diff options
Diffstat (limited to 'llvm/lib/Transforms/Vectorize/LoopVectorize.cpp')
| -rw-r--r-- | llvm/lib/Transforms/Vectorize/LoopVectorize.cpp | 9 |
1 files changed, 6 insertions, 3 deletions
diff --git a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp index 23dc8f39eea..5c9933a2c72 100644 --- a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp +++ b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp @@ -5004,8 +5004,11 @@ LoopVectorizationCostModel::selectUnrollFactor(bool OptForSize, // registers. These registers are used by all of the unrolled instances. // Next, divide the remaining registers by the number of registers that is // required by the loop, in order to estimate how many parallel instances - // fit without causing spills. - unsigned UF = (TargetNumRegisters - R.LoopInvariantRegs) / R.MaxLocalUsers; + // fit without causing spills. All of this is rounded down if necessary to be + // a power of two. We want power of two unroll factors to simplify any + // addressing operations or alignment considerations. + unsigned UF = PowerOf2Floor((TargetNumRegisters - R.LoopInvariantRegs) / + R.MaxLocalUsers); // Clamp the unroll factor ranges to reasonable factors. unsigned MaxUnrollSize = TTI.getMaximumUnrollFactor(); @@ -5045,7 +5048,7 @@ LoopVectorizationCostModel::selectUnrollFactor(bool OptForSize, DEBUG(dbgs() << "LV: Loop cost is " << LoopCost << '\n'); if (LoopCost < SmallLoopCost) { DEBUG(dbgs() << "LV: Unrolling to reduce branch cost.\n"); - unsigned NewUF = SmallLoopCost / (LoopCost + 1); + unsigned NewUF = PowerOf2Floor(SmallLoopCost / LoopCost); return std::min(NewUF, UF); } |
