diff --git a/llvm/lib/Transforms/Utils/LoopUnrollAndJam.cpp b/llvm/lib/Transforms/Utils/LoopUnrollAndJam.cpp --- a/llvm/lib/Transforms/Utils/LoopUnrollAndJam.cpp +++ b/llvm/lib/Transforms/Utils/LoopUnrollAndJam.cpp @@ -831,6 +831,23 @@ if (SubLoopsSize != 1) return false; + // Only loops with a single exit block can be unrolled and jammed. + // The function getExitBlock() is used for this check, rather than + // getUniqueExitBlock() to ensure loops with mulitple exit edges are + // disallowed. + if (!L->getExitBlock()) { + LLVM_DEBUG(dbgs() << "Won't unroll-and-jam; only loops with single exit " + "blocks can be unrolled and jammed.\n"); + return false; + } + + // Only loops with a single exiting block can be unrolled and jammed. + if (!L->getExitingBlock()) { + LLVM_DEBUG(dbgs() << "Won't unroll-and-jam; only loops with single " + "exiting blocks can be unrolled and jammed.\n"); + return false; + } + L = L->getSubLoops()[0]; } while (L); diff --git a/llvm/test/Transforms/LoopUnrollAndJam/multiple_exit_blocks.ll b/llvm/test/Transforms/LoopUnrollAndJam/multiple_exit_blocks.ll new file mode 100644 --- /dev/null +++ b/llvm/test/Transforms/LoopUnrollAndJam/multiple_exit_blocks.ll @@ -0,0 +1,49 @@ +; REQUIRES: asserts +; RUN: opt -debug-only=loop-unroll-and-jam -passes="loop-unroll-and-jam" -enable-unroll-and-jam -allow-unroll-and-jam -unroll-and-jam-count=8 -disable-output %s 2>&1 | FileCheck %s + +; CHECK: Loop Unroll and Jam: F[h] Loop %bb8 +; CHECK: Won't unroll-and-jam; only loops with single exit blocks can be unrolled and jammed + +@a = external global i16, align 2 +@e = external global i32, align 4 +@f = external global i16, align 2 +@b = external global i16, align 2 +@c = external global i64, align 8 + +define void @h() { +bb: + store i32 4, i32* @e, align 4 + %i15 = load i16, i16* @b, align 2 + %i17 = icmp slt i16 %i15, 1 + br label %bb8 + +bb8: ; preds = %bb, %bb47 + %storemerge15 = phi i32 [ 4, %bb ], [ %i49, %bb47 ] + br label %bb24 + +bb24: ; preds = %bb43, %bb8 + %storemerge312 = phi i16 [ 0, %bb8 ], [ %i45, %bb43 ] + br i1 %i17, label %bb46.preheader, label %bb43 + +bb46.preheader: ; preds = %bb24 + store i16 %storemerge312, i16* @f, align 2 + br label %bb46 + +bb43: ; preds = %bb24 + %i45 = add nuw nsw i16 %storemerge312, 1 + %i13 = icmp ult i16 %storemerge312, 7 + br i1 %i13, label %bb24, label %bb47 + +bb46: ; preds = %bb46.preheader, %bb46 + br label %bb46 + +bb47: ; preds = %bb43 + %i49 = add nsw i32 %storemerge15, -1 + store i32 %i49, i32* @e, align 4 + %i7.not = icmp eq i32 %i49, 0 + br i1 %i7.not, label %bb50, label %bb8 + +bb50: ; preds = %bb47 + store i16 %i45, i16* @f, align 2 + ret void +}