MdeModulePkg: 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: Feng Tian <feng.tian@intel.com>

2 files changed, 5 insertions, 5 deletions

diff --git a/MdeModulePkg/Universal/Acpi/BootScriptExecutorDxe/ScriptExecute.c b/MdeModulePkg/Universal/Acpi/BootScriptExecutorDxe/ScriptExecute.c
index 22d4349..5147e66 100644
--- a/MdeModulePkg/Universal/Acpi/BootScriptExecutorDxe/ScriptExecute.c
+++ b/MdeModulePkg/Universal/Acpi/BootScriptExecutorDxe/ScriptExecute.c
@@ -4,7 +4,7 @@
   This driver is dispatched by Dxe core and the driver will reload itself to ACPI reserved memory

   in the entry point. The functionality is to interpret and restore the S3 boot script

 

-Copyright (c) 2006 - 2016, Intel Corporation. All rights reserved.<BR>

+Copyright (c) 2006 - 2017, Intel Corporation. All rights reserved.<BR>

 Copyright (c) 2017, AMD Incorporated. All rights reserved.<BR>

 

 This program and the accompanying materials

@@ -327,7 +327,7 @@ ReadyToLockEventNotify (
   // Align buffer on section boundary

   //

   ImageContext.ImageAddress += ImageContext.SectionAlignment - 1;

-  ImageContext.ImageAddress &= ~((EFI_PHYSICAL_ADDRESS)(ImageContext.SectionAlignment - 1));

+  ImageContext.ImageAddress &= ~((EFI_PHYSICAL_ADDRESS)ImageContext.SectionAlignment - 1);

   //

   // Load the image to our new buffer

   //

diff --git a/MdeModulePkg/Universal/Acpi/S3SaveStateDxe/AcpiS3ContextSave.c b/MdeModulePkg/Universal/Acpi/S3SaveStateDxe/AcpiS3ContextSave.c
index a973d2d..dcfd61c 100644
--- a/MdeModulePkg/Universal/Acpi/S3SaveStateDxe/AcpiS3ContextSave.c
+++ b/MdeModulePkg/Universal/Acpi/S3SaveStateDxe/AcpiS3ContextSave.c
@@ -1,7 +1,7 @@
 /** @file

   This is the implementation to save ACPI S3 Context.

 

-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

@@ -401,9 +401,9 @@ S3AllocatePageTablesBuffer (
     // We need calculate whole page size then allocate once, because S3 restore page table does not know each page in Nvs.

     //

     if (!Page1GSupport) {

-      TotalPageTableSize = (UINTN)(1 + NumberOfPml4EntriesNeeded + NumberOfPml4EntriesNeeded * NumberOfPdpEntriesNeeded);

+      TotalPageTableSize = 1 + NumberOfPml4EntriesNeeded + NumberOfPml4EntriesNeeded * NumberOfPdpEntriesNeeded;

     } else {

-      TotalPageTableSize = (UINTN)(1 + NumberOfPml4EntriesNeeded);

+      TotalPageTableSize = 1 + NumberOfPml4EntriesNeeded;

     }

 

     TotalPageTableSize += ExtraPageTablePages;