Invalidate struct layout cache

Author: s-barannikov

llvm/lib/IR/DataLayout.cpp

@@ -117,6 +117,29 @@ unsigned StructLayout::getElementContainingOffset(uint64_t FixedOffset) const {
   return SI - MemberOffsets.begin();
 }
 
+namespace {
+
+class StructLayoutMap {
+  using LayoutInfoTy = DenseMap<StructType*, StructLayout*>;
+  LayoutInfoTy LayoutInfo;
+
+public:
+  ~StructLayoutMap() {
+    // Remove any layouts.
+    for (const auto &I : LayoutInfo) {
+      StructLayout *Value = I.second;
+      Value->~StructLayout();
+      free(Value);
+    }
+  }
+
+  StructLayout *&operator[](StructType *STy) {
+    return LayoutInfo[STy];
+  }
+};
+
+} // end anonymous namespace
+
 //===----------------------------------------------------------------------===//
 // LayoutAlignElem, LayoutAlign support
 //===----------------------------------------------------------------------===//
@@ -214,7 +237,8 @@ DataLayout::DataLayout(StringRef LayoutString) {
 }
 
 DataLayout &DataLayout::operator=(const DataLayout &Other) {
-  // Copy everything except for LayoutMap, which will be recomputed on demand.
+  delete static_cast<StructLayoutMap *>(LayoutMap);
+  LayoutMap = nullptr;
   StringRepresentation = Other.StringRepresentation;
   BigEndian = Other.BigEndian;
   AllocaAddrSpace = Other.AllocaAddrSpace;
@@ -687,29 +711,6 @@ Align DataLayout::getIntegerAlignment(uint32_t BitWidth,
   return abi_or_pref ? I->ABIAlign : I->PrefAlign;
 }
 
-namespace {
-
-class StructLayoutMap {
-  using LayoutInfoTy = DenseMap<StructType*, StructLayout*>;
-  LayoutInfoTy LayoutInfo;
-
-public:
-  ~StructLayoutMap() {
-    // Remove any layouts.
-    for (const auto &I : LayoutInfo) {
-      StructLayout *Value = I.second;
-      Value->~StructLayout();
-      free(Value);
-    }
-  }
-
-  StructLayout *&operator[](StructType *STy) {
-    return LayoutInfo[STy];
-  }
-};
-
-} // end anonymous namespace
-
 DataLayout::~DataLayout() { delete static_cast<StructLayoutMap *>(LayoutMap); }
 
 const StructLayout *DataLayout::getStructLayout(StructType *Ty) const {

llvm/unittests/IR/DataLayoutTest.cpp

@@ -19,6 +19,23 @@ using namespace llvm;
 
 namespace {
 
+TEST(DataLayoutTest, CopyAssignmentInvalidatesStructLayout) {
+  DataLayout DL1 = cantFail(DataLayout::parse("p:32:32"));
+  DataLayout DL2 = cantFail(DataLayout::parse("p:64:64"));
+
+  LLVMContext Ctx;
+  StructType *Ty = StructType::get(PointerType::getUnqual(Ctx));
+
+  // Initialize struct layout caches.
+  EXPECT_EQ(DL1.getStructLayout(Ty)->getAlignment(), Align(4));
+  EXPECT_EQ(DL2.getStructLayout(Ty)->getAlignment(), Align(8));
+
+  // The copy should invalidate DL1's cache.
+  DL1 = DL2;
+  EXPECT_EQ(DL1.getStructLayout(Ty)->getAlignment(), Align(8));
+  EXPECT_EQ(DL2.getStructLayout(Ty)->getAlignment(), Align(8));
+}
+
 TEST(DataLayoutTest, FunctionPtrAlign) {
   EXPECT_EQ(MaybeAlign(0), DataLayout("").getFunctionPtrAlign());
   EXPECT_EQ(MaybeAlign(1), DataLayout("Fi8").getFunctionPtrAlign());