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[edk2,4/7] OvmfPkg: QemuVideoDxe: the VBE shim needs no 64-bit shifts (VS2010)

Message ID 1415801041-17550-5-git-send-email-lersek@redhat.com
State New
Headers show

Commit Message

Laszlo Ersek Nov. 12, 2014, 2:03 p.m. UTC 
From: Scott Duplichan <scott@notabs.org>

The SegmentC local variable has type EFI_PHYSICAL_ADDRESS for (justified)
style reasons. However, the 64-bit bit-shifts that it undergoes result in
intrinsic calls when built with VS2010 for Ia32 / NOOPT.

The concrete value of SegmentC, 0xC0000, and the results  of the bitops
that are based on it, are statically computeable. Cast SegmentC to UINT32
before subjecting it to bitwise operations; we can see in advance that
this won't lead to range loss.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Scott Duplichan <scott@notabs.org>
[lersek@redhat.com: dropped now superfluous outermost parens; commit msg]
Signed-off-by: Laszlo Ersek <lersek@redhat.com>

Signed-off-by: Laszlo Ersek <lersek@redhat.com>
---
 OvmfPkg/QemuVideoDxe/VbeShim.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)
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Patch

diff --git a/OvmfPkg/QemuVideoDxe/VbeShim.c b/OvmfPkg/QemuVideoDxe/VbeShim.c
index 81c1166..6bb175b 100644
--- a/OvmfPkg/QemuVideoDxe/VbeShim.c
+++ b/OvmfPkg/QemuVideoDxe/VbeShim.c
@@ -153,13 +153,13 @@  InstallVbeShim (
   CopyMem (VbeInfo->Signature, "VESA", 4);
   VbeInfo->VesaVersion = 0x0300;
 
-  VbeInfo->OemNameAddress = (UINT32)(SegmentC << 12 | (UINT16)(UINTN)Ptr);
+  VbeInfo->OemNameAddress = (UINT32)SegmentC << 12 | (UINT16)(UINTN)Ptr;
   CopyMem (Ptr, "QEMU", 5);
   Ptr += 5;
 
   VbeInfo->Capabilities = BIT0; // DAC can be switched into 8-bit mode
 
-  VbeInfo->ModeListAddress = (UINT32)(SegmentC << 12 | (UINT16)(UINTN)Ptr);
+  VbeInfo->ModeListAddress = (UINT32)SegmentC << 12 | (UINT16)(UINTN)Ptr;
   *(UINT16*)Ptr = 0x00f1; // mode number
   Ptr += 2;
   *(UINT16*)Ptr = 0xFFFF; // mode list terminator
@@ -168,17 +168,17 @@  InstallVbeShim (
   VbeInfo->VideoMem64K = (UINT16)((1024 * 768 * 4 + 65535) / 65536);
   VbeInfo->OemSoftwareVersion = 0x0000;
 
-  VbeInfo->VendorNameAddress = (UINT32)(SegmentC << 12 | (UINT16)(UINTN)Ptr);
+  VbeInfo->VendorNameAddress = (UINT32)SegmentC << 12 | (UINT16)(UINTN)Ptr;
   CopyMem (Ptr, "OVMF", 5);
   Ptr += 5;
 
-  VbeInfo->ProductNameAddress = (UINT32)(SegmentC << 12 | (UINT16)(UINTN)Ptr);
+  VbeInfo->ProductNameAddress = (UINT32)SegmentC << 12 | (UINT16)(UINTN)Ptr;
   Printed = AsciiSPrint ((CHAR8 *)Ptr,
               sizeof VbeInfoFull->Buffer - (Ptr - VbeInfoFull->Buffer), "%s",
               CardName);
   Ptr += Printed + 1;
 
-  VbeInfo->ProductRevAddress = (UINT32)(SegmentC << 12 | (UINT16)(UINTN)Ptr);
+  VbeInfo->ProductRevAddress = (UINT32)SegmentC << 12 | (UINT16)(UINTN)Ptr;
   CopyMem (Ptr, mProductRevision, sizeof mProductRevision);
   Ptr += sizeof mProductRevision;
 
@@ -268,7 +268,7 @@  InstallVbeShim (
   //
   // Second, point the Int10h vector at the shim.
   //
-  Int0x10->Segment = (UINT16) (SegmentC >> 4);
+  Int0x10->Segment = (UINT16) ((UINT32)SegmentC >> 4);
   Int0x10->Offset  = (UINT16) ((UINTN) (VbeModeInfo + 1) - SegmentC);
 
   DEBUG ((EFI_D_INFO, "%a: VBE shim installed\n", __FUNCTION__));