Clean up unused LLVM SIMD intrinsics

[RalfJung]

rust-lang/stdarch#1928 and other PRs have replaced LLVM-intrinsic-based implementations in stdarch with ones that use the portable SIMD intrinsics. That means we should be able to remove a bunch of code from Miri. :)

@sayantn can you give us a list of PRs that did such replacements? Then someone can check which of those have Miri implementations.

Cc @eduardosm

[RalfJung]

@Amanieu for the future, would be nice to get a ping when x86 intrinsics are updated to remove their LLVM dependencies. (But I realize it's hard to always remember to send the right pings. Not a big deal when it doesn't happen, just a bit of dead code we'll hopefully notice eventually.)

[folkertdev]

Something that I threw together that appears to find a bunch of cases at least

#!/usr/bin/env bash

CORE_ARCH_DIR="/home/folkertdev/rust/stdarch/crates/core_arch"   
SHIM_PATH="/home/folkertdev/rust/rust/src/tools/miri/src/shims/x86/avx.rs"

while IFS= read -r sym; do
  # skip blanks
  [ -z "$sym" ] && continue

  esc_sym=$(printf '%s\n' "$sym" | sed 's/[.[\*^$()+?{}|]/\\&/g')

  if grep -RIlq --include='*.rs' -E '#\[link_name *= *"[^"]*'"$esc_sym"'[^"]*"' "$CORE_ARCH_DIR"; then
    # print as: <symbol>\t<file>:<line>\t<entire line>
    # grep -RIn --include='*.rs' -E '#\[link_name *= *"[^"]*'"$esc_sym"'[^"]*"' "$CORE_ARCH_DIR" | awk -v s="$sym" -F: '{print s "\t" $1 ":" $2 "\t" $3}'
    continue
  else
    printf '%s\tNOT FOUND\n' "$sym"
  fi
done < <( 
    grep -Eo '"[^"]*"' "$SHIM_PATH" \
      | sed 's/"//g' \
      | grep -Ev '(^|\.)(avx|llvm\.x86\.avx\.)' \
      | sort -u
    )

That finds

hadd.pd.256	NOT FOUND
hadd.ps.256	NOT FOUND
hsub.pd.256	NOT FOUND
hsub.ps.256	NOT FOUND
ptestc.256	NOT FOUND
ptestz.256	NOT FOUND
vperm2f128.pd.256	NOT FOUND
vperm2f128.ps.256	NOT FOUND
vperm2f128.si.256	NOT FOUND

Those all seem real.

[sayantn]

By a manual review (too lazy to write a script), I found these

sse.cvtsi{64}2ss
sse2.pmadd.wd
sse2.cvtss2sd
sse41.ptest{z,c}
ssse3.pabs.{b,w,d}.128
ssse3.ph{add,sub}.{w,d}
avx.h{add,sub}.{ps,pd}.256
avx.vperm2f128.{ps,pd,si}.256
avx.ptest{z,c}.256
avx.vtest{z,c}.{pd,ps}
avx2.ph{add,sub}.{w,d}
avx2.pmadd.wd
avx2.vperm2i128

[eduardosm]

I will take care of them once the Miri repository is synced.

[RalfJung]

A sync happened this morning.

[RalfJung]

@sayantn are there any PRs besides rust-lang/stdarch#1928 and rust-lang/stdarch#1932 we should be checking for this?

[sayantn]

There should be a few more, but I believe all of them deal with avx512 intrinsics, so these should be mostly enough

[RalfJung]

Yeah Miri doesn't have any avx512 support at the moment. Too many intrinsics ;)

[RalfJung]

Re-opening this for rust-lang/stdarch#1953.