This reverts commit 6fd2db04d0f22ea22c5317d98ce2126aa64b6a73 since it
broke GreenDragon LLDB-Incremental bot:

https://green.lab.llvm.org/green/job/lldb-cmake/37560/console

Signed-off-by: Med Ismail Bennani <medismail.bennani@gmail.com>

This is a new draft of D28234. I previously did the unorthodox thing of
pushing to it when I wasn't the original author, but since this version

- Uses `GNUInstallDirs`, rather than mimics it, as the original author
  was hesitant to do but others requested.

- Is much broader, effecting many more projects than LLVM itself.

I figured it was time to make a new revision.

I am using this patch (and many back-ports) as the basis of
https://github.com/NixOS/nixpkgs/pull/111487 for my distro (NixOS). It
looked like people were generally on board in D28234, but I make note of
this here in case extra motivation is useful.

---

As pointed out in the original issue, a central tension is that LLVM
already has some partial support for these sorts of things. For example
`LLVM_LIBDIR_SUFFIX`, or `COMPILER_RT_INSTALL_PATH`. Because it's not
quite clear yet what to do about those, we are holding off on changing
libdirs and `compiler-rt`. for this initial PR.

---

On the advice of @lebedev.ri, I am splitting this up a bit per
subproject, starting with LLVM. To allow it to be more easily reviewed. This and the subsequent patch must be landed together, as this will not build alone. But the rest can be landed on their own.

Reviewed By: compnerd

Differential Revision: https://reviews.llvm.org/D100810

The rounding during type conversion uses multiple conversions, selecting
between them to try to discover if rounding occurred. This appears to
not have been tested, since it would generate code of the form:
    float convert_float_rtp(char x)
    {
      float r = convert_float(x);
      char y = convert_char(y);
      [...]
    }

which will access uninitialised data. The idea appears to have been to
have done a char -> float -> char roundtrip in order to discover the
rounding, so do this.

Discovered by inspection.

Signed-off-by: Daniel Stone <daniels@collabora.com>

Reviewed By: jvesely

Differential Revision: https://reviews.llvm.org/D81999

cf3ef15a6ec5e5b45c6c54e8fbe3769255e815ce ("[OpenCL] Add builtin
declarations by default.")
 switched behaviour to include "opencl-c-base.h". We don't want or need
 that for libclc so pass the flag to revert to old behaviour.

Fixes build since cf3ef15a6ec5e5b45c6c54e8fbe3769255e815ce

Reviewed By: tstellar

Differential Revision: https://reviews.llvm.org/D99794

Stop using the compatibility spellings of `OF_{None,Text,Append}`
left behind by 1f67a3cba9b09636c56e2109d8a35ae96dc15782. A follow-up
will remove them.

Differential Revision: https://reviews.llvm.org/D101650

Add clspv as a new target for libclc. clspv is an open-source compiler that compiles OpenCL C to Vulkan SPIR-V. Compiles for the spir target.

The clspv target differs from the the spirv target in the following ways:
* fma is modified to use uint2 instead of ulong for mantissas. This results in lower performance fma, but provides a implementation that can be used on more Vulkan devices where 64-bit integer support is less common.
* Use of a software implementation of nextafter because the generic implementation depends on nextafter being a defined builtin function for which clspv has no definition.
* Full optimization of the library (-O3) and no conversion to SPIR-V

This library is close to what would be produced by running opt -O3 < builtins.opt.spirv-mesa3d-.bc > builtins.opt.clspv--.bc and continuing the build from that point.

Reviewer: jvesely

Differential Revision: https://reviews.llvm.org/D94013

The script's shebang wants Python 3, so we use FindPython3. The
original code didn't work when an unversioned python was not available.
This is explicitly allowed in PEP 394. ("Distributors may choose to set
the behavior of the python command as follows: python2, python3, not
provide python command, allow python to be configurable by an end user
or a system administrator.")

Also I think it's actually required, so let the configuration fail if we
can't find it.

Lastly remove the shebang, since the script is only run via interpreter
and doesn't have the executable bit set anyway.

Reviewed By: jvesely

Differential Revision: https://reviews.llvm.org/D88366

Reviewer: jenatali jvesely
Differential Revision: https://reviews.llvm.org/D85910

Fixes: 060c8e083dd637866854acb6a0823c45b2ef68ef
Signed-off-by: Jan Vesely <jan.vesely@rutgers.edu>

Adds fma,fmod,ldexp.

Reviewer: jenatali jvesely

Differential Revision: https://reviews.llvm.org/D85911