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Merge pull request #3002 from afonso360/aarch64-i128-br
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aarch64 implement brz,brnz,br_icmp for i128 values
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@cfallin
cfallin authored Jun 21, 2021
2 parents cb93726 + 45faace commit 18cd2f6
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190 changes: 178 additions & 12 deletions cranelift/codegen/src/isa/aarch64/lower.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1226,12 +1226,43 @@ pub(crate) fn maybe_input_insn_via_conv<C: LowerCtx<I = Inst>>(
None
}

pub(crate) fn lower_icmp_or_ifcmp_to_flags<C: LowerCtx<I = Inst>>(
/// Specifies what [lower_icmp] should do when lowering
#[derive(Debug, Clone, PartialEq)]
pub(crate) enum IcmpOutput {
/// Only sets flags, discarding the results
Flags,
/// Materializes the results into a register. The flags set may be incorrect
Register(Writable<Reg>),
}

impl IcmpOutput {
pub fn reg(&self) -> Option<Writable<Reg>> {
match self {
IcmpOutput::Flags => None,
IcmpOutput::Register(reg) => Some(*reg),
}
}
}

/// Lower an icmp comparision
///
/// We can lower into the status flags, or materialize the result into a register
/// This is controlled by the `output` parameter.
pub(crate) fn lower_icmp<C: LowerCtx<I = Inst>>(
ctx: &mut C,
insn: IRInst,
is_signed: bool,
) {
debug!("lower_icmp_or_ifcmp_to_flags: insn {}", insn);
condcode: IntCC,
output: IcmpOutput,
) -> CodegenResult<()> {
debug!(
"lower_icmp: insn {}, condcode: {}, output: {:?}",
insn, condcode, output
);

let rd = output.reg().unwrap_or(writable_zero_reg());
let inputs = insn_inputs(ctx, insn);
let cond = lower_condcode(condcode);
let is_signed = condcode_is_signed(condcode);
let ty = ctx.input_ty(insn, 0);
let bits = ty_bits(ty);
let narrow_mode = match (bits <= 32, is_signed) {
Expand All @@ -1240,14 +1271,149 @@ pub(crate) fn lower_icmp_or_ifcmp_to_flags<C: LowerCtx<I = Inst>>(
(false, true) => NarrowValueMode::SignExtend64,
(false, false) => NarrowValueMode::ZeroExtend64,
};
let inputs = [InsnInput { insn, input: 0 }, InsnInput { insn, input: 1 }];
let ty = ctx.input_ty(insn, 0);
let rn = put_input_in_reg(ctx, inputs[0], narrow_mode);
let rm = put_input_in_rse_imm12(ctx, inputs[1], narrow_mode);
debug!("lower_icmp_or_ifcmp_to_flags: rn = {:?} rm = {:?}", rn, rm);
let alu_op = choose_32_64(ty, ALUOp::SubS32, ALUOp::SubS64);
let rd = writable_zero_reg();
ctx.emit(alu_inst_imm12(alu_op, rd, rn, rm));

if ty == I128 {
let lhs = put_input_in_regs(ctx, inputs[0]);
let rhs = put_input_in_regs(ctx, inputs[1]);

let tmp1 = ctx.alloc_tmp(I64).only_reg().unwrap();
let tmp2 = ctx.alloc_tmp(I64).only_reg().unwrap();

match condcode {
IntCC::Equal | IntCC::NotEqual => {
// eor tmp1, lhs_lo, rhs_lo
// eor tmp2, lhs_hi, rhs_hi
// adds xzr, tmp1, tmp2
// cset dst, {eq, ne}

ctx.emit(Inst::AluRRR {
alu_op: ALUOp::Eor64,
rd: tmp1,
rn: lhs.regs()[0],
rm: rhs.regs()[0],
});
ctx.emit(Inst::AluRRR {
alu_op: ALUOp::Eor64,
rd: tmp2,
rn: lhs.regs()[1],
rm: rhs.regs()[1],
});
ctx.emit(Inst::AluRRR {
alu_op: ALUOp::AddS64,
rd: writable_zero_reg(),
rn: tmp1.to_reg(),
rm: tmp2.to_reg(),
});

