diff options
Diffstat (limited to 'lib/Transforms')
| -rw-r--r-- | lib/Transforms/Scalar/LoopStrengthReduce.cpp | 27 |
1 files changed, 27 insertions, 0 deletions
diff --git a/lib/Transforms/Scalar/LoopStrengthReduce.cpp b/lib/Transforms/Scalar/LoopStrengthReduce.cpp index 7e894ca..436f25b 100644 --- a/lib/Transforms/Scalar/LoopStrengthReduce.cpp +++ b/lib/Transforms/Scalar/LoopStrengthReduce.cpp @@ -1199,6 +1199,30 @@ void LoopStrengthReduce::OptimizeIndvars(Loop *L) { CondUse->isUseOfPostIncrementedValue = true; } +namespace { + // Constant strides come first which in turns are sorted by their absolute + // values. If absolute values are the same, then positive strides comes first. + // e.g. + // 4, -1, X, 1, 2 ==> 1, -1, 2, 4, X + struct StrideCompare { + bool operator()(const SCEVHandle &LHS, const SCEVHandle &RHS) { + SCEVConstant *LHSC = dyn_cast<SCEVConstant>(LHS); + SCEVConstant *RHSC = dyn_cast<SCEVConstant>(RHS); + if (LHSC && RHSC) { + int64_t LV = LHSC->getValue()->getSExtValue(); + int64_t RV = RHSC->getValue()->getSExtValue(); + uint64_t ALV = (LV < 0) ? -LV : LV; + uint64_t ARV = (RV < 0) ? -RV : RV; + if (ALV == ARV) + return LV > RV; + else + return ALV < ARV; + } else + return (LHSC && !RHSC); + } + }; +} + void LoopStrengthReduce::runOnLoop(Loop *L) { // First step, transform all loops nesting inside of this loop. for (LoopInfo::iterator I = L->begin(), E = L->end(); I != E; ++I) @@ -1241,6 +1265,9 @@ void LoopStrengthReduce::runOnLoop(Loop *L) { // IVsByStride keeps IVs for one particular loop. IVsByStride.clear(); + // Sort the StrideOrder so we process larger strides first. + std::stable_sort(StrideOrder.begin(), StrideOrder.end(), StrideCompare()); + // Note: this processes each stride/type pair individually. All users passed // into StrengthReduceStridedIVUsers have the same type AND stride. Also, // node that we iterate over IVUsesByStride indirectly by using StrideOrder. |