[msan] Mark fork.cc unsupported on mips64 (and make it possible to do so)

[dsanders]

Summary

fork.cc currently hangs for mips64, preventing 'check-all' from finishing
in the 3.8 release.

We can't xfail it since that still runs the test, so we must mark it
'unsupported' instead. Unfortunately, the target triple that lit checks against
is the default target triple which in our case is different to the actual
target triple.

This patch resolves this by making '${target_arch}-arch' an available feature
for use in lit directives. We can then use that to correctly mark the test
'unsupported'. The reason for the '-arch' suffix is so that 'mips64' doesn't
also match 'mips64el' which currently passes this test.

Depends on D16855.

[samsonov]

test/msan/lit.cfg

29

Can this go to test/lit.common.cfg instead?

test/msan/fork.cc

 // Test that chained origins are fork-safe.
 // Run a number of threads that create new chained origins, then fork
 // and verify that origin reads do not deadlock in the child process.
 
 // RUN: %clangxx_msan -std=c++11 -fsanitize-memory-track-origins=2 -g -O3 %s -o %t
 // RUN: MSAN_OPTIONS=store_context_size=1000,origin_history_size=0,origin_history_per_stack_limit=0 %run %t |& FileCheck %s
 
 // Fun fact: if test output is redirected to a file (as opposed to
 // being piped directly to FileCheck), we may lose some "done"s due to
 // a kernel bug:
 // https://lkml.org/lkml/2014/2/17/324
 
+// Big-endian mips64 currently hangs on this test. Mark it unsupported to allow
+// llvm-lit to finish.
+// UNSUPPORTED: mips64-arch
 
 #include <pthread.h>
 #include <unistd.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <sys/types.h>
 #include <sys/wait.h>
 #include <sys/time.h>

test/msan/lit.cfg

 clang_msan_cxxflags = config.cxx_mode_flags + clang_msan_cflags
 
 def build_invocation(compile_flags):
   return " " + " ".join([config.clang] + compile_flags) + " "
 
 config.substitutions.append( ("%clang_msan ", build_invocation(clang_msan_cflags)) )
 config.substitutions.append( ("%clangxx_msan ", build_invocation(clang_msan_cxxflags)) )
 
+config.available_features.add(config.target_arch + '-arch')
+
 # Default test suffixes.
 config.suffixes = ['.c', '.cc', '.cpp']
 
 # MemorySanitizer tests are currently supported on Linux only.
 if config.host_os not in ['Linux']:
   config.unsupported = True

test/msan/lit.site.cfg.in

 ## Autogenerated by LLVM/Clang configuration.
 # Do not edit!
 
 # Load common config for all compiler-rt lit tests.
 lit_config.load_config(config, "@COMPILER_RT_BINARY_DIR@/test/lit.common.configured")
 
 # Tool-specific config options.
 config.name_suffix = "@MSAN_TEST_CONFIG_SUFFIX@"
+config.target_arch = "@arch@"
 config.target_cflags = "@MSAN_TEST_TARGET_CFLAGS@"
 # Load tool-specific config that would do the real work.
 lit_config.load_config(config, "@MSAN_LIT_SOURCE_DIR@/lit.cfg")