedCFIInstr = true;
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- }
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- PrevMBBInfo = &MBBInfo;
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- }
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- return InsertedCFIInstr;
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-}
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-
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-void CFIInstrInserter::report(const char *msg, MachineBasicBlock &MBB) {
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- errs() << '\n';
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- errs() << "*** " << msg << " ***\n"
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- << "- function: " << MBB.getParent()->getName() << "\n";
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- errs() << "- basic block: BB#" << MBB.getNumber() << ' ' << MBB.getName()
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- << " (" << (const void *)&MBB << ')';
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- errs() << '\n';
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-}
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-
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-unsigned CFIInstrInserter::verify(MachineFunction &MF) {
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- unsigned ErrorNum = 0;
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- for (MachineBasicBlock &CurrMBB : MF) {
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- const struct MBBCFAInfo& CurrMBBInfo = MBBVector[CurrMBB.getNumber()];
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- for (MachineBasicBlock *Pred : CurrMBB.predecessors()) {
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- const struct MBBCFAInfo& PredMBBInfo = MBBVector[Pred->getNumber()];
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- // Check that outgoing offset values of predecessors match the incoming
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- // offset value of CurrMBB
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- if (PredMBBInfo.OutgoingCFAOffset != CurrMBBInfo.IncomingCFAOffset) {
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- report("The outgoing offset of a predecessor is inconsistent.",
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- CurrMBB);
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- errs() << "Predecessor BB#" << Pred->getNumber()
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- << " has outgoing offset (" << PredMBBInfo.OutgoingCFAOffset
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- << "), while BB#" << CurrMBB.getNumber()
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- << " has incoming offset (" << CurrMBBInfo.IncomingCFAOffset
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- << ").\n";
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- ErrorNum++;
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- }
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- // Check that outgoing register values of predecessors match the incoming
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- // register value of CurrMBB
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- if (PredMBBInfo.OutgoingCFARegister != CurrMBBInfo.IncomingCFARegister) {
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- report("The outgoing register of a predecessor is inconsistent.",
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- CurrMBB);
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- errs() << "Predecessor BB#" << Pred->getNumber()
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- << " has outgoing register (" << PredMBBInfo.OutgoingCFARegister
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- << "), while BB#" << CurrMBB.getNumber()
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- << " has incoming register (" << CurrMBBInfo.IncomingCFARegister
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- << ").\n";
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- ErrorNum++;
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- }
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- }
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-
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- for (MachineBasicBlock *Succ : CurrMBB.successors()) {
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- const struct MBBCFAInfo& SuccMBBInfo = MBBVector[Succ->getNumber()];
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- // Check that incoming offset values of successors match the outgoing
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- // offset value of CurrMBB
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- if (SuccMBBInfo.IncomingCFAOffset != CurrMBBInfo.OutgoingCFAOffset) {
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- report("The incoming offset of a successor is inconsistent.", CurrMBB);
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- errs() << "Successor BB#" << Succ->getNumber()
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- << " has incoming offset (" << SuccMBBInfo.IncomingCFAOffset
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- << "), while BB#" << CurrMBB.getNumber()
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- << " has outgoing offset (" << CurrMBBInfo.OutgoingCFAOffset
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- << ").\n";
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- ErrorNum++;
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- }
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- // Check that incoming register values of successors match the outgoing
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- // register value of CurrMBB
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- if (SuccMBBInfo.IncomingCFARegister != CurrMBBInfo.OutgoingCFARegister) {
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- report("The incoming register of a successor is inconsistent.",
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- CurrMBB);
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- errs() << "Successor BB#" << Succ->getNumber()
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- << " has incoming register (" << SuccMBBInfo.IncomingCFARegister
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- << "), while BB#" << CurrMBB.getNumber()
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- << " has outgoing register (" << CurrMBBInfo.OutgoingCFARegister
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- << ").\n";
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- ErrorNum++;
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- }
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- }
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- }
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- return ErrorNum;
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-}
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