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author | Evan Cheng <evan.cheng@apple.com> | 2007-06-05 23:46:14 +0000 |
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committer | Evan Cheng <evan.cheng@apple.com> | 2007-06-05 23:46:14 +0000 |
commit | 993fc9594eca60ef5294b4c90cb2e36dd2503163 (patch) | |
tree | 8596354a361436ca7e286e7768fbe427801c5d77 /lib/CodeGen | |
parent | 1d4eb6ab0df28044d5ea43926390e8f20cf27874 (diff) | |
download | external_llvm-993fc9594eca60ef5294b4c90cb2e36dd2503163.zip external_llvm-993fc9594eca60ef5294b4c90cb2e36dd2503163.tar.gz external_llvm-993fc9594eca60ef5294b4c90cb2e36dd2503163.tar.bz2 |
Fix diamond shape ifcvt bugs.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@37444 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'lib/CodeGen')
-rw-r--r-- | lib/CodeGen/IfConversion.cpp | 102 |
1 files changed, 41 insertions, 61 deletions
diff --git a/lib/CodeGen/IfConversion.cpp b/lib/CodeGen/IfConversion.cpp index e06fb26..b44ad2e 100644 --- a/lib/CodeGen/IfConversion.cpp +++ b/lib/CodeGen/IfConversion.cpp @@ -284,7 +284,7 @@ void IfConverter::StructuralAnalysis(MachineBasicBlock *BB) { } } else if (TrueBBI.TrueBB == FalseBBI.TrueBB && CanRevCond && TrueBBI.BB->pred_size() == 1 && - TrueBBI.BB->pred_size() == 1 && + FalseBBI.BB->pred_size() == 1 && // Check the 'true' and 'false' blocks if either isn't ended with // a branch. If the block does not fallthrough to another block // then we need to add a branch to its successor. @@ -301,7 +301,7 @@ void IfConverter::StructuralAnalysis(MachineBasicBlock *BB) { // TBB FBB // \ / // TailBB - // Note MBB can be empty in case both TBB and FBB are return blocks. + // Note TailBB can be empty. BBI.Kind = ICDiamond; TrueBBI.Kind = FalseBBI.Kind = ICChild; BBI.TailBB = TrueBBI.TrueBB; @@ -611,74 +611,58 @@ bool IfConverter::IfConvertDiamond(BBInfo &BBI) { --TrueBBI.NonPredSize; } - // Check the 'true' and 'false' blocks if either isn't ended with a branch. - // Either the block fallthrough to another block or it ends with a - // return. If it's the former, add a branch to its successor. - bool TrueNeedBr = !TrueBBI.TrueBB && BBI.TrueBB->succ_size(); - bool FalseNeedBr = !FalseBBI.TrueBB && BBI.FalseBB->succ_size(); - // Merge the 'true' and 'false' blocks by copying the instructions // from the 'false' block to the 'true' block. That is, unless the true // block would clobber the predicate, in that case, do the opposite. + BBInfo *BBI1 = &TrueBBI; + BBInfo *BBI2 = &FalseBBI; std::vector<MachineOperand> RevCond(BBI.BrCond); TII->ReverseBranchCondition(RevCond); - BBInfo *CvtBBI; - if (!TrueBBI.ModifyPredicate) { - // Predicate the 'true' block after removing its branch. - TrueBBI.NonPredSize -= TII->RemoveBranch(*BBI.TrueBB); - PredicateBlock(TrueBBI, BBI.BrCond); - - // Predicate the 'false' block. - PredicateBlock(FalseBBI, RevCond, true); - - if (TrueNeedBr) - TII->InsertBranch(*BBI.TrueBB, *BBI.TrueBB->succ_begin(), NULL, - BBI.BrCond); - // Add an unconditional branch from 'false' to to 'false' successor if it - // will not be the fallthrough block. - if (FalseNeedBr && - !isNextBlock(BBI.BB, *BBI.FalseBB->succ_begin())) - InsertUncondBranch(BBI.FalseBB, *BBI.FalseBB->succ_begin(), TII); - MergeBlocks(TrueBBI, FalseBBI); - CvtBBI = &TrueBBI; - } else { - // Predicate