if let IcmpOutput::Register(rd) = output {
materialize_bool_result(ctx, insn, rd, cond);
}
}
IntCC::Overflow | IntCC::NotOverflow => {
// We can do an 128bit add while throwing away the results
// and check the overflow flags at the end.
//
// adds xzr, lhs_lo, rhs_lo
// adcs xzr, lhs_hi, rhs_hi
// cset dst, {vs, vc}

ctx.emit(Inst::AluRRR {
alu_op: ALUOp::AddS64,
rd: writable_zero_reg(),
rn: lhs.regs()[0],
rm: rhs.regs()[0],
});
ctx.emit(Inst::AluRRR {
alu_op: ALUOp::AdcS64,
rd: writable_zero_reg(),
rn: lhs.regs()[1],
rm: rhs.regs()[1],
});

if let IcmpOutput::Register(rd) = output {
materialize_bool_result(ctx, insn, rd, cond);
}
}
_ => {
// cmp lhs_lo, rhs_lo
// cset tmp1, unsigned_cond
// cmp lhs_hi, rhs_hi
// cset tmp2, cond
// csel dst, tmp1, tmp2, eq

let rd = output.reg().unwrap_or(tmp1);
let unsigned_cond = lower_condcode(condcode.unsigned());

ctx.emit(Inst::AluRRR {
alu_op: ALUOp::SubS64,
rd: writable_zero_reg(),
rn: lhs.regs()[0],
rm: rhs.regs()[0],
});
materialize_bool_result(ctx, insn, tmp1, unsigned_cond);
ctx.emit(Inst::AluRRR {
alu_op: ALUOp::SubS64,
rd: writable_zero_reg(),
rn: lhs.regs()[1],
rm: rhs.regs()[1],
});
materialize_bool_result(ctx, insn, tmp2, cond);
ctx.emit(Inst::CSel {
cond: Cond::Eq,
rd,
rn: tmp1.to_reg(),
rm: tmp2.to_reg(),
});

if output == IcmpOutput::Flags {
// We only need to guarantee that the flags for `cond` are correct, so we can
// compare rd with 0 or 1

// If we are doing compare or equal, we want to compare with 1 instead of zero
if condcode.without_equal() != condcode {
lower_constant_u64(ctx, tmp2, 1);
}

let xzr = zero_reg();
let rd = rd.to_reg();
let tmp2 = tmp2.to_reg();
let (rn, rm) = match condcode {
IntCC::SignedGreaterThanOrEqual => (rd, tmp2),
IntCC::UnsignedGreaterThanOrEqual => (rd, tmp2),
IntCC::SignedLessThanOrEqual => (tmp2, rd),
IntCC::UnsignedLessThanOrEqual => (tmp2, rd),
IntCC::SignedGreaterThan => (rd, xzr),
IntCC::UnsignedGreaterThan => (rd, xzr),
IntCC::SignedLessThan => (xzr, rd),
IntCC::UnsignedLessThan => (xzr, rd),
_ => unreachable!(),
};

ctx.emit(Inst::AluRRR {
alu_op: ALUOp::SubS64,
rd: writable_zero_reg(),
rn,
rm,
});
}
}
}
} else if !ty.is_vector() {
let alu_op = choose_32_64(ty, ALUOp::SubS32, ALUOp::SubS64);
let rn = put_input_in_reg(ctx, inputs[0], narrow_mode);
let rm = put_input_in_rse_imm12(ctx, inputs[1], narrow_mode);
ctx.emit(alu_inst_imm12(alu_op, writable_zero_reg(), rn, rm));

if let IcmpOutput::Register(rd) = output {
materialize_bool_result(ctx, insn, rd, cond);
}
} else {
let rn = put_input_in_reg(ctx, inputs[0], narrow_mode);
let rm = put_input_in_reg(ctx, inputs[1], narrow_mode);
lower_vector_compare(ctx, rd, rn, rm, ty, cond)?;
}

Ok(())
}

pub(crate) fn lower_fcmp_or_ffcmp_to_flags<C: LowerCtx<I = Inst>>(ctx: &mut C, insn: IRInst) {
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