[PATCH] Changing the Back-end when Target Options Change

[Andrea_DiBiagio at sn.scee.net]

Hi Bill,

> From: Bill Wendling <wendling at apple.com>
> So...ping?
> 
> Anyone else have a problems with or comments on the patch? (Other 
> than the cleanup that Stefanus mentioned.)
> 
> -bw

I've done some small experiments with attributes generating x86-64 code 
and everything was working as expected.
The change looks good to me. This feature will be extremely useful for a 
piece of work that I plan to do soon so I'd certainly be interested to see 
it committed.

Andrea Di Biagio
SN Systems - Sony Computer Entertainment Group

> 
> On Jun 21, 2013, at 11:14 AM, Bill Wendling <wendling at apple.com> wrote:
> 
> > On Jun 20, 2013, at 6:48 AM, "Du Toit, Stefanus" 
> <stefanus.du.toit at intel.com> wrote:
> > 
> >> Hi Bill,
> >> 
> >> From:  Bill Wendling <wendling at apple.com>
> >>> For those not interested in slugging their way through a ton of
> >>> refactoring code, here's a cleaner patch.
> >>> 
> >>> The executive summary:
> >>> 
> >>> This regenerates the TargetMachine object if the any of the values 
in
> >>> TargetOptions changes. The regeneration is recursive, because 
creating
> >>> TargetMachine pretty much creates all of the other back-end objects 
that
> >>> are needed for code generation.
> >> 
> >> You could use the "curiously recurring template pattern" and add an
> >> instance of a class template in the middle of the inheritance 
hierarchy,
> >> e.g. something alone the lines of:
> >> 
> >> template<typename Derived>
> >> class TargetMachineHelper : public TargetMachine {
> >> TargetMachine *
> >> regenerateWithOptionsImpl(const TargetOptions &Opts,
> >>                           Reloc::Model RM,
> >>                           CodeModel::Model CM,
> >>                           CodeGenOpt::Level OptLvl,
> >>                           std::string &targetTriple,
> >>                           std::string &targetCPU,
> >>                           std::string &targetFS) {
> >>   TargetPassConfig *TPC = PassConfig;
> >> 
> >>   this->~Derived();
> >>   Derived *NewTM = new (this)
> >>     Derived(TheTarget, targetTriple, targetCPU, targetFS,
> >>             Opts, RM, CM, OptLvl);
> >> 
> >>   if (TPC)
> >>     NewTM->PassConfig = TPC->regenerateWithTargetMachine(NewTM);
> >> 
> >>   return NewTM;
> >> }
> >> };
> >> 
> >> // Then, for each backend, change the inheritance like so:
> >> 
> >> class MyTargetMachine : public TargetMachineHelper<MyTargetMachine> {
> >> // ...
> >> 
> >> (I'm sure there are errors in the above, but hopefully it gets the 
idea
> >> across)
> >> 
> >> This would remove the need to define all of these similar-looking
> >> functions in the backends. Should work for PassConfig too.
> >> 
> > Not a bad idea. I'll look into it. Thanks!
> > 
> > -bw
> > 
> > _______________________________________________
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> > llvm-commits at cs.uiuc.edu
> > http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits
> 
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