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

[Quentin Colombet]

On Feb 18, 2014, at 10:30 AM, Tom Stellard <tom at stellard.net> wrote:

> On Tue, Feb 18, 2014 at 09:47:21AM -0800, Quentin Colombet wrote:
>> 
>> 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
> 
> Oh, I didn't see that.  That should work.
Almost there.
I am seeing a link error when creating the bugpoint executable.

llvm[2]: Linking Release executable bugpoint (without symbols)
Undefined symbols for architecture x86_64:
  "llvm::TargetLoweringBase::InstructionOpcodeToISD(unsigned int) const", referenced from:
      (anonymous namespace)::AddressingModeMatcher::MatchOperationAddr(llvm::User*, unsigned int, unsigned int, bool*) in libLLVMScalarOpts.a(CodeGenPrepare.o)
ld: symbol(s) not found for architecture x86_64

The thing that I do not understand is why the linker is not find this function, whereas it does not complain about TargetLoweringBase::isLegalAddressingMode.
I may have missed something obvious, but I do not see it.

Any idea?

Thanks,
-Quentin
> 
> -Tom
>> 
>>> 
>>> Cheers,
>>> Quentin
>>>> 
>>>> Thanks,
>>>> Tom
>>>> <update-cgp-test.case.diff>
>>> 
>>> _______________________________________________
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>>> llvm-commits at cs.uiuc.edu
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