From 1e9879991b8e7f6f841c2c152cac7b04d291b4c8 Mon Sep 17 00:00:00 2001
From: John McCall <rjmccall@apple.com>
Date: Wed, 10 Apr 2019 18:07:18 +0000
Subject: [PATCH] Fix an off-by-one mistake in IRGen's copy-construction
 special cases in the presence of zero-length arrays.

Patch by Joran Bigalet!

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@358115 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/CodeGen/CGClass.cpp                |  2 +-
 test/CodeGenCXX/pod-member-memcpys.cpp | 14 ++++++++++++++
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/lib/CodeGen/CGClass.cpp b/lib/CodeGen/CGClass.cpp
index d16cae676d..9e1312b786 100644
--- a/lib/CodeGen/CGClass.cpp
+++ b/lib/CodeGen/CGClass.cpp
@@ -1008,7 +1008,7 @@ namespace {
       if (FOffset < FirstFieldOffset) {
         FirstField = F;
         FirstFieldOffset = FOffset;
-      } else if (FOffset > LastFieldOffset) {
+      } else if (FOffset >= LastFieldOffset) {
         LastField = F;
         LastFieldOffset = FOffset;
       }
diff --git a/test/CodeGenCXX/pod-member-memcpys.cpp b/test/CodeGenCXX/pod-member-memcpys.cpp
index 9facb8ad50..a43706cb37 100644
--- a/test/CodeGenCXX/pod-member-memcpys.cpp
+++ b/test/CodeGenCXX/pod-member-memcpys.cpp
@@ -45,6 +45,13 @@ struct ArrayMember {
   int w, x, y, z;
 };
 
+struct ZeroLengthArrayMember {
+    NonPOD np;
+    int a;
+    int b[0];
+    int c;
+};
+
 struct VolatileMember {
   int a, b, c, d;
   volatile int v;
@@ -109,6 +116,7 @@ CALL_AO(Basic)
 CALL_AO(PODMember)
 CALL_AO(PODLikeMember)
 CALL_AO(ArrayMember)
+CALL_AO(ZeroLengthArrayMember)
 CALL_AO(VolatileMember)
 CALL_AO(BitfieldMember)
 CALL_AO(InnerClassMember)
@@ -142,6 +150,12 @@ CALL_AO(PackedMembers)
 // CHECK: call void @llvm.memcpy.p0i8.p0i8.i64({{.*}} align 4 {{.*}} align 4 {{.*}}i64 64, i1 {{.*}})
 // CHECK: ret %struct.ArrayMember*
 
+// ZeroLengthArrayMember copy-assignment:
+// CHECK-LABEL: define linkonce_odr dereferenceable({{[0-9]+}}) %struct.ZeroLengthArrayMember* @_ZN21ZeroLengthArrayMemberaSERKS_(%struct.ZeroLengthArrayMember* %this, %struct.ZeroLengthArrayMember* dereferenceable({{[0-9]+}}))
+// CHECK: call dereferenceable({{[0-9]+}}) %struct.NonPOD* @_ZN6NonPODaSERKS_
+// CHECK: call void @llvm.memcpy.p0i8.p0i8.i64({{.*}} align 4 {{.*}} align 4 {{.*}}i64 8, i1 {{.*}})
+// CHECK: ret %struct.ZeroLengthArrayMember*
+
 // VolatileMember copy-assignment:
 // CHECK-LABEL: define linkonce_odr dereferenceable({{[0-9]+}}) %struct.VolatileMember* @_ZN14VolatileMemberaSERKS_(%struct.VolatileMember* %this, %struct.VolatileMember* dereferenceable({{[0-9]+}}))
 // CHECK: call void @llvm.memcpy.p0i8.p0i8.i64({{.*}} align 4 {{.*}} align 4 {{.*}}i64 16, i1 {{.*}})
-- 
2.50.1