-
- return true;
-}
-
-
-
-/// PointsToConstantGlobal - Return true if V (possibly indirectly) points to
-/// some part of a constant global variable. This intentionally only accepts
-/// constant expressions because we don't can't rewrite arbitrary instructions.
-static bool PointsToConstantGlobal(Value *V) {
- if (GlobalVariable *GV = dyn_cast<GlobalVariable>(V))
- return GV->isConstant();
- if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V))
- if (CE->getOpcode() == Instruction::BitCast ||
- CE->getOpcode() == Instruction::GetElementPtr)
- return PointsToConstantGlobal(CE->getOperand(0));
- return false;
-}
-
-/// isOnlyCopiedFromConstantGlobal - Recursively walk the uses of a (derived)
-/// pointer to an alloca. Ignore any reads of the pointer, return false if we
-/// see any stores or other unknown uses. If we see pointer arithmetic, keep
-/// track of whether it moves the pointer (with isOffset) but otherwise traverse
-/// the uses. If we see a memcpy/memmove that targets an unoffseted pointer to
-/// the alloca, and if the source pointer is a pointer to a constant global, we
-/// can optimize this.
-static bool isOnlyCopiedFromConstantGlobal(Value *V, MemTransferInst *&TheCopy,
- bool isOffset) {
- for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI!=E; ++UI) {
- User *U = cast<Instruction>(*UI);
-
- if (LoadInst *LI = dyn_cast<LoadInst>(U)) {
- // Ignore non-volatile loads, they are always ok.
- if (LI->isVolatile()) return false;
- continue;
- }
-
- if (BitCastInst *BCI = dyn_cast<BitCastInst>(U)) {
- // If uses of the bitcast are ok, we are ok.
- if (!isOnlyCopiedFromConstantGlobal(BCI, TheCopy, isOffset))
- return false;
- continue;
- }
- if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(U)) {
- // If the GEP has all zero indices, it doesn't offset the pointer. If it
- // doesn't, it does.
- if (!isOnlyCopiedFromConstantGlobal(GEP, TheCopy,
- isOffset || !GEP->hasAllZeroIndices()))
- return false;
- continue;
- }
-
- if (CallSite CS = U) {
- // If this is the function being called then we treat it like a load and
- // ignore it.
- if (CS.isCallee(UI))
- continue;