[compiler-rt] Fix a broken asan 64-bit test using ld_preload

[etienneb]

Summary

The 'asan_preload_test-1.cc' is not working with the i686 architecture.
To repro the error, run on a linux 64-bit:

ninja check-asan-dynamic

The following error occurs:

--
Exit Code: 1

Command Output (stderr):
--
/home/llvm/llvm/projects/compiler-rt/test/asan/TestCases/Linux/asan_preload_test-1.cc:18:12: error: expected string not found in input
 // CHECK: AddressSanitizer: heap-buffer-overflow
           ^
<stdin>:1:1: note: scanning from here
ERROR: ld.so: object 'libclang_rt.asan-i686.so' from LD_PRELOAD cannot be preloaded (wrong ELF class: ELFCLASS32): ignored.
^
<stdin>:2:10: note: possible intended match here
==25982==AddressSanitizer CHECK failed: /home/llvm/llvm/projects/compiler-rt/lib/asan/asan_interceptors.cc:736 "((__interception::real_memcpy)) != (0)" (0x0, 0x0)

The unittest is running (where %shared_libasan is replaced by libclang_rt.asan-i686.so):

// RUN: env LD_PRELOAD=%shared_libasan not %run %t 2>&1 | FileCheck %s

But the executable also has a dependancy on libclang_rt.asan-i386.so (added by the clang driver):

linux-gate.so.1 =>  (0xf77cc000)
libclang_rt.asan-i386.so => not found
libstdc++.so.6 => /usr/lib/i386-linux-gnu/libstdc++.so.6 (0xf76ba000)
libm.so.6 => /lib/i386-linux-gnu/libm.so.6 (0xf7673000)
libgcc_s.so.1 => /lib/i386-linux-gnu/libgcc_s.so.1 (0xf7656000)
libc.so.6 => /lib/i386-linux-gnu/libc.so.6 (0xf74a7000)

By looking to the clang driver (tools.cpp) we can see that every x86 architecture are mapped to 'i386'.

StringRef MyArch;
   switch (getToolChain().getArch()) {
   case llvm::Triple::arm:
     MyArch = "arm";
     break;
   case llvm::Triple::x86:
     MyArch = "i386";
     break;
   case llvm::Triple::x86_64:
     MyArch = "amd64";
     break;
   default:
     llvm_unreachable("Unsupported architecture");
   }

This patch is implementing the same mapping but in the compiler-rt unittest.

[etienneb]

fix comment

[vitalybuka]

LGTM

test/asan/lit.cfg

clang_wrapper = os.path.join(asan_lit_source_dir,
                                "android_commands", "android_compile.py") + " "
 else:
   config.available_features.add('not-android')
   clang_wrapper = ""
 
 def build_invocation(compile_flags):
   return " " + " ".join([clang_wrapper, config.clang] + compile_flags) + " "
 
+# Clang driver link 'x86' (i686) architecture to 'i386'.
+target_arch = config.target_arch
+if (target_arch == "i686"):
+  target_arch = "i386"
+
 config.substitutions.append( ("%clang ", build_invocation(target_cflags)) )
 config.substitutions.append( ("%clangxx ", build_invocation(target_cxxflags)) )
 config.substitutions.append( ("%clang_asan ", build_invocation(clang_asan_cflags)) )
 config.substitutions.append( ("%clangxx_asan ", build_invocation(clang_asan_cxxflags)) )
-config.substitutions.append( ("%shared_libasan", "libclang_rt.asan-%s.so" % config.target_arch))
+config.substitutions.append( ("%shared_libasan", "libclang_rt.asan-%s.so" % target_arch))
 if config.asan_dynamic:
   config.substitutions.append( ("%clang_asan_static ", build_invocation(clang_asan_static_cflags)) )
   config.substitutions.append( ("%clangxx_asan_static ", build_invocation(clang_asan_static_cxxflags)) )
 
 # Windows-specific tests might also use the clang-cl.exe driver.
 if platform.system() == 'Windows':
   clang_cl_asan_cxxflags = ["-fsanitize=address",
                             "-Wno-deprecated-declarations",