From: Michael Kinney <michael.d.kinney@intel.com>
Date: Wed, 3 May 2017 00:23:22 +0000 (-0700)
Subject: PcAtChipsetPkg/SerialIoLib: Remove negative value shift
X-Git-Tag: edk2-stable201903~4015
X-Git-Url: https://git.proxmox.com/?p=mirror_edk2.git;a=commitdiff_plain;h=bbd61de5dbc6ad146dc7250e9646cb662604b5f3;hp=da0df6ca8f8f118866e53c7fb770598c199993a6

PcAtChipsetPkg/SerialIoLib: Remove negative value shift

https://bugzilla.tianocore.org/show_bug.cgi?id=553

Remove left shift of negative values that always evaluate
to 0 to address build errors from the llvm/clang compiler
used in the XCODE5 tool chain.

Clang rightfully complains about left-shifting ~DLAB. DLAB is #defined
as 0x01 (an "int"), hence ~DLAB has value (-2) on all edk2 platforms.
Left-shifting a negative int is undefined behavior.

Rather than replacing ~DLAB with ~(UINT32)DLAB, realize that the nonzero
bits of (~(UINT32)DLAB << 7) would all be truncated away in the final
conversion to UINT8 anyway. So just remove (~DLAB << 7).

Cc: Ruiyu Ni <ruiyu.ni@intel.com>
Cc: Andrew Fish <afish@apple.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Michael D Kinney <michael.d.kinney@intel.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
---

diff --git a/PcAtChipsetPkg/Library/SerialIoLib/SerialPortLib.c b/PcAtChipsetPkg/Library/SerialIoLib/SerialPortLib.c
index 95e0db70ad..0a2e20c1d9 100644
--- a/PcAtChipsetPkg/Library/SerialIoLib/SerialPortLib.c
+++ b/PcAtChipsetPkg/Library/SerialIoLib/SerialPortLib.c
@@ -102,7 +102,7 @@ SerialPortInitialize (
   //
   // Switch back to bank 0
   //
-  OutputData = (UINT8) ((~DLAB << 7) | (gBreakSet << 6) | (gParity << 3) | (gStop << 2) | Data);
+  OutputData = (UINT8) ( (gBreakSet << 6) | (gParity << 3) | (gStop << 2) | Data);
   IoWrite8 (gUartBase + LCR_OFFSET, OutputData);
 
   return RETURN_SUCCESS;
@@ -481,7 +481,7 @@ SerialPortSetAttributes (
   //
   // Switch back to bank 0
   //
-  OutputData = (UINT8) ((~DLAB << 7) | (gBreakSet << 6) | (LcrParity << 3) | (LcrStop << 2) | LcrData);
+  OutputData = (UINT8) ((gBreakSet << 6) | (LcrParity << 3) | (LcrStop << 2) | LcrData);
   IoWrite8 (gUartBase + LCR_OFFSET, OutputData);
 
   return RETURN_SUCCESS;