diff options
| -rw-r--r-- | llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp | 5 | ||||
| -rw-r--r-- | llvm/test/Transforms/LoopStrengthReduce/dont_reverse.ll | 21 |
2 files changed, 26 insertions, 0 deletions
diff --git a/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp b/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp index 3a71d279772..adfa5272a9c 100644 --- a/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp +++ b/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp @@ -2456,6 +2456,11 @@ void LoopStrengthReduce::OptimizeLoopCountIV(Loop *L) { SCEVHandle One = SE->getIntegerSCEV(1, BackedgeTakenCount->getType()); if (!AR || !AR->isAffine() || AR->getStepRecurrence(*SE) != One) return; + // If the RHS of the comparison is defined inside the loop, the rewrite + // cannot be done. + if (Instruction *CR = dyn_cast<Instruction>(Cond->getOperand(1))) + if (L->contains(CR->getParent())) + return; // Make sure the IV is only used for counting. Value may be preinc or // postinc; 2 uses in either case. diff --git a/llvm/test/Transforms/LoopStrengthReduce/dont_reverse.ll b/llvm/test/Transforms/LoopStrengthReduce/dont_reverse.ll new file mode 100644 index 00000000000..39eca6c9630 --- /dev/null +++ b/llvm/test/Transforms/LoopStrengthReduce/dont_reverse.ll @@ -0,0 +1,21 @@ +; RUN: llvm-as < %s | opt -loop-reduce | llvm-dis \ +; RUN: | grep {icmp eq i2 %lsr.iv.next, %xmp4344} + +; Don't reverse the iteration if the rhs of the compare is defined +; inside the loop. + +define void @Fill_Buffer() nounwind { +entry: + br label %bb8 + +bb8: + %indvar34 = phi i32 [ 0, %entry ], [ %indvar.next35, %bb8 ] + %indvar3451 = trunc i32 %indvar34 to i2 + %xmp4344 = xor i2 0, -1 + %xmp104 = icmp eq i2 %indvar3451, %xmp4344 + %indvar.next35 = add i32 %indvar34, 1 + br i1 %xmp104, label %bb10, label %bb8 + +bb10: + unreachable +} |
