shchenz 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) {
----------------
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.
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D152924/new/
https://reviews.llvm.org/D152924
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