diff --git a/lib/Transforms/Utils/SimplifyCFG.cpp b/lib/Transforms/Utils/SimplifyCFG.cpp index e7bd75e0493..366021e6480 100644 --- a/lib/Transforms/Utils/SimplifyCFG.cpp +++ b/lib/Transforms/Utils/SimplifyCFG.cpp @@ -386,6 +386,7 @@ static bool DominatesMergePoint(Value *V, BasicBlock *BB, // We can hoist loads that are non-volatile and obviously cannot trap. if (cast(I)->isVolatile()) return false; + // FIXME: A computation of a constant can trap! if (!isa(I->getOperand(0)) && !isa(I->getOperand(0))) return false; @@ -494,6 +495,19 @@ static bool GatherValueComparisons(Instruction *Cond, Value *&CompVal, return false; } +static void EraseTerminatorInstAndDCECond(TerminatorInst *TI) { + Instruction* Cond = 0; + if (SwitchInst *SI = dyn_cast(TI)) { + Cond = dyn_cast(SI->getCondition()); + } else if (BranchInst *BI = dyn_cast(TI)) { + if (BI->isConditional()) + Cond = dyn_cast(BI->getCondition()); + } + + TI->eraseFromParent(); + if (Cond) RecursivelyDeleteTriviallyDeadInstructions(Cond); +} + /// isValueEqualityComparison - Return true if the specified terminator checks /// to see if a value is equal to constant integer value. static Value *isValueEqualityComparison(TerminatorInst *TI) { @@ -617,11 +631,10 @@ static bool SimplifyEqualityComparisonWithOnlyPredecessor(TerminatorInst *TI, // PredCases. If there are any cases in ThisCases that are in PredCases, we // can simplify TI. if (ValuesOverlap(PredCases, ThisCases)) { - if (BranchInst *BTI = dyn_cast(TI)) { + if (isa(TI)) { // Okay, one of the successors of this condbr is dead. Convert it to a // uncond br. assert(ThisCases.size() == 1 && "Branch can only have one case!"); - Value *Cond = BTI->getCondition(); // Insert the new branch. Instruction *NI = BranchInst::Create(ThisDef, TI); @@ -631,10 +644,7 @@ static bool SimplifyEqualityComparisonWithOnlyPredecessor(TerminatorInst *TI, DOUT << "Threading pred instr: " << *Pred->getTerminator() << "Through successor TI: " << *TI << "Leaving: " << *NI << "\n"; - TI->eraseFromParent(); // Nuke the old one. - // If condition is now dead, nuke it. - if (Instruction *CondI = dyn_cast(Cond)) - RecursivelyDeleteTriviallyDeadInstructions(CondI); + EraseTerminatorInstAndDCECond(TI); return true; } else { @@ -697,12 +707,8 @@ static bool SimplifyEqualityComparisonWithOnlyPredecessor(TerminatorInst *TI, DOUT << "Threading pred instr: " << *Pred->getTerminator() << "Through successor TI: " << *TI << "Leaving: " << *NI << "\n"; - Instruction *Cond = 0; - if (BranchInst *BI = dyn_cast(TI)) - Cond = dyn_cast(BI->getCondition()); - TI->eraseFromParent(); // Nuke the old one. - if (Cond) RecursivelyDeleteTriviallyDeadInstructions(Cond); + EraseTerminatorInstAndDCECond(TI); return true; } return false; @@ -811,14 +817,7 @@ static bool FoldValueComparisonIntoPredecessors(TerminatorInst *TI) { for (unsigned i = 0, e = PredCases.size(); i != e; ++i) NewSI->addCase(PredCases[i].first, PredCases[i].second); - Instruction *DeadCond = 0; - if (BranchInst *BI = dyn_cast(PTI)) - // If PTI is a branch, remember the condition. - DeadCond = dyn_cast(BI->getCondition()); - Pred->getInstList().erase(PTI); - - // If the condition is dead now, remove the instruction tree. - if (DeadCond) RecursivelyDeleteTriviallyDeadInstructions(DeadCond); + EraseTerminatorInstAndDCECond(PTI); // Okay, last check. If BB is still a successor of PSI, then we must // have an infinite loop case. If so, add an infinitely looping block @@ -921,7 +920,7 @@ HoistTerminator: for (succ_iterator SI = succ_begin(BB1), E = succ_end(BB1); SI != E; ++SI) AddPredecessorToBlock(*SI, BIParent, BB1); - BI->eraseFromParent(); + EraseTerminatorInstAndDCECond(BI); return true; } @@ -1331,7 +1330,7 @@ static bool SimplifyCondBranchToTwoReturns(BranchInst *BI) { TrueSucc->removePredecessor(BI->getParent()); FalseSucc->removePredecessor(BI->getParent()); ReturnInst::Create(0, BI); - BI->eraseFromParent(); + EraseTerminatorInstAndDCECond(BI); return true; } @@ -1386,10 +1385,8 @@ static bool SimplifyCondBranchToTwoReturns(BranchInst *BI) { << "\n " << *BI << "NewRet = " << *RI << "TRUEBLOCK: " << *TrueSucc << "FALSEBLOCK: "<< *FalseSucc; - BI->eraseFromParent(); - - if (Instruction *BrCondI = dyn_cast(BrCond)) - RecursivelyDeleteTriviallyDeadInstructions(BrCondI); + EraseTerminatorInstAndDCECond(BI); + return true; } @@ -1910,10 +1907,10 @@ bool llvm::SimplifyCFG(BasicBlock *BB) { } else { if (BI->getSuccessor(0) == BB) { BranchInst::Create(BI->getSuccessor(1), BI); - BI->eraseFromParent(); + EraseTerminatorInstAndDCECond(BI); } else if (BI->getSuccessor(1) == BB) { BranchInst::Create(BI->getSuccessor(0), BI); - BI->eraseFromParent(); + EraseTerminatorInstAndDCECond(BI); Changed = true; } } @@ -2086,11 +2083,7 @@ bool llvm::SimplifyCFG(BasicBlock *BB) { } // Erase the old branch instruction. - (*PI)->getInstList().erase(BI); - - // Erase the potentially condition tree that was used to computed the - // branch condition. - RecursivelyDeleteTriviallyDeadInstructions(Cond); + EraseTerminatorInstAndDCECond(BI); return true; } } diff --git a/test/Transforms/SimplifyCFG/2008-12-16-DCECond.ll b/test/Transforms/SimplifyCFG/2008-12-16-DCECond.ll new file mode 100644 index 00000000000..b52d10dc3bc --- /dev/null +++ b/test/Transforms/SimplifyCFG/2008-12-16-DCECond.ll @@ -0,0 +1,46 @@ +; RUN: llvm-as < %s | opt -simplifycfg | llvm-dis | not grep icmp +; ModuleID = '/tmp/x.bc' +target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:128:128" +target triple = "i686-pc-linux-gnu" + +define i32 @x(i32 %x) { +entry: + %cmp = icmp eq i32 %x, 8 ; [#uses=1] + br i1 %cmp, label %ifthen, label %ifend + +ifthen: ; preds = %entry + %call = call i32 (...)* @foo() ; [#uses=0] + br label %ifend + +ifend: ; preds = %ifthen, %entry + %cmp2 = icmp ne i32 %x, 8 ; [#uses=1] + br i1 %cmp2, label %ifthen3, label %ifend5 + +ifthen3: ; preds = %ifend + %call4 = call i32 (...)* @foo() ; [#uses=0] + br label %ifend5 + +ifend5: ; preds = %ifthen3, %ifend + %cmp7 = icmp eq i32 %x, 9 ; [#uses=1] + br i1 %cmp7, label %ifthen8, label %ifend10 + +ifthen8: ; preds = %ifend5 + %call9 = call i32 (...)* @bar() ; [#uses=0] + br label %ifend10 + +ifend10: ; preds = %ifthen8, %ifend5 + %cmp12 = icmp ne i32 %x, 9 ; [#uses=1] + br i1 %cmp12, label %ifthen13, label %ifend15 + +ifthen13: ; preds = %ifend10 + %call14 = call i32 (...)* @bar() ; [#uses=0] + br label %ifend15 + +ifend15: ; preds = %ifthen13, %ifend10 + ret i32 0 +} + +declare i32 @foo(...) + +declare i32 @bar(...) +