diff --git a/include/llvm/BasicBlock.h b/include/llvm/BasicBlock.h index b02c249c7ee..3b953c06a81 100644 --- a/include/llvm/BasicBlock.h +++ b/include/llvm/BasicBlock.h @@ -138,6 +138,12 @@ public: return const_cast(this)->getFirstNonPHIOrDbg(); } + // Same as above, but also skip lifetime intrinsics. + Instruction* getFirstNonPHIOrDbgOrLifetime(); + const Instruction* getFirstNonPHIOrDbgOrLifetime() const { + return const_cast(this)->getFirstNonPHIOrDbgOrLifetime(); + } + /// removeFromParent - This method unlinks 'this' from the containing /// function, but does not delete it. /// diff --git a/lib/Transforms/Utils/Local.cpp b/lib/Transforms/Utils/Local.cpp index b1dd733ffe5..00469454851 100644 --- a/lib/Transforms/Utils/Local.cpp +++ b/lib/Transforms/Utils/Local.cpp @@ -536,9 +536,9 @@ static bool CanPropagatePredecessorsForPHIs(BasicBlock *BB, BasicBlock *Succ) { /// TryToSimplifyUncondBranchFromEmptyBlock - BB is known to contain an /// unconditional branch, and contains no instructions other than PHI nodes, -/// potential debug intrinsics and the branch. If possible, eliminate BB by -/// rewriting all the predecessors to branch to the successor block and return -/// true. If we can't transform, return false. +/// potential side-effect free intrinsics and the branch. If possible, +/// eliminate BB by rewriting all the predecessors to branch to the successor +/// block and return true. If we can't transform, return false. bool llvm::TryToSimplifyUncondBranchFromEmptyBlock(BasicBlock *BB) { assert(BB != &BB->getParent()->getEntryBlock() && "TryToSimplifyUncondBranchFromEmptyBlock called on entry block!"); @@ -613,13 +613,15 @@ bool llvm::TryToSimplifyUncondBranchFromEmptyBlock(BasicBlock *BB) { } } - while (PHINode *PN = dyn_cast(&BB->front())) { - if (Succ->getSinglePredecessor()) { - // BB is the only predecessor of Succ, so Succ will end up with exactly - // the same predecessors BB had. - Succ->getInstList().splice(Succ->begin(), - BB->getInstList(), BB->begin()); - } else { + if (Succ->getSinglePredecessor()) { + // BB is the only predecessor of Succ, so Succ will end up with exactly + // the same predecessors BB had. + + // Copy over any phi, debug or lifetime instruction. + BB->getTerminator()->eraseFromParent(); + Succ->getInstList().splice(Succ->begin(), BB->getInstList()); + } else { + while (PHINode *PN = dyn_cast(&BB->front())) { // We explicitly check for such uses in CanPropagatePredecessorsForPHIs. assert(PN->use_empty() && "There shouldn't be any uses here!"); PN->eraseFromParent(); diff --git a/lib/Transforms/Utils/SimplifyCFG.cpp b/lib/Transforms/Utils/SimplifyCFG.cpp index 7b93b4a8e25..49726d5533d 100644 --- a/lib/Transforms/Utils/SimplifyCFG.cpp +++ b/lib/Transforms/Utils/SimplifyCFG.cpp @@ -2604,7 +2604,7 @@ bool SimplifyCFGOpt::SimplifyUncondBranch(BranchInst *BI, IRBuilder<> &Builder){ BasicBlock *BB = BI->getParent(); // If the Terminator is the only non-phi instruction, simplify the block. - BasicBlock::iterator I = BB->getFirstNonPHIOrDbg(); + BasicBlock::iterator I = BB->getFirstNonPHIOrDbgOrLifetime(); if (I->isTerminator() && BB != &BB->getParent()->getEntryBlock() && TryToSimplifyUncondBranchFromEmptyBlock(BB)) return true; diff --git a/lib/VMCore/BasicBlock.cpp b/lib/VMCore/BasicBlock.cpp index 7d470440aff..70265c899d7 100644 --- a/lib/VMCore/BasicBlock.cpp +++ b/lib/VMCore/BasicBlock.cpp @@ -147,6 +147,26 @@ Instruction* BasicBlock::getFirstNonPHIOrDbg() { return &*i; } +Instruction* BasicBlock::getFirstNonPHIOrDbgOrLifetime() { + // All valid basic blocks should have a terminator, + // which is not a PHINode. If we have an invalid basic + // block we'll get an assertion failure when dereferencing + // a past-the-end iterator. + BasicBlock::iterator i = begin(); + for (;; ++i) { + if (isa(i) || isa(i)) + continue; + + const IntrinsicInst *II = dyn_cast(i); + if (!II) + break; + if (II->getIntrinsicID() != Intrinsic::lifetime_start && + II->getIntrinsicID() != Intrinsic::lifetime_end) + break; + } + return &*i; +} + void BasicBlock::dropAllReferences() { for(iterator I = begin(), E = end(); I != E; ++I) I->dropAllReferences(); diff --git a/test/Transforms/SimplifyCFG/lifetime.ll b/test/Transforms/SimplifyCFG/lifetime.ll new file mode 100644 index 00000000000..b7942217253 --- /dev/null +++ b/test/Transforms/SimplifyCFG/lifetime.ll @@ -0,0 +1,29 @@ +; RUN: opt < %s -simplifycfg -S | FileCheck %s + +; Test that a lifetime intrinsic doesn't prevent us from simplifying this. + +; CHECK: foo +; CHECK: entry: +; CHECK-NOT: bb0: +; CHECK-NOT: bb1: +; CHECK: ret +define void @foo(i1 %x) { +entry: + %a = alloca i8 + call void @llvm.lifetime.start(i64 -1, i8* %a) nounwind + br i1 %x, label %bb0, label %bb1 + +bb0: + call void @llvm.lifetime.end(i64 -1, i8* %a) nounwind + br label %bb1 + +bb1: + call void @f() + ret void +} + +declare void @f() + +declare void @llvm.lifetime.start(i64, i8* nocapture) nounwind + +declare void @llvm.lifetime.end(i64, i8* nocapture) nounwind