On Dec 28, 2007, at 11:56 PM, Christopher Lamb wrote: > URL: http://llvm.org/viewvc/llvm-project?rev=45403&view=rev > Log: > Disable null pointer folding transforms for non-generic address > spaces. This should probably be a target-specific predicate based > on address space. That way for targets where this isn't applicable > the predicate can be optimized away.
Hi Christopher, Is this really needed? There are a variety of places in the compiler that assume that a null pointer load/store is invalid. For example, I think we turn "x = load p; c = p == null" into "x = load p; c = false" for example. Is there any other solution to the problem you've hit? -Chris > Modified: > llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp > llvm/trunk/lib/Transforms/Scalar/SCCP.cpp > > Modified: llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp > URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/ > Scalar/InstructionCombining.cpp?rev=45403&r1=45402&r2=45403&view=diff > > ====================================================================== > ======== > --- llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp > (original) > +++ llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp Sat > Dec 29 01:56:53 2007 > @@ -9338,8 +9338,11 @@ > return ReplaceInstUsesWith(LI, LIB); > } > > - if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(Op)) > - if (isa<ConstantPointerNull>(GEPI->getOperand(0))) { > + if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(Op)) { > + const Value *GEPI0 = GEPI->getOperand(0); > + // TODO: Consider a target hook for valid address spaces for > this xform. > + if (isa<ConstantPointerNull>(GEPI0) && > + cast<PointerType>(GEPI0->getType())->getAddressSpace() == > 0) { > // Insert a new store to null instruction before the load to > indicate > // that this code is not reachable. We do this instead of > inserting > // an unreachable instruction directly because we cannot > modify the > @@ -9348,10 +9351,13 @@ > Constant::getNullValue(Op->getType()), &LI); > return ReplaceInstUsesWith(LI, UndefValue::get(LI.getType())); > } > + } > > if (Constant *C = dyn_cast<Constant>(Op)) { > // load null/undef -> undef > - if ((C->isNullValue() || isa<UndefValue>(C))) { > + // TODO: Consider a target hook for valid address spaces for > this xform. > + if (isa<UndefValue>(C) || (C->isNullValue() && > + cast<PointerType>(Op->getType())->getAddressSpace() == 0)) { > // Insert a new store to null instruction before the load to > indicate that > // this code is not reachable. We do this instead of > inserting an > // unreachable instruction directly because we cannot modify > the CFG. > > Modified: llvm/trunk/lib/Transforms/Scalar/SCCP.cpp > URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/ > Scalar/SCCP.cpp?rev=45403&r1=45402&r2=45403&view=diff > > ====================================================================== > ======== > --- llvm/trunk/lib/Transforms/Scalar/SCCP.cpp (original) > +++ llvm/trunk/lib/Transforms/Scalar/SCCP.cpp Sat Dec 29 01:56:53 2007 > @@ -1015,7 +1015,9 @@ > if (PtrVal.isUndefined()) return; // The pointer is not > resolved yet! > if (PtrVal.isConstant() && !I.isVolatile()) { > Value *Ptr = PtrVal.getConstant(); > - if (isa<ConstantPointerNull>(Ptr)) { > + // TODO: Consider a target hook for valid address spaces for > this xform. > + if (isa<ConstantPointerNull>(Ptr) && > + cast<PointerType>(Ptr->getType())->getAddressSpace() == 0) { > // load null -> null > markConstant(IV, &I, Constant::getNullValue(I.getType())); > return; > > > _______________________________________________ > llvm-commits mailing list > llvm-commits@cs.uiuc.edu > http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits _______________________________________________ llvm-commits mailing list llvm-commits@cs.uiuc.edu http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits
