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MdePkg/BaseMemoryLibOptDxe ARM: fix Thumb-2 bug in ScanMem() 

The ARM ScanMem() in BaseMemoryLibOptDxe contains code from the open
source cortex-strings library, and inherited a bug from it where the
conditional execution of a sequence of instructions is erroneously
made dependent on the same condition. Since the final 'addeq' is
supposed to be dependent on the preceding 'tsteq' instruction, they
cannot be part of the same IT block.

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 2016-09-26 15:51:45 -07:00
parent 7807dea57f
commit c4f637077e
1 changed files with 5 additions and 4 deletions
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9
MdePkg/Library/BaseMemoryLibOptDxe/Arm/ScanMem.S
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@ -134,11 +134,12 @@ ASM_PFX(InternalMemScanMem8):
bne 61f
adds r0, r0, #1
tst r5, #CHARTSTMASK(1) // 2nd character
ittt eq
addeq r0, r0 ,#1
tsteq r5, #(3 << 15) // 2nd & 3rd character
bne 61f
adds r0, r0 ,#1
tst r5, #(3 << 15) // 2nd & 3rd character
// If not the 3rd must be the last one
addeq r0, r0, #1
it eq
addeq.n r0, r0, #1
61:
pop {r4-r7}