[PATCH] D102742: [IR] make stack-protector-guard-* flags into module attrs

[Teresa Johnson via Phabricator via cfe-commits]

tejohnson added a comment.

In D102742#2774639 <https://reviews.llvm.org/D102742#2774639>, @nickdesaulniers wrote:

> In D102742#2774562 <https://reviews.llvm.org/D102742#2774562>, @tejohnson wrote:
>
>> In D102742#2774185 <https://reviews.llvm.org/D102742#2774185>, @nickdesaulniers wrote:
>>
>>> - upgrade module merge strategy to Error
>>
>> Probably want a test using llvm-link or llvm-lto to check this behavior (that alike flags are getting propagated as expected and that conflicting ones error)
>
> Not many tests under llvm/test/LTO or llvm/test/ThinLTO use `llvm-link`; is there a more appropriate subdir for such a test for conflicting module attributes?

Hmm, maybe in llvm/test/Linker? Or you could presumably use llvm-lto.



================
Comment at: clang/include/clang/Driver/Options.td:3429
   HelpText<"Use the given reg for addressing the stack-protector guard">,
-  MarshallingInfoString<CodeGenOpts<"StackProtectorGuardReg">, [{"none"}]>;
+  MarshallingInfoString<CodeGenOpts<"StackProtectorGuardReg">>;
 def mfentry : Flag<["-"], "mfentry">, HelpText<"Insert calls to fentry at function entry (x86/SystemZ only)">,
----------------
nickdesaulniers wrote:
> tejohnson wrote:
> > What's the effect of or reason for this change?
> Of the 3 options added in D88631 (`mstack_protector_guard_EQ`, `mstack_protector_guard_offset_EQ`, `mstack_protector_guard_reg_EQ`) 2 are strings (`mstack_protector_guard_EQ` and `mstack_protector_guard_reg_EQ`).  It was inconsistent that one could be unspecified, where as the other could be unspecified or `"none"` (but those 2 values were equivalent).
> 
> Without this change, in clang/lib/CodeGen/CodeGenModule.cpp I'd need to check that `StackProtectorGuardReg != "none"` rather than `!StackProtectorGuardReg.empty()` below.
> 
> I can change it back, but I think the asymmetry between `mstack_protector_guard_EQ` and `mstack_protector_guard_reg_EQ` in D88631, and I missed that in code review.
> 
> I don't think there would be any other observers of such a change.
I see. Does unspecified mean something like just "-mstack-protector-guard-reg=" with nothing after the =? I didn't realize that was supported.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D102742/new/

https://reviews.llvm.org/D102742