> On 15 Jan 2021, at 22:10, Martin Storsjö <[email protected]> wrote:
>
> On Mon, 11 Jan 2021, [email protected] wrote:
>
>> From: Reimar Döffinger <[email protected]>
>>
>> Trivially expand hscale assembler to support > 8 bit formats
>> both for input and output.
>> 16-bit input is not supported as I am not certain how to
>> get sufficient test coverage.
>> ---
>> libswscale/aarch64/hscale.S | 53 ++++++++++++++++++++++++++----------
>> libswscale/aarch64/swscale.c | 49 +++++++++++++++++++++++++++++++--
>> 2 files changed, 85 insertions(+), 17 deletions(-)
>>
>> diff --git a/libswscale/aarch64/hscale.S b/libswscale/aarch64/hscale.S
>> index af55ffe2b7..3b42d39dac 100644
>> --- a/libswscale/aarch64/hscale.S
>> +++ b/libswscale/aarch64/hscale.S
>> @@ -20,7 +20,11 @@
>> #include "libavutil/aarch64/asm.S"
>> -function ff_hscale_8_to_15_neon, export=1
>> +.macro hscale srcbits, dstbits, ldt, lds, c
>> +function ff_hscale_\srcbits\()_to_\dstbits\()_neon, export=1
>> +.if \dstbits >= 16
>> + movi v20.4S, #(0x1 << (\dstbits - 16)), msl #16
>> +.endif
>> sbfiz x7, x6, #1, #32 // filterSize*2 (*2
>> because int16)
>> 1: ldr w8, [x5], #4 // filterPos[idx]
>> ldr w0, [x5], #4 // filterPos[idx + 1]
>> @@ -34,30 +38,30 @@ function ff_hscale_8_to_15_neon, export=1
>> movi v1.2D, #0 // val sum part 2 (for
>> dst[1])
>> movi v2.2D, #0 // val sum part 3 (for
>> dst[2])
>> movi v3.2D, #0 // val sum part 4 (for
>> dst[3])
>> - add x17, x3, w8, UXTW // srcp + filterPos[0]
>> - add x8, x3, w0, UXTW // srcp + filterPos[1]
>> - add x0, x3, w11, UXTW // srcp + filterPos[2]
>> - add x11, x3, w9, UXTW // srcp + filterPos[3]
>> + add x17, x3, w8, UXTW #!!(\srcbits > 8) // srcp +
>> filterPos[0]
>> + add x8, x3, w0, UXTW #!!(\srcbits > 8) // srcp +
>> filterPos[1]
>> + add x0, x3, w11, UXTW #!!(\srcbits > 8) // srcp +
>> filterPos[2]
>> + add x11, x3, w9, UXTW #!!(\srcbits > 8) // srcp +
>> filterPos[3]
>
> This construct breaks with llvm's assembler and armasm64 - they don't
> evaluate !! here, ending up with errors like these:
>
> <instantiation>:19:31: error: expected integer shift amount
> add x8, x3, w0, UXTW #!!(8 > 8)
>
> libswscale\aarch64\hscale.o.asm(3093) : error A2007: wrong operand type for
> :LNOT:
> add x17, x3, w8, UXTW #!!0
>
> While less elegant, I guess this can be handled easily by adding a macro
> parameter that represents the evaluated value of \srcbits > 8.
It’s actually easier. I just need 0 or 1 here, the thing I was missing
that caused me to add the !! is that a true condition does not evaluate
to 1 but to -1, so (\srcbits <= 8) + 1 works with both.
>> mov w15, w6 // filterSize counter
>> -2: ld1 {v4.8B}, [x17], #8 // srcp[filterPos[0] +
>> {0..7}]
>> +2: ld1 {v4.\ldt}, [x17], \lds // srcp[filterPos[0] +
>> {0..7}]
>> ld1 {v5.8H}, [x16], #16 // load 8x16-bit filter
>> values, part 1
>> - ld1 {v6.8B}, [x8], #8 // srcp[filterPos[1] +
>> {0..7}]
>> + ld1 {v6.\ldt}, [x8], \lds // srcp[filterPos[1] +
>> {0..7}]
>> ld1 {v7.8H}, [x12], #16 // load 8x16-bit at
>> filter+filterSize
>> - uxtl v4.8H, v4.8B // unpack part 1 to
>> 16-bit
>> +\c\c uxtl v4.8H, v4.8B // unpack part 1 to
>> 16-bit
>
> With gas-preprocessor and armasm64, // isn't considered a comment char by
> armasm64, only by the C preprocessor invoked by gas-preprocessor, so it
> doesn't strip out these lines properly. I guess one could add more code to
> gas-preprocessor to handle that, but that's probably a bit overkill...
That is a whole another fun topic, I’ll be sending patches related to
gas-preprocessor.
Admittedly might consider some of the issues my fault for not cross-compiling
and also preferring WSL over msys2 or such...
And then I might get around to addressing the rest.
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