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author | Andrew Trick <atrick@apple.com> | 2011-10-04 03:50:44 +0000 |
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committer | Andrew Trick <atrick@apple.com> | 2011-10-04 03:50:44 +0000 |
commit | f143b79b78d1d244809fa59320f2af2edf4e1a86 (patch) | |
tree | d98851fb9036648d18eeb33137346849071a4847 | |
parent | 2aeb8027d649320d5ad3a30d9bbeb71c783b50d4 (diff) | |
download | llvm-f143b79b78d1d244809fa59320f2af2edf4e1a86.tar.gz llvm-f143b79b78d1d244809fa59320f2af2edf4e1a86.tar.bz2 llvm-f143b79b78d1d244809fa59320f2af2edf4e1a86.tar.xz |
LSR should avoid redundant edge splitting.
This handles the case in which LSR rewrites an IV user that is a phi and
splits critical edges originating from a switch.
Fixes <rdar://problem/6453893> LSR is not splitting edges "nicely"
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@141059 91177308-0d34-0410-b5e6-96231b3b80d8
4 files changed, 55 insertions, 6 deletions
diff --git a/include/llvm/Transforms/Utils/BasicBlockUtils.h b/include/llvm/Transforms/Utils/BasicBlockUtils.h index 97364512eb..6fcd160e64 100644 --- a/include/llvm/Transforms/Utils/BasicBlockUtils.h +++ b/include/llvm/Transforms/Utils/BasicBlockUtils.h @@ -109,7 +109,8 @@ bool isCriticalEdge(const TerminatorInst *TI, unsigned SuccNum, /// to. /// BasicBlock *SplitCriticalEdge(TerminatorInst *TI, unsigned SuccNum, - Pass *P = 0, bool MergeIdenticalEdges = false); + Pass *P = 0, bool MergeIdenticalEdges = false, + bool DontDeleteUselessPHIs = false); inline BasicBlock *SplitCriticalEdge(BasicBlock *BB, succ_iterator SI, Pass *P = 0) { @@ -136,13 +137,15 @@ inline bool SplitCriticalEdge(BasicBlock *Succ, pred_iterator PI, Pass *P = 0) { /// described above. inline BasicBlock *SplitCriticalEdge(BasicBlock *Src, BasicBlock *Dst, Pass *P = 0, - bool MergeIdenticalEdges = false) { + bool MergeIdenticalEdges = false, + bool DontDeleteUselessPHIs = false) { TerminatorInst *TI = Src->getTerminator(); unsigned i = 0; while (1) { assert(i != TI->getNumSuccessors() && "Edge doesn't exist!"); if (TI->getSuccessor(i) == Dst) - return SplitCriticalEdge(TI, i, P, MergeIdenticalEdges); + return SplitCriticalEdge(TI, i, P, MergeIdenticalEdges, + DontDeleteUselessPHIs); ++i; } } diff --git a/lib/Transforms/Scalar/LoopStrengthReduce.cpp b/lib/Transforms/Scalar/LoopStrengthReduce.cpp index 7b1a340156..4b6c55e162 100644 --- a/lib/Transforms/Scalar/LoopStrengthReduce.cpp +++ b/lib/Transforms/Scalar/LoopStrengthReduce.cpp @@ -3677,7 +3677,9 @@ void LSRInstance::RewriteForPHI(PHINode *PN, // Split the critical edge. BasicBlock *NewBB = 0; if (!Parent->isLandingPad()) { - NewBB = SplitCriticalEdge(BB, Parent, P); + NewBB = SplitCriticalEdge(BB, Parent, P, + /*MergeIdenticalEdges=*/true, + /*DontDeleteUselessPhis=*/true); } else { SmallVector<BasicBlock*, 2> NewBBs; SplitLandingPadPredecessors(Parent, BB, "", "", P, NewBBs); diff --git a/lib/Transforms/Utils/BreakCriticalEdges.cpp b/lib/Transforms/Utils/BreakCriticalEdges.cpp index 4648f49645..c052910881 100644 --- a/lib/Transforms/Utils/BreakCriticalEdges.cpp +++ b/lib/Transforms/Utils/BreakCriticalEdges.cpp @@ -167,7 +167,8 @@ static void CreatePHIsForSplitLoopExit(SmallVectorImpl<BasicBlock *> &Preds, /// to. /// BasicBlock *llvm::SplitCriticalEdge(TerminatorInst *TI, unsigned SuccNum, - Pass *P, bool MergeIdenticalEdges) { + Pass *P, bool MergeIdenticalEdges, + bool DontDeleteUselessPhis) { if (!isCriticalEdge(TI, SuccNum, MergeIdenticalEdges)) return 0; assert(!isa<IndirectBrInst>(TI) && @@ -224,7 +225,7 @@ BasicBlock *llvm::SplitCriticalEdge(TerminatorInst *TI, unsigned SuccNum, if (TI->getSuccessor(i) != DestBB) continue; // Remove an entry for TIBB from DestBB phi nodes. - DestBB->removePredecessor(TIBB); + DestBB->removePredecessor(TIBB, DontDeleteUselessPhis); // We found another edge to DestBB, go to NewBB instead. TI->setSuccessor(i, NewBB); diff --git a/test/Transforms/LoopStrengthReduce/2011-10-03-CritEdgeMerge.ll b/test/Transforms/LoopStrengthReduce/2011-10-03-CritEdgeMerge.ll new file mode 100644 index 0000000000..a6996a81fb --- /dev/null +++ b/test/Transforms/LoopStrengthReduce/2011-10-03-CritEdgeMerge.ll @@ -0,0 +1,43 @@ +; RUN: opt -loop-reduce -S < %s | FileCheck %s +; +; Test LSR's use of SplitCriticalEdge during phi rewriting. +; Verify that identical edges are merged. rdar://problem/6453893 + +target triple = "x86-apple-darwin" + +; CHECK: @test +; CHECK: bb89: +; CHECK: phi i8* [ %lsr.iv.next1, %bbA.bb89_crit_edge ], [ %lsr.iv.next1, %bbB.bb89_crit_edge ]{{$}} + +define i8* @test() { +entry: + br label %loop + +loop: + %rec = phi i32 [ %next, %loop ], [ 0, %entry ] + %next = add i32 %rec, 1 + %tmp75 = getelementptr i8* null, i32 %next + br i1 false, label %loop, label %loopexit + +loopexit: + br i1 false, label %bbA, label %bbB + +bbA: + switch i32 0, label %bb89 [ + i32 47, label %bb89 + i32 58, label %bb89 + ] + +bbB: + switch i8 0, label %bb89 [ + i8 47, label %bb89 + i8 58, label %bb89 + ] + +bb89: + %tmp75phi = phi i8* [ %tmp75, %bbA ], [ %tmp75, %bbA ], [ %tmp75, %bbA ], [ %tmp75, %bbB ], [ %tmp75, %bbB ], [ %tmp75, %bbB ] + br label %exit + +exit: + ret i8* %tmp75phi +} |