diff options
Diffstat (limited to 'lib')
| -rw-r--r-- | lib/Transforms/Scalar/LoopRotation.cpp | 20 |
1 files changed, 20 insertions, 0 deletions
diff --git a/lib/Transforms/Scalar/LoopRotation.cpp b/lib/Transforms/Scalar/LoopRotation.cpp index 1e4bfa94be..31957ddac1 100644 --- a/lib/Transforms/Scalar/LoopRotation.cpp +++ b/lib/Transforms/Scalar/LoopRotation.cpp @@ -261,6 +261,26 @@ bool LoopRotate::rotateLoop(Loop *Lp, LPPassManager &LPM) { // NewHeader is now the header of the loop. L->moveToHeader(NewHeader); + // Move the original header to the bottom of the loop, where it now more + // naturally belongs. This isn't necessary for correctness, and CodeGen can + // usually reorder blocks on its own to fix things like this up, but it's + // still nice to keep the IR readable. + // + // The original header should have only one predecessor at this point, since + // we checked that the loop had a proper preheader and unique backedge before + // we started. + assert(OrigHeader->getSinglePredecessor() && + "Original loop header has too many predecessors after loop rotation!"); + OrigHeader->moveAfter(OrigHeader->getSinglePredecessor()); + + // Also, since this original header only has one predecessor, zap its + // PHI nodes, which are now trivial. + FoldSingleEntryPHINodes(OrigHeader); + + // TODO: We could just go ahead and merge OrigHeader into its predecessor + // at this point, if we don't mind updating dominator info. + + // Establish a new preheader, update dominators, etc. preserveCanonicalLoopForm(LPM); ++NumRotated; |