Instruction *InstCombiner::visitFreeInst(FreeInst &FI) {
Value *Op = FI.getOperand(0);
- // Change free <ty>* (cast <ty2>* X to <ty>*) into free <ty2>* X
- if (CastInst *CI = dyn_cast<CastInst>(Op))
- if (isa<PointerType>(CI->getOperand(0)->getType())) {
- FI.setOperand(0, CI->getOperand(0));
- return &FI;
- }
-
// free undef -> unreachable.
if (isa<UndefValue>(Op)) {
// Insert a new store to null because we cannot modify the CFG here.
UndefValue::get(PointerType::get(Type::Int1Ty)), &FI);
return EraseInstFromFunction(FI);
}
-
+
// If we have 'free null' delete the instruction. This can happen in stl code
// when lots of inlining happens.
if (isa<ConstantPointerNull>(Op))
return EraseInstFromFunction(FI);
+
+ // Change free <ty>* (cast <ty2>* X to <ty>*) into free <ty2>* X
+ if (BitCastInst *CI = dyn_cast<BitCastInst>(Op)) {
+ FI.setOperand(0, CI->getOperand(0));
+ return &FI;
+ }
+
+ // Change free (gep X, 0,0,0,0) into free(X)
+ if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(Op)) {
+ if (GEPI->hasAllZeroIndices()) {
+ AddToWorkList(GEPI);
+ FI.setOperand(0, GEPI->getOperand(0));
+ return &FI;
+ }
+ }
+
+ // Change free(malloc) into nothing, if the malloc has a single use.
+ if (MallocInst *MI = dyn_cast<MallocInst>(Op))
+ if (MI->hasOneUse()) {
+ EraseInstFromFunction(FI);
+ return EraseInstFromFunction(*MI);
+ }
return 0;
}