ppc64 ld : linker synthesized _savegpr* and _restgpr*

[Fangrui Song]

On 2020-05-06, Alan Modra wrote:
>On Tue, May 05, 2020 at 03:41:04PM -0700, Fangrui Song wrote:
>> Isn't it cleaner and more elegant to define these functions in libgcc, like
>> everything else does?
>
>No, and there is another benefit to having the linker generate
>out-of-line register save and restore functions: If the binary is so
>large that "bl" can't reach them from some location, the linker
>inserts multiple copies of those functions rather than bouncing
>through long branch trampolines.

But why are _savegpr* and _restgpr* given first-class priorities?
(linker defined as opposed to runtime libs)


cat > a.s <<e
   .globl _start; _start:
     bl _savegpr0_20
     nop
     .space (1<<25)
     bl _savegpr0_20
     nop
e

powerpc64le-linux-gnu-gcc -nostdlib a.s -o a
=> (verified with binutils HEAD built with ./configure --target=powerpc64le)

(.text+0x2000008): relocation truncated to fit: R_PPC64_REL24 (stub) against symbol `_savegpr0_20' defined in .sfpr section in linker stubs

STB_LOCAL also looks a bit strange.

What shall happen if the functions are taken address?