diff options
| -rw-r--r-- | llvm/lib/Transforms/Scalar/InstructionCombining.cpp | 19 |
1 files changed, 19 insertions, 0 deletions
diff --git a/llvm/lib/Transforms/Scalar/InstructionCombining.cpp b/llvm/lib/Transforms/Scalar/InstructionCombining.cpp index 0c089120ead..5b9f31892ea 100644 --- a/llvm/lib/Transforms/Scalar/InstructionCombining.cpp +++ b/llvm/lib/Transforms/Scalar/InstructionCombining.cpp @@ -19,6 +19,7 @@ #include "llvm/ConstantHandling.h" #include "llvm/iMemory.h" #include "llvm/iOther.h" +#include "llvm/iPHINode.h" #include "llvm/iOperators.h" #include "llvm/Pass.h" #include "llvm/Support/InstIterator.h" @@ -69,6 +70,7 @@ namespace { Instruction *visitSetCondInst(BinaryOperator *I); Instruction *visitShiftInst(Instruction *I); Instruction *visitCastInst(CastInst *CI); + Instruction *visitPHINode(PHINode *PN); Instruction *visitGetElementPtrInst(GetElementPtrInst *GEP); Instruction *visitMemAccessInst(MemAccessInst *MAI); @@ -412,6 +414,8 @@ static inline bool isEliminableCastOfCast(const CastInst *CI, // CastInst simplification // Instruction *InstCombiner::visitCastInst(CastInst *CI) { + if (CI->use_empty()) return 0; // Don't fix dead instructions... + // If the user is casting a value to the same type, eliminate this cast // instruction... if (CI->getType() == CI->getOperand(0)->getType() && !CI->use_empty()) { @@ -436,6 +440,21 @@ Instruction *InstCombiner::visitCastInst(CastInst *CI) { } +// PHINode simplification +// +Instruction *InstCombiner::visitPHINode(PHINode *PN) { + if (PN->use_empty()) return 0; // Don't fix dead instructions... + + // If the PHI node only has one incoming value, eliminate the PHI node... + if (PN->getNumIncomingValues() == 1) { + AddUsesToWorkList(PN); // Add all modified instrs to worklist + PN->replaceAllUsesWith(PN->getIncomingValue(0)); + return PN; + } + + return 0; +} + Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst *GEP) { // Is it getelementptr %P, uint 0 |
