[wasm] Add WidenUpper and WidenLower SIMD intrins #80117
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This improves performance in string related areas. Example code:
> wa-info -d -f Ascii.*WidenFourAsciiBytesToUtf16AndWriteToBuffer dotnet.wasm
(func corlib_System_Text_Ascii_WidenFourAsciiBytesToUtf16AndWriteToBuffer_char__uint(param $0 i32, $1 i32, $2 i32))
local.get $0
i32.eqz
if
call mini_llvmonly_throw_nullref_exception
unreachable
local.get $0
local.get $1
i32x4.splat [SIMD]
i16x8.extend.low.i8x16.u [SIMD]
v128.store64.lane 0 [SIMD]
It is also visible in the bench sample Json task, where it improves
serialization times:
| measurement | before | after |
|-:|-:|-:|
| Json, non-ASCII text serialize | 0.2939ms | 0.2174ms |
| Json, small serialize | 0.0274ms | 0.0262ms |
| Json, large serialize | 7.5466ms | 7.0948ms |
It would be enough to do zero/sign extensions instead of zero shifts, I
left the shifts in place though as I am not sure whether there is
a reason for that on arm64.
radekdoulik
requested review from
vargaz,
lambdageek and
SamMonoRT
as code owners
ghost
assigned 
vargaz
approved these changes
Jan 3, 2023
lewing
approved these changes
Jan 3, 2023
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This improves performance in string related areas. Example code:
It is also visible in the bench sample Json task, where it improves serialization times:
It would be enough to do zero/sign extensions instead of zero shifts, I left the shifts in place though as I am not sure whether there is a reason for that on arm64.