Tidy x86 assembler.

Use helper functions to compute when the kind has a SIB, a ModRM and RegReg
form.

Change-Id: I86a5cb944eec62451c63281265e6974cd7a08e07
diff --git a/compiler/dex/quick/arm/codegen_arm.h b/compiler/dex/quick/arm/codegen_arm.h
index 8db7d4e..95bcfbd 100644
--- a/compiler/dex/quick/arm/codegen_arm.h
+++ b/compiler/dex/quick/arm/codegen_arm.h
@@ -87,7 +87,7 @@
     std::string BuildInsnString(const char* fmt, LIR* lir, unsigned char* base_addr);
     ResourceMask GetPCUseDefEncoding() const OVERRIDE;
     uint64_t GetTargetInstFlags(int opcode);
-    int GetInsnSize(LIR* lir);
+    size_t GetInsnSize(LIR* lir) OVERRIDE;
     bool IsUnconditionalBranch(LIR* lir);
 
     // Check support for volatile load/store of a given size.