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[X86] Correct dwarf unwind information in function epilogue
CFI instructions that set appropriate cfa offset and cfa register are now inserted in emitEpilogue() in X86FrameLowering. Majority of the changes in this patch: 1. Ensure that CFI instructions do not affect code generation. 2. Enable maintaining correct information about cfa offset and cfa register in a function when basic blocks are reordered, merged, split, duplicated. These changes are target independent and described below. Changed CFI instructions so that they: 1. are duplicable 2. are not counted as instructions when tail duplicating or tail merging 3. can be compared as equal Add information to each MachineBasicBlock about cfa offset and cfa register that are valid at its entry and exit (incoming and outgoing CFI info). Add support for updating this information when basic blocks are merged, split, duplicated, created. Add a verification pass (CFIInfoVerifier) that checks that outgoing cfa offset and register of predecessor blocks match incoming values of their successors. Incoming and outgoing CFI information is used by a late pass (CFIInstrInserter) that corrects CFA calculation rule for a basic block if needed. That means that additional CFI instructions get inserted at basic block beginning to correct the rule for calculating CFA. Having CFI instructions in function epilogue can cause incorrect CFA calculation rule for some basic blocks. This can happen if, due to basic block reordering, or the existence of multiple epilogue blocks, some of the blocks have wrong cfa offset and register values set by the epilogue block above them. Patch by Violeta Vukobrat. Differential Revision: https://reviews.llvm.org/D18046 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@306529 91177308-0d34-0410-b5e6-96231b3b80d8
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,123 @@ | ||
| //===----------- CFIInfoVerifier.cpp - CFI Information Verifier -----------===// | ||
| // | ||
| // The LLVM Compiler Infrastructure | ||
| // | ||
| // This file is distributed under the University of Illinois Open Source | ||
| // License. See LICENSE.TXT for details. | ||
| // | ||
| //===----------------------------------------------------------------------===// | ||
| // | ||
| // This pass verifies incoming and outgoing CFI information of basic blocks. CFI | ||
| // information is information about offset and register set by CFI directives, | ||
| // valid at the start and end of a basic block. This pass checks that outgoing | ||
| // information of predecessors matches incoming information of their successors. | ||
| //===----------------------------------------------------------------------===// | ||
|
|
||
| #include "llvm/CodeGen/MachineFunctionPass.h" | ||
| #include "llvm/CodeGen/MachineModuleInfo.h" | ||
| #include "llvm/CodeGen/Passes.h" | ||
| #include "llvm/Target/TargetMachine.h" | ||
| using namespace llvm; | ||
|
|
||
| namespace { | ||
| class CFIInfoVerifier : public MachineFunctionPass { | ||
| public: | ||
| static char ID; | ||
|
|
||
| CFIInfoVerifier() : MachineFunctionPass(ID) { | ||
| initializeCFIInfoVerifierPass(*PassRegistry::getPassRegistry()); | ||
| } | ||
|
|
||
| void getAnalysisUsage(AnalysisUsage &AU) const override { | ||
| AU.setPreservesAll(); | ||
| MachineFunctionPass::getAnalysisUsage(AU); | ||
| } | ||
|
|
||
| bool runOnMachineFunction(MachineFunction &MF) override { | ||
| bool NeedsDwarfCFI = (MF.getMMI().hasDebugInfo() || | ||
| MF.getFunction()->needsUnwindTableEntry()) && | ||
| (!MF.getTarget().getTargetTriple().isOSDarwin() && | ||
| !MF.getTarget().getTargetTriple().isOSWindows()); | ||
