Introduce WITH(OUT)_LTO? (was: Re: svn commit: r362987 - in head: contrib/bc usr.bin/gh-bc) (LLVMgold.so and gnu's ld.gold)

[Mark Millard]

On 2020-Jul-8, at 01:28, Stefan Eßer <se at freebsd.org> wrote:

> Am 08.07.20 um 09:01 schrieb Mark Millard:
>> The following is more informational than anything as far
>> as I'm concerned. But there may be implications that I'm
>> unaware of. (I sometimes experiment with toolchain use
>> to see what the current status is for such use.)
>> 
>> I attempted to build a system for 32-bit powerpc using clang
>> and binutils, building head -r363000 ( from -r363000 ). (This
>> was a cross build, amd64 -> powerpc.) It got a new type of
>> failure, compared to my past experience:
> 
> Hi Mark,
> 
> thank you for the report. I have tested with "make universe" (with
> default settings) that this version builds on all architectures,
> but Ed Maste has already disabled -flto for powerpc64, due to run
> time issues (floating point exception, IIRC).
> 
> I know that you are actively working on PowerPC and I'd appreciate,
> if you could provide me with information on which parameters cause
> breakage and which work for you. The combination of CLANG with LTO
> and GNU binutils cannot work - CLANG and GCC use incompatible file
> formats to represent the intermediate object files.

Hmm. It looks a little more complicated than that . . .

Looks like the devel/llvm80 devel/llvm90 and devel/llvm10
options for powerpc64 include one for:

     GOLD=on: Build the LLVM Gold plugin for LTO

That produces a plugin (LLVMgold.so) for use with gnu's
ld.gold ( from devel/binutils ).

The system-clang/llvm materials do not seem to include
LLVMgold.so and so prevent use of that toolchain for
LTO via devel/binutils . (A FreeBSD choice rather than
a llvm* vs. binutils technically-blocking issue?)

devel/binutils builds and installs /usr/local/bin/ld.gold
for both 32-bit powerpc contexts and for powerpc64 contexts.

However, for the 32-bit powerpc context, the devel/llvm*
do not include an option to enable building LLVMgold.so .
I do not know if this is just a ports choice vs. if this
has a technically-blocking issue involved.


===
Mark Millard
marklmi at yahoo.com
( dsl-only.net went
away in early 2018-Mar)