Quick compiler: fix for missing defs

When the verifier replaces a Dex instruction, it may cause us
to lose a definition, making the SSA graph invalid.  This CL
deals with this situation by introducing dummy definitions.

With this CL, run-tests 042 and 075 pass.  The only remaining
run-test failures are related to missing exception edges in the CFG.
The old compiler could infer some of them, while llvm requires all
to be explicit.

Change-Id: I471fa515d8717aa102713a05b0e4115bf656b78e
diff --git a/src/compiler/CompilerIR.h b/src/compiler/CompilerIR.h
index 7420bda..1ecf61a 100644
--- a/src/compiler/CompilerIR.h
+++ b/src/compiler/CompilerIR.h
@@ -420,6 +420,7 @@
       irb(NULL),
       placeholderBB(NULL),
       entryBB(NULL),
+      entryTargetBB(NULL),
       tempName(0),
       requireShadowFrame(false),
       numShadowFrameEntries(0),
@@ -589,6 +590,7 @@
   greenland::IRBuilder* irb;
   llvm::BasicBlock* placeholderBB;
   llvm::BasicBlock* entryBB;
+  llvm::BasicBlock* entryTargetBB;
   std::string bitcode_filename;
   GrowableList llvmValues;
   int32_t tempName;