Greetings!
We are trying to implement an .efi application that validates some ARM
architecture instructions.
For this application, an assembly code was created, with the help of
AsmMacroIoLibV8, present in edk2. The implementation can be seen below.
>
> #include <AsmMacroIoLibV8.h>
>
> .data
>
> OneHundredSeventy: .word 0b0000000010101010
>
> Filter32bit: .word 4294967295
>
> .bss
>
> EmptyVar: .space 64
>
> .text
>
> ASM_FUNC(SQXTNInstruction)
>
> ldr x1,=OneHundredSeventy
> ldr x2,=EmptyVar
> mov x3,#2147483647
> mov x5,Filter32bit // The error happens here
>
> LD1 {V0.16B},[x1]
> SQXTN V1.2S, V0.2D
> MOV x2,V1.D[0]
>
> and x4,x2,x5
>
> cmp x3,x4
> b.ne Error
> b End
>
> Error:
> mov x0,x4
> ret
> End:
> mov x0,#0
> ret
>
When using the value defined for Filter32bit, as it is in the code, the return
of this instruction is 1 (error). However, when directly loading the hardcoded
value into register x5, the return is 0 (success).
This behavior happened on a machine with a Snapdragon(TM) 8cx @ 2.84 GHz -
QUALCOMM processor.
We would like to know if there is any bug in the implementation or if there is
an explanation for this behavior.
Best regards!
Gabriel.
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