Optimize SIMD codegen for (in)equality check against zero that produces bool result.

[sivarv]

As per Intel TechEmPower benchmark analysis, Kestrel.Internal.Infrastructure.MemoryPoolIterator.Seek() is one of the hot methods. This method uses equality against Vector.Zero

var data = new Vector<byte>(array, index);

// The below logic is repeated 3 times in the method
// against 3 different vectors.
var byte0Equals = Vector.Equals(data, byte0Vector);
if (!byte0Equals.Equals(Vector<byte>.Zero))
{
     byte0Index = FindFirstEqualByte(ref byte0Equals);
}

That is, SIMD API used is

bool Vector<T>.Equals(Vector<T> v)

Right now RyuJIT backend is generating the following

// Assume that byte0Equals in ymm0 reg
// Code generated for 
// byte0Equals.Equals(Vector<byte>.Zero)

vpxor ymm1, ymm1, ymm1
vmovaps ymm2, ymm0
vpcmpeqd ymm2, ymm2, ymm1
vextractf128 xmm3, ymm2, 0x1
vandps ymm2, ymm2, ymm3
vpshufd xmm3, xmm2, 0x4e
vandps ymm2, ymm2, ymm3
vpshufd xmm3, xmm2, 0x1
vpand ymm2, ymm2, ymm3
vmovd edi, xmm2
cmp edi, 0xffffffff
setz dil
movzx edi, dil

RyuJIT backend should be able to detect equality check against is Vector.Zero and generate the following optimal code

ptest ymm0, ymm0
setz dil
movzx edx, dil

Similarly for in-equality check against zero, we can generate

ptest ymm0, ymm0
setnz dil
movzx edx, dil

Fix #7358

[sivarv]

@dotnet-bot test Windows_NT jitstressregs1
@dotnet-bot test Windows_NT jitstressregs2
@dotnet-bot test Windows_NT jitstressregs3
@dotnet-bot test Windows_NT jitstressregs4
@dotnet-bot test Windows_NT jitstressregs8
@dotnet-bot test Windows_NT jitstressregs0x10
@dotnet-bot test Windows_NT jitstressregs0x80
@dotnet-bot test Windows_NT jitstress2
@dotnet-bot test Windows_NT corefx_baseline
@dotnet-bot test Ubuntu jitstressregs1
@dotnet-bot test Ubuntu jitstressregs2
@dotnet-bot test Ubuntu jitstressregs3
@dotnet-bot test Ubuntu jitstressregs4
@dotnet-bot test Ubuntu jitstressregs8
@dotnet-bot test Ubuntu jitstressregs0x10
@dotnet-bot test Ubuntu jitstressregs0x80
@dotnet-bot test Ubuntu jitstress2
@dotnet-bot test Ubuntu corefx_baseline

[sivarv]

@CarolEidt - Please review this.
CC @dotnet/jit-contrib

[CarolEidt]

Nice. LGTM.

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In reply to: 249947330 [](ancestors = 249947330)

[CarolEidt]