[LLVMdev] RFC: CondCodeActions refactor (was RE: Why is this assertion here?)

[Villmow, Micah]

Yeah just the ordering are the real difference. Also, I  use shifts and masks instead of conditionals and modules. My patch is attached. For me either patch is fine, but what LLVM has now is broken.

Either patch is fine, just need approval from someone to submit.

Micah

> -----Original Message-----
> From: Hal Finkel [mailto:hfinkel at anl.gov]
> Sent: Thursday, July 26, 2012 2:39 PM
> To: Villmow, Micah
> Cc: Developers Mailing List
> Subject: Re: [LLVMdev] RFC: CondCodeActions refactor (was RE: Why is
> this assertion here?)
> 
> On Thu, 26 Jul 2012 21:15:35 +0000
> "Villmow, Micah" <Micah.Villmow at amd.com> wrote:
> 
> > Well, I found out the reason why this assert is here, and this is
> > problematic.
> >
> > CondCodeActions only supports up to 32 different value types. Since we
> > are past 32, what LLVM has is broken.
> >
> > Currently the 4 different Legalize states are stored in successive
> > bits and packed into a uin64_t, see TargetLowering.h. ///
> > CondCodeActions - For each condition code (ISD::CondCode) keep a ///
> > LegalizeAction that indicates how instruction selection should ///
> > deal with the condition code. uint64_t
> > CondCodeActions[ISD::SETCC_INVALID];
> >
> > What I suggest is the following:
> > Change the definition of CondCodeAction to:
> >   uint64_t CondCodeActions[ISD::SETCC_INVALID][2];
> >
> > setCondCodeAction then becomes:
> > void setCondCodeAction(ISD::CondCode CC, MVT VT,
> >                          LegalizeAction Action) {
> >     assert(VT < MVT::LAST_VALUETYPE &&
> >            (unsigned)CC < array_lengthof(CondCodeActions) &&
> >            "Table isn't big enough!");
> >     CondCodeActions[(unsigned)CC][VT.SimplyTy >> 5] &=
> > ~(uint64_t(3UL)  << (VT.SimpleTy - 32)*2);
> > CondCodeActions[(unsigned)CC][VT.SimpleTy >> 5] |= (uint64_t)Action <<
> > (VT.SimpleTy - 32)*2; }
> >
> > getCondCodeAction then becomes:
> > LegalizeAction
> >   getCondCodeAction(ISD::CondCode CC, EVT VT) const {
> >     assert((unsigned)CC < array_lengthof(CondCodeActions) &&
> >            (unsigned)VT.getSimpleVT().SimpleTy <
> > MVT::LAST_VECTOR_VALUETYPE && "Table isn't big enough!");
> >     LegalizeAction Action = (LegalizeAction)
> >       ((CondCodeActions[CC][VT.getSimpleVT().SimpleTy >> 5] >>
> > (2*(VT.getSimpleVT().SimpleTy - 32))) & 3); assert(Action != Promote
> > && "Can't promote condition code!"); return Action;
> >   }
> >
> >
> > The other options are to use a BitVector, or to have a different array
> > for each Legalized action. This approach however seems to use the
> > minimum amount of memory/instructions.
> >
> >
> > Ideas?
> 
> Your approach seems very similar to how I've fixed this problem locally
> (I think that the only difference is the order of the arrays).
> I've attached my version of the fix so that you can compare. I think
> that, as a practical matter, this is the most economical approach.
> 
>  -Hal
> 
> > Micah
> >
> > From: llvmdev-bounces at cs.uiuc.edu
> > [mailto:llvmdev-bounces at cs.uiuc.edu] On Behalf Of Villmow, Micah
> > Sent: Thursday, July 26, 2012 11:29 AM To: Developers Mailing List
> > Subject: [LLVMdev] Why is this assertion here?
> >
> > I'm trying to understand why this assertion is here.
> > LegalizeAction
> >   getCondCodeAction(ISD::CondCode CC, EVT VT) const {
> >     assert((unsigned)CC < array_lengthof(CondCodeActions) &&
> >            (unsigned)VT.getSimpleVT().SimpleTy <
> > sizeof(CondCodeActions[0])*4 && "Table isn't big enough!");
> >     LegalizeAction Action = (LegalizeAction)
> >       ((CondCodeActions[CC] >> (2*VT.getSimpleVT().SimpleTy)) & 3);
> >     assert(Action != Promote && "Can't promote condition code!");
> >     return Action;
> >   }
> >
> > The first part of the assertion I can understand, but why is there an
> > assertion that there are only 32 types? in TOT LLVM if this code is
> > called with v8f32,v2f64 or v4f64, this assert is triggered.
> > Shouldn't the assert be:
> > (unsigned)VT.getSimpleVT().SimpleTy < MVT::MAX_ALLOWED_VALUETYPE && or
> > (unsigned)VT.getSimpleVT().SimpleTy < MVT::LAST_VECTOR_VALUETYPE && ?
> >
> > Thanks,
> > Micah
> >
> >
> 
> 
> 
> --
> Hal Finkel
> Postdoctoral Appointee
> Leadership Computing Facility
> Argonne National Laboratory
-------------- next part --------------
A non-text attachment was scrubbed...
Name: support_ccodes_over_32_types.patch
Type: application/octet-stream
Size: 1537 bytes
Desc: support_ccodes_over_32_types.patch
URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20120726/608071d6/attachment.obj>