A the `default_triple` feature to MLIR test suite

[mehdi_amini]

Summary

This feature was added to LLVM in d178f4fc8 in order to be able to
run the LLVM tests without having the host targets configured in.
With this change, ninja check passes without the host target, i.e.
this config:

cmake ../llvm -DLLVM_TARGETS_TO_BUILD="" -DLLVM_DEFAULT_TARGET_TRIPLE="" -DLLVM_ENABLE_PROJECTS=mlir -GNinja

[bondhugula]

Thanks for allowing this. I think the commit title's start is broken.

[bondhugula]

Nit: I think the commit title doesn't accurately reflect empty target info.

mlir/test/mlir-cpu-runner/lit.local.cfg

7

Missing period at the end.

mlir/test/lit.cfg.py

 
 llvm_config.add_tool_substitutions(tools, tool_dirs)
 
 
 # FileCheck -enable-var-scope is enabled by default in MLIR test
 # This option avoids to accidentally reuse variable across -LABEL match,
 # it can be explicitly opted-in by prefixing the variable name with $
 config.environment['FILECHECK_OPTS'] = "-enable-var-scope"
+
+
+# LLVM can be configured with an empty default triple
+# by passing ` -DLLVM_DEFAULT_TARGET_TRIPLE="" `.
+# This is how LLVM filters tests that require the host target
+# to be available for JIT tests.
+if config.target_triple:
+    config.available_features.add('default_triple')

mlir/test/mlir-cpu-runner/lit.local.cfg

 import sys
 
 # FIXME: llvm orc does not support the COFF rtld.
 if sys.platform == 'win32':
-    config.unsupported = True
+    config.unsupported = True
+
+# Requires a non-empty default triple for these tests.
+# Passing ` -DLLVM_DEFAULT_TARGET_TRIPLE="" ` when the
+# host target isn't available is how LLVM filters
+# tests that require the host target to be available
+# for JIT tests.
+if 'default_triple' not in config.available_features:
+    config.unsupported = True
+