armagnac 0.3.0

//! Implements ASR (Arithmetic Shift Right) instruction.

use super::ArmVersion::{V6M, V7EM, V7M, V8M};
use super::Encoding::{self, T1, T2};
use super::{rdn_args_string, unpredictable, DecodeHelper, Instruction, Pattern, Qualifier};
use crate::qualifier_wide_match;
use crate::{
    arith::{shift_c, Shift},
    core::ItState,
    core::{Effect, Processor, RunError},
    decoder::DecodeError,
    helpers::BitAccess,
    registers::RegisterIndex,
};

/// ASR (immediate) instruction.
pub struct AsrImm {
    /// Destination register.
    rd: RegisterIndex,
    /// First operand register.
    rm: RegisterIndex,
    /// Shift to be applied to Rm.
    shift: u8,
    /// True if condition flags are updated.
    set_flags: bool,
    /// Encoding.
    encoding: Encoding,
}

impl Instruction for AsrImm {
    fn patterns() -> &'static [Pattern] {
        &[
            Pattern {
                encoding: T1,
                versions: &[V6M, V7M, V7EM, V8M],
                expression: "00010xxxxxxxxxxx",
            },
            Pattern {
                encoding: T2,
                versions: &[V7M, V7EM, V8M],
                expression: "11101010010x1111(0)xxxxxxxxx10xxxx",
            },
        ]
    }

    fn try_decode(encoding: Encoding, ins: u32, state: ItState) -> Result<Self, DecodeError> {
        Ok(match encoding {
            T1 => Self {
                rd: ins.reg3(0),
                rm: ins.reg3(3),
                shift: Shift::from_bits(2, ins.imm5(6)).n as u8,
                set_flags: !state.in_it_block(),
                encoding,
            },
            T2 => {
                let rm = ins.reg4(0);
                let rd = ins.reg4(8);
                unpredictable(rd.is_sp_or_pc() || rm.is_sp_or_pc())?;
                let imm5 = (ins.imm3(12) << 2) | ins.imm2(6);
                Self {
                    rd,
                    rm,
                    shift: imm5 as u8,
                    set_flags: ins.bit(20),
                    encoding,
                }
            }
            _ => panic!(),
        })
    }

    fn execute(&self, proc: &mut Processor) -> Result<Effect, RunError> {
        let carry_in = proc.registers.psr.c();
        let (result, carry) = shift_c(proc[self.rm], Shift::asr(self.shift as u32), carry_in);
        proc.set(self.rd, result);
        if self.set_flags {
            proc.registers.psr.set_nz(result).set_c(carry);
        }
        Ok(Effect::None)
    }

    fn name(&self) -> String {
        "asr".into()
    }

    fn sets_flags(&self) -> bool {
        self.set_flags
    }

    fn qualifier(&self) -> super::Qualifier {
        qualifier_wide_match!(self.encoding, T2)
    }

    fn args(&self, _pc: u32) -> String {
        format!("{}, {}, #{}", self.rd, self.rm, self.shift)
    }
}

/// ASR (register) instruction.
pub struct AsrReg {
    /// Destination register.
    rd: RegisterIndex,
    /// First operand register.
    rn: RegisterIndex,
    /// Shift amount register.
    rm: RegisterIndex,
    /// True if condition flags are updated.
    set_flags: bool,
    /// Encoding.
    encoding: Encoding,
}

impl Instruction for AsrReg {
    fn patterns() -> &'static [Pattern] {
        &[
            Pattern {
                encoding: T1,
                versions: &[V6M, V7M, V7EM, V8M],
                expression: "0100000100xxxxxx",
            },
            Pattern {
                encoding: T2,
                versions: &[V7M, V7EM, V8M],
                expression: "11111010010xxxxx1111xxxx0000xxxx",
            },
        ]
    }

    fn try_decode(encoding: Encoding, ins: u32, state: ItState) -> Result<Self, DecodeError> {
        Ok(match encoding {
            T1 => {
                let rdn = ins.reg3(0);
                Self {
                    rd: rdn,
                    rn: rdn,
                    rm: ins.reg3(3),
                    set_flags: !state.in_it_block(),
                    encoding,
                }
            }
            T2 => {
                let rm = ins.reg4(0);
                let rd = ins.reg4(8);
                let rn = ins.reg4(16);
                unpredictable(rd.is_sp_or_pc() || rn.is_sp_or_pc() || rm.is_sp_or_pc())?;
                Self {
                    rd,
                    rn,
                    rm,
                    set_flags: ins.bit(20),
                    encoding,
                }
            }
            _ => panic!(),
        })
    }

    fn execute(&self, proc: &mut Processor) -> Result<Effect, RunError> {
        let shift_n = proc[self.rm] & 0xff;
        let carry_in = proc.registers.psr.c();
        let (result, carry) = shift_c(proc[self.rn], Shift::asr(shift_n), carry_in);
        proc.set(self.rd, result);
        if self.set_flags {
            proc.registers.psr.set_nz(result).set_c(carry);
        }
        Ok(Effect::None)
    }

    fn name(&self) -> String {
        "asr".into()
    }

    fn sets_flags(&self) -> bool {
        self.set_flags
    }

    fn qualifier(&self) -> Qualifier {
        qualifier_wide_match!(self.encoding, T2)
    }

    fn args(&self, _pc: u32) -> String {
        format!(
            "{}, {}",
            rdn_args_string(self.rd, self.rn, self.encoding == T1),
            self.rm
        )
    }
}