Fix resetting the DataLayout in a Module.

No tool does this currently, but as everything else in a module we should be
able to change its DataLayout.

Most of the fix is in DataLayout to make sure it can be reset properly.

The test uses Module::setDataLayout since the fact that we mutate a DataLayout
is an implementation detail. The module could hold a OwningPtr<DataLayout> and
the DataLayout itself could be immutable.

Thanks to Philip Reames for pushing me in the right direction.

llvm-svn: 202198

2 files changed, 19 insertions, 5 deletions

diff --git a/llvm/lib/IR/DataLayout.cpp b/llvm/lib/IR/DataLayout.cpp
index d60c79f52e8..ccdaec5e554 100644
--- a/llvm/lib/IR/DataLayout.cpp
+++ b/llvm/lib/IR/DataLayout.cpp
@@ -176,7 +176,9 @@ static const LayoutAlignElem DefaultAlignments[] = {
   { AGGREGATE_ALIGN, 0, 0, 8 }   // struct
 };
 
-void DataLayout::init(StringRef Desc) {
+void DataLayout::reset(StringRef Desc) {
+  clear();
+
   LayoutMap = 0;
   LittleEndian = false;
   StackNaturalAlign = 0;
@@ -344,12 +346,12 @@ void DataLayout::parseSpecifier(StringRef Desc) {
   }
 }
 
-DataLayout::DataLayout(const Module *M) {
+DataLayout::DataLayout(const Module *M) : LayoutMap(0) {
   const DataLayout *Other = M->getDataLayout();
   if (Other)
     *this = *Other;
   else
-    init("");
+    reset("");
 }
 
 void
@@ -469,8 +471,16 @@ public:
 
 } // end anonymous namespace
 
+void DataLayout::clear() {
+  LegalIntWidths.clear();
+  Alignments.clear();
+  Pointers.clear();
+  delete static_cast<StructLayoutMap *>(LayoutMap);
+  LayoutMap = 0;
+}
+
 DataLayout::~DataLayout() {
-  delete static_cast<StructLayoutMap*>(LayoutMap);
+  clear();
 }
 
 const StructLayout *DataLayout::getStructLayout(StructType *Ty) const {
diff --git a/llvm/lib/IR/Module.cpp b/llvm/lib/IR/Module.cpp
index 739f8888f96..4204c8ef5fc 100644
--- a/llvm/lib/IR/Module.cpp
+++ b/llvm/lib/IR/Module.cpp
@@ -339,17 +339,21 @@ void Module::addModuleFlag(MDNode *Node) {
 }
 
 void Module::setDataLayout(StringRef Desc) {
+  DL.reset(Desc);
+
   if (Desc.empty()) {
     DataLayoutStr = "";
   } else {
-    DL.init(Desc);
     DataLayoutStr = DL.getStringRepresentation();
+    // DataLayoutStr is now equivalent to Desc, but since the representation
+    // is not unique, they may not be identical.
   }
 }
 
 void Module::setDataLayout(const DataLayout *Other) {
   if (!Other) {
     DataLayoutStr = "";
+    DL.reset("");
   } else {
     DL = *Other;
     DataLayoutStr = DL.getStringRepresentation();