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>

1 files changed, 2 insertions, 2 deletions

diff --git a/MdeModulePkg/Library/PiDxeS3BootScriptLib/BootScriptSave.c b/MdeModulePkg/Library/PiDxeS3BootScriptLib/BootScriptSave.c
index 1f8aaf47c8..fe2d3a0284 100644
--- a/MdeModulePkg/Library/PiDxeS3BootScriptLib/BootScriptSave.c
+++ b/MdeModulePkg/Library/PiDxeS3BootScriptLib/BootScriptSave.c
@@ -691,7 +691,7 @@ S3BootScriptGetBootTimeEntryAddAddress (
    // Here we do not count the reserved memory for runtime script table.

    PageNumber = (UINT16) (mS3BootScriptTablePtr->TableMemoryPageNumber - PcdGet16(PcdS3BootScriptRuntimeTableReservePageNumber));

    TableLength =  mS3BootScriptTablePtr->TableLength;

-   if ((UINTN) EFI_PAGES_TO_SIZE ((UINTN) PageNumber) < (UINTN) (TableLength + EntryLength + sizeof (EFI_BOOT_SCRIPT_TERMINATE))) {

+   if (EFI_PAGES_TO_SIZE ((UINTN) PageNumber) < (TableLength + EntryLength + sizeof (EFI_BOOT_SCRIPT_TERMINATE))) {

      //

      // The buffer is too small to hold the table, Reallocate the buffer

      //

@@ -752,7 +752,7 @@ S3BootScriptGetRuntimeEntryAddAddress (
    //

    // Check if the memory range reserved for S3 Boot Script table is large enough to hold the node.

    //

-   if ((UINTN) (mS3BootScriptTablePtr->TableLength + EntryLength + sizeof (EFI_BOOT_SCRIPT_TERMINATE)) <= (UINTN) EFI_PAGES_TO_SIZE ((UINTN) (mS3BootScriptTablePtr->TableMemoryPageNumber))) {

+   if ((mS3BootScriptTablePtr->TableLength + EntryLength + sizeof (EFI_BOOT_SCRIPT_TERMINATE)) <= EFI_PAGES_TO_SIZE ((UINTN) (mS3BootScriptTablePtr->TableMemoryPageNumber))) {

      NewEntryPtr = mS3BootScriptTablePtr->TableBase + mS3BootScriptTablePtr->TableLength;

      mS3BootScriptTablePtr->TableLength = mS3BootScriptTablePtr->TableLength + EntryLength;

      //