Index: lib/Transforms/Scalar/LoopIdiomRecognize.cpp
===================================================================
--- lib/Transforms/Scalar/LoopIdiomRecognize.cpp
+++ lib/Transforms/Scalar/LoopIdiomRecognize.cpp
@@ -384,6 +384,13 @@
   StoreRefsForMemsetPattern.clear();
   StoreRefsForMemcpy.clear();
   for (Instruction &I : *BB) {
+    if (I.mayThrow()) {
+      StoreRefsForMemset.clear();
+      StoreRefsForMemsetPattern.clear();
+      StoreRefsForMemcpy.clear();
+      return;
+    }
+
     StoreInst *SI = dyn_cast<StoreInst>(&I);
     if (!SI)
       continue;
Index: test/Transforms/LoopIdiom/unwind.ll
===================================================================
--- /dev/null
+++ test/Transforms/LoopIdiom/unwind.ll
@@ -0,0 +1,51 @@
+; ModuleID = 'tmp.cpp'
+; RUN: opt -loop-idiom < %s -S | FileCheck %s
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+@_ZTIi = external constant i8*
+@ff = global void ()* @f, align 8
+@gg = global void (i8*, i32)* @g, align 8
+
+define void @f() {
+entry:
+  %exception = tail call i8* @__cxa_allocate_exception(i64 4) #5
+  %0 = bitcast i8* %exception to i32*
+  store i32 1, i32* %0, align 16
+  tail call void @__cxa_throw(i8* %exception, i8* bitcast (i8** @_ZTIi to i8*), i8* null)
+  unreachable
+}
+
+declare i8* @__cxa_allocate_exception(i64)
+
+declare void @__cxa_throw(i8*, i8*, i8*)
+
+define void @g(i8* noalias nocapture %base, i32 %size) {
+entry:
+  %cmp4 = icmp eq i32 %size, 0
+  br i1 %cmp4, label %for.cond.cleanup, label %for.body.preheader
+
+for.body.preheader:                               ; preds = %entry
+  br label %for.body
+
+for.cond.cleanup.loopexit:                        ; preds = %for.body
+  br label %for.cond.cleanup
+
+for.cond.cleanup:                                 ; preds = %for.cond.cleanup.loopexit, %entry
+  ret void
+
+for.body:                                         ; preds = %for.body.preheader, %for.body
+  %indvars.iv = phi i64 [ %indvars.iv.next, %for.body ], [ 0, %for.body.preheader ]
+  %0 = load void ()*, void ()** @ff, align 8
+  tail call void %0()
+  %arrayidx = getelementptr inbounds i8, i8* %base, i64 %indvars.iv
+  store i8 0, i8* %arrayidx, align 1
+  %indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
+  %lftr.wideiv = trunc i64 %indvars.iv.next to i32
+  %exitcond = icmp eq i32 %lftr.wideiv, %size
+  br i1 %exitcond, label %for.cond.cleanup.loopexit, label %for.body
+; CHECK-LABEL: @g(
+; CHECK-NOT: llvm.memset
+}
+