From c146c780600a8d3a2c3d94a889c13d2213221ce4 Mon Sep 17 00:00:00 2001 From: Dan Gohman Date: Mon, 9 Nov 2009 18:28:24 +0000 Subject: Generalize LCSSA to handle loops with exits with predecessors outside the loop. This is needed because with indirectbr it may not be possible for LoopSimplify to guarantee that all loop exit predecessors are inside the loop. This fixes PR5437. LCCSA no longer actually requires LoopSimplify form, but for now it must still have the dependency because the PassManager doesn't know how to schedule LoopSimplify otherwise. llvm-svn: 86569 --- llvm/lib/Transforms/Utils/LCSSA.cpp | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-) (limited to 'llvm/lib/Transforms/Utils/LCSSA.cpp') diff --git a/llvm/lib/Transforms/Utils/LCSSA.cpp b/llvm/lib/Transforms/Utils/LCSSA.cpp index a8813eb1ff6..b4afedab7ba 100644 --- a/llvm/lib/Transforms/Utils/LCSSA.cpp +++ b/llvm/lib/Transforms/Utils/LCSSA.cpp @@ -63,6 +63,9 @@ namespace { /// virtual void getAnalysisUsage(AnalysisUsage &AU) const { AU.setPreservesCFG(); + + // LCSSA doesn't actually require LoopSimplify, but the PassManager + // doesn't know how to schedule LoopSimplify by itself. AU.addRequiredID(LoopSimplifyID); AU.addPreservedID(LoopSimplifyID); AU.addRequiredTransitive(); @@ -214,7 +217,7 @@ bool LCSSA::ProcessInstruction(Instruction *Inst, SSAUpdate.Initialize(Inst); // Insert the LCSSA phi's into all of the exit blocks dominated by the - // value., and add them to the Phi's map. + // value, and add them to the Phi's map. for (SmallVectorImpl::const_iterator BBI = ExitBlocks.begin(), BBE = ExitBlocks.end(); BBI != BBE; ++BBI) { BasicBlock *ExitBB = *BBI; @@ -228,8 +231,17 @@ bool LCSSA::ProcessInstruction(Instruction *Inst, PN->reserveOperandSpace(PredCache.GetNumPreds(ExitBB)); // Add inputs from inside the loop for this PHI. - for (BasicBlock **PI = PredCache.GetPreds(ExitBB); *PI; ++PI) + for (BasicBlock **PI = PredCache.GetPreds(ExitBB); *PI; ++PI) { PN->addIncoming(Inst, *PI); + + // If the exit block has a predecessor not within the loop, arrange for + // the incomging value use corresponding to that predecessor to be + // rewritten in terms of a different LCSSA PHI. + if (!inLoop(*PI)) + UsesToRewrite.push_back( + &PN->getOperandUse( + PN->getOperandNumForIncomingValue(PN->getNumIncomingValues()-1))); + } // Remember that this phi makes the value alive in this block. SSAUpdate.AddAvailableValue(ExitBB, PN); -- cgit v1.2.3