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Substantive Comments Please: GCC vs. LLMV

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  Substantive Comments Please: GCC vs. LLMV Leroy H <lh@somewhere.net> - 2026-10-31 03:11 +0000
    Re: Substantive Comments Please: GCC vs. LLMV Computer Nerd Kev <not@telling.you.invalid> - 2026-10-31 17:28 +1000
      Re: Substantive Comments Please: GCC vs. LLMV Leroy H <lh@somewhere.net> - 2026-10-31 13:25 +0000
    Re: Substantive Comments Please: GCC vs. LLMV jayjwa <jayjwa@atr2.ath.cx.invalid> - 2026-10-31 10:30 -0400
      Re: Substantive Comments Please: GCC vs. LLMV Leroy H <lh@somewhere.net> - 2026-10-31 15:12 +0000
      Re: Substantive Comments Please: GCC vs. LLMV rbowman <bowman@montana.com> - 2026-10-31 19:21 +0000
      Re: GCC vs. LLVM Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-10-31 21:06 +0000
        Re: GCC vs. LLVM Nuno Silva <nunojsilva@invalid.invalid> - 2026-11-01 00:39 +0000
          Re: GCC vs. LLVM rbowman <bowman@montana.com> - 2026-11-01 01:45 +0000
            Re: GCC vs. LLVM Nuno Silva <nunojsilva@invalid.invalid> - 2026-11-01 09:05 +0000
        Re: GCC vs. LLVM c186282 <c186282@nnada.net> - 2026-11-01 03:51 -0500
          Re: GCC vs. LLVM Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-11-01 02:16 -0800
    Re: Substantive Comments Please: GCC vs. LLMV Chris Ahlstrom <OFeem1987@teleworm.us> - 2026-11-01 10:07 -0500
      Re: Substantive Comments Please: GCC vs. LLMV Nuno Silva <nunojsilva@invalid.invalid> - 2026-11-01 18:31 +0000

#94820 — Substantive Comments Please: GCC vs. LLMV

I should have, but I have never seriously researched the differences
and advantages/disadvantages of the GNU Compiler Collection (GCC)
versus the LLVM/Clang compiler (only the C compiler interests me).

All of my GNU/Linux systems are built using GCC.  It has good
hardware optimization options, Link Time Optimization (LTO), and
even, if desired, Profile Guided Optimization (PGO).

But LLVM/Clang has been around for a long while as an alternative
C compiler.  I have never used LLVM/Clang but others will claim
benefits and advantages.

To me, LLVM/Clang seems limited compared to GCC, especially in terms
of SIMD hardware support, but that assessment is based on incomplete
knowledge.

Can anyone offer more insight into this issue?

Basically, which compiler is truly "better?"

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#94822

Leroy H <lh@somewhere.net> wrote:
> Can anyone offer more insight into this issue?
> 
> Basically, which compiler is truly "better?"

All I know is that libllvm is _huge_ and I've worked hard to avoid
installing it on systems that I try to keep small. That sort of
bloat really annoys me.

According to these speed benchmarks of different libraries built
with GCC and Clang, they're about evenly matched overall, but in
some specific cases one can be significantly faster than the other:

https://www.phoronix.com/review/gcc-16-vs-clang-22

-- 
__          __
#_ < |\| |< _#

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#94842

On 31 Oct 2026 17:28:10 +1000, Computer Nerd Kev wrote:

> 
> All I know is that libllvm is _huge_ and I've worked hard to avoid
> installing it on systems that I try to keep small. That sort of
> bloat really annoys me.
> 

In some cases it cannot be avoided.  One example is Mesa that uses
llvm for software rendering:

<https://docs.mesa3d.org/drivers/llvmpipe.html>


Firefox releases are also built with llvm which means that Mozilla
has chosen it over GCC:

<https://www.phoronix.com/news/Firefox-Clang-LTO-All-Platforms>




>
> According to these speed benchmarks of different libraries built
> with GCC and Clang, they're about evenly matched overall, but in
> some specific cases one can be significantly faster than the other:
> 
> https://www.phoronix.com/review/gcc-16-vs-clang-22
>

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#94847

Leroy H <lh@somewhere.net> writes:

> I should have, but I have never seriously researched the differences
> and advantages/disadvantages of the GNU Compiler Collection (GCC)
> versus the LLVM/Clang compiler (only the C compiler interests me).
Clang whines alot on perfectly good code, but some of the graphics stuff
requires it. I think Mesa and also AMD ROCm. They have a special
LLVM/Clang needed for ROCm:

/opt/rocm/lib/llvm/bin/clang --version
AMD clang version 24.0.0git (https://github.com/ROCm/llvm-project.git d6f6cb691863e9258034ab48c1dfce21689d5606)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /opt/rocm/lib/llvm/bin
Configuration file: /opt/rocm/lib/llvm/bin/clang.cfg

If you're not building such things, you probably don't need it. I hear
the LLVM license is more permissive, though that doesn't affect me. 

