Index: lib/Target/X86/X86ISelLowering.cpp
===================================================================
--- lib/Target/X86/X86ISelLowering.cpp
+++ lib/Target/X86/X86ISelLowering.cpp
@@ -2833,7 +2833,7 @@
   if (Flags.isByVal()) {
     unsigned Bytes = Flags.getByValSize();
     if (Bytes == 0) Bytes = 1; // Don't create zero-sized stack objects.
-    int FI = MFI.CreateFixedObject(Bytes, VA.getLocMemOffset(), isImmutable);
+    int FI = MFI.CreateFixedObject(Bytes, VA.getLocMemOffset(), isImmutable, true);
     // Adjust SP offset of interrupt parameter.
     if (CallConv == CallingConv::X86_INTR) {
       MFI.setObjectOffset(FI, Offset);
Index: test/CodeGen/X86/pr30290.ll
===================================================================
--- /dev/null
+++ test/CodeGen/X86/pr30290.ll
@@ -0,0 +1,86 @@
+; RUN: lli -mcpu=btver2 %s | FileCheck %s
+; CHECK: 5
+; Test desc: two functions (foo, bar) with byval arguments, should not have
+; reads/writes from/to byval storage re-ordered.
+source_filename = "test.c"
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-pc-linux-gnu"
+
+%struct.face = type { [7 x i32] }
+
+@.str = private unnamed_addr constant [4 x i8] c"%d\0A\00", align 1
+
+; Function Attrs: noinline nounwind uwtable
+define void @baz(%struct.face* byval nocapture readonly align 8) local_unnamed_addr #0 {
+  %2 = getelementptr inbounds %struct.face, %struct.face* %0, i64 0, i32 0, i64 0
+  %3 = load i32, i32* %2, align 8, !tbaa !2
+  %4 = getelementptr inbounds %struct.face, %struct.face* %0, i64 0, i32 0, i64 1
+  %5 = load i32, i32* %4, align 4, !tbaa !2
+  %6 = getelementptr inbounds %struct.face, %struct.face* %0, i64 0, i32 0, i64 2
+  %7 = load i32, i32* %6, align 8, !tbaa !2
+  %8 = getelementptr inbounds %struct.face, %struct.face* %0, i64 0, i32 0, i64 3
+  %9 = bitcast i32* %8 to <4 x i32>*
+  %10 = load <4 x i32>, <4 x i32>* %9, align 4, !tbaa !2
+  %11 = shufflevector <4 x i32> %10, <4 x i32> undef, <4 x i32> <i32 2, i32 3, i32 undef, i32 undef>
+  %12 = add nsw <4 x i32> %10, %11
+  %13 = shufflevector <4 x i32> %12, <4 x i32> undef, <4 x i32> <i32 1, i32 undef, i32 undef, i32 undef>
+  %14 = add nsw <4 x i32> %12, %13
+  %15 = extractelement <4 x i32> %14, i32 0
+  %16 = add nsw i32 %15, %7
+  %17 = add nsw i32 %16, %5
+  %18 = add nsw i32 %17, %3
+  %19 = tail call i32 (i8*, ...) @printf(i8* getelementptr inbounds ([4 x i8], [4 x i8]* @.str, i64 0, i64 0), i32 %18)
+  ret void
+}
+
+; Function Attrs: argmemonly nounwind
+declare void @llvm.lifetime.start.p0i8(i64, i8* nocapture) #1
+
+; Function Attrs: argmemonly nounwind
+declare void @llvm.lifetime.end.p0i8(i64, i8* nocapture) #1
+
+; Function Attrs: nounwind
+declare i32 @printf(i8* nocapture readonly, ...) local_unnamed_addr #2
+
+; Function Attrs: noinline nounwind uwtable
+define void @foo(%struct.face* byval nocapture align 8) local_unnamed_addr #0 {
+  %2 = bitcast %struct.face* %0 to <4 x i32>*
+  store <4 x i32> <i32 1, i32 1, i32 1, i32 1>, <4 x i32>* %2, align 8, !tbaa !2
+  %3 = getelementptr inbounds %struct.face, %struct.face* %0, i64 0, i32 0, i64 4
+  store i32 1, i32* %3, align 8, !tbaa !2
+; XXX XXX XXX
+; Fault happens here: five "1" constants have just been written into the byval
+; %struct.face, but the subsequent byval read of that struct (next call)
+; gets re-ordered with those writes, illegally.
+  call void @baz(%struct.face* byval nonnull align 8 %0)
+  ret void
+}
+
+; Function Attrs: noinline nounwind uwtable
+define i32 @main() local_unnamed_addr #0 {
+  %1 = alloca %struct.face, align 8
+  %2 = bitcast %struct.face* %1 to i8*
+  call void @llvm.lifetime.start.p0i8(i64 28, i8* nonnull %2) #3
+  call void @llvm.memset.p0i8.i64(i8* nonnull %2, i8 0, i64 28, i32 8, i1 false)
+  call void @foo(%struct.face* byval nonnull align 8 %1)
+  call void @llvm.lifetime.end.p0i8(i64 28, i8* nonnull %2) #3
+  ret i32 0
+}
+
+; Function Attrs: argmemonly nounwind
+declare void @llvm.memset.p0i8.i64(i8* nocapture writeonly, i8, i64, i32, i1) #1
+
+attributes #0 = { noinline nounwind uwtable "correctly-rounded-divide-sqrt-fp-math"="false" "disable-tail-calls"="false" "less-precise-fpmad"="false" "no-frame-pointer-elim"="false" "no-infs-fp-math"="false" "no-jump-tables"="false" "no-nans-fp-math"="false" "no-signed-zeros-fp-math"="false" "no-trapping-math"="false" "stack-protector-buffer-size"="8" "target-cpu"="btver2" "target-features"="+aes,+avx,+bmi,+cx16,+f16c,+fxsr,+lzcnt,+mmx,+movbe,+pclmul,+popcnt,+prfchw,+sse,+sse2,+sse3,+sse4.1,+sse4.2,+sse4a,+ssse3,+x87,+xsave,+xsaveopt" "unsafe-fp-math"="false" "use-soft-float"="false" }
+attributes #1 = { argmemonly nounwind }
+attributes #2 = { nounwind "correctly-rounded-divide-sqrt-fp-math"="false" "disable-tail-calls"="false" "less-precise-fpmad"="false" "no-frame-pointer-elim"="false" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "no-signed-zeros-fp-math"="false" "no-trapping-math"="false" "stack-protector-buffer-size"="8" "target-cpu"="btver2" "target-features"="+aes,+avx,+bmi,+cx16,+f16c,+fxsr,+lzcnt,+mmx,+movbe,+pclmul,+popcnt,+prfchw,+sse,+sse2,+sse3,+sse4.1,+sse4.2,+sse4a,+ssse3,+x87,+xsave,+xsaveopt" "unsafe-fp-math"="false" "use-soft-float"="false" }
+attributes #3 = { nounwind }
+
+!llvm.module.flags = !{!0}
+!llvm.ident = !{!1}
+
+!0 = !{i32 1, !"wchar_size", i32 4}
+!1 = !{!"clang version 6.0.0-svn326550-1~exp1~20180404173613.65 (branches/release_60)"}
+!2 = !{!3, !3, i64 0}
+!3 = !{!"int", !4, i64 0}
+!4 = !{!"omnipotent char", !5, i64 0}
+!5 = !{!"Simple C/C++ TBAA"}