From 44da7ca4213333bcade57a407a890970351db494 Mon Sep 17 00:00:00 2001 From: Chris Lattner Date: Tue, 14 Dec 2010 07:41:39 +0000 Subject: [PATCH] clean up logic, convert std::set to SmallPtrSet, handle the case when all 2-entry phis are simplified away. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@121760 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/Transforms/Utils/SimplifyCFG.cpp | 117 ++++++++++++++------------- 1 file changed, 61 insertions(+), 56 deletions(-) diff --git a/lib/Transforms/Utils/SimplifyCFG.cpp b/lib/Transforms/Utils/SimplifyCFG.cpp index 5f7eb9e3801..288ff0462bc 100644 --- a/lib/Transforms/Utils/SimplifyCFG.cpp +++ b/lib/Transforms/Utils/SimplifyCFG.cpp @@ -199,7 +199,7 @@ static Value *GetIfCondition(BasicBlock *BB, BasicBlock *&IfTrue, /// non-trapping. If both are true, the instruction is inserted into the set /// and true is returned. static bool DominatesMergePoint(Value *V, BasicBlock *BB, - std::set *AggressiveInsts) { + SmallPtrSet *AggressiveInsts) { Instruction *I = dyn_cast(V); if (!I) { // Non-instructions all dominate instructions, but not all constantexprs @@ -217,50 +217,49 @@ static bool DominatesMergePoint(Value *V, BasicBlock *BB, // If this instruction is defined in a block that contains an unconditional // branch to BB, then it must be in the 'conditional' part of the "if - // statement". - if (BranchInst *BI = dyn_cast(PBB->getTerminator())) - if (BI->isUnconditional() && BI->getSuccessor(0) == BB) { - if (!AggressiveInsts) return false; - // Okay, it looks like the instruction IS in the "condition". Check to - // see if it's a cheap instruction to unconditionally compute, and if it - // only uses stuff defined outside of the condition. If so, hoist it out. - if (!I->isSafeToSpeculativelyExecute()) - return false; + // statement". If not, it definitely dominates the region. + BranchInst *BI = dyn_cast(PBB->getTerminator()); + if (BI == 0 || BI->isConditional() || BI->getSuccessor(0) != BB) + return true; - switch (I->getOpcode()) { - default: return false; // Cannot hoist this out safely. - case Instruction::Load: { - // We have to check to make sure there are no instructions before the - // load in its basic block, as we are going to hoist the loop out to - // its predecessor. - BasicBlock::iterator IP = PBB->begin(); - while (isa(IP)) - IP++; - if (IP != BasicBlock::iterator(I)) - return false; - break; - } - case Instruction::Add: - case Instruction::Sub: - case Instruction::And: - case Instruction::Or: - case Instruction::Xor: - case Instruction::Shl: - case Instruction::LShr: - case Instruction::AShr: - case Instruction::ICmp: - break; // These are all cheap and non-trapping instructions. - } + // If we aren't allowing aggressive promotion anymore, then don't consider + // instructions in the 'if region'. + if (AggressiveInsts == 0) return false; + + // Okay, it looks like the instruction IS in the "condition". Check to + // see if it's a cheap instruction to unconditionally compute, and if it + // only uses stuff defined outside of the condition. If so, hoist it out. + if (!I->isSafeToSpeculativelyExecute()) + return false; - // Okay, we can only really hoist these out if their operands are not - // defined in the conditional region. - for (User::op_iterator i = I->op_begin(), e = I->op_end(); i != e; ++i) - if (!DominatesMergePoint(*i, BB, 0)) - return false; - // Okay, it's safe to do this! Remember this instruction. - AggressiveInsts->insert(I); - } + switch (I->getOpcode()) { + default: return false; // Cannot hoist this out safely. + case Instruction::Load: + // We have to check to