[PATCH] D98895: [X86][clang] Disable long double type for -mno-x87 option

[Andrew Savonichev via Phabricator via cfe-commits]

asavonic added inline comments.


================
Comment at: clang/lib/Sema/SemaDecl.cpp:9573
 
-  checkTypeSupport(NewFD->getType(), D.getBeginLoc(), NewFD);
+  if (D.getFunctionDefinitionKind() != FunctionDefinitionKind::Declaration)
+    checkTypeSupport(NewFD->getType(), D.getBeginLoc(), NewFD);
----------------
erichkeane wrote:
> Why are we not checking declarations here?  This doesn't seem right to me.  At least in the offload languages, we still need to check declarations.  Also, if something is a problem with a declaration, why is it not a problem with defaulted/deleted?
> Why are we not checking declarations here?  This doesn't seem right to me.  At least in the offload languages, we still need to check declarations.

I assume that if if a function is declared and not used, then it is discarded and no code is generated for it. So it should not really matter if it uses an "unsupported" type.
This is important for `long double`, because there are C standard library functions that have `long double` arguments. We skip diagnostics for declarations to avoid errors from standard library headers when the type is actually not used.

> Also, if something is a problem with a declaration, why is it not a problem with defaulted/deleted?

If we can expect that defaulted or deleted functions never result in a code with unsupported types, then we can exclude them as well. Something like this perhaps?
```
void no_long_double(long double) = delete;
```


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D98895/new/

https://reviews.llvm.org/D98895