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Re: Better info for combine results in worse code generated
- From: Segher Boessenkool <segher at kernel dot crashing dot org>
- To: gcc at gcc dot gnu dot org
- Date: Tue, 2 Jun 2015 11:28:09 -0500
- Subject: Re: Better info for combine results in worse code generated
- Authentication-results: sourceware.org; auth=none
- References: <20150528194222 dot GA12574 at gate dot crashing dot org> <20150529031120 dot GN14752 at bubble dot grove dot modra dot org> <20150529125838 dot GA17397 at gate dot crashing dot org> <20150529135008 dot GO14752 at bubble dot grove dot modra dot org> <20150529150004 dot GA31466 at gate dot crashing dot org> <20150530011727 dot GR14752 at bubble dot grove dot modra dot org> <20150530130220 dot GA22014 at gate dot crashing dot org> <20150601020318 dot GS14752 at bubble dot grove dot modra dot org> <20150601133905 dot GA15905 at gate dot crashing dot org> <20150601231937 dot GU14752 at bubble dot grove dot modra dot org>
On Tue, Jun 02, 2015 at 08:49:37AM +0930, Alan Modra wrote:
> > > In and<mode>3 expander I think you want the following since
> > > and64_2_operand covers the extra double-rotate cases, not all DImode.
> > >
> > > - if ((<MODE>mode == DImode && !and64_2_operand (operands[2], <MODE>mode))
> > > - || (<MODE>mode != DImode && !and_operand (operands[2], <MODE>mode)))
> > > + if (!and_operand (operands[2], <MODE>mode)
> > > + && (<MODE>mode != DImode || !and64_2_operand (operands[2], <MODE>mode)))
> >
> > and64_2_operand includes all of and_operand. I agree it is a mess.
>
> but and64_2_operand doesn't include all of and_operand!
Maybe I'm slow today, but I don't see it? Do you have an example?
> > > get rid of WORD_REGISTER_OPERATIONS,
> >
> > rs6000 should not define it. What e.g. does it mean for mullw? Or,
> > worse, mulhw? Pretty much anything with "w" in its name is problematic.
>
> In many places WORD_REGISTER_OPERATIONS is used, it is saying "don't
> trust the high bits". At the moment we definitely do need it defined!
I don't see that either; do you have a pointer for me?
I've run some bootstraps and tests with WORD_REGISTER_OPERATIONS
undefined: 32-bit code becomes very slightly bigger, and 64-bit code
becomes slightly smaller. No change in testresults.
Segher