[ADT] Make Twine's copy constructor private.

There's a lot of misuse of Twine scattered around LLVM.  This
ranges in severity from benign (returning a Twine from a function
by value that is just a string literal) to pretty sketchy (storing
a Twine by value in a class).  While there are some uses for
copying Twines, most of the very compelling ones are confined
to the Twine class implementation itself, and other uses are
either dubious or easily worked around.

This patch makes Twine's copy constructor private, and fixes up
all callsites.

Differential Revision: https://reviews.llvm.org/D38767

llvm-svn: 315530

1 files changed, 10 insertions, 11 deletions

diff --git a/llvm/lib/Transforms/Scalar/SROA.cpp b/llvm/lib/Transforms/Scalar/SROA.cpp
index b968cb8c892..c64c0408758 100644
--- a/llvm/lib/Transforms/Scalar/SROA.cpp
+++ b/llvm/lib/Transforms/Scalar/SROA.cpp
@@ -130,18 +130,15 @@ namespace {
 class IRBuilderPrefixedInserter : public IRBuilderDefaultInserter {
   std::string Prefix;
 
-  const Twine getNameWithPrefix(const Twine &Name) const {
-    return Name.isTriviallyEmpty() ? Name : Prefix + Name;
-  }
-
 public:
   void SetNamePrefix(const Twine &P) { Prefix = P.str(); }
 
 protected:
   void InsertHelper(Instruction *I, const Twine &Name, BasicBlock *BB,
                     BasicBlock::iterator InsertPt) const {
-    IRBuilderDefaultInserter::InsertHelper(I, getNameWithPrefix(Name), BB,
-                                           InsertPt);
+    const Twine &Prefixed = Prefix + Name;
+    IRBuilderDefaultInserter::InsertHelper(
+        I, Name.isTriviallyEmpty() ? Name : Prefixed, BB, InsertPt);
   }
 };
 
@@ -1355,7 +1352,8 @@ static void speculateSelectInstLoads(SelectInst &SI) {
 /// This will return the BasePtr if that is valid, or build a new GEP
 /// instruction using the IRBuilder if GEP-ing is needed.
 static Value *buildGEP(IRBuilderTy &IRB, Value *BasePtr,
-                       SmallVectorImpl<Value *> &Indices, Twine NamePrefix) {
+                       SmallVectorImpl<Value *> &Indices,
+                       const Twine &NamePrefix) {
   if (Indices.empty())
     return BasePtr;
 
@@ -1380,7 +1378,7 @@ static Value *buildGEP(IRBuilderTy &IRB, Value *BasePtr,
 static Value *getNaturalGEPWithType(IRBuilderTy &IRB, const DataLayout &DL,
                                     Value *BasePtr, Type *Ty, Type *TargetTy,
                                     SmallVectorImpl<Value *> &Indices,
-                                    Twine NamePrefix) {
+                                    const Twine &NamePrefix) {
   if (Ty == TargetTy)
     return buildGEP(IRB, BasePtr, Indices, NamePrefix);
 
@@ -1425,7 +1423,7 @@ static Value *getNaturalGEPRecursively(IRBuilderTy &IRB, const DataLayout &DL,
                                        Value *Ptr, Type *Ty, APInt &Offset,
                                        Type *TargetTy,
                                        SmallVectorImpl<Value *> &Indices,
-                                       Twine NamePrefix) {
+                                       const Twine &NamePrefix) {
   if (Offset == 0)
     return getNaturalGEPWithType(IRB, DL, Ptr, Ty, TargetTy, Indices,
                                  NamePrefix);
@@ -1498,7 +1496,7 @@ static Value *getNaturalGEPRecursively(IRBuilderTy &IRB, const DataLayout &DL,
 static Value *getNaturalGEPWithOffset(IRBuilderTy &IRB, const DataLayout &DL,
                                       Value *Ptr, APInt Offset, Type *TargetTy,
                                       SmallVectorImpl<Value *> &Indices,
-                                      Twine NamePrefix) {
+                                      const Twine &NamePrefix) {
   PointerType *Ty = cast<PointerType>(Ptr->getType());
 
   // Don't consider any GEPs through an i8* as natural unless the TargetTy is
@@ -1536,7 +1534,8 @@ static Value *getNaturalGEPWithOffset(IRBuilderTy &IRB, const DataLayout &DL,
 /// a single GEP as possible, thus making each GEP more independent of the
 /// surrounding code.
 static Value *getAdjustedPtr(IRBuilderTy &IRB, const DataLayout &DL, Value *Ptr,
-                             APInt Offset, Type *PointerTy, Twine NamePrefix) {
+                             APInt Offset, Type *PointerTy,
+                             const Twine &NamePrefix) {
   // Even though we don't look through PHI nodes, we could be called on an
   // instruction in an unreachable block, which may be on a cycle.
   SmallPtrSet<Value *, 4> Visited;