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

[Tom Stellard]

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.

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