diff options
| -rw-r--r-- | llvm/lib/Transforms/Utils/LoopUnrollPeel.cpp | 7 | ||||
| -rw-r--r-- | llvm/test/Transforms/LoopUnroll/peel-loop-irreducible.ll | 36 |
2 files changed, 43 insertions, 0 deletions
diff --git a/llvm/lib/Transforms/Utils/LoopUnrollPeel.cpp b/llvm/lib/Transforms/Utils/LoopUnrollPeel.cpp index b8147fcb697..ea3e37d9c59 100644 --- a/llvm/lib/Transforms/Utils/LoopUnrollPeel.cpp +++ b/llvm/lib/Transforms/Utils/LoopUnrollPeel.cpp @@ -56,6 +56,13 @@ static bool canPeel(Loop *L) { if (!L->getExitingBlock() || !L->getUniqueExitBlock()) return false; + // Don't try to peel loops where the latch is not the exiting block. + // This can be an indication of two different things: + // 1) The loop is not rotated. + // 2) The loop contains irreducible control flow that involves the latch. + if (L->getLoopLatch() != L->getExitingBlock()) + return false; + return true; } diff --git a/llvm/test/Transforms/LoopUnroll/peel-loop-irreducible.ll b/llvm/test/Transforms/LoopUnroll/peel-loop-irreducible.ll new file mode 100644 index 00000000000..32a7a0732e1 --- /dev/null +++ b/llvm/test/Transforms/LoopUnroll/peel-loop-irreducible.ll @@ -0,0 +1,36 @@ +; RUN: opt < %s -S -loop-unroll -unroll-force-peel-count=1 | FileCheck %s + +; Check we don't peel loops where the latch is not the exiting block. +; CHECK-LABEL: @invariant_backedge_irreducible +; CHECK: entry: +; CHECK: br label %header +; CHECK-NOT: peel +; CHECK: header: +; CHECK: br i1 {{.*}} label %latch, label %exiting +; CHECK: latch: +; CHECK: br i1 {{.*}} label %header, label %exiting +; CHECK: exiting: +; CHECK: br i1 {{.*}} label %latch, label %exit + +define i32 @invariant_backedge_irreducible(i32 %a, i32 %b) { +entry: + br label %header + +header: + %i = phi i32 [ 0, %entry ], [ %inc, %latch ] + %cmp.phi = phi i1 [ false, %entry ], [ %cmp, %latch ] + br i1 %cmp.phi, label %latch, label %exiting + +latch: + %inc = add i32 %i, 1 + %cmp = icmp slt i32 %i, 1000 + br i1 %cmp, label %header, label %exiting + +exiting: + %cmp.exiting = phi i1 [ %cmp.phi, %header ], [ %cmp, %latch ] + br i1 %cmp.exiting, label %latch, label %exit + +exit: + ret i32 0 +} + |
