diff options
Diffstat (limited to 'llvm/lib/Target/ARM')
| -rw-r--r-- | llvm/lib/Target/ARM/ARMBaseInstrInfo.cpp | 27 |
1 files changed, 17 insertions, 10 deletions
diff --git a/llvm/lib/Target/ARM/ARMBaseInstrInfo.cpp b/llvm/lib/Target/ARM/ARMBaseInstrInfo.cpp index 79ab692c76a..abb1fdad080 100644 --- a/llvm/lib/Target/ARM/ARMBaseInstrInfo.cpp +++ b/llvm/lib/Target/ARM/ARMBaseInstrInfo.cpp @@ -1670,11 +1670,14 @@ isProfitableToIfCvt(MachineBasicBlock &MBB, } // Attempt to estimate the relative costs of predication versus branching. - unsigned UnpredCost = Probability.scale(NumCycles); - UnpredCost += 1; // The branch itself - UnpredCost += Subtarget.getMispredictionPenalty() / 10; - - return (NumCycles + ExtraPredCycles) <= UnpredCost; + // Here we scale up each component of UnpredCost to avoid precision issue when + // scaling NumCycles by Probability. + const unsigned ScalingUpFactor = 1024; + unsigned UnpredCost = Probability.scale(NumCycles * ScalingUpFactor); + UnpredCost += ScalingUpFactor; // The branch itself + UnpredCost += Subtarget.getMispredictionPenalty() * ScalingUpFactor / 10; + + return (NumCycles + ExtraPredCycles) * ScalingUpFactor <= UnpredCost; } bool ARMBaseInstrInfo:: @@ -1687,13 +1690,17 @@ isProfitableToIfCvt(MachineBasicBlock &TMBB, return false; // Attempt to estimate the relative costs of predication versus branching. - unsigned TUnpredCost = Probability.scale(TCycles); - unsigned FUnpredCost = Probability.getCompl().scale(FCycles); + // Here we scale up each component of UnpredCost to avoid precision issue when + // scaling TCycles/FCycles by Probability. + const unsigned ScalingUpFactor = 1024; + unsigned TUnpredCost = Probability.scale(TCycles * ScalingUpFactor); + unsigned FUnpredCost = + Probability.getCompl().scale(FCycles * ScalingUpFactor); unsigned UnpredCost = TUnpredCost + FUnpredCost; - UnpredCost += 1; // The branch itself - UnpredCost += Subtarget.getMispredictionPenalty() / 10; + UnpredCost += 1 * ScalingUpFactor; // The branch itself + UnpredCost += Subtarget.getMispredictionPenalty() * ScalingUpFactor / 10; - return (TCycles + FCycles + TExtra + FExtra) <= UnpredCost; + return (TCycles + FCycles + TExtra + FExtra) * ScalingUpFactor <= UnpredCost; } bool |
