r201439 - [CodeGenPrepare][AddressingModeMatcher] Give up on type promotion if the

[Quentin Colombet]

On Feb 18, 2014, at 9:37 AM, Quentin Colombet <qcolombet at apple.com> wrote:

> Hi Tom,
> 
> On Feb 18, 2014, at 9:21 AM, Tom Stellard <tom at stellard.net> wrote:
> 
>> Hi Quentin,
>> 
>> Sorry I missed this on the first time around: 
>> 
>>> --- a/lib/Transforms/Scalar/CodeGenPrepare.cpp
>>> +++ b/lib/Transforms/Scalar/CodeGenPrepare.cpp
>>> @@ -1728,6 +1730,35 @@
>>> TypePromotionHelper::promoteOperandForOther(Instruction *SExt,
>>> return SExtOpnd;
>>> }
>>> 
>>> +/// IsPromotionProfitable - Check whether or not promoting an
>>> instruction
>>> +/// to a wider type was profitable.
>>> +/// \p MatchedSize gives the number of instructions that have been
>>> matched
>>> +/// in the addressing mode after the promotion was applied.
>>> +/// \p SizeWithPromotion gives the number of created instructions for
>>> +/// the promotion plus the number of instructions that have been
>>> +/// matched in the addressing mode before the promotion.
>>> +/// \p PromotedOperand is the value that has been promoted.
>>> +/// \return True if the promotion is profitable, false otherwise.
>>> +bool
>>> +AddressingModeMatcher::IsPromotionProfitable(unsigned MatchedSize,
>>> +                                             unsigned SizeWithPromotion,
>>> +                                             Value *PromotedOperand) const {
>>> +  // We folded less instructions than what we created to promote the operand.
>>> +  // This is not profitable.
>>> +  if (MatchedSize < SizeWithPromotion)
>>> +    return false;
>>> +  if (MatchedSize > SizeWithPromotion)
>>> +    return true;
>>> +  // The promotion is neutral but it may help folding the signextension in
>>> +  // loads for instance.
>>> +  // Check that we did not create an illegal instruction.
>>> +  Instruction *PromotedInst = dyn_cast<Instruction>(PromotedOperand);
>>> +  if (!PromotedInst)
>>> +    return false;
>>> +  return TLI.isOperationLegalOrCustom(PromotedInst->getOpcode(),
>>> +                                      EVT::getEVT(PromotedInst->getType()));
>> 
>> This won't work, because the IR Instructions and SelectionDAG Opcodes
>> have different enumeration values.
> Right, good catch!
> 
>> The original test case must have
>> passed, because it is using a default TargetLowering implementation
>> rather than the one from R600.
>> 
>> I've attached an updated version of the original test case which compiles
>> the program using llc and triggers the bug again.
>> 
>> I couldn't find other transforms that use the isOperation* callbacks, so
>> I think you may have to add a function to convert from IR Instruction to
>> SelectionDAG Opcodes or implement this some other way.
> I think a specific hook in TargetLowering may be the best approach here.
> Let me see what I can come up with.
> If you have ideas on the naming, let me know :).
In fact, we may be able to use this:
int TargetLoweringBase::InstructionOpcodeToISD(unsigned Opcode)const

> 
> Cheers,
> Quentin
>> 
>> Thanks,
>> Tom
>> <update-cgp-test.case.diff>
> 
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