| if (!NeedsDwarfCFI) return false; | ||
| verify(MF); | ||
| return false; | ||
| } | ||
|
|
||
| private: | ||
| // Go through each MBB in a function and check that outgoing offset and | ||
| // register of its predecessors match incoming offset and register of that | ||
| // MBB, as well as that incoming offset and register of its successors match | ||
| // outgoing offset and register of the MBB. | ||
| void verify(MachineFunction &MF); | ||
| void report(const char *msg, MachineBasicBlock &MBB); | ||
| }; | ||
| } | ||
|
|
||
| char CFIInfoVerifier::ID = 0; | ||
| INITIALIZE_PASS(CFIInfoVerifier, "cfiinfoverifier", | ||
| "Verify that corresponding in/out CFI info matches", false, | ||
| false) | ||
| FunctionPass *llvm::createCFIInfoVerifier() { return new CFIInfoVerifier(); } | ||
|
|
||
| void CFIInfoVerifier::verify(MachineFunction &MF) { | ||
| for (auto &CurrMBB : MF) { | ||
| for (auto Pred : CurrMBB.predecessors()) { | ||
| // Check that outgoing offset values of predecessors match the incoming | ||
| // offset value of CurrMBB | ||
| if (Pred->getOutgoingCFAOffset() != CurrMBB.getIncomingCFAOffset()) { | ||
| report("The outgoing offset of a predecessor is inconsistent.", | ||
| CurrMBB); | ||
| errs() << "Predecessor BB#" << Pred->getNumber() | ||
| << " has outgoing offset (" << Pred->getOutgoingCFAOffset() | ||
| << "), while BB#" << CurrMBB.getNumber() | ||
| << " has incoming offset (" << CurrMBB.getIncomingCFAOffset() | ||
| << ").\n"; | ||
| } | ||
| // Check that outgoing register values of predecessors match the incoming | ||
| // register value of CurrMBB | ||
| if (Pred->getOutgoingCFARegister() != CurrMBB.getIncomingCFARegister()) { | ||
| report("The outgoing register of a predecessor is inconsistent.", | ||
| CurrMBB); | ||
| errs() << "Predecessor BB#" << Pred->getNumber() | ||
| << " has outgoing register (" << Pred->getOutgoingCFARegister() | ||
| << "), while BB#" << CurrMBB.getNumber() | ||
| << " has incoming register (" << CurrMBB.getIncomingCFARegister() | ||
| << ").\n"; | ||
| } | ||
| } | ||
|
|
||
| for (auto Succ : CurrMBB.successors()) { | ||
| // Check that incoming offset values of successors match the outgoing | ||
| // offset value of CurrMBB | ||
| if (Succ->getIncomingCFAOffset() != CurrMBB.getOutgoingCFAOffset()) { | ||
| report("The incoming offset of a successor is inconsistent.", CurrMBB); | ||
| errs() << "Successor BB#" << Succ->getNumber() | ||
| << " has incoming offset (" << Succ->getIncomingCFAOffset() | ||
| << "), while BB#" << CurrMBB.getNumber() | ||
| << " has outgoing offset (" << CurrMBB.getOutgoingCFAOffset() | ||
| << ").\n"; | ||
| } | ||
| // Check that incoming register values of successors match the outgoing | ||
| // register value of CurrMBB | ||
| if (Succ->getIncomingCFARegister() != CurrMBB.getOutgoingCFARegister()) { | ||
| report("The incoming register of a successor is inconsistent.", | ||
| CurrMBB); | ||
| errs() << "Successor BB#" << Succ->getNumber() | ||
| << " has incoming register (" << Succ->getIncomingCFARegister() | ||
| << "), while BB#" << CurrMBB.getNumber() | ||
| << " has outgoing register (" << CurrMBB.getOutgoingCFARegister() | ||
| << ").\n"; | ||
| } | ||
| } | ||
| } | ||
| } | ||
|
|
||
| void CFIInfoVerifier::report(const char *msg, MachineBasicBlock &MBB) { | ||
| assert(&MBB); | ||
| errs() << '\n'; | ||
| errs() << "*** " << msg << " ***\n" | ||
| << "- function: " << MBB.getParent()->getName() << "\n"; | ||
| errs() << "- basic block: BB#" << MBB.getNumber() << ' ' << MBB.getName() | ||
| << " (" << (const void *)&MBB << ')'; | ||
| errs() << '\n'; | ||
| } |
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