sravan/system76-edk2
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

MdePkg/BaseMemoryLib: widen aligned accesses to 32 or 64 bits

Browse Source 
Since the default BaseMemoryLib should be callable from any context,
including ones where unaligned accesses are not allowed, it implements
InternalCopyMem() and InternalSetMem() using byte accesses only.
However, especially in a context where the MMU is off, such narrow
accesses may be disproportionately costly, and so if the size and
alignment of the access allow it, use 32-bit or even 64-bit loads and
stores (the latter may be beneficial even on a 32-bit architectures like
ARM, which has load pair/store pair instructions)

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Liming Gao <liming.gao@intel.com>
This commit is contained in:
Ard Biesheuvel
2016-09-02 08:26:23 +01:00
parent 94a3845be6
commit 01f688be90
3 changed files with 140 additions and 14 deletions
Download Patch File Download Diff File Expand all files Collapse all files

40
MdePkg/Library/BaseMemoryLib/SetMem.c
View File

@@ -5,6 +5,9 @@
is desired.
Copyright (c) 2006 - 2010, Intel Corporation. All rights reserved.<BR>
Copyright (c) 2012 - 2013, ARM Ltd. All rights reserved.<BR>
Copyright (c) 2016, Linaro Ltd. 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
@@ -43,11 +46,42 @@ InternalMemSetMem (
// volatile to prevent the optimizer from replacing this function with
// the intrinsic memset()
//
volatile UINT8 *Pointer;
volatile UINT8 *Pointer8;
volatile UINT32 *Pointer32;
volatile UINT64 *Pointer64;
UINT32 Value32;
UINT64 Value64;
Pointer = (UINT8*)Buffer;
if ((((UINTN)Buffer & 0x7) == 0) && (Length >= 8)) {
// Generate the 64bit value
Value32 = (Value << 24) | (Value << 16) | (Value << 8) | Value;
Value64 = LShiftU64 (Value32, 32) | Value32;
Pointer64 = (UINT64*)Buffer;
while (Length >= 8) {
*(Pointer64++) = Value64;
Length -= 8;
}
// Finish with bytes if needed
Pointer8 = (UINT8*)Pointer64;
} else if ((((UINTN)Buffer & 0x3) == 0) && (Length >= 4)) {
// Generate the 32bit value
Value32 = (Value << 24) | (Value << 16) | (Value << 8) | Value;
Pointer32 = (UINT32*)Buffer;
while (Length >= 4) {
*(Pointer32++) = Value32;
Length -= 4;
}
// Finish with bytes if needed
Pointer8 = (UINT8*)Pointer32;
} else {
Pointer8 = (UINT8*)Buffer;
}
while (Length-- > 0) {
*(Pointer++) = Value;
*(Pointer8++) = Value;
}
return Buffer;
}