Index: llvm/trunk/lib/Transforms/Vectorize/LoopVectorize.cpp
===================================================================
--- llvm/trunk/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ llvm/trunk/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -5926,7 +5926,12 @@
 
       // Ignore A if it's already in a group or isn't the same kind of memory
       // operation as B.
-      if (isInterleaved(A) || A->mayReadFromMemory() != B->mayReadFromMemory())
+      // Note that mayReadFromMemory() isn't mutually exclusive to mayWriteToMemory
+      // in the case of atomic loads. We shouldn't see those here, canVectorizeMemory()
+      // should have returned false - except for the case we asked for optimization
+      // remarks.
+      if (isInterleaved(A) || (A->mayReadFromMemory() != B->mayReadFromMemory())
+          || (A->mayWriteToMemory() != B->mayWriteToMemory()))
         continue;
 
       // Check rules 1 and 2. Ignore A if its stride or size is different from
Index: llvm/trunk/test/Transforms/LoopVectorize/interleaved-acess-with-remarks.ll
===================================================================
--- llvm/trunk/test/Transforms/LoopVectorize/interleaved-acess-with-remarks.ll
+++ llvm/trunk/test/Transforms/LoopVectorize/interleaved-acess-with-remarks.ll
@@ -0,0 +1,43 @@
+; RUN: opt -S -loop-vectorize -instcombine -force-vector-width=4 -force-vector-interleave=1 -enable-interleaved-mem-accesses=true -runtime-memory-check-threshold=24 --pass-remarks=loop-vectorize < %s | FileCheck %s
+
+target datalayout = "e-m:e-i64:64-i128:128-n32:64-S128"
+
+
+; This only tests that asking for remarks doesn't lead to compiler crashing
+; (or timing out). We just check for output. To be sure, we also check we didn't
+; vectorize.
+; CHECK-LABEL: @atomicLoadsBothWriteAndReadMem
+; CHECK-NOT: <{{[0-9]+}} x i8>
+
+%"struct.std::__atomic_base" = type { i32 }
+%"struct.std::atomic" = type { %"struct.std::__atomic_base" }
+%union.anon = type { i64 }
+%MyStruct = type { i32, %"struct.std::atomic", %union.anon }
+
+define void @atomicLoadsBothWriteAndReadMem(%MyStruct *%a, %MyStruct *%b, %MyStruct *%lim) {
+entry:
+  br label %loop
+
+loop:
+  %0 = phi %MyStruct* [ %a, %entry ], [ %ainc, %loop ]
+  %1 = phi %MyStruct* [ %b, %entry ], [ %binc, %loop ]
+  %2 = getelementptr %MyStruct, %MyStruct* %1, i64 0, i32 0
+  %3 = load i32, i32* %2, align 8
+  %4 = getelementptr inbounds %MyStruct, %MyStruct* %0, i64 0, i32 0
+  store i32 %3, i32* %4, align 8
+  %5 = getelementptr inbounds %MyStruct, %MyStruct* %1, i64 0, i32 1, i32 0, i32 0
+  %6 = load atomic i32, i32* %5 monotonic, align 4
+  %7 = getelementptr inbounds %MyStruct, %MyStruct* %0, i64 0, i32 1, i32 0, i32 0
+  store atomic i32 %6, i32* %7 monotonic, align 4
+  %8 = getelementptr inbounds %MyStruct, %MyStruct* %1, i64 0, i32 2, i32 0
+  %9 = getelementptr inbounds %MyStruct, %MyStruct* %0, i64 0, i32 2, i32 0
+  %10 = load i64, i64* %8, align 8
+  store i64 %10, i64* %9, align 8
+  %binc = getelementptr inbounds %MyStruct, %MyStruct* %1, i64 1
+  %ainc = getelementptr inbounds %MyStruct, %MyStruct* %0, i64 1
+  %cond = icmp eq %MyStruct* %binc, %lim
+  br i1 %cond, label %exit, label %loop
+
+exit:
+  ret void
+}