diff options
Diffstat (limited to 'llvm/lib/Transforms/Utils')
| -rw-r--r-- | llvm/lib/Transforms/Utils/SimplifyCFG.cpp | 21 |
1 files changed, 15 insertions, 6 deletions
diff --git a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp index ab45c1d21a5..50ebdb77158 100644 --- a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp +++ b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp @@ -3486,6 +3486,21 @@ GetCaseResults(SwitchInst *SI, continue; } else if (Constant *C = ConstantFold(I, ConstantPool, DL)) { // Instruction is side-effect free and constant. + + // If the instruction has uses outside this block or a phi node slot for + // the block, it is not safe to bypass the instruction since it would then + // no longer dominate all its uses. + for (auto &Use : I->uses()) { + User *User = Use.getUser(); + if (Instruction *I = dyn_cast<Instruction>(User)) + if (I->getParent() == CaseDest) + continue; + if (PHINode *Phi = dyn_cast<PHINode>(User)) + if (Phi->getIncomingBlock(Use) == CaseDest) + continue; + return false; + } + ConstantPool.insert(std::make_pair(I, C)); } else { break; @@ -3511,12 +3526,6 @@ GetCaseResults(SwitchInst *SI, if (!ConstVal) return false; - // Note: If the constant comes from constant-propagating the case value - // through the CaseDest basic block, it will be safe to remove the - // instructions in that block. They cannot be used (except in the phi nodes - // we visit) outside CaseDest, because that block does not dominate its - // successor. If it did, we would not be in this phi node. - // Be conservative about which kinds of constants we support. if (!ValidLookupTableConstant(ConstVal)) return false; |
