[llvm-dev] -fpic ELF default: reclaim some -fno-semantic-interposition optimization opportunities?

Joerg Sonnenberger via llvm-dev llvm-dev at lists.llvm.org
Sun Jun 6 07:08:02 PDT 2021

On Sat, Jun 05, 2021 at 06:08:57PM -0700, Fāng-ruì Sòng via llvm-dev wrote:
> On 2021-06-06, Joerg Sonnenberger wrote:
> > On Fri, Jun 04, 2021 at 03:26:53PM -0700, Fāng-ruì Sòng via llvm-dev wrote:
> > > Fixing the last point is actually easy: let -fno-pic use GOT when
> > > taking the address of an non-definition function.
> > 
> > I'd far prefer to have an attribute to explicitly say that the address
> > of a given symbol should always be computed indirectly (e.g. via GOT).
> > That gives the explicit control necessary for libraries without
> > penalizing the larger executables like clang.
> > 
> > Joerg
> Taking the address (in code) of a non-definition function is rare,
> rarer after optimization. At least when building clang, I cannot find
> any penalizing.

I was not talking about just functions. I can't even think of a case
where pointer equality for function pointers matters. But the case I
care far more about is being able to avoid copy relocations for global
variables and that's the same problem (loading the address of a symbol).


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