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Support wasm select instruction with V128-typed operands on AArch64.

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* this requires upgrading to wasmparser 0.67.0.

* There are no CLIF side changes because the CLIF `select` instruction is
  polymorphic enough.

* on aarch64, there is unfortunately no conditional-move (csel) instruction on
  vectors.  This patch adds a synthetic instruction `VecCSel` which *does*
  behave like that.  At emit time, this is emitted as an if-then-else diamond
  (4 insns).

* aarch64 implementation is otherwise straightforwards.
This commit is contained in:
Julian Seward
2020-11-11 17:09:57 +01:00
committed by julian-seward1
parent 9ced345aed
commit 41e87a2f99
15 changed files with 122 additions and 18 deletions
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40
cranelift/codegen/src/isa/aarch64/inst/emit.rs
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@@ -1909,6 +1909,46 @@ impl MachInstEmit for Inst {
sink.put4(enc_ldst_vec(q, size, rn, rd));
}
&Inst::VecCSel { rd, rn, rm, cond } => {
/* Emit this:
b.cond else
mov rd, rm
b out
else:
mov rd, rn
out:
Note, we could do better in the cases where rd == rn or rd == rm.
*/
let else_label = sink.get_label();
let out_label = sink.get_label();
// b.cond else
let br_else_offset = sink.cur_offset();
sink.put4(enc_conditional_br(
BranchTarget::Label(else_label),
CondBrKind::Cond(cond),
));
sink.use_label_at_offset(br_else_offset, else_label, LabelUse::Branch19);
// mov rd, rm
sink.put4(enc_vecmov(/* 16b = */ true, rd, rm));
// b out
let b_out_offset = sink.cur_offset();
sink.use_label_at_offset(b_out_offset, out_label, LabelUse::Branch26);
sink.add_uncond_branch(b_out_offset, b_out_offset + 4, out_label);
sink.put4(enc_jump26(0b000101, 0 /* will be fixed up later */));
// else:
sink.bind_label(else_label);
// mov rd, rn
sink.put4(enc_vecmov(/* 16b = */ true, rd, rn));
// out:
sink.bind_label(out_label);
}
&Inst::MovToNZCV { rn } => {
sink.put4(0xd51b4200 | machreg_to_gpr(rn));
}