From bbbc509fe5df6b22eb6dbe26ae7a536aa5d0ff02 Mon Sep 17 00:00:00 2001
From: Hao Wu <hao.a.wu@intel.com>
Date: Fri, 17 Feb 2017 09:46:27 +0800
Subject: [PATCH] PcAtChipsetPkg: Refine casting expression result to bigger
 size

There are cases that the operands of an expression are all with rank less
than UINT64/INT64 and the result of the expression is explicitly cast to
UINT64/INT64 to fit the target size.

An example will be:
UINT32 a,b;
// a and b can be any unsigned int type with rank less than UINT64, like
// UINT8, UINT16, etc.
UINT64 c;
c = (UINT64) (a + b);

Some static code checkers may warn that the expression result might
overflow within the rank of "int" (integer promotions) and the result is
then cast to a bigger size.

The commit refines codes by the following rules:
1). When the expression is possible to overflow the range of unsigned int/
int:
c = (UINT64)a + b;

2). When the expression will not overflow within the rank of "int", remove
the explicit type casts:
c = a + b;

3). When the expression will be cast to pointer of possible greater size:
UINT32 a,b;
VOID *c;
c = (VOID *)(UINTN)(a + b); --> c = (VOID *)((UINTN)a + b);

4). When one side of a comparison expression contains only operands with
rank less than UINT32:
UINT8 a;
UINT16 b;
UINTN c;
if ((UINTN)(a + b) > c) {...} --> if (((UINT32)a + b) > c) {...}

For rule 4), if we remove the 'UINTN' type cast like:
if (a + b > c) {...}
The VS compiler will complain with warning C4018 (signed/unsigned
mismatch, level 3 warning) due to promoting 'a + b' to type 'int'.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Hao Wu <hao.a.wu@intel.com>
Reviewed-by: Ruiyu Ni <ruiyu.ni@intel.com>
---
 .../Library/SerialIoLib/SerialPortLib.c        | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/PcAtChipsetPkg/Library/SerialIoLib/SerialPortLib.c b/PcAtChipsetPkg/Library/SerialIoLib/SerialPortLib.c
index dcb43fac62..95e0db70ad 100644
--- a/PcAtChipsetPkg/Library/SerialIoLib/SerialPortLib.c
+++ b/PcAtChipsetPkg/Library/SerialIoLib/SerialPortLib.c
@@ -1,7 +1,7 @@
 /** @file
   UART Serial Port library functions
 
-  Copyright (c) 2006 - 2016, Intel Corporation. All rights reserved.<BR>
+  Copyright (c) 2006 - 2017, Intel Corporation. All rights reserved.<BR>
   This program and the accompanying materials
   are licensed and made available under the terms and conditions of the BSD License
   which accompanies this distribution.  The full text of the license may be found at
@@ -91,19 +91,19 @@ SerialPortInitialize (
   // Set communications format
   //
   OutputData = (UINT8) ((DLAB << 7) | (gBreakSet << 6) | (gParity << 3) | (gStop << 2) | Data);
-  IoWrite8 ((UINTN) (gUartBase + LCR_OFFSET), OutputData);
+  IoWrite8 (gUartBase + LCR_OFFSET, OutputData);
 
   //
   // Configure baud rate
   //
-  IoWrite8 ((UINTN) (gUartBase + BAUD_HIGH_OFFSET), (UINT8) (Divisor >> 8));
-  IoWrite8 ((UINTN) (gUartBase + BAUD_LOW_OFFSET), (UINT8) (Divisor & 0xff));
+  IoWrite8 (gUartBase + BAUD_HIGH_OFFSET, (UINT8) (Divisor >> 8));
+  IoWrite8 (gUartBase + BAUD_LOW_OFFSET, (UINT8) (Divisor & 0xff));
 
   //
   // Switch back to bank 0
   //
   OutputData = (UINT8) ((~DLAB << 7) | (gBreakSet << 6) | (gParity << 3) | (gStop << 2) | Data);
-  IoWrite8 ((UINTN) (gUartBase + LCR_OFFSET), OutputData);
+  IoWrite8 (gUartBase + LCR_OFFSET, OutputData);
 
   return RETURN_SUCCESS;
 }
@@ -470,19 +470,19 @@ SerialPortSetAttributes (
   // Set communications format
   //
   OutputData = (UINT8) ((DLAB << 7) | (gBreakSet << 6) | (LcrParity << 3) | (LcrStop << 2) | LcrData);
-  IoWrite8 ((UINTN) (gUartBase + LCR_OFFSET), OutputData);
+  IoWrite8 (gUartBase + LCR_OFFSET, OutputData);
 
   //
   // Configure baud rate
   //
-  IoWrite8 ((UINTN) (gUartBase + BAUD_HIGH_OFFSET), (UINT8) (Divisor >> 8));
-  IoWrite8 ((UINTN) (gUartBase + BAUD_LOW_OFFSET), (UINT8) (Divisor & 0xff));
+  IoWrite8 (gUartBase + BAUD_HIGH_OFFSET, (UINT8) (Divisor >> 8));
+  IoWrite8 (gUartBase + BAUD_LOW_OFFSET, (UINT8) (Divisor & 0xff));
 
   //
   // Switch back to bank 0
   //
   OutputData = (UINT8) ((~DLAB << 7) | (gBreakSet << 6) | (LcrParity << 3) | (LcrStop << 2) | LcrData);
-  IoWrite8 ((UINTN) (gUartBase + LCR_OFFSET), OutputData);
+  IoWrite8 (gUartBase + LCR_OFFSET, OutputData);
 
   return RETURN_SUCCESS;
 }
-- 
2.39.2