[LLVMdev] prevents instruction-scheduler from interfereing instruction pair

[Andrew Trick]

On Nov 23, 2013, at 6:11 AM, Liu Xin <navy.xliu at gmail.com> wrote:

> I think this after a second. I got your point. I can define a pseudo instruction for an instr-pair and expand it after post-RA-sched. as you said, in preEmitPass. 
>  
> The original intrinsic can also be kept. I just convert the intrinsic to pseudo instruction in TargetLower. Thank you for your enlightening suggestion!  

FYI: If you did want to use the existing ExpandPostRAPseudo pass, then you could probably expand the pseudo into a bundle of machine instructions. See MIBundleBuilder. The PostRAScheduler schedules bundles as a single instructions.

-Andy

> 
> thanks,
> --lx
> 
> 
> 
> On Sat, Nov 23, 2013 at 8:37 PM, Amara Emerson <amara.emerson at gmail.com> wrote:
> What I meant was to write your own expansion pass and run it after the
> scheduler passes, e.g. in the pre-emit stage.
> > if (addPreEmitPass())
>     printAndVerify("After PreEmit passes")
> 
> Though if it's too hacky for you then fair enough.
> 
> Amara
> 
> On 23 November 2013 03:17, Liu Xin <navy.xliu at gmail.com> wrote:
> > Amara,
> >
> > first, thank you for answering.  but I found expandPsuedo instructions
> > actually happens before post-RA, like the following code showing:
> > your approach is a little hacky, right? : )
> >
> > // Expand pseudo instructions before second scheduling pass.
> >   addPass(&ExpandPostRAPseudosID);
> >   printAndVerify("After ExpandPostRAPseudos");
> >
> >   // Run pre-sched2 passes.
> >   if (addPreSched2())
> >     printAndVerify("After PreSched2 passes");
> >
> >   // Second pass scheduler.
> >   if (getOptLevel() != CodeGenOpt::None) {
> >     addPass(&PostRASchedulerID);
> >     printAndVerify("After PostRAScheduler");
> >   }
> >
> >
> > secondly, psuedo instruction is kind of compiler internal representation. I
> > wish our instruction pair can disclose to programmer. intrinsics can do
> > that.
> >
> > thanks,
> > --lx
> >
> >
> > On Fri, Nov 22, 2013 at 9:45 PM, Amara Emerson <amara.emerson at arm.com>
> > wrote:
> >>
> >> What about describing the instruction pairs as pseudo-instructions, and
> >> then expanding them in a machine function pass at the pre-emit stage?
> >>
> >>
> >>
> >> Amara
> >
> >
> >
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> 
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