the 'false' block after removing its branch. - FalseBBI.NonPredSize -= TII->RemoveBranch(*BBI.FalseBB); - PredicateBlock(FalseBBI, RevCond); - - // Predicate the 'false' block. - PredicateBlock(TrueBBI, BBI.BrCond, true); - - // Add a conditional branch from 'false' to 'false' successor if needed. - if (FalseNeedBr) - TII->InsertBranch(*BBI.FalseBB, *BBI.FalseBB->succ_begin(), NULL, - RevCond); - // Add an unconditional branch from 'true' to to 'true' successor if it - // will not be the fallthrough block. - if (TrueNeedBr && - !isNextBlock(BBI.BB, *BBI.TrueBB->succ_begin())) - InsertUncondBranch(BBI.TrueBB, *BBI.TrueBB->succ_begin(), TII); - MergeBlocks(FalseBBI, TrueBBI); - CvtBBI = &FalseBBI; + std::vector<MachineOperand> *Cond1 = &BBI.BrCond; + std::vector<MachineOperand> *Cond2 = &RevCond; + if (TrueBBI.ModifyPredicate) { + std::swap(BBI1, BBI2); + std::swap(Cond1, Cond2); } + // Check the 'true' and 'false' blocks if either isn't ended with a branch. + // Either the block fallthrough to another block or it ends with a + // return. If it's the former, add a branch to its successor. + bool NeedBr1 = !BBI1->TrueBB && BBI1->BB->succ_size(); + bool NeedBr2 = !BBI2->TrueBB && BBI1->BB->succ_size(); + + // Predicate the 'true' block after removing its branch. + BBI1->NonPredSize -= TII->RemoveBranch(*BBI1->BB); + PredicateBlock(*BBI1, *Cond1); + + // Add an early exit branch if needed. + if (NeedBr1) + TII->InsertBranch(*BBI1->BB, *BBI1->BB->succ_begin(), NULL, *Cond1); + + // Predicate the 'false' block. + PredicateBlock(*BBI2, *Cond2, true); + + // Add an unconditional branch from 'false' to to 'false' successor if it + // will not be the fallthrough block. + if (NeedBr2 && !isNextBlock(BBI2->BB, *BBI2->BB->succ_begin())) + InsertUncondBranch(BBI2->BB, *BBI2->BB->succ_begin(), TII); + + // Keep them as two separate blocks if there is an early exit. + if (!NeedBr1) + MergeBlocks(*BBI1, *BBI2); + else if (!isNextBlock(BBI1->BB, BBI2->BB)) + InsertUncondBranch(BBI1->BB, BBI2->BB, TII); + // Remove the conditional branch from entry to the blocks. BBI.NonPredSize -= TII->RemoveBranch(*BBI.BB); - bool OkToIfcvt = true; - // Merge the combined block into the entry of the diamond if the entry - // block is its only predecessor. Otherwise, insert an unconditional - // branch from entry to the if-converted block. - if (CvtBBI->BB->pred_size() == 1) { - MergeBlocks(BBI, *CvtBBI); - CvtBBI = &BBI; - OkToIfcvt = false; - } else if (!isNextBlock(BBI.BB, CvtBBI->BB)) - InsertUncondBranch(BBI.BB, CvtBBI->BB, TII); + // Merge the combined block into the entry of the diamond. + MergeBlocks(BBI, *BBI1); // If the if-converted block fallthrough or unconditionally branch into the // tail block, and the tail block does not have other predecessors, then // fold the tail block in as well. + BBInfo *CvtBBI = NeedBr1 ? BBI2 : &BBI; if (BBI.TailBB && BBI.TailBB->pred_size() == 1 && CvtBBI->BB->succ_size() == 1) { CvtBBI->NonPredSize -= TII->RemoveBranch(*CvtBBI->BB); @@ -687,11 +671,7 @@ bool IfConverter::IfConvertDiamond(BBInfo &BBI) { TailBBI.Kind = ICDead; } - // Update block info. BB may be iteratively if-converted. - if (OkToIfcvt) { - BBI.Kind = ICReAnalyze; - ReTryPreds(BBI.BB); - } + // Update block info. TrueBBI.Kind = ICDead; FalseBBI.Kind = ICDead; |