Index: llvm/lib/CodeGen/HardwareLoops.cpp
===================================================================
--- llvm/lib/CodeGen/HardwareLoops.cpp
+++ llvm/lib/CodeGen/HardwareLoops.cpp
@@ -402,8 +402,16 @@
BasicBlock *BB = L->getLoopPreheader();
if (UseLoopGuard && BB->getSinglePredecessor() &&
- cast<BranchInst>(BB->getTerminator())->isUnconditional())
- BB = BB->getSinglePredecessor();
+ cast<BranchInst>(BB->getTerminator())->isUnconditional()) {
+ auto *Predecessor = BB->getSinglePredecessor();
+ // If it's not safe to create a while loop then don't force it and create a
+ // do-while loop instead
+ if (!isSafeToExpandAt(ExitCount, Predecessor->getTerminator(), SE))
+ UseLoopGuard = false;
+ else {
+ BB = Predecessor;
+ }
+ }
if (!isSafeToExpandAt(ExitCount, BB->getTerminator(), SE)) {
LLVM_DEBUG(dbgs() << "- Bailing, unsafe to expand ExitCount "
Index: llvm/test/CodeGen/Thumb2/LowOverheadLoops/exitcount.ll
===================================================================
--- /dev/null
+++ llvm/test/CodeGen/Thumb2/LowOverheadLoops/exitcount.ll
@@ -0,0 +1,89 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc -mtriple=thumbv8.1m.main-none-none-eabi -mattr=+mve.fp -verify-machineinstrs -disable-mve-tail-predication=false -o - %s | FileCheck %s
+%struct.SpeexPreprocessState_ = type { i32, i32, half*, half* }
+
+define void @foo(%struct.SpeexPreprocessState_* nocapture readonly %st, i16* %x) {
+; CHECK-LABEL: foo:
+; CHECK: @ %bb.0: @ %entry
+; CHECK: dlstp.16 lr, r4
+; CHECK-NEXT: .LBB0_1: @ %do.body
+; CHECK-NEXT: @ =>This Inner Loop Header: Depth=1
+; CHECK-NEXT: vldrh.u16 q0, [r2], #16
+; CHECK-NEXT: vstrh.16 q0, [r3], #16
+; CHECK-NEXT: letp lr, .LBB0_1
+; CHECK: dlstp.16 lr, r3
+; CHECK-NEXT: .LBB0_3: @ %do.body6
+; CHECK-NEXT: @ =>This Inner Loop Header: Depth=1
+; CHECK-NEXT: vldrh.u16 q1, [r1], #16
+; CHECK-NEXT: vcvt.f16.s16 q1, q1
+; CHECK-NEXT: vmul.f16 q1, q1, q0
+; CHECK-NEXT: vstrh.16 q1, [r0], #16
+; CHECK-NEXT: letp lr, .LBB0_3
+; CHECK-NEXT: @ %bb.4: @ %do.end13
+; CHECK-NEXT: pop {r4, pc}
+entry:
+ %ps_size = getelementptr inbounds %struct.SpeexPreprocessState_, %struct.SpeexPreprocessState_* %st, i32 0, i32 1
+ %0 = load i32, i32* %ps_size, align 4
+ %mul = shl nsw i32 %0, 1
+ %frame_size = getelementptr inbounds %struct.SpeexPreprocessState_, %struct.SpeexPreprocessState_* %st, i32 0, i32 0
+ %1 = load i32, i32* %frame_size, align 4
+ %sub = sub nsw i32 %mul, %1
+ %inbuf = getelementptr inbounds %struct.SpeexPreprocessState_, %struct.SpeexPreprocessState_* %st, i32 0, i32 3
+ %2 = load half*, half** %inbuf, align 4
+ %frame = getelementptr inbounds %struct.SpeexPreprocessState_, %struct.SpeexPreprocessState_* %st, i32 0, i32 2
+ %3 = load half*, half** %frame, align 4
+ br label %do.body
+
+do.body: ; preds = %do.body, %entry
+ %pinbuff16.0 = phi half* [ %2, %entry ], [ %add.ptr, %do.body ]
