[MIPS] Add remaining parts for building tests for MIPS

tests/exception_test/exception_test.c

 /*
  * Copyright (c) 2012 The Native Client Authors. All rights reserved.
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include <assert.h>
 #include <errno.h>
 #include <pthread.h>
 #include <setjmp.h>
@@ skipping 45 matching lines @@
 /*
  * We do this check in a separate function in an attempt to prevent
  * the compiler from optimising away the check for a stack-allocated
  * variable.
  *
  * We test for an alignment that is small enough for the compiler to
  * assume on x86-32, even if sel_ldr sets up a larger alignment.
  */
 __attribute__((noinline))
 void check_pointer_is_aligned(void *pointer) {
+#if defined(__mips__)
+  assert((uintptr_t) pointer % 8 == 0);

[Mark Seaborn, 2013/02/13 22:14:09]

But we declared it with __attribute__((aligned(16))), so no conditional should
be needed for this to pass

[petarj, 2013/03/05 17:50:04]

attribute aligned does not work for variables on stack on MIPS.
Speaking of which, what is the meaning of check_stack_is_aligned
if you are putting a 16-byte aligned struct on stack and then
checking if it is aligned? It looks more like you are checking that
attribute aligned works correctly rather than checking that stack
pointer is aligned.

[Mark Seaborn, 2013/03/14 15:48:00]

Answering your earlier question...

On 2013/03/05 17:50:04, petarj wrote:
Do you mean it does not actually align the address of the variable?  That would
be a bug, right?  Do you mean that the "align" attribute of LLVM's "alloca"
instruction doesn't work on MIPS?

Or do you just mean the backend does not make any assumptions about the
alignment of the stack?
No, we are checking that the stack pointer is aligned, but the check only works
if the compiler makes use of the ABI's stack alignment and does not force a
realignment of the stack pointer.

So this check isn't very reliable, and you are welcome to remove
check_stack_is_aligned().  This check is made obsolete by the later check,
assert(frame_base % STACK_ALIGNMENT == 0).

+#else
   assert((uintptr_t) pointer % 16 == 0);
+#endif
 }
 
 void check_stack_is_aligned(void) {
   struct AlignedType var;
   check_pointer_is_aligned(&var);
 }
 
 
 void crash_at_known_address(void);
 extern char prog_ctr_at_crash[];
@@ skipping 268 matching lines @@
   RUN_TEST(test_unsetting_x86_direction_flag);
 #endif
 
   fprintf(stderr, "** intended_exit_status=0\n");
   return 0;
 }
 
 int main(void) {
   return RunTests(TestMain);
 }