Index: include/llvm/Target/TargetLowering.h =================================================================== --- include/llvm/Target/TargetLowering.h +++ include/llvm/Target/TargetLowering.h @@ -1504,23 +1504,24 @@ return false; } - /// Return true if it's free to truncate a value of type Ty1 to type - /// Ty2. e.g. On x86 it's free to truncate a i32 value in register EAX to i16 + /// Return true if it's free to truncate a value of type FromTy to type + /// ToTy. e.g. On x86 it's free to truncate a i32 value in register EAX to i16 /// by referencing its sub-register AX. - virtual bool isTruncateFree(Type * /*Ty1*/, Type * /*Ty2*/) const { + /// Targets must return false when FromTy <= ToTy. + virtual bool isTruncateFree(Type *FromTy, Type *ToTy) const { return false; } - /// Return true if a truncation from Ty1 to Ty2 is permitted when deciding + /// Return true if a truncation from FromTy to ToTy is permitted when deciding /// whether a call is in tail position. Typically this means that both results /// would be assigned to the same register or stack slot, but it could mean /// the target performs adequate checks of its own before proceeding with the - /// tail call. - virtual bool allowTruncateForTailCall(Type * /*Ty1*/, Type * /*Ty2*/) const { + /// tail call. Targets must return false when FromTy <= ToTy. + virtual bool allowTruncateForTailCall(Type *FromTy, Type *ToTy) const { return false; } - virtual bool isTruncateFree(EVT /*VT1*/, EVT /*VT2*/) const { + virtual bool isTruncateFree(EVT FromVT, EVT ToVT) const { return false; } @@ -1561,11 +1562,12 @@ /// isTruncateFree(Ty2, Ty1) is true, this does not necessarily apply to /// truncate instructions. e.g. on x86-64, all instructions that define 32-bit /// values implicit zero-extend the result out to 64 bits. - virtual bool isZExtFree(Type * /*Ty1*/, Type * /*Ty2*/) const { + /// Targets must return false when FromTy >= ToTy. + virtual bool isZExtFree(Type *FromTy, Type *ToTy) const { return false; } - virtual bool isZExtFree(EVT /*VT1*/, EVT /*VT2*/) const { + virtual bool isZExtFree(EVT FromTy, EVT ToTy) const { return false; } Index: lib/CodeGen/SelectionDAG/DAGCombiner.cpp =================================================================== --- lib/CodeGen/SelectionDAG/DAGCombiner.cpp +++ lib/CodeGen/SelectionDAG/DAGCombiner.cpp @@ -9719,8 +9719,8 @@ void addSliceGain(const LoadedSlice &LS) { // Each slice saves a truncate. const TargetLowering &TLI = LS.DAG->getTargetLoweringInfo(); - if (!TLI.isTruncateFree(LS.Inst->getValueType(0), - LS.Inst->getOperand(0).getValueType())) + if (!TLI.isTruncateFree(LS.Inst->getOperand(0).getValueType(), + LS.Inst->getValueType(0))) ++Truncates; // If there is a shift amount, this slice gets rid of it. if (LS.Shift)