MIPS: Add flag for testing long branch mode.

TEST=
BUG=
R=jkummerow@chromium.org, plind44@gmail.com

Review URL: https://codereview.chromium.org/173773003

Patch from Dusan Milosavljevic <Dusan.Milosavljevic@rt-rk.com>.

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@19520 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/flag-definitions.h

@@ -398,6 +398,8 @@ DEFINE_bool(enable_32dregs, ENABLE_32DREGS_DEFAULT,
             "enable use of d16-d31 registers on ARM - this requires VFP3")
 DEFINE_bool(enable_vldr_imm, false,
             "enable use of constant pools for double immediate (ARM only)")
+DEFINE_bool(force_long_branches, false,
+            "force all emitted branches to be in long mode (MIPS only)")
 
 // bootstrapper.cc
 DEFINE_string(expose_natives_as, NULL, "expose natives in global object")

src/mips/assembler-mips.cc

@@ -313,11 +313,12 @@ Assembler::Assembler(Isolate* isolate, void* buffer, int buffer_size)
   trampoline_pool_blocked_nesting_ = 0;
   // We leave space (16 * kTrampolineSlotsSize)
   // for BlockTrampolinePoolScope buffer.
-  next_buffer_check_ = kMaxBranchOffset - kTrampolineSlotsSize * 16;
+  next_buffer_check_ = FLAG_force_long_branches
+      ? kMaxInt : kMaxBranchOffset - kTrampolineSlotsSize * 16;
   internal_trampoline_exception_ = false;
   last_bound_pos_ = 0;
 
-  trampoline_emitted_ = false;
+  trampoline_emitted_ = FLAG_force_long_branches;
   unbound_labels_count_ = 0;
   block_buffer_growth_ = false;