Rarely, I've had some things not build with GCC that did build with
Clang. With today's disk sizes, it's easy to keep both handy. I have a
very strong development environment here: between Linux and the virtual
machines hosts under it (and illumos), you'd have a hard time naming a
language I don't have access to. SNOBOL? Yeah, got that. 

> Basically, which compiler is truly "better?"
Use case of course. But you knew that already. 

-- 
PGP Key ID: 781C A3E2 C6ED 70A6 B356  7AF5 B510 542E D460 5CAE
       "The Internet should always be the Wild West!"

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#94850

On Sat, 31 Oct 2026 10:30:39 -0400, jayjwa wrote:

> 
> Rarely, I've had some things not build with GCC that did build with
> Clang. With today's disk sizes, it's easy to keep both handy.
>

You also need a Rust compiler.  More and more packages now require
it.  Librsvg, which I believe is the only SVG rendering library
available for GNU/Linux, is just one example.  No Rust, no SVG.

Another C/C++ alternative would be the Intel icc compiler, which
is now part of Intel OneAPI.  The icc compiler was once quite superior
to GCC but supposedly GCC has closed the gap over the years.

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#94862

On Sat, 31 Oct 2026 10:30:39 -0400, jayjwa wrote:

> If you're not building such things, you probably don't need it. I hear
> the LLVM license is more permissive, though that doesn't affect me.

It now uses the Apache 2.0 license as does Clang.  Apple originally tried 
to use gcc with LLVM for Objective C. There were technical difficulties 
plus the GPL. 

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#94864 — Re: GCC vs. LLVM

On Sat, 31 Oct 2026 10:30:39 -0400, jayjwa wrote:

> Clang whines alot on perfectly good code, but some of the graphics
> stuff requires it. I think Mesa and also AMD ROCm.

Why Clang and not GCC?

Because those companies are afraid of the GPL, aren’t they?

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#94871 — Re: GCC vs. LLVM

On 2026-10-31, Lawrence D’Oliveiro wrote:

> On Sat, 31 Oct 2026 10:30:39 -0400, jayjwa wrote:
>
>> Clang whines alot on perfectly good code, but some of the graphics
>> stuff requires it. I think Mesa and also AMD ROCm.
>
> Why Clang and not GCC?
>
> Because those companies are afraid of the GPL, aren’t they?

Didn't a recent post to this group suggest Apple invested in clang+llvm
because of absurd "fear" of GPLv3?

Well, even if that was a driving factor, I welcome there being one more
compiler collection. That kind of diversity is useful. Their long build
times, on the other hand...

-- 
Nuno Silva

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#94874 — Re: GCC vs. LLVM

On Sun, 01 Nov 2026 00:39:59 +0000, Nuno Silva wrote:

> On 2026-10-31, Lawrence D’Oliveiro wrote:
> 
>> On Sat, 31 Oct 2026 10:30:39 -0400, jayjwa wrote:
>>
>>> Clang whines alot on perfectly good code, but some of the graphics
>>> stuff requires it. I think Mesa and also AMD ROCm.
>>
>> Why Clang and not GCC?
>>
>> Because those companies are afraid of the GPL, aren’t they?
> 
> Didn't a recent post to this group suggest Apple invested in clang+llvm
> because of absurd "fear" of GPLv3?

I wouldn't call it fear. Apple initially attempted to use ggc as the front 
end to llvm. There was little interest in the gcc maintainers to support 
Objective C so Apple would have had to modify gcc, taking a big bite out 
of the poisoned apple.

Which is more free, one of the many permissive licenses or GPLv3? 

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#94877 — Re: GCC vs. LLVM

On 2026-11-01, rbowman wrote:

> On Sun, 01 Nov 2026 00:39:59 +0000, Nuno Silva wrote:
>
>> On 2026-10-31, Lawrence D’Oliveiro wrote:
>> 
>>> On Sat, 31 Oct 2026 10:30:39 -0400, jayjwa wrote:
>>>
>>>> Clang whines alot on perfectly good code, but some of the graphics
>>>> stuff requires it. I think Mesa and also AMD ROCm.
>>>
>>> Why Clang and not GCC?
>>>
>>> Because those companies are afraid of the GPL, aren’t they?
>> 
>> Didn't a recent post to this group suggest Apple invested in clang+llvm
>> because of absurd "fear" of GPLv3?
>
> I wouldn't call it fear. Apple initially attempted to use ggc as the front 
> end to llvm. There was little interest in the gcc maintainers to support 
> Objective C so Apple would have had to modify gcc, taking a big bite out 
> of the poisoned apple.

Ha!

> Which is more free, one of the many permissive licenses or GPLv3? 

