Index: include/llvm/Transforms/Utils/UnrollLoop.h =================================================================== --- include/llvm/Transforms/Utils/UnrollLoop.h +++ include/llvm/Transforms/Utils/UnrollLoop.h @@ -53,7 +53,8 @@ bool PreserveLCSSA); void computePeelCount(Loop *L, unsigned LoopSize, - TargetTransformInfo::UnrollingPreferences &UP); + TargetTransformInfo::UnrollingPreferences &UP, + unsigned &TripCount); bool peelLoop(Loop *L, unsigned PeelCount, LoopInfo *LI, ScalarEvolution *SE, DominatorTree *DT, AssumptionCache *AC, bool PreserveLCSSA); Index: lib/Transforms/Scalar/LoopUnrollPass.cpp =================================================================== --- lib/Transforms/Scalar/LoopUnrollPass.cpp +++ lib/Transforms/Scalar/LoopUnrollPass.cpp @@ -784,7 +784,15 @@ } } - // 4rd priority is partial unrolling. + // 4th priority is loop peeling + computePeelCount(L, LoopSize, UP, TripCount); + if (UP.PeelCount) { + UP.Runtime = false; + UP.Count = 1; + return ExplicitUnroll; + } + + // 5th priority is partial unrolling. // Try partial unroll only when TripCount could be staticaly calculated. if (TripCount) { UP.Partial |= ExplicitUnroll; @@ -847,14 +855,6 @@ << "Unable to fully unroll loop as directed by unroll(full) pragma " "because loop has a runtime trip count."); - // 5th priority is loop peeling - computePeelCount(L, LoopSize, UP); - if (UP.PeelCount) { - UP.Runtime = false; - UP.Count = 1; - return ExplicitUnroll; - } - // 6th priority is runtime unrolling. // Don't unroll a runtime trip count loop when it is disabled. if (HasRuntimeUnrollDisablePragma(L)) { Index: lib/Transforms/Utils/LoopUnrollPeel.cpp =================================================================== --- lib/Transforms/Utils/LoopUnrollPeel.cpp +++ lib/Transforms/Utils/LoopUnrollPeel.cpp @@ -61,7 +61,8 @@ // Return the number of iterations we want to peel off. void llvm::computePeelCount(Loop *L, unsigned LoopSize, - TargetTransformInfo::UnrollingPreferences &UP) { + TargetTransformInfo::UnrollingPreferences &UP, + unsigned &TripCount) { UP.PeelCount = 0; if (!canPeel(L)) return; @@ -70,6 +71,11 @@ if (!L->empty()) return; + // Bail if we know the statically calculated trip count. + // In this case we rather prefer partial unrolling. + if (TripCount) + return; + // If the user provided a peel count, use that. bool UserPeelCount = UnrollForcePeelCount.getNumOccurrences() > 0; if (UserPeelCount) {