[WebAssembly] Add end-to-end codegen tests for wasm_simd128.h

Add a test checking that each SIMD intrinsic produces the expected instruction.
Since this test spans both clang and LLVM, place it in a new
intrinsic-header-tests subdirectory of cross-project-tests.

This revives D101684 now that cross-project-tests exists. In practice, the tests
of lowering from wasm_simd128.h to LLVM IR were not as useful as this end-to-end
test.

Updates the version check of gdb in cross-project-tests/lit.cfg.py so that
unexpected version formats do not prevent the new tests from running.

Depends on D121661.

Differential Revision: https://reviews.llvm.org/D121662

cross-project-tests/CMakeLists.txt

@@ -78,10 +78,18 @@ add_lit_testsuite(check-debuginfo "Running debuginfo tests"
   DEPENDS ${CROSS_PROJECT_TEST_DEPS}
   )
 
+# Add alias for intrinsic header test subset.
+add_lit_testsuite(check-intrinsic-headers "Running intrinsic header tests"
+  ${CMAKE_CURRENT_BINARY_DIR}/intrinsic-header-tests
+  EXCLUDE_FROM_CHECK_ALL
+  DEPENDS ${CROSS_PROJECT_TEST_DEPS}
+  )
+
 # Add check-cross-project-* targets.
 add_lit_testsuites(CROSS_PROJECT ${CMAKE_CURRENT_SOURCE_DIR}
   DEPENDS ${CROSS_PROJECT_TEST_DEPS}
   )
 
 set_target_properties(check-cross-project PROPERTIES FOLDER "Tests")
 set_target_properties(check-debuginfo PROPERTIES FOLDER "Tests")
+set_target_properties(check-intrinsic-headers PROPERTIES FOLDER "Tests")

cross-project-tests/intrinsic-header-tests/README.txt

@@ -0,0 +1,3 @@
+                                                                   -*- rst -*-
+This is a collection of tests to check that the expected assembly is generated
+from clang intrinsic headers.

cross-project-tests/intrinsic-header-tests/lit.local.cfg

@@ -0,0 +1,2 @@
+if 'clang' not in config.available_features:
+    config.unsupported = True