This is a refinement for the existing hack. With this,
the default target will have neither wavefrontsize feature
present, unless it was explicitly specified. That is,
getWavefrontSize() == 64 no longer implies +wavefrontsize64.
getWavefrontSize() == 32 does imply +wavefrontsize32.
Continue to assume the value is 64 with no wavesize feature.
This maintains the codegenable property without any code
that directly cares about the wavesize needing to worry about it.
Introduce an isWaveSizeKnown helper to check if we know the
wavesize is accurate based on having one of the features explicitly
set, or a known target-cpu.
I'm not sure what's going on in wave_any.s. It's testing what
happens when both wavesizes are enabled, but this is treated
as an error in codegen. We now treat wave32 as the winning
case, so some cases that were previously printed as vcc are now
vcc_lo.
In graphics shaders it is better overall to use NSA encoding for IMAGE
instructions, because the benefit of less constrained register
allocation outweighs the cost of larger encoding. In particular NSA form
often avoids the need for extra V_MOV_B32 instructions between IMAGE
instructions, which can allow the IMAGE instructions to be claused.
Note that in GFX12 there is no longer a bit in the encoding to choose
between NSA and non-NSA forms, so this only affects GFX10 and GFX11.
Change the names of the TableGen features to match the names used by
AMDGPUSubtarget. "Addressable" refers to the amount that can be accessed
by a single workgroup. Add some explanatory comments. NFC.
The generic subtarget has neither of these features. Rather than forcing
HasMovrel on, it is simpler to expand dynamic vector indexing to a
sequence of compare/select instructions.
NFC for real subtargets.
