Compiler constant handling rework

In preparation for de-optimization, reworked the constant
handling mechanism.  Also took advantage of knowledge of
constant operands (particularly for long operations).

Significant performance improvements for Mandelbrot
(~60 seconds to ~34 seconds).  Minor improvements in other
benchmarks.

The new constant handling breaks two of the existing
optimization passes: "Skip Large Method" and "Load/Store
Elimization."

I don't intend to update the large method optimization
because it will be superceeded by the upcoming interpreter/
fingerprinting mechanism.  Leaving the code in place for
now in order to compare compile-time improvements with
fingerprinting/interpret.  All related code will be deleted
when that is complete.

The load/store elimination pass needs some rework to handle
uses of multiple-register loads and stores.  It will be
updated & restored in a future CL.

Change-Id: Ia979abaf51b8ae81bbb0428031cbcea854625fac
diff --git a/src/compiler/codegen/mir_to_gbc.cc b/src/compiler/codegen/mir_to_gbc.cc
index f67f760..ba90269 100644
--- a/src/compiler/codegen/mir_to_gbc.cc
+++ b/src/compiler/codegen/mir_to_gbc.cc
@@ -1018,7 +1018,7 @@
         }
         EmitPopShadowFrame(cu);
         cu->irb->CreateRet(GetLLVMValue(cu, rl_src[0].orig_sreg));
-        bb->has_return = true;
+        DCHECK(bb->has_return);
       }
       break;
 
@@ -1028,7 +1028,7 @@
         }
         EmitPopShadowFrame(cu);
         cu->irb->CreateRetVoid();
-        bb->has_return = true;
+        DCHECK(bb->has_return);
       }
       break;
 
@@ -2572,8 +2572,7 @@
   RegLocation rl_dest = GetLoc(cu, call_inst);
   RegLocation rl_result = EvalLoc(cu, rl_dest, kAnyReg, true);
   if (rl_dest.wide) {
-    cg->LoadConstantValueWide(cu, rl_result.low_reg, rl_result.high_reg,
-                          (immval) & 0xffffffff, (immval >> 32) & 0xffffffff);
+    cg->LoadConstantWide(cu, rl_result.low_reg, rl_result.high_reg, immval);
     cg->StoreValueWide(cu, rl_dest, rl_result);
   } else {
     int immediate = immval & 0xffffffff;