This would not be about GPL in general, but about the protections that
were hardened specifically in GPLv3, so your question would be between
GPLv2 and GPLv3.



-- 
Nuno Silva

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#94876 — Re: GCC vs. LLVM

On 10/31/26 17:06, Lawrence D’Oliveiro wrote:
> On Sat, 31 Oct 2026 10:30:39 -0400, jayjwa wrote:
> 
>> Clang whines alot on perfectly good code, but some of the graphics
>> stuff requires it. I think Mesa and also AMD ROCm.
> 
> Why Clang and not GCC?
> 
> Because those companies are afraid of the GPL, aren’t they?

   IHMO - *both* GCC and Clang/LLVM are Very Good.
   No reason for any prejudice at this time. I tend
   to install 'em all by reflex. Code::Blocks can
   cope with them all. Also install 'TCC' - which
   is suprisingly good and creates more compact
   code more quickly - but don't expect the more
   'esoteric' libraries.

   As for "whining" ... that seems to be a 'feature'
   of the modern compilers. They are SO tuned for
   "potential" issues that they pester you to death.
   Let 'em have their way and half yer code would
   be compiler flags and such turning off the 'whining'.
   Just write solid code and you'll be fine.

   It shouldn't BE this complicated ...... one reason
   I mostly switched to Python .... no whining.
   Python mostly IS 'C' ... all the libs are 'C' ...
   just interpreted steps between lib calls - a tad
   slower but much easier to deal with on many levels.

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#94883 — Re: GCC vs. LLVM

c186282 <c186282@nnada.net> writes:
[...]
>                     Also install 'TCC' - which
> is suprisingly good and creates more compact
> code more quickly - but don't expect the more
> 'esoteric' libraries.

Why would using tcc not give you access to "esoteric" libraries?

-- 
Keith Thompson (The_Other_Keith) Keith.S.Thompson+u@gmail.com
void Void(void) { Void(); } /* The recursive call of the void */

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#94891

Leroy H wrote this screed in ALL-CAPS (fixed):

> I should have, but I have never seriously researched the differences
> and advantages/disadvantages of the GNU Compiler Collection (GCC)
> versus the LLVM/Clang compiler (only the C compiler interests me).
>
> All of my GNU/Linux systems are built using GCC.  It has good
> hardware optimization options, Link Time Optimization (LTO), and
> even, if desired, Profile Guided Optimization (PGO).
>
> But LLVM/Clang has been around for a long while as an alternative
> C compiler.  I have never used LLVM/Clang but others will claim
> benefits and advantages.
>
> To me, LLVM/Clang seems limited compared to GCC, especially in terms
> of SIMD hardware support, but that assessment is based on incomplete
> knowledge.
>
> Can anyone offer more insight into this issue?
>
> Basically, which compiler is truly "better?"

My recent projects are set up to use either one. Clang seems to be
the "native" compiler on FreeBSD. GCC and Clang seem to me to be
comparable and somewhat supporting the same options. Clang seems
to increment versions more frequently.  It finds some issues that
g++ does not find, and g++ finds some issues that clang++ does
not. They're roughly comparable in speed if cache is dropped
between builds.

As far as hardware support and C go, I have nothing to add.
So sue me.

-- 
I wasn't kissing her, I was whispering in her mouth.
		-- Chico Marx

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#94896

On 2026-11-01, Chris Ahlstrom wrote:

> Leroy H wrote this screed in ALL-CAPS (fixed):
>
>> I should have, but I have never seriously researched the differences
>> and advantages/disadvantages of the GNU Compiler Collection (GCC)
>> versus the LLVM/Clang compiler (only the C compiler interests me).
>>
>> All of my GNU/Linux systems are built using GCC.  It has good
>> hardware optimization options, Link Time Optimization (LTO), and
>> even, if desired, Profile Guided Optimization (PGO).
>>
>> But LLVM/Clang has been around for a long while as an alternative
>> C compiler.  I have never used LLVM/Clang but others will claim
>> benefits and advantages.
>>
>> To me, LLVM/Clang seems limited compared to GCC, especially in terms
>> of SIMD hardware support, but that assessment is based on incomplete
>> knowledge.
>>
>> Can anyone offer more insight into this issue?
>>
>> Basically, which compiler is truly "better?"
>
> My recent projects are set up to use either one. Clang seems to be
> the "native" compiler on FreeBSD. GCC and Clang seem to me to be
> comparable and somewhat supporting the same options. Clang seems
> to increment versions more frequently.  It finds some issues that
> g++ does not find, and g++ finds some issues that clang++ does
> not. They're roughly comparable in speed if cache is dropped
> between builds.

When you say "find issues" you mean merely in warning outputs or in
differences owing to UB, or are you using their static analyzers?

> As far as hardware support and C go, I have nothing to add.
> So sue me.

-- 
Nuno Silva

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