Struct Pipeline 

pub struct Pipeline {
    pub fetch: Insn,
    pub decode: Insn,
    pub execute: Insn,
    /* private fields */
}

The 3-stage Fetch/Decode/Execute pipeline (Mesen2 ArmV3CpuPipeline).

This is the ENTIRE mechanism behind ARM’s well-known “PC reads as address+8” quirk: r15 (owned by Regs, threaded through Self::process rather than duplicated here) tracks the FETCH stage’s address, two stages ahead of whatever instruction is currently in Execute. No +8 constant exists anywhere in this port — it falls straight out of this stage timing, which is exactly why getting this model right BEFORE porting any instruction that reads R15 as an operand matters (see docs/st018-arm-notes.md’s pipeline section).

Bus-side access-mode bits (Sequential/Word/Byte/Prefetch, used by the board wrapper for its own cycle-timing bookkeeping) are deliberately NOT modeled here yet — they don’t affect address/opcode sequencing, only the caller’s read_code timing side effects, and land with the board wrapper (docs/st018-arm-notes.md step 9).

Fields

fetch: Insn

The most recently fetched, not-yet-decoded word.

decode: Insn

The word decoded on the prior step, about to become execute on the next one.

execute: Insn

The instruction actually running on the current step.

Implementations

impl Pipeline

pub const fn request_reload(&mut self)

Request a full pipeline flush + refill on the next Self::process call — set whenever an instruction writes R15 (a taken branch, a data-processing MOV PC, ..., an LDR PC, ..., an exception entry, etc.). Not yet wired to any register-write path (that lands with instruction execute); exposed now so the pipeline model itself is independently testable.

pub fn process(&mut self, r15: &mut u32, read_code: impl FnMut(u32) -> u32)

Advance the pipeline by one stage (Mesen2 ProcessPipeline): reload first if requested, then unconditionally shift Execute←Decode←Fetch←(a fresh fetch at r15+4). Call this once per CPU step, AFTER the current Execute-stage instruction has run.

Trait Implementations

impl Clone for Pipeline

fn clone(&self) -> Pipeline

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Pipeline

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for Pipeline

fn default() -> Pipeline

Returns the “default value” for a type.

impl Copy for Pipeline