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digitalmars.D - lld status

reply Andrei Alexandrescu <SeeWebsiteForEmail erdani.org> writes:
I only became aware today about https://lld.llvm.org, llvm's own linker. 
I wonder how that changes distribution dynamics for us - I heard ldc 
already uses its embedded variant for linking programs (on Widows? 
Posix? 32bit? 64bit?). Can we distribute it as an alternative to 
optlink? Thanks! -- Andrei
Dec 21 2017
next sibling parent David Nadlinger <code klickverbot.at> writes:
On Thursday, 21 December 2017 at 18:40:54 UTC, Andrei 
Alexandrescu wrote:

 I heard ldc already uses its embedded variant for linking 
 programs (on Widows? Posix? 32bit? 64bit?)


Internal linking is currently enabled by a separate command-line 
flag; we still use the system linker by default (just as a 
precaution to avoid needless breakage because of a new feature).

lld works for COFF, ELF as well as Mach-O. For the latter, there 
is the problem of locating the appropriate C runtime libraries to 
consider, though (those that the `gcc` linker driver implicitly 
passes to the underlying `ld`).


 Can we distribute it as an alternative to optlink?


Yes, that should work. As far as I know, it doesn't support OMF, 
though, so we would need to find COFF C/system libraries we can 
redistribute - it is unclear whether Microsoft's license allows 
redistribution of their static libraries.

  - David
Dec 21 2017
prev sibling next sibling parent kinke <noone nowhere.com> writes:
On Thursday, 21 December 2017 at 18:40:54 UTC, Andrei 
Alexandrescu wrote:

 I heard ldc already uses its embedded variant for linking 
 programs (on Widows? Posix? 32bit? 64bit?).


Currently only for Windows-MSVC targets (both 32 and 64 bits) and 
only when specifying the `-link-internally` switch. The host 
platform doesn't matter, i.e., it works for cross-linking from 
any Posix system too, even on ARM etc.
['Embedded variant' => we're linking in the static LLD libs and 
so share the common LLVM code in a single executable.]


 Can we distribute it as an alternative to optlink?


Now that it's capable of outputting debuginfo .pdb's too (since 
v5.0, at least on Windows hosts), it should basically be fine.

There's one catch though, and that's the rather big size of the 
executable (26 MB for the v5.0.1 32-bit executable when linked 
against the static MS runtime with VS 2017, with enabled LLVM 
backends for x86[_64], ARM, AArch64 and Nvidia PTX).
That's due to LLD being a cross-linker by default, capable of 
outputting Windows, ELF and Mach-O binaries, and because of 
included codegen capabilities (for Link-Time Optimization), i.e., 
stuff that DMD doesn't need. Unfortunately, those features cannot 
be simply opted-out via CMake.
Dec 21 2017
prev sibling parent reply Atila Neves <atila.neves gmail.com> writes:
On Thursday, 21 December 2017 at 18:40:54 UTC, Andrei 
Alexandrescu wrote:

 I only became aware today about https://lld.llvm.org, llvm's 
 own linker. I wonder how that changes distribution dynamics for 
 us - I heard ldc already uses its embedded variant for linking 
 programs (on Widows? Posix? 32bit? 64bit?). Can we distribute 
 it as an alternative to optlink? Thanks! -- Andrei


I tried lld on Linux for D binaries and some of them crash. That 
might not mean anything on Windows, but given that I've run into 
2 dmd bugs so far in which picking one of ld.bfd or ld.gold 
produced crashing binaries, I'd be wary of using lld on Windows 
until it's thoroughly tested on dozens of executables.

Atila
Dec 21 2017
parent reply Jacob Carlborg <doob me.com> writes:
On 2017-12-22 00:11, Atila Neves wrote:


 I tried lld on Linux for D binaries and some of them crash. That might 
 not mean anything on Windows, but given that I've run into 2 dmd bugs so 
 far in which picking one of ld.bfd or ld.gold produced crashing 
 binaries, I'd be wary of using lld on Windows until it's thoroughly 
 tested on dozens of executables.


I tried to use lld to cross compile to macOS on Linux. It crashed on the 
first try, might even have been a C program.

-- 
/Jacob Carlborg
Dec 22 2017
parent Paolo Invernizzi <paolo.invernizzi gmail.com> writes:
On Friday, 22 December 2017 at 09:46:40 UTC, Jacob Carlborg wrote:

 On 2017-12-22 00:11, Atila Neves wrote:


 I tried lld on Linux for D binaries and some of them crash. 
 That might not mean anything on Windows, but given that I've 
 run into 2 dmd bugs so far in which picking one of ld.bfd or 
 ld.gold produced crashing binaries, I'd be wary of using lld 
 on Windows until it's thoroughly tested on dozens of 
 executables.


 I tried to use lld to cross compile to macOS on Linux. It 
 crashed on the first try, might even have been a C program.


It worked for me the other way round, to Linux on macOS, and 
worked also to Win64 on macOS.

/Paolo
Dec 22 2017