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add ac_yield_load and ac_yield_tail for delay slot optimization opportunities.

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ed
2026-08-04 17:25:02 -04:00
parent 888ffce859
commit b5953a723b
7 changed files with 185 additions and 19 deletions
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scripts/passes/static_analysis.lua
+127 -3
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@@ -124,7 +124,7 @@ local OUTPUT_EXTENSION = ".static_analysis.txt"
--- @field info table[] -- finding-level info (kind == "info"); distinct from per-source scanned/cycles summary rows
--- @alias AtomName string -- lower_snake_case atom nameMacroName string -- lower_snake_case macro identifier
--- @alias CheckName string -- "transfer_hazards" | "control_transfer_delay_slot_use" | "mac_yield_uniformity" | "abi_handoff" | "gpu_portstore_shape" | "per_atom_cycle_budget" | "enum_alias_membership" | "atom_type_consistency" | "binds_no_substruct_deref"
--- @alias CheckName string -- "transfer_hazards" | "control_transfer_delay_slot_use" | "mac_yield_uniformity" | "yield_load_tail_pairing" | "abi_handoff" | "gpu_portstore_shape" | "per_atom_cycle_budget" | "enum_alias_membership" | "atom_type_consistency" | "binds_no_substruct_deref"
--- @class AtomBody
--- @field line integer -- source line of the atom declaration
@@ -277,7 +277,10 @@ local function classify_tokens(tokens)
if ident == "nop" then nop_words = 1
elseif ident == "nop2" then nop_words = 2 end
local is_yield = ident == "mac_yield"
-- `mac_yield_tail` is the canonical end-of-atom terminator when paired with `mac_yield_load`
-- in a preceding branch's BD-slot. It runs `addiu_self R_TapePtr; jr R_AtomJmp; nop` — the
-- "tail" half of the lego split. Treat it as a yield for the `mac_yield_uniformity` check.
local is_yield = ident == "mac_yield" or ident == "mac_yield_tail"
local is_atom_label = false
local label_name = nil
local is_branch = false
@@ -1574,7 +1577,127 @@ local function check_mac_yield_uniformity(atom, pipe_ctx, findings)
end
-- ════════════════════════════════════════════════════════════════════════════
-- Check #3: Binding handoff discipline
-- Check #3: mac_yield_load / mac_yield_tail pairing (the lego split)
-- ════════════════════════════════════════════════════════════════════════════
--- The lego split — `mac_yield_load()` in a branch BD-slot + `mac_yield_tail()` at the branch's target
--- label — must be used as a pair. Otherwise `R_AtomJmp` is not loaded for the tail's `jr R_AtomJmp`,
--- and the tape runtime would jump to garbage.
---
--- Rules:
--- 1. Every `mac_yield_load()` must be in a branch BD-slot (the immediately preceding token must be a branch).
--- 2. Every `mac_yield_tail()` must be the first instruction after an `atom_label()`, AND
--- at least one branch targeting that label must have `mac_yield_load()` in its BD-slot.
--- 3. `mac_yield_tail()` as the atom-end terminator (last token) is a WARNING, not an error
--- (the safe default for atom-endings is `mac_yield()` which re-loads `R_AtomJmp`).
---
--- Per-atom. Runtime-helper atoms (`debug_skip`) are exempt.
--- Takes `(atom, pipe_ctx, findings)`; `pipe_ctx` is unused.
local function check_yield_load_tail_pairing(atom, _pipe_ctx, findings)
if atom.kind ~= "atom" then return end
if is_runtime_helper(atom) then return end
local tokens = atom.paths.tokens
local line_in_body = atom.paths.line_in_body
local tc = atom.paths.tok_class
local n = #tokens
local function line_for(idx)
return atom.line + line_in_body[tokens[idx].rel]
end
-- ── Rule 1: every `mac_yield_load()` must be in a branch BD-slot.
for tok_idx = 1, n do
local c = tc[tok_idx]
if c.ident == "mac_yield_load" then
if tok_idx < 2 or not tc[tok_idx - 1].is_branch then
local prev_ident = (tok_idx >= 2) and (tc[tok_idx - 1].ident or "?") or "<none>"
findings[#findings + 1] = {
atom = atom.name,
line = tok_idx >= 2 and line_for(tok_idx) or atom.line,
check = "yield_load_tail_pairing",
kind = "error",
msg = string.format(
"%s at line %d has `mac_yield_load()` at word %d but the previous token is `%s`, not a branch — `mac_yield_load()` must fill a branch BD-slot."
