[lit] Expose clang search_env string as a use_clang argument

[Amir]

Summary

Add an ability to provide a custom environment variable for clang,
to be used in BOLT tests (D117446)

[Amir]

Remove BOLT changes

[thopre]

What's the reason for not using CLANG instead of BOLT_CLANG_EXE?

[Amir]

In D117445#3247857, @thopre wrote:

What's the reason for not using CLANG instead of BOLT_CLANG_EXE?

I'm a bit worried about an interference with other project tests (ie when bolt and clang are enabled and tests for both are invoked). But I agree it's unlikely to be an issue in practice.

[thopre]

In D117445#3249325, @Amir wrote:

In D117445#3247857, @thopre wrote:

What's the reason for not using CLANG instead of BOLT_CLANG_EXE?

I'm a bit worried about an interference with other project tests (ie when bolt and clang are enabled and tests for both are invoked). But I agree it's unlikely to be an issue in practice.

That's precisely what I cannot understand: why would you want the two projects to use a different clang? Sorry if the answer is obvious, I'm not familiar with bolt.

[Amir]

In D117445#3249645, @thopre wrote:

In D117445#3249325, @Amir wrote:

In D117445#3247857, @thopre wrote:

What's the reason for not using CLANG instead of BOLT_CLANG_EXE?

I'm a bit worried about an interference with other project tests (ie when bolt and clang are enabled and tests for both are invoked). But I agree it's unlikely to be an issue in practice.

That's precisely what I cannot understand: why would you want the two projects to use a different clang? Sorry if the answer is obvious, I'm not familiar with bolt.

Yes, indeed, setting the CLANG env variable is sufficient. Thank you again for asking the right question!

llvm/utils/lit/lit/llvm/config.py

def use_llvm_tool(self, name, search_env=None, required=False, quiet=False,
 
         if tool:
             tool = os.path.normpath(tool)
             if not self.lit_config.quiet and not quiet:
                 self.lit_config.note('using {}: {}'.format(name, tool))
         return tool
 
     def use_clang(self, additional_tool_dirs=[], additional_flags=[],
-                  required=True, use_installed=False):
+                  required=True, use_installed=False, search_env='CLANG'):
         """Configure the test suite to be able to invoke clang.
 
         Sets up some environment variables important to clang, locates a
         just-built or optionally an installed clang, and add a set of standard
         substitutions useful to any test suite that makes use of clang.
 
         """
         # Clear some environment variables that might affect Clang.
def use_clang(self, additional_tool_dirs=[], additional_flags=[],
         pext = getattr(self.config, 'llvm_plugin_ext', None)
         if shl:
             self.config.substitutions.append(('%llvmshlibdir', shl))
         if pext:
             self.config.substitutions.append(('%pluginext', pext))
 
         # Discover the 'clang' and 'clangcc' to use.
         self.config.clang = self.use_llvm_tool(
-            'clang', search_env='CLANG', required=required,
+            'clang', search_env=search_env, required=required,
             search_paths=paths, use_installed=use_installed)
         if self.config.clang:
           self.config.available_features.add('clang')
           builtin_include_dir = self.get_clang_builtin_include_dir(
               self.config.clang)
           tool_substitutions = [
               ToolSubst('%clang', command=self.config.clang,
                         extra_args=additional_flags),