See #3799 for the bulk of the issue explanation. Ensures that emulated
SSE operation on aarch64 don't end up obliterating the upper 128-bit
lane when SVE-256 is present (Adv. SIMD operations zero-extend)
Knocks out quite a few SSE instructions right off the jump.
We had a few places that were using Bind, and a few other places
that were using specializations as a means to composing the instruction
tables. Instead, we can just use Bind consistently, which lets us tidy
up a bunch of the implementations (and gets rid of some unnecessary
codegen).
Both the default F80 softfloat wrappers (FXTRACT_SIG/FXTRACT_EXP) and
the reduced-precision F64 dispatcher fell through to the generic
exponent/significand extraction for Inf and NaN inputs, producing
finite garbage. The F80 wrapper returns input unchanged in the
significand slot and +Inf (or NaN) in the exponent slot; the F64
dispatcher detects the exponent-all-ones case and selects the proper
Inf/NaN result before the existing zero-case fold.
The special-value check masked the biased exponent with 0x7fff and
then used TestNZ, so it triggered on Exp==0 (denormals) instead of
Exp==0x7fff (NaN/Inf). Replace the TestNZ with SubWithFlags against
0x7fff so EQ only fires for genuine NaN/Inf.
Noticed this while benchmarking that the FIST* operations were
converting to a GPR, and then storing to memory using an atomic TSO
operation. This should be instead listening to the vector TSO
configuration option. This gives a 3.8x - 6.05x improvement in my
microbench.
Additionally when possible, make sure to use vector conversion
instructions when possible. It's lower cost to avoid the FPR->GPR
transfer, but we can only use it for 64-bit FIST operations. Microbench
couldn't show a difference for that on my platform, but that's because
it's float pipeline bounded regardless. Should help X-class Cortex and
newer Cortex-A.
Death Stranding 2 is using this instruction instead of `vbroadcastss`
for some reason. Optimize its specific case and add a note that when we
know sources match that we can optimize more patterns easily.
LC