radiance · commit

regalloc: Fuse mapping lookup and removal

54343bcb75381ee8b3ae5ab09afda198395dafb2bb58260716f4a6ea78ea8534

Last-use handling searched the active register map once to find the
physical register and again to remove the same mapping.

Return the physical register from `rmapRemove`, allowing one
traversal to both remove the mapping and release its physical
register.

Assisted-by: Codex:gpt-5.6-sol

Alexis Sellier committed 1 month ago 1 parent 80166a83

lib/std/lang/gen/regalloc/assign.rad +6 -6

    set rmap.virtRegs[rmap.n] = virtReg;
    set rmap.physRegs[rmap.n] = physReg;
    set rmap.n += 1;
}

/// Remove a mapping from register map.
fn rmapRemove(rmap: *mut RegMap, virtReg: u32) {
/// Remove a mapping from the register map and return its physical register.
fn rmapRemove(rmap: *mut RegMap, virtReg: u32) -> ?gen::Reg {
    for i in 0..rmap.n {
        if rmap.virtRegs[i] == virtReg {
            let phys = rmap.physRegs[i];
            // Swap with last and decrement.
            set rmap.n -= 1;
            if i < rmap.n {
                set rmap.virtRegs[i] = rmap.virtRegs[rmap.n];
                set rmap.physRegs[i] = rmap.physRegs[rmap.n];
            }
            return;
            return phys;
        }
    }
    panic "rmapRemove: register not found";
    return nil;
}

/// Find first free register in pool, allocate it, return it.
fn findFreeInPool(usedRegs: *mut bitset::Bitset, current: *mut RegMap, ssaReg: u32, pool: *[gen::Reg]) -> ?gen::Reg {
    for i in 0..pool.len {


/// Callback for [`il::forEachReg`]: free last uses and allocate missing uses.
fn processInstrRegCb(reg: il::Reg, ctxPtr: *mut opaque) {
    let ctx = ctxPtr as *mut InstrCtx;
    if not liveness::hasLaterUse(ctx.live, ctx.func, ctx.blockIdx, ctx.instrIdx, reg) {
        if let phys = rmapFind(ctx.current, reg.n) {
        if let phys = rmapRemove(ctx.current, reg.n) {
            bitset::clear(ctx.usedRegs, *phys as u32);
            rmapRemove(ctx.current, reg.n);
        }
    }
    assert reg.n < ctx.assignments.len, "processInstrRegCb: register out of bounds";
    if spill::isSpilled(ctx.spillInfo, reg) {
        return; // Spilled values don't get physical registers.

218	218		set rmap.virtRegs[rmap.n] = virtReg;
219	219		set rmap.physRegs[rmap.n] = physReg;
220	220		set rmap.n += 1;
221	221		}
222	222
223		-	/// Remove a mapping from register map.
224		-	fn rmapRemove(rmap: *mut RegMap, virtReg: u32) {
	223	+	/// Remove a mapping from the register map and return its physical register.
	224	+	fn rmapRemove(rmap: *mut RegMap, virtReg: u32) -> ?gen::Reg {
225	225		for i in 0..rmap.n {
226	226		if rmap.virtRegs[i] == virtReg {
	227	+	let phys = rmap.physRegs[i];
227	228		// Swap with last and decrement.
228	229		set rmap.n -= 1;
229	230		if i < rmap.n {
230	231		set rmap.virtRegs[i] = rmap.virtRegs[rmap.n];
231	232		set rmap.physRegs[i] = rmap.physRegs[rmap.n];
232	233		}
233		-	return;
	234	+	return phys;
234	235		}
235	236		}
236		-	panic "rmapRemove: register not found";
	237	+	return nil;
237	238		}
238	239
239	240		/// Find first free register in pool, allocate it, return it.
240	241		fn findFreeInPool(usedRegs: mut bitset::Bitset, current: mut RegMap, ssaReg: u32, pool: *[gen::Reg]) -> ?gen::Reg {
241	242		for i in 0..pool.len {

280	281
281	282		/// Callback for [`il::forEachReg`]: free last uses and allocate missing uses.
282	283		fn processInstrRegCb(reg: il::Reg, ctxPtr: *mut opaque) {
283	284		let ctx = ctxPtr as *mut InstrCtx;
284	285		if not liveness::hasLaterUse(ctx.live, ctx.func, ctx.blockIdx, ctx.instrIdx, reg) {
285		-	if let phys = rmapFind(ctx.current, reg.n) {
	286	+	if let phys = rmapRemove(ctx.current, reg.n) {
286	287		bitset::clear(ctx.usedRegs, *phys as u32);
287		-	rmapRemove(ctx.current, reg.n);
288	288		}
289	289		}
290	290		assert reg.n < ctx.assignments.len, "processInstrRegCb: register out of bounds";
291	291		if spill::isSpilled(ctx.spillInfo, reg) {
292	292		return; // Spilled values don't get physical registers.