[MIPS] Adding validator for MIPS architecture.

src/trusted/validator_mips/testdata/test_jmp_imm.S

+# Copyright 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.
+# Copyright 2012 MIPS Technologies / RT-RK.
+
+# test cases for jmps/branches
+# there are several kinds of jmps/branches in regards to destination address
+# 1. jmps into 0-0x10000, null guard region, where everything is considered OK
+# 2. jmps into 0x10000-0x20000, trampoline code section, jmps need to be bundle aligned

[Brad Chen, 2012/04/13 00:50:52]

Please try to stick with 80-columns unless syntactically impossible.

+# 3. jmps into code section, jmps need to be bundle aligned
+# beside destination address we also check the position of jmp/b and link

[Brad Chen, 2012/04/13 00:50:52]

Standard capitalization makes the comments more readable. I don't want to be a
grammar nanny, but we usually try to stick with standard English and
punctuation.

+# instructions, which need to bundle offset +8
+
+
+.globl _start
+_start:
+.align 4
+.set noreorder
+
+bundle_b_to_0_0x1000:
+   b   _start - 0x10000    #destination addres is 0x10000 - OK
+    nop

[Brad Chen, 2012/04/13 00:50:52]

It looks like the convention you are using is an indented nop to indicate a
delay slot? This may be confusing to some of your reviewers, but if that is the
standard MIPS convention then you should probably stick with it. Maybe you could
comment the first such nop just so that a new reader might understand more
quickly. 

+   b   _start - 0x1fff4    #destination addres is 0xc (null guard region)- OK
+    nop
+
+bundle_b_to_0x1000_0x20000:
+   b   _start - 0x10000    # ok - trampoline start
+    nop
+   b   _start - 0xfff4     # dest_addr = 0x1000c, error (middle of the trampoline)
+    nop
+
+bundle_b_to_code_area:
+   b   _start + 0x1000     # ok
+    nop
+   b   _start + 0x1004     # ok, not on pseudo instruction
+    nop
+   b   _start + 0x10       # ok
+    nop
+   b   end_of_code         # ok
+    nop
+
+bundle_j_to_0_0x1000:
+#all is allowed, b/c that is guard region
+   j       0x0
+    nop
+   j       0x4
+    nop
+
+bundle_j_trampoline_area:
+   j       0x10000
+    nop
+   jal     0x10004         # kProblemUnalignedJumpToTrampoline (not a trampoline start)
+    nop
+
+   nop
+   nop
+   jal     0x10010         # ok - not a trampoline start, but there is a halt, so ok.
+    nop
+
+   nop
+   nop
+   jal     0x10020         # ok
+    nop
+
+bundle_j_negative:
+   j       -0x4            # ok
+    nop
+   j       -0x10           # ok
+    nop
+
+bundle_1st:
+   and     $a0, $a0, $t7
+bundle_2nd:
+   sw      $ra, 24($a0)
+   addiu   $v0, $v0, 4
+   addiu   $v0, $v1, 0
+
+bl_check:
+   nop
+   nop
+   bal     bundle_1st      #ok
+    nop
+
+bundle_check_b_dest_addr:
+   b       bundle_1st      # ok
+    nop
+   b       bundle_2nd      # kProblemBranchSplitsPattern
+    nop
+
+   bal     0x10000         #error misaligned call
+    nop
+   jalx    0x3ffffff0      #error, forbidden instruction
+    nop
+
+   jal     0x10000         #error misaligned call
+    nop
+   jal     0x3fffff0       #ok
+    nop
+
+   b       bundle_2nd      # kProblemBranchSplitsPattern
+     nop
+     nop
+     nop
+
+end_of_code: