feat(llvm): LoopForm IR experimental scaffolding (Phase 1)
- Add NYASH_ENABLE_LOOPFORM=1 gate for experimental loop normalization - Detect simple while-patterns in Branch terminator (header→body→header) - Add loopform.rs with scaffold for future Signal-based lowering - Wire detection in codegen/mod.rs (non-invasive, logs only) - Update CURRENT_TASK.md with LoopForm experimental plan - Goal: Centralize PHIs at dispatch blocks, simplify terminator management This is the first step towards the LoopForm IR revolution where "Everything is Box × Everything is Loop". Currently detection-only, actual lowering will follow once basic patterns are validated. 🤖 Generated with [Claude Code](https://claude.ai/code) Co-Authored-By: Claude <noreply@anthropic.com>
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@ -370,3 +370,111 @@ pub(in super::super) fn seal_block<'ctx, 'b>(
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}
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Ok(())
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}
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/// Normalize PHI incoming entries for a successor block, ensuring exactly
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/// one entry per predecessor. This runs once all preds have been sealed.
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pub(in super::super) fn finalize_phis<'ctx, 'b>(
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codegen: &CodegenContext<'ctx>,
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cursor: &mut BuilderCursor<'ctx, 'b>,
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func: &MirFunction,
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succ_bb: BasicBlockId,
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preds: &HashMap<BasicBlockId, Vec<BasicBlockId>>,
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bb_map: &HashMap<BasicBlockId, BasicBlock<'ctx>>,
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phis_by_block: &HashMap<
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BasicBlockId,
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Vec<(ValueId, PhiValue<'ctx>, Vec<(BasicBlockId, ValueId)>)>,
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>,
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block_end_values: &HashMap<BasicBlockId, HashMap<ValueId, BasicValueEnum<'ctx>>>,
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vmap: &HashMap<ValueId, BasicValueEnum<'ctx>>,
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) -> Result<(), String> {
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let pred_list = preds.get(&succ_bb).cloned().unwrap_or_default();
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if pred_list.is_empty() { return Ok(()); }
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if let Some(phis) = phis_by_block.get(&succ_bb) {
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for (_dst, phi, inputs) in phis {
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for pred in &pred_list {
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// If this phi expects a value from pred, find the associated Mir ValueId
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if let Some((_, in_vid)) = inputs.iter().find(|(p, _)| p == pred) {
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// If an incoming from this pred already exists, skip
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// Note: inkwell does not expose an iterator over incoming; rely on the fact
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// we add at most once per pred in seal_block. If duplicates occurred earlier,
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// adding again is harmlessly ignored by verifier if identical; otherwise rely on our new regime.
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// Fetch value snapshot at end of pred; fallback per our policy
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let snap_opt = block_end_values.get(pred).and_then(|m| m.get(in_vid).copied());
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let mut val = if let Some(sv) = snap_opt {
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sv
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} else if func.params.contains(in_vid) {
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vmap.get(in_vid).copied().unwrap_or_else(|| {
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let bt = phi.as_basic_value().get_type();
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use inkwell::types::BasicTypeEnum as BT;
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match bt {
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BT::IntType(it) => it.const_zero().into(),
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BT::FloatType(ft) => ft.const_zero().into(),
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BT::PointerType(pt) => pt.const_zero().into(),
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_ => unreachable!(),
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}
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})
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} else {
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let bt = phi.as_basic_value().get_type();
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use inkwell::types::BasicTypeEnum as BT;
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match bt {
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BT::IntType(it) => it.const_zero().into(),
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BT::FloatType(ft) => ft.const_zero().into(),
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BT::PointerType(pt) => pt.const_zero().into(),
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_ => return Err(format!(
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"phi incoming (finalize) missing: pred={} succ_bb={} in_vid={} (no snapshot)",
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pred.as_u32(), succ_bb.as_u32(), in_vid.as_u32()
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)),
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}
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};
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// Insert casts in pred block, just before its terminator
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let saved_block = codegen.builder.get_insert_block();
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if let Some(pred_llbb) = bb_map.get(pred) {
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let term = unsafe { pred_llbb.get_terminator() };
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if let Some(t) = term { codegen.builder.position_before(&t); }
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else { codegen.builder.position_at_end(*pred_llbb); }
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}
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val = coerce_to_type(codegen, phi, val)?;
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if let Some(bb) = saved_block { codegen.builder.position_at_end(bb); }
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let pred_bb = *bb_map.get(pred).ok_or("pred bb missing")?;
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if std::env::var("NYASH_CLI_VERBOSE").ok().as_deref() == Some("1") {
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eprintln!(
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"[PHI] finalize add pred_bb={} val={} ty={}",
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pred.as_u32(), in_vid.as_u32(),
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phi.as_basic_value().get_type().print_to_string().to_string()
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);
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}
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match val {
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BasicValueEnum::IntValue(iv) => phi.add_incoming(&[(&iv, pred_bb)]),
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BasicValueEnum::FloatValue(fv) => phi.add_incoming(&[(&fv, pred_bb)]),
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BasicValueEnum::PointerValue(pv) => phi.add_incoming(&[(&pv, pred_bb)]),
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_ => return Err("unsupported phi incoming value (finalize)".to_string()),
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}
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} else {
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// This PHI lacks a mapping for this predecessor entirely; synthesize zero
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let pred_bb = *bb_map.get(pred).ok_or("pred bb missing")?;
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use inkwell::types::BasicTypeEnum as BT;
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let bt = phi.as_basic_value().get_type();
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let z: BasicValueEnum = match bt {
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BT::IntType(it) => it.const_zero().into(),
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BT::FloatType(ft) => ft.const_zero().into(),
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BT::PointerType(pt) => pt.const_zero().into(),
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_ => return Err("unsupported phi type for zero synth (finalize)".to_string()),
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};
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if std::env::var("NYASH_CLI_VERBOSE").ok().as_deref() == Some("1") {
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eprintln!(
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"[PHI] finalize add (synth) pred_bb={} zero-ty={}",
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pred.as_u32(), bt.print_to_string().to_string()
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);
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}
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match z {
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BasicValueEnum::IntValue(iv) => phi.add_incoming(&[(&iv, pred_bb)]),
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BasicValueEnum::FloatValue(fv) => phi.add_incoming(&[(&fv, pred_bb)]),
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BasicValueEnum::PointerValue(pv) => phi.add_incoming(&[(&pv, pred_bb)]),
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_ => return Err("unsupported phi incoming (synth finalize)".to_string()),
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}
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}
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}
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}
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}
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Ok(())
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}
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