, atom.name, tok_idx >= 2 and line_for(tok_idx) or atom.line, tok_idx, prev_ident),
}
end
end
end
-- ── Rule 2: every `mac_yield_tail()` must be at a labeled target whose branch BD-slot is `mac_yield_load()`.
for tok_idx = 1, n do
local c = tc[tok_idx]
if c.ident ~= "mac_yield_tail" then goto continue end
-- The immediately preceding token must be an `atom_label()` (no instructions between them).
local prev_idx = tok_idx - 1
if prev_idx < 1 or not tc[prev_idx].is_atom_label then
if tok_idx == n then
-- Atom-ending case: last token is `mac_yield_tail()` without a preceding label. WARNING.
findings[#findings + 1] = {
atom = atom.name,
line = line_for(tok_idx),
check = "yield_load_tail_pairing",
kind = "warning",
msg = string.format(
"%s at line %d has `mac_yield_tail()` as the atom-end terminator. The safe default for atom-endings is `mac_yield()` (which re-loads R_AtomJmp). The split is for BD-slot fill, not atom-endings."
, atom.name, line_for(tok_idx)),
}
else
findings[#findings + 1] = {
atom = atom.name,
line = line_for(tok_idx),
check = "yield_load_tail_pairing",
kind = "error",
msg = string.format(
"%s at line %d has `mac_yield_tail()` at word %d but it's not the first instruction after an `atom_label()` — `mac_yield_tail()` must be the first token of its target label's body."
, atom.name, line_for(tok_idx), tok_idx),
}
end
goto continue
end
local label_name = tc[prev_idx].label_name
-- Find at least one branch targeting `label_name` whose BD-slot is `mac_yield_load()`.
local found_pairing = false
for branch_idx = 1, n do
local bt = tc[branch_idx]
if bt.is_branch and bt.branch_label == label_name then
local bd_idx = branch_idx + 1
local bd_tc = bd_idx <= n and tc[bd_idx] or nil
if bd_tc and bd_tc.ident == "mac_yield_load" then
found_pairing = true
else
findings[#findings + 1] = {
atom = atom.name,
line = line_for(branch_idx),
check = "yield_load_tail_pairing",
kind = "error",
msg = string.format(
"%s at line %d has `mac_yield_tail()` at label `%s` (word %d) but the branch targeting it (at word %d) has BD-slot `%s` instead of `mac_yield_load()`."
, atom.name, line_for(branch_idx), label_name, tok_idx, branch_idx, bd_tc and bd_tc.ident or "?"),
}
end
end
end
if not found_pairing then
findings[#findings + 1] = {
atom = atom.name,
line = line_for(tok_idx),
check = "yield_load_tail_pairing",
kind = "error",
msg = string.format(
"%s at line %d has `mac_yield_tail()` at label `%s` but no branch in the body targets this label with `mac_yield_load()` in its BD-slot — R_AtomJmp would not be loaded."
, atom.name, line_for(tok_idx), label_name),
}
end
::continue::
end
end
-- ════════════════════════════════════════════════════════════════════════════
-- Check #4: Binding handoff discipline
-- ════════════════════════════════════════════════════════════════════════════
--- For every atom with `atom_bind(Binds_X)`, verify the atom body reads every field of `Binds_X` from R_TapePtr (in any order)
@@ -2178,6 +2301,7 @@ local CHECK_RULES = {
{ name = "control_transfer_delay_slot_use",per_atom = check_control_transfer_delay_slot_use},
{ name = "load_delay_violation", per_atom = check_load_delay_slots },
{ name = "mac_yield_uniformity", per_atom = check_mac_yield_uniformity },
{ name = "yield_load_tail_pairing", per_atom = check_yield_load_tail_pairing },
{ name = "abi_handoff", per_atom = check_abi_handoff },
{ name = "gpu_portstore_shape", per_atom = check_gpu_portstore_shape },
{ name = "per_atom_cycle_budget", per_atom = check_per_atom_cycle_budget },