2 files changed, 7 insertions, 5 deletions
diff --git a/MdePkg/Library/BaseLib/CheckSum.c b/MdePkg/Library/BaseLib/CheckSum.c
index 957a2224f9..e851164998 100644
--- a/MdePkg/Library/BaseLib/CheckSum.c
+++ b/MdePkg/Library/BaseLib/CheckSum.c
@@ -47,7 +47,7 @@ CalculateSum8 (
   ASSERT (Length <= (MAX_ADDRESS - ((UINTN) Buffer) + 1));
 
   for (Sum = 0, Count = 0; Count < Length; Count++) {
-    Sum = Sum + *(Buffer + Count);
+    Sum = (UINT8) (Sum + *(Buffer + Count));
   }
   
   return Sum;
@@ -126,7 +126,7 @@ CalculateSum16 (
 
 
   for (Sum = 0, Count = 0; Count < Length; Count++) {
-    Sum = Sum + *(Buffer + Count);
+    Sum = (UINT16) (Sum + *(Buffer + Count));
   }
   
   return Sum;
diff --git a/MdePkg/Library/BaseLib/String.c b/MdePkg/Library/BaseLib/String.c
index 402d676631..fefadc4337 100644
--- a/MdePkg/Library/BaseLib/String.c
+++ b/MdePkg/Library/BaseLib/String.c
@@ -528,7 +528,7 @@ InternalCharToUpper (
   )
 {
   if (Char >= L'a' && Char <= L'z') {
-    return Char - (L'a' - L'A');
+    return (CHAR16) (Char - (L'a' - L'A'));
   }
 
   return Char;
@@ -919,7 +919,8 @@ StrHexToUint64 (
       (InternalHexCharToUintn (*String) <= REMINDER_MAX_UINT64_DIVIDED_BY_16))
       );
 
-    Result = LShiftU64 (Result, 4) + InternalHexCharToUintn (*String);
+    Result = LShiftU64 (Result, 4);
+    Result = Result + InternalHexCharToUintn (*String);
     String++;
   }
 
@@ -1930,7 +1931,8 @@ AsciiStrHexToUint64 (
       (InternalAsciiHexCharToUintn (*String) <= REMINDER_MAX_UINT64_DIVIDED_BY_16))
       );
 
-    Result = LShiftU64 (Result, 4) + InternalAsciiHexCharToUintn (*String);
+    Result = LShiftU64 (Result, 4);
+    Result = Result + InternalAsciiHexCharToUintn (*String);
     String++;
   }