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Fix PHIElimination optimization that uses MBB->getBasicBlock.
The BasicBlock associated with a MachineBasicBlock does not necessarily correspond to the code in the MBB. Don't insert a new IR BasicBlock when splitting critical edges. We are not supposed to modify the IR during codegen, and we should be able to do just fine with a NULL BB. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@88707 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -15,8 +15,6 @@
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#define DEBUG_TYPE "phielim"
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#include "PHIElimination.h"
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#include "llvm/BasicBlock.h"
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#include "llvm/Instructions.h"
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#include "llvm/CodeGen/LiveVariables.h"
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#include "llvm/CodeGen/Passes.h"
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#include "llvm/CodeGen/MachineFunctionPass.h"
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@ -126,26 +124,28 @@ static bool isSourceDefinedByImplicitDef(const MachineInstr *MPhi,
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return true;
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}
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// FindCopyInsertPoint - Find a safe place in MBB to insert a copy from SrcReg.
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// This needs to be after any def or uses of SrcReg, but before any subsequent
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// point where control flow might jump out of the basic block.
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// FindCopyInsertPoint - Find a safe place in MBB to insert a copy from SrcReg
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// when following the CFG edge to SuccMBB. This needs to be after any def of
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// SrcReg, but before any subsequent point where control flow might jump out of
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// the basic block.
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MachineBasicBlock::iterator
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llvm::PHIElimination::FindCopyInsertPoint(MachineBasicBlock &MBB,
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MachineBasicBlock &SuccMBB,
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unsigned SrcReg) {
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// Handle the trivial case trivially.
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if (MBB.empty())
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return MBB.begin();
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// If this basic block does not contain an invoke, then control flow always
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// reaches the end of it, so place the copy there. The logic below works in
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// this case too, but is more expensive.
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if (!isa<InvokeInst>(MBB.getBasicBlock()->getTerminator()))
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// Usually, we just want to insert the copy before the first terminator
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// instruction. However, for the edge going to a landing pad, we must insert
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// the copy before the call/invoke instruction.
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if (!SuccMBB.isLandingPad())
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return MBB.getFirstTerminator();
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// Discover any definition/uses in this basic block.
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// Discover any definitions in this basic block.
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SmallPtrSet<MachineInstr*, 8> DefUsesInMBB;
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for (MachineRegisterInfo::reg_iterator RI = MRI->reg_begin(SrcReg),
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RE = MRI->reg_end(); RI != RE; ++RI) {
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for (MachineRegisterInfo::def_iterator RI = MRI->def_begin(SrcReg),
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RE = MRI->def_end(); RI != RE; ++RI) {
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MachineInstr *DefUseMI = &*RI;
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if (DefUseMI->getParent() == &MBB)
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DefUsesInMBB.insert(DefUseMI);
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@ -153,14 +153,14 @@ llvm::PHIElimination::FindCopyInsertPoint(MachineBasicBlock &MBB,
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MachineBasicBlock::iterator InsertPoint;
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if (DefUsesInMBB.empty()) {
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// No def/uses. Insert the copy at the start of the basic block.
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// No defs. Insert the copy at the start of the basic block.
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InsertPoint = MBB.begin();
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} else if (DefUsesInMBB.size() == 1) {
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// Insert the copy immediately after the definition/use.
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// Insert the copy immediately after the def.
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InsertPoint = *DefUsesInMBB.begin();
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++InsertPoint;
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} else {
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// Insert the copy immediately after the last definition/use.
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// Insert the copy immediately after the last def.
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InsertPoint = MBB.end();
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while (!DefUsesInMBB.count(&*--InsertPoint)) {}
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++InsertPoint;
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@ -272,7 +272,8 @@ void llvm::PHIElimination::LowerAtomicPHINode(
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// Find a safe location to insert the copy, this may be the first terminator
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// in the block (or end()).
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MachineBasicBlock::iterator InsertPos = FindCopyInsertPoint(opBlock, SrcReg);
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MachineBasicBlock::iterator InsertPos =
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FindCopyInsertPoint(opBlock, MBB, SrcReg);
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// Insert the copy.
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TII->copyRegToReg(opBlock, InsertPos, IncomingReg, SrcReg, RC, RC);
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@ -427,21 +428,8 @@ MachineBasicBlock *PHIElimination::SplitCriticalEdge(MachineBasicBlock *A,
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assert(A && B && "Missing MBB end point");
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++NumSplits;
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BasicBlock *ABB = const_cast<BasicBlock*>(A->getBasicBlock());
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BasicBlock *BBB = const_cast<BasicBlock*>(B->getBasicBlock());
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assert(ABB && BBB && "End points must have a basic block");
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BasicBlock *BB = BasicBlock::Create(BBB->getContext(),
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ABB->getName() + "." + BBB->getName() +
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"_phi_edge");
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Function *F = ABB->getParent();
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F->getBasicBlockList().insert(F->end(), BB);
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BranchInst::Create(BBB, BB);
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// We could do more here to produce correct IR, compare
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// llvm::SplitCriticalEdge
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MachineFunction *MF = A->getParent();
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MachineBasicBlock *NMBB = MF->CreateMachineBasicBlock(BB);
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MachineBasicBlock *NMBB = MF->CreateMachineBasicBlock();
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MF->push_back(NMBB);
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DEBUG(errs() << "PHIElimination splitting critical edge:"
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" BB#" << A->getNumber()
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@ -110,11 +110,12 @@ namespace llvm {
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MachineBasicBlock *SplitCriticalEdge(MachineBasicBlock *A,
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MachineBasicBlock *B);
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// FindCopyInsertPoint - Find a safe place in MBB to insert a copy from
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// SrcReg. This needs to be after any def or uses of SrcReg, but before
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// any subsequent point where control flow might jump out of the basic
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// block.
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/// FindCopyInsertPoint - Find a safe place in MBB to insert a copy from
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/// SrcReg when following the CFG edge to SuccMBB. This needs to be after
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/// any def of SrcReg, but before any subsequent point where control flow
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/// might jump out of the basic block.
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MachineBasicBlock::iterator FindCopyInsertPoint(MachineBasicBlock &MBB,
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MachineBasicBlock &SuccMBB,
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unsigned SrcReg);
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// SkipPHIsAndLabels - Copies need to be inserted after phi nodes and
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