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Fix diamond shape ifcvt bugs.
llvm-svn: 37444
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3aa2107b02
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@ -284,7 +284,7 @@ void IfConverter::StructuralAnalysis(MachineBasicBlock *BB) {
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}
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} else if (TrueBBI.TrueBB == FalseBBI.TrueBB && CanRevCond &&
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TrueBBI.BB->pred_size() == 1 &&
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TrueBBI.BB->pred_size() == 1 &&
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FalseBBI.BB->pred_size() == 1 &&
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// Check the 'true' and 'false' blocks if either isn't ended with
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// a branch. If the block does not fallthrough to another block
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// then we need to add a branch to its successor.
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@ -301,7 +301,7 @@ void IfConverter::StructuralAnalysis(MachineBasicBlock *BB) {
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// TBB FBB
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// \ /
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// TailBB
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// Note MBB can be empty in case both TBB and FBB are return blocks.
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// Note TailBB can be empty.
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BBI.Kind = ICDiamond;
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TrueBBI.Kind = FalseBBI.Kind = ICChild;
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BBI.TailBB = TrueBBI.TrueBB;
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@ -611,74 +611,58 @@ bool IfConverter::IfConvertDiamond(BBInfo &BBI) {
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--TrueBBI.NonPredSize;
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}
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// Check the 'true' and 'false' blocks if either isn't ended with a branch.
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// Either the block fallthrough to another block or it ends with a
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// return. If it's the former, add a branch to its successor.
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bool TrueNeedBr = !TrueBBI.TrueBB && BBI.TrueBB->succ_size();
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bool FalseNeedBr = !FalseBBI.TrueBB && BBI.FalseBB->succ_size();
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// Merge the 'true' and 'false' blocks by copying the instructions
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// from the 'false' block to the 'true' block. That is, unless the true
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// block would clobber the predicate, in that case, do the opposite.
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BBInfo *BBI1 = &TrueBBI;
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BBInfo *BBI2 = &FalseBBI;
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std::vector<MachineOperand> RevCond(BBI.BrCond);
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TII->ReverseBranchCondition(RevCond);
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BBInfo *CvtBBI;
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if (!TrueBBI.ModifyPredicate) {
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// Predicate the 'true' block after removing its branch.
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TrueBBI.NonPredSize -= TII->RemoveBranch(*BBI.TrueBB);
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PredicateBlock(TrueBBI, BBI.BrCond);
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// Predicate the 'false' block.
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PredicateBlock(FalseBBI, RevCond, true);
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if (TrueNeedBr)
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TII->InsertBranch(*BBI.TrueBB, *BBI.TrueBB->succ_begin(), NULL,
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BBI.BrCond);
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// Add an unconditional branch from 'false' to to 'false' successor if it
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// will not be the fallthrough block.
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if (FalseNeedBr &&
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!isNextBlock(BBI.BB, *BBI.FalseBB->succ_begin()))
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InsertUncondBranch(BBI.FalseBB, *BBI.FalseBB->succ_begin(), TII);
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MergeBlocks(TrueBBI, FalseBBI);
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CvtBBI = &TrueBBI;
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} else {
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// Predicate the 'false' block after removing its branch.
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FalseBBI.NonPredSize -= TII->RemoveBranch(*BBI.FalseBB);
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PredicateBlock(FalseBBI, RevCond);
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// Predicate the 'false' block.
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PredicateBlock(TrueBBI, BBI.BrCond, true);
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// Add a conditional branch from 'false' to 'false' successor if needed.
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if (FalseNeedBr)
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TII->InsertBranch(*BBI.FalseBB, *BBI.FalseBB->succ_begin(), NULL,
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RevCond);
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// Add an unconditional branch from 'true' to to 'true' successor if it
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// will not be the fallthrough block.
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if (TrueNeedBr &&
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!isNextBlock(BBI.BB, *BBI.TrueBB->succ_begin()))
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InsertUncondBranch(BBI.TrueBB, *BBI.TrueBB->succ_begin(), TII);
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MergeBlocks(FalseBBI, TrueBBI);
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CvtBBI = &FalseBBI;
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std::vector<MachineOperand> *Cond1 = &BBI.BrCond;
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std::vector<MachineOperand> *Cond2 = &RevCond;
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if (TrueBBI.ModifyPredicate) {
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std::swap(BBI1, BBI2);
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std::swap(Cond1, Cond2);
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}
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// Check the 'true' and 'false' blocks if either isn't ended with a branch.
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// Either the block fallthrough to another block or it ends with a
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// return. If it's the former, add a branch to its successor.
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bool NeedBr1 = !BBI1->TrueBB && BBI1->BB->succ_size();
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bool NeedBr2 = !BBI2->TrueBB && BBI1->BB->succ_size();
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// Predicate the 'true' block after removing its branch.
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BBI1->NonPredSize -= TII->RemoveBranch(*BBI1->BB);
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PredicateBlock(*BBI1, *Cond1);
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// Add an early exit branch if needed.
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if (NeedBr1)
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TII->InsertBranch(*BBI1->BB, *BBI1->BB->succ_begin(), NULL, *Cond1);
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// Predicate the 'false' block.
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PredicateBlock(*BBI2, *Cond2, true);
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// Add an unconditional branch from 'false' to to 'false' successor if it
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// will not be the fallthrough block.
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if (NeedBr2 && !isNextBlock(BBI2->BB, *BBI2->BB->succ_begin()))
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InsertUncondBranch(BBI2->BB, *BBI2->BB->succ_begin(), TII);
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// Keep them as two separate blocks if there is an early exit.
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if (!NeedBr1)
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MergeBlocks(*BBI1, *BBI2);
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else if (!isNextBlock(BBI1->BB, BBI2->BB))
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InsertUncondBranch(BBI1->BB, BBI2->BB, TII);
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// Remove the conditional branch from entry to the blocks.
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BBI.NonPredSize -= TII->RemoveBranch(*BBI.BB);
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bool OkToIfcvt = true;
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// Merge the combined block into the entry of the diamond if the entry
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// block is its only predecessor. Otherwise, insert an unconditional
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// branch from entry to the if-converted block.
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if (CvtBBI->BB->pred_size() == 1) {
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MergeBlocks(BBI, *CvtBBI);
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CvtBBI = &BBI;
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OkToIfcvt = false;
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} else if (!isNextBlock(BBI.BB, CvtBBI->BB))
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InsertUncondBranch(BBI.BB, CvtBBI->BB, TII);
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// Merge the combined block into the entry of the diamond.
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MergeBlocks(BBI, *BBI1);
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// If the if-converted block fallthrough or unconditionally branch into the
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// tail block, and the tail block does not have other predecessors, then
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// fold the tail block in as well.
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BBInfo *CvtBBI = NeedBr1 ? BBI2 : &BBI;
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if (BBI.TailBB &&
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BBI.TailBB->pred_size() == 1 && CvtBBI->BB->succ_size() == 1) {
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CvtBBI->NonPredSize -= TII->RemoveBranch(*CvtBBI->BB);
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@ -687,11 +671,7 @@ bool IfConverter::IfConvertDiamond(BBInfo &BBI) {
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TailBBI.Kind = ICDead;
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}
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// Update block info. BB may be iteratively if-converted.
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if (OkToIfcvt) {
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BBI.Kind = ICReAnalyze;
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ReTryPreds(BBI.BB);
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}
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// Update block info.
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TrueBBI.Kind = ICDead;
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FalseBBI.Kind = ICDead;
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