+ %blkCnt.0 = phi i32 [ %sub, %entry ], [ %sub2, %do.body ]
+ %pframef16.0 = phi half* [ %3, %entry ], [ %add.ptr1, %do.body ]
+ %4 = tail call <8 x i1> @llvm.arm.mve.vctp16(i32 %blkCnt.0)
+ %5 = bitcast half* %pinbuff16.0 to <8 x half>*
+ %6 = tail call fast <8 x half> @llvm.masked.load.v8f16.p0v8f16(<8 x half>* %5, i32 2, <8 x i1> %4, <8 x half> zeroinitializer)
+ %7 = bitcast half* %pframef16.0 to <8 x half>*
+ tail call void @llvm.masked.store.v8f16.p0v8f16(<8 x half> %6, <8 x half>* %7, i32 2, <8 x i1> %4)
+ %add.ptr = getelementptr inbounds half, half* %pinbuff16.0, i32 8
+ %add.ptr1 = getelementptr inbounds half, half* %pframef16.0, i32 8
+ %sub2 = add nsw i32 %blkCnt.0, -8
+ %cmp = icmp sgt i32 %blkCnt.0, 8
+ br i1 %cmp, label %do.body, label %do.end
+
+do.end: ; preds = %do.body
+ %8 = load half*, half** %frame, align 4
+ %add.ptr4 = getelementptr inbounds half, half* %8, i32 %sub
+ %9 = load i32, i32* %frame_size, align 4
+ br label %do.body6
+
+do.body6: ; preds = %do.body6, %do.end
+ %px.0 = phi i16* [ %x, %do.end ], [ %add.ptr8, %do.body6 ]
+ %blkCnt.1 = phi i32 [ %9, %do.end ], [ %sub10, %do.body6 ]
+ %pframef16.1 = phi half* [ %add.ptr4, %do.end ], [ %add.ptr9, %do.body6 ]
+ %10 = tail call <8 x i1> @llvm.arm.mve.vctp16(i32 %blkCnt.1)
+ %11 = bitcast i16* %px.0 to <8 x i16>*
+ %12 = tail call <8 x i16> @llvm.masked.load.v8i16.p0v8i16(<8 x i16>* %11, i32 2, <8 x i1> %10, <8 x i16> zeroinitializer)
+ %13 = tail call fast <8 x half> @llvm.arm.mve.vcvt.fp.int.predicated.v8f16.v8i16.v8i1(<8 x i16> %12, i32 0, <8 x i1> %10, <8 x half> undef)
+ %14 = tail call fast <8 x half> @llvm.arm.mve.mul.predicated.v8f16.v8i1(<8 x half> %13, <8 x half> <half 0xH1800, half 0xH1800, half 0xH1800, half 0xH1800, half 0xH1800, half 0xH1800, half 0xH1800, half 0xH1800>, <8 x i1> %10, <8 x half> undef)
+ %15 = bitcast half* %pframef16.1 to <8 x half>*
+ tail call void @llvm.masked.store.v8f16.p0v8f16(<8 x half> %14, <8 x half>* %15, i32 2, <8 x i1> %10)
+ %add.ptr8 = getelementptr inbounds i16, i16* %px.0, i32 8
+ %add.ptr9 = getelementptr inbounds half, half* %pframef16.1, i32 8
+ %sub10 = add nsw i32 %blkCnt.1, -8
+ %cmp12 = icmp sgt i32 %blkCnt.1, 8
+ br i1 %cmp12, label %do.body6, label %do.end13
+
+do.end13: ; preds = %do.body6
+ ret void
+}
+
+declare <8 x i1> @llvm.arm.mve.vctp16(i32)
+
+declare <8 x half> @llvm.masked.load.v8f16.p0v8f16(<8 x half>*, i32 immarg, <8 x i1>, <8 x half>)
+
+declare void @llvm.masked.store.v8f16.p0v8f16(<8 x half>, <8 x half>*, i32 immarg, <8 x i1>)
+
+declare <8 x i16> @llvm.masked.load.v8i16.p0v8i16(<8 x i16>*, i32 immarg, <8 x i1>, <8 x i16>)
+
+declare <8 x half> @llvm.arm.mve.vcvt.fp.int.predicated.v8f16.v8i16.v8i1(<8 x i16>, i32, <8 x i1>, <8 x half>)
+
+declare <8 x half> @llvm.arm.mve.mul.predicated.v8f16.v8i1(<8 x half>, <8 x half>, <8 x i1>, <8 x half>)