diff options
| -rw-r--r-- | lib/Transforms/Scalar/LoopDeletion.cpp | 24 |
1 files changed, 11 insertions, 13 deletions
diff --git a/lib/Transforms/Scalar/LoopDeletion.cpp b/lib/Transforms/Scalar/LoopDeletion.cpp index aa67674e410..95e36d764f7 100644 --- a/lib/Transforms/Scalar/LoopDeletion.cpp +++ b/lib/Transforms/Scalar/LoopDeletion.cpp @@ -31,19 +31,20 @@ using namespace llvm; STATISTIC(NumDeleted, "Number of loops deleted"); /// This function deletes dead loops. The caller of this function needs to -/// guarantee that the loop is infact dead. Here we handle two kinds of dead +/// guarantee that the loop is infact dead. Here we handle two kinds of dead /// loop. The first kind (\p isLoopDead) is where only invariant values from /// within the loop are used outside of it. The second kind (\p /// isLoopNeverExecuted) is where the loop is provably never executed. We can -/// always remove never executed loops since they will not cause any difference -/// to program behaviour. +/// always remove never executed loops since they will not cause any +/// difference to program behaviour. /// /// This also updates the relevant analysis information in \p DT, \p SE, and \p /// LI. It also updates the loop PM if an updater struct is provided. // TODO: This function will be used by loop-simplifyCFG as well. So, move this // to LoopUtils.cpp static void deleteDeadLoop(Loop *L, DominatorTree &DT, ScalarEvolution &SE, - LoopInfo &LI, LPMUpdater *Updater = nullptr); + LoopInfo &LI, bool LoopIsNeverExecuted, + LPMUpdater *Updater = nullptr); /// Determines if a loop is dead. /// /// This assumes that we've already checked for unique exit and exiting blocks, @@ -167,13 +168,7 @@ static bool deleteLoopIfDead(Loop *L, DominatorTree &DT, ScalarEvolution &SE, BasicBlock *ExitBlock = L->getUniqueExitBlock(); if (ExitBlock && isLoopNeverExecuted(L)) { - // Set incoming value to undef for phi nodes in the exit block. - BasicBlock::iterator BI = ExitBlock->begin(); - while (PHINode *P = dyn_cast<PHINode>(BI)) { - for (unsigned i = 0; i < P->getNumIncomingValues(); i++) - P->setIncomingValue(i, UndefValue::get(P->getType())); - } - deleteDeadLoop(L, DT, SE, LI, Updater); + deleteDeadLoop(L, DT, SE, LI, true /* LoopIsNeverExecuted */, Updater); ++NumDeleted; return true; } @@ -201,14 +196,15 @@ static bool deleteLoopIfDead(Loop *L, DominatorTree &DT, ScalarEvolution &SE, if (isa<SCEVCouldNotCompute>(S)) return Changed; - deleteDeadLoop(L, DT, SE, LI, Updater); + deleteDeadLoop(L, DT, SE, LI, false /* LoopIsNeverExecuted */, Updater); ++NumDeleted; return true; } static void deleteDeadLoop(Loop *L, DominatorTree &DT, ScalarEvolution &SE, - LoopInfo &LI, LPMUpdater *Updater) { + LoopInfo &LI, bool LoopIsNeverExecuted, + LPMUpdater *Updater) { assert(L->isLCSSAForm(DT) && "Expected LCSSA!"); auto *Preheader = L->getLoopPreheader(); assert(Preheader && "Preheader should exist!"); @@ -250,6 +246,8 @@ static void deleteDeadLoop(Loop *L, DominatorTree &DT, ScalarEvolution &SE, // other incoming values. Given the loop has dedicated exits, all other // incoming values must be from the exiting blocks. int PredIndex = 0; + if (LoopIsNeverExecuted) + P->setIncomingValue(PredIndex, UndefValue::get(P->getType())); P->setIncomingBlock(PredIndex, Preheader); // Removes all incoming values from all other exiting blocks (including // duplicate values from an exiting block). |