llvm dev - May 2008 - [LLVMdev] implementing PIC for linux x86-64

Hello, Rafael
> On linux X86_64, calls to local but externally visible functions
> should use the PLT. Access to local (same compilation unit), variables
> can just use RIP relative access.
Right, this is just optimization. AFAIR, current code already does this
for 'normal' PIC - it just checks for linkage and doesn't assemble
call
via PLT for stuff with internal linkage.
> Looks like we need a second variable (say PICCallStyle). With it we
> would have something like:
This seems to be PIC vs Dynamic-No-PIC relocation style issue, I don't
see, why something new is needed here.

-- 
With best regards, Anton Korobeynikov.

Faculty of Mathematics & Mechanics, Saint Petersburg State University.

> Right, this is just optimization. AFAIR, current code already does this
> for 'normal' PIC - it just checks for linkage and doesn't
assemble call
> via PLT for stuff with internal linkage.
It is not using the PLT even for externally visible ones. Try

; RUN: llvm-as < %s | \
; RUN:   llc -mtriple=x86_64-pc-linux -relocation-model=pic -o %t1 -f
; RUN: grep {call       f at plt} %t1

define void @g() {
entry:
        call void @f( )
        ret void
}

declare void @f()


Cheers,
-- 
Rafael Avila de Espindola

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