Compile-time tuning: assembly phase

Not as much compile-time gain from reworking the assembly phase as I'd
hoped, but still worthwhile.  Should see ~2% improvement thanks to
the assembly rework.  On the other hand, expect some huge gains for some
application thanks to better detection of large machine-generated init
methods.  Thinkfree shows a 25% improvement.

The major assembly change was to establish thread the LIR nodes that
require fixup into a fixup chain.  Only those are processed during the
final assembly pass(es).  This doesn't help for methods which only
require a single pass to assemble, but does speed up the larger methods
which required multiple assembly passes.

Also replaced the block_map_ basic block lookup table (which contained
space for a BasicBlock* for each dex instruction unit) with a block id
map - cutting its space requirements by half in a 32-bit pointer
environment.

Changes:
  o Reduce size of LIR struct by 12.5% (one of the big memory users)
  o Repurpose the use/def portion of the LIR after optimization complete.
  o Encode instruction bits to LIR
  o Thread LIR nodes requiring pc fixup
  o Change follow-on assembly passes to only consider fixup LIRs
  o Switch on pc-rel fixup kind
  o Fast-path for small methods - single pass assembly
  o Avoid using cb[n]z for null checks (almost always exceed displacement)
  o Improve detection of large initialization methods.
  o Rework def/use flag setup.
  o Remove a sequential search from FindBlock using lookup table of 16-bit
    block ids rather than full block pointers.
  o Eliminate pcRelFixup and use fixup kind instead.
  o Add check for 16-bit overflow on dex offset.

Change-Id: I4c6615f83fed46f84629ad6cfe4237205a9562b4
diff --git a/compiler/dex/frontend.cc b/compiler/dex/frontend.cc
index fefcab9..2952570 100644
--- a/compiler/dex/frontend.cc
+++ b/compiler/dex/frontend.cc
@@ -117,6 +117,11 @@
 #endif
 ) {
   VLOG(compiler) << "Compiling " << PrettyMethod(method_idx, dex_file) << "...";
+  if (code_item->insns_size_in_code_units_ >= 0x10000) {
+    LOG(INFO) << "Method size exceeds compiler limits: " << code_item->insns_size_in_code_units_
+              << " in " << PrettyMethod(method_idx, dex_file);
+    return NULL;
+  }
 
   ClassLinker* class_linker = Runtime::Current()->GetClassLinker();
   CompilationUnit cu(&compiler.GetArenaPool());
@@ -151,7 +156,7 @@
    */
 
   if (compiler_backend == kPortable) {
-    // Fused long branches not currently usseful in bitcode.
+    // Fused long branches not currently useful in bitcode.
     cu.disable_opt |= (1 << kBranchFusing);
   }