diff options
Diffstat (limited to 'llvm/lib/Transforms/Scalar/InstructionCombining.cpp')
| -rw-r--r-- | llvm/lib/Transforms/Scalar/InstructionCombining.cpp | 15 |
1 files changed, 14 insertions, 1 deletions
diff --git a/llvm/lib/Transforms/Scalar/InstructionCombining.cpp b/llvm/lib/Transforms/Scalar/InstructionCombining.cpp index 47a02bd8427..006d67b6034 100644 --- a/llvm/lib/Transforms/Scalar/InstructionCombining.cpp +++ b/llvm/lib/Transforms/Scalar/InstructionCombining.cpp @@ -326,7 +326,7 @@ namespace { // instruction. Instead, visit methods should return the value returned by // this function. Instruction *EraseInstFromFunction(Instruction &I) { - DEBUG(errs() << "IC: erase " << I); + DEBUG(errs() << "IC: erase " << I << '\n'); assert(I.use_empty() && "Cannot erase instruction that is used!"); // Make sure that we reprocess all operands now that we reduced their @@ -10401,6 +10401,10 @@ Instruction *InstCombiner::FoldPHIArgGEPIntoPHI(PHINode &PN) { // This is true if all GEP bases are allocas and if all indices into them are // constants. bool AllBasePointersAreAllocas = true; + + // We don't want to replace this phi if the replacement would require + // more than one phi. + bool NeededPhi = false; // Scan to see if all operands are the same opcode, all have one use, and all // kill their operands (i.e. the operands have one use). @@ -10432,7 +10436,16 @@ Instruction *InstCombiner::FoldPHIArgGEPIntoPHI(PHINode &PN) { if (FirstInst->getOperand(op)->getType() !=GEP->getOperand(op)->getType()) return 0; + + // If we already needed a PHI for an earlier operand, and another operand + // also requires a PHI, we'd be introducing more PHIs than we're + // eliminating, which increases register pressure on entry to the PHI's + // block. + if (NeededPhi) + return 0; + FixedOperands[op] = 0; // Needs a PHI. + NeededPhi = true; } } |
