[PATCH] D94458: [PowerPC] Only use some extend mne if assembler is modern enough

Thu Jan 14 07:07:18 PST 2021

jsji added inline comments.

================
Comment at: llvm/lib/Target/PowerPC/PPC.td:60
                                         "Enable 64-bit instructions">;
+def FeatureModernAs     : SubtargetFeature<"modern-as","HasModernAs", "true",
+                                        "Has new Assembler" >;
----------------
sfertile wrote:
> jsji wrote:
> > sfertile wrote:
> > > Minor nit: I think name, option, description string, etc should explicitly reflect its the AIX assembler.
> > I updated the description and comments to mention AIX, but not the naming of feature. 
> > As I think we should leave this as a general feature that can be used in the future for similar workaround, not necessary AIX only.
> If we find a bug in gas that necessitate disabling an alias and we attempt to use this same feature it would mean also disabling `xxspltd` and `mtudscr` on Linux breaking compatibility with gas. Likewise we would be disabling said alias on AIX breaking compatibility with the AIX system as for a gas bug. 
Yes, unless we want to give one feature for each assembler limitation , there will be situation like, compiler will try to be conservative. 

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  https://reviews.llvm.org/D94458/new/

https://reviews.llvm.org/D94458