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use super::{InlineAsmArch, InlineAsmType, Target};
use rustc_data_structures::stable_set::FxHashSet;
use rustc_macros::HashStable_Generic;
use rustc_span::{sym, Symbol};
use std::fmt;

def_reg_class! {
    Bpf BpfInlineAsmRegClass {
        reg,
        wreg,
    }
}

impl BpfInlineAsmRegClass {
    pub fn valid_modifiers(self, _arch: InlineAsmArch) -> &'static [char] {
        &[]
    }

    pub fn suggest_class(self, _arch: InlineAsmArch, _ty: InlineAsmType) -> Option<Self> {
        None
    }

    pub fn suggest_modifier(
        self,
        _arch: InlineAsmArch,
        _ty: InlineAsmType,
    ) -> Option<(char, &'static str)> {
        None
    }

    pub fn default_modifier(self, _arch: InlineAsmArch) -> Option<(char, &'static str)> {
        None
    }

    pub fn supported_types(
        self,
        _arch: InlineAsmArch,
    ) -> &'static [(InlineAsmType, Option<Symbol>)] {
        match self {
            Self::reg => types! { _: I8, I16, I32, I64; },
            Self::wreg => types! { alu32: I8, I16, I32; },
        }
    }
}

fn only_alu32(
    _arch: InlineAsmArch,
    target_features: &FxHashSet<Symbol>,
    _target: &Target,
) -> Result<(), &'static str> {
    if !target_features.contains(&sym::alu32) {
        Err("register can't be used without the `alu32` target feature")
    } else {
        Ok(())
    }
}

def_regs! {
    Bpf BpfInlineAsmReg BpfInlineAsmRegClass {
        r0: reg = ["r0"],
        r1: reg = ["r1"],
        r2: reg = ["r2"],
        r3: reg = ["r3"],
        r4: reg = ["r4"],
        r5: reg = ["r5"],
        r6: reg = ["r6"],
        r7: reg = ["r7"],
        r8: reg = ["r8"],
        r9: reg = ["r9"],
        w0: wreg = ["w0"] % only_alu32,
        w1: wreg = ["w1"] % only_alu32,
        w2: wreg = ["w2"] % only_alu32,
        w3: wreg = ["w3"] % only_alu32,
        w4: wreg = ["w4"] % only_alu32,
        w5: wreg = ["w5"] % only_alu32,
        w6: wreg = ["w6"] % only_alu32,
        w7: wreg = ["w7"] % only_alu32,
        w8: wreg = ["w8"] % only_alu32,
        w9: wreg = ["w9"] % only_alu32,

        #error = ["r10", "w10"] =>
            "the stack pointer cannot be used as an operand for inline asm",
    }
}

impl BpfInlineAsmReg {
    pub fn emit(
        self,
        out: &mut dyn fmt::Write,
        _arch: InlineAsmArch,
        _modifier: Option<char>,
    ) -> fmt::Result {
        out.write_str(self.name())
    }

    pub fn overlapping_regs(self, mut cb: impl FnMut(BpfInlineAsmReg)) {
        cb(self);

        macro_rules! reg_conflicts {
            (
                $(
                    $r:ident : $w:ident
                ),*
            ) => {
                match self {
                    $(
                        Self::$r => {
                            cb(Self::$w);
                        }
                        Self::$w => {
                            cb(Self::$r);
                        }
                    )*
                }
            };
        }

        reg_conflicts! {
            r0 : w0,
            r1 : w1,
            r2 : w2,
            r3 : w3,
            r4 : w4,
            r5 : w5,
            r6 : w6,
            r7 : w7,
            r8 : w8,
            r9 : w9
        }
    }
}