[lit] Allow specification of LLD variant paths via environment variable

[jhenderson]

Summary

With this patch, the environment variables LDLLD, LLDLINK, LD64LLD, and WASMLD can be used to specify the path to ld.lld, lld-link, ld64.lld and wasm-ld respectively, in a similar manner to how the CLANG variable points to clang.

[jhenderson]

Fix typo.

[thopre]

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

607

This is already in the other patch, do you want to rebase this one on top?

[jhenderson]

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

607

Oops. Messed up making my diff. The actual version I've got locally is correct.

[jhenderson]

Fix diff. I'm going to hold off landing this for now until the discussion on the mailing list (https://lists.llvm.org/pipermail/llvm-dev/2021-May/150428.html) has reached a conclusion.

[jhenderson]

The discussion seems to be leaning towards not adding the variable unless necessary. As such, I think this patch can be abandoned.

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

def use_lld(self, additional_tool_dirs=[], required=True):
                          'lld_libs_dir', 'llvm_libs_dir']
         paths = [getattr(self.config, pp) for pp in lib_dir_props
                  if getattr(self.config, pp, None)]
 
         self.with_environment('LD_LIBRARY_PATH', paths, append_path=True)
 
         # Discover the 'clang' and 'clangcc' to use.
 
-        ld_lld = self.use_llvm_tool('ld.lld', required=required)
-        lld_link = self.use_llvm_tool('lld-link', required=required)
-        ld64_lld = self.use_llvm_tool('ld64.lld', required=required)
-        wasm_ld = self.use_llvm_tool('wasm-ld', required=required)
+        ld_lld = self.use_llvm_tool('ld.lld', search_env='LDLLD', required=required)
+        lld_link = self.use_llvm_tool('lld-link', search_env='LLDLINK', required=required)
+        ld64_lld = self.use_llvm_tool('ld64.lld', search_env='LD64LLD', required=required)
+        wasm_ld = self.use_llvm_tool('wasm-ld', search_env='WASMLD', required=required)
 
         was_found = ld_lld and lld_link and ld64_lld and wasm_ld
         tool_substitutions = []
         if ld_lld:
             tool_substitutions.append(ToolSubst(r'ld\.lld', command=ld_lld))
         if lld_link:
             tool_substitutions.append(ToolSubst('lld-link', command=lld_link))
         if ld64_lld:
             tool_substitutions.append(ToolSubst(r'ld64\.lld', command=ld64_lld))
         if wasm_ld:
             tool_substitutions.append(ToolSubst('wasm-ld', command=wasm_ld))
         self.add_tool_substitutions(tool_substitutions)
         return was_found

llvm/utils/lit/tests/Inputs/lld-search-env/lit.cfg

+import lit.formats
+config.name = 'search-env'
+config.suffixes = ['.txt']
+config.test_format = lit.formats.ShTest()
+config.test_source_root = None
+config.test_exec_root = None
+config.llvm_tools_dir = ''
+import lit.llvm
+lit.llvm.initialize(lit_config, config)
+import os.path
+curdir = os.path.dirname(__file__)
+lit.llvm.llvm_config.with_environment('LDLLD', os.path.join(curdir, 'tool1'))
+lit.llvm.llvm_config.with_environment('LLDLINK', os.path.join(curdir, 'tool2'))
+lit.llvm.llvm_config.with_environment('LD64LLD', os.path.join(curdir, 'tool3'))
+lit.llvm.llvm_config.with_environment('WASMLD', os.path.join(curdir, 'tool4'))
+lit.llvm.llvm_config.use_lld()

llvm/utils/lit/tests/Inputs/lld-search-env/true.txt

+# RUN: true

llvm/utils/lit/tests/lld-search-env.py

+## Show that lit uses a set of environment variables to locate the LLD variants.
+
+# RUN: %{lit} %{inputs}/lld-search-env 2>&1 | FileCheck %s -DDIR=%p
+
+# CHECK: note: using ld.lld: [[DIR]]{{[\\/]}}Inputs{{[\\/]}}lld-search-env{{[\\/]}}tool1
+# CHECK: note: using lld-link: [[DIR]]{{[\\/]}}Inputs{{[\\/]}}lld-search-env{{[\\/]}}tool2
+# CHECK: note: using ld64.lld: [[DIR]]{{[\\/]}}Inputs{{[\\/]}}lld-search-env{{[\\/]}}tool3
+# CHECK: note: using wasm-ld: [[DIR]]{{[\\/]}}Inputs{{[\\/]}}lld-search-env{{[\\/]}}tool4