make sure there are no instructions before the + // load in its basic block, as we are going to hoist the load out to its + // predecessor. + if (PBB->getFirstNonPHIOrDbg() != I) + return false; + break; + case Instruction::Add: + case Instruction::Sub: + case Instruction::And: + case Instruction::Or: + case Instruction::Xor: + case Instruction::Shl: + case Instruction::LShr: + case Instruction::AShr: + case Instruction::ICmp: + break; // These are all cheap and non-trapping instructions. + } + // Okay, we can only really hoist these out if their operands are not + // defined in the conditional region. + for (User::op_iterator i = I->op_begin(), e = I->op_end(); i != e; ++i) + if (!DominatesMergePoint(*i, BB, 0)) + return false; + // Okay, it's safe to do this! Remember this instruction. + AggressiveInsts->insert(I); return true; } @@ -1164,7 +1163,7 @@ static bool FoldTwoEntryPHINode(PHINode *PN, const TargetData *TD) { // Loop over the PHI's seeing if we can promote them all to select // instructions. While we are at it, keep track of the instructions // that need to be moved to the dominating block. - std::set AggressiveInsts; + SmallPtrSet AggressiveInsts; BasicBlock::iterator AfterPHIIt = BB->begin(); while (isa(AfterPHIIt)) { @@ -1179,17 +1178,23 @@ static bool FoldTwoEntryPHINode(PHINode *PN, const TargetData *TD) { return false; } + // If we folded the the first phi, PN dangles at this point. Refresh it. If + // we ran out of PHIs then we simplified them all. + PN = dyn_cast(BB->begin()); + if (PN == 0) return true; + // If we all PHI nodes are promotable, check to make sure that all // instructions in the predecessor blocks can be promoted as well. If // not, we won't be able to get rid of the control flow, so it's not // worth promoting to select instructions. - BasicBlock *DomBlock = 0, *IfBlock1 = 0, *IfBlock2 = 0; - PN = cast(BB->begin()); - BasicBlock *Pred = PN->getIncomingBlock(0); - if (cast(Pred->getTerminator())->isUnconditional()) { - IfBlock1 = Pred; - DomBlock = *pred_begin(Pred); - for (BasicBlock::iterator I = Pred->begin(); !isa(I); ++I) + BasicBlock *DomBlock = 0; + BasicBlock *IfBlock1 = PN->getIncomingBlock(0); + BasicBlock *IfBlock2 = PN->getIncomingBlock(1); + if (cast(IfBlock1->getTerminator())->isConditional()) { + IfBlock1 = 0; + } else { + DomBlock = *pred_begin(IfBlock1); + for (BasicBlock::iterator I = IfBlock1->begin();!isa(I);++I) if (!AggressiveInsts.count(I) && !isa(I)) { // This is not an aggressive instruction that we can promote. // Because of this, we won't be able to get rid of the control @@ -1198,11 +1203,11 @@ static bool FoldTwoEntryPHINode(PHINode *PN, const TargetData *TD) { } } - Pred = PN->getIncomingBlock(1); - if (cast(Pred->getTerminator())->isUnconditional()) { - IfBlock2 = Pred; - DomBlock = *pred_begin(Pred); - for (BasicBlock::iterator I = Pred->begin(); !isa(I); ++I) + if (cast(IfBlock2->getTerminator())->isConditional()) { + IfBlock2 = 0; + } else { + DomBlock = *pred_begin(IfBlock2); + for (BasicBlock::iterator I = IfBlock2->begin();!isa(I);++I) if (!AggressiveInsts.count(I) && !isa(I)) { // This is not an aggressive instruction that we can promote. // Because of this, we won't be able to get rid of the control @@ -1212,7 +1217,7 @@ static bool FoldTwoEntryPHINode(PHINode *PN, const TargetData *TD) { } DEBUG(dbgs() << "FOUND IF CONDITION! " << *IfCond << " T: " - << IfTrue->getName() << " F: " << IfFalse->getName() << "\n"); + << IfTrue->getName() << " F: " << IfFalse->getName() << "\n"); // If we can still promote the PHI nodes after this gauntlet of tests, // do all of the PHI's now.