[PATCH] D152924: [libLTO][AIX] Respect `-f[no]-integrated-as` on AIX

[Qiongsi Wu via Phabricator via llvm-commits]

qiongsiwu1 marked 3 inline comments as done.
qiongsiwu1 added inline comments.


================
Comment at: clang/lib/Driver/ToolChains/CommonArgs.cpp:700
+    CmdArgs.push_back(Args.MakeArgString(
+        Twine(PluginOptPrefix) + "-no-integrated-as=" + NoIntegratedAs));
+  else if (!UseIntegratedAs) {
----------------
MaskRay wrote:
> shchenz wrote:
> > qiongsiwu1 wrote:
> > > shchenz wrote:
> > > > qiongsiwu1 wrote:
> > > > > shchenz wrote:
> > > > > > Seems other options leverage the default value in the back end, for example the default value for `DisableIntegratedAS` in backend is false, so when the front end requires integrated-as, maybe we can save the option here?
> > > > > Ah thanks for the comment! 
> > > > > 
> > > > > > maybe we can save the option here?
> > > > > 
> > > > > Could you help me understand what we mean by "the option"? Do we mean saving (or using?) the value of `-f[no]-integrated-as` explicitly here somehow instead of relying on `ToolChain.useIntegratedAs()`? How do we intend to use the saved option value? My understanding is that `DisableIntegratedAS` takes its value from the option `-no-integrated-as` if `-no-integrated-as` is specified. As pointed out eariler, `DisableIntegratedAS` is false by default. This code explicitly sets `-no-integrated-as` to `0` or `1`, so for the LTO use case, we overwrite the back end default since the option is always present. 
> > > > For example, if front-end requires to use integrated-assembler which is same with back-end's default value, we don't need to pass `-no-integrated-as=0`? We only pass the option `-no-integrated-as=1` when `if (IsOSAIX && !UseIntegratedAs)`.
> > > Ah I see! Thanks for the clarification! 
> > > 
> > > @w2yehia and I discussed this and we preferred setting the option explicitly regardless of the backend's default. The reason was that we did not want to leave a hanging case where the option was not passed to the backend, a case in which we would rely on a non-local option(`DisableIntegratedAS`)'s default value to control the backend. In other words, always passing in the option allowed us to reason about this code locally within this file. @w2yehia feel free to chime in if I am not describing our discussion correctly. 
> > > 
> > > Could you help me understand the benefit of not passing in the option for the default case? 
> > > Could you help me understand the benefit of not passing in the option for the default case?
> > 
> > Too many options pass from front-end to back-end is a reason. And another reason is: I met one case that there is a back-end option has no default value, so each front-end, like clang and FORTRAN will have to explicitly pass the same option. I was asked to set a default in the back-end, so no need to explicitly set the options in each front-end.
> > 
> > If what I read is right, some bool type options like `EmulatedTLS`, `EnableStackSizeSection` are only passed when their values are not the same with the back-end's default.
> > 
> > I am ok to keep it as now if you guys already have an agreement. This is just minor I think.
> If you are going to add `-no-integrated-as=0`, I suggest that you rename the option to `-integrated-as` and use `-integrated-as=1` instead.
`-no-integrated-as=0` is no longer added. The backend default will take care of the case.


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  https://reviews.llvm.org/D152924/new/

https://reviews.llvm.org/D152924