Fix build.

Change-Id: I088c4ff64453d98caf2964128e6d1b4f77f6f32e
diff --git a/runtime/arch/x86/context_x86.h b/runtime/arch/x86/context_x86.h
index 031fc92..1c51026 100644
--- a/runtime/arch/x86/context_x86.h
+++ b/runtime/arch/x86/context_x86.h
@@ -44,12 +44,12 @@
   }
 
   virtual uintptr_t* GetGPRAddress(uint32_t reg) {
-    DCHECK_LT(reg, kNumberOfCpuRegisters);
+    DCHECK_LT(reg, static_cast<uint32_t>(kNumberOfCpuRegisters));
     return gprs_[reg];
   }
 
   virtual uintptr_t GetGPR(uint32_t reg) {
-    DCHECK_LT(reg, kNumberOfCpuRegisters);
+    DCHECK_LT(reg, static_cast<uint32_t>(kNumberOfCpuRegisters));
     return *gprs_[reg];
   }
 
diff --git a/runtime/arch/x86_64/context_x86_64.h b/runtime/arch/x86_64/context_x86_64.h
index 37cd74c..78ef89c 100644
--- a/runtime/arch/x86_64/context_x86_64.h
+++ b/runtime/arch/x86_64/context_x86_64.h
@@ -44,12 +44,12 @@
   }
 
   virtual uintptr_t* GetGPRAddress(uint32_t reg) {
-    DCHECK_LT(reg, kNumberOfCpuRegisters);
+    DCHECK_LT(reg, static_cast<uint32_t>(kNumberOfCpuRegisters));
     return gprs_[reg];
   }
 
   virtual uintptr_t GetGPR(uint32_t reg) {
-    DCHECK_LT(reg, kNumberOfCpuRegisters);
+    DCHECK_LT(reg, static_cast<uint32_t>(kNumberOfCpuRegisters));
     return *gprs_[reg];
   }