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selfhost+cstage+test: graduate frame growth to first-use+fail-loud (#15)

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Subsumes #36. Drop wwstage scanlocals pre-pass; both stages converge on
first-use+fail-loud frame growth, rule-10 polarity DOWN to leaner side.
#36's surfaces (frame-total divergence on match-arm case-let; sibling
offset divergence in variadic+iter+match-prev compositions) close
naturally — running-max c.frame includes every first-use binding.

selfhost/cmd/wcc: add atlocals persistent @-prefix registry surviving
cgblock save/restore; add cgoutbuf/cgoutmode/cgout_enable/disable/flush
for deferred prologue (emit body to buffer, finalise c.frame, then