diff options
author | Arnold Schwaighofer <aschwaighofer@apple.com> | 2013-12-17 01:11:01 +0000 |
---|---|---|
committer | Arnold Schwaighofer <aschwaighofer@apple.com> | 2013-12-17 01:11:01 +0000 |
commit | 83196a9fcb863dec7a66242f2aa971dd3a273c15 (patch) | |
tree | 224e6664f6305ecf52f1df72600952079c0a8da8 /lib | |
parent | a6380c22e4461e8386cbf802b72ebe67a873154e (diff) |
LoopVectorizer: Don't if-convert constant expressions that can trap
A phi node operand or an instruction operand could be a constant expression that
can trap (division). Check that we don't vectorize such cases.
PR16729
radar://15653590
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@197449 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'lib')
-rw-r--r-- | lib/Transforms/Vectorize/LoopVectorize.cpp | 32 |
1 files changed, 31 insertions, 1 deletions
diff --git a/lib/Transforms/Vectorize/LoopVectorize.cpp b/lib/Transforms/Vectorize/LoopVectorize.cpp index 45ddeaf9336..d83aa7642e6 100644 --- a/lib/Transforms/Vectorize/LoopVectorize.cpp +++ b/lib/Transforms/Vectorize/LoopVectorize.cpp @@ -2804,6 +2804,23 @@ void InnerLoopVectorizer::updateAnalysis() { DEBUG(DT->verifyAnalysis()); } +/// \brief Check whether it is safe to if-convert this phi node. +/// +/// Phi nodes with constant expressions that can trap are not safe to if +/// convert. +static bool canIfConvertPHINodes(BasicBlock *BB) { + for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) { + PHINode *Phi = dyn_cast<PHINode>(I); + if (!Phi) + return true; + for (unsigned p = 0, e = Phi->getNumIncomingValues(); p != e; ++p) + if (Constant *C = dyn_cast<Constant>(Phi->getIncomingValue(p))) + if (C->canTrap()) + return false; + } + return true; +} + bool LoopVectorizationLegality::canVectorizeWithIfConvert() { if (!EnableIfConversion) return false; @@ -2830,6 +2847,7 @@ bool LoopVectorizationLegality::canVectorizeWithIfConvert() { } // Collect the blocks that need predication. + BasicBlock *Header = TheLoop->getHeader(); for (Loop::block_iterator BI = TheLoop->block_begin(), BE = TheLoop->block_end(); BI != BE; ++BI) { BasicBlock *BB = *BI; @@ -2839,8 +2857,12 @@ bool LoopVectorizationLegality::canVectorizeWithIfConvert() { return false; // We must be able to predicate all blocks that need to be predicated. - if (blockNeedsPredication(BB) && !blockCanBePredicated(BB, SafePointes)) + if (blockNeedsPredication(BB)) { + if (!blockCanBePredicated(BB, SafePointes)) + return false; + } else if (BB != Header && !canIfConvertPHINodes(BB)) return false; + } // We can if-convert this loop. @@ -4394,6 +4416,14 @@ bool LoopVectorizationLegality::blockCanBePredicated(BasicBlock *BB, if (it->mayWriteToMemory() || it->mayThrow()) return false; + // Check that we don't have a constant expression that can trap as operand. + for (Instruction::op_iterator OI = it->op_begin(), OE = it->op_end(); + OI != OE; ++OI) { + if (Constant *C = dyn_cast<Constant>(*OI)) + if (C->canTrap()) + return false; + } + // The instructions below can trap. switch (it->getOpcode()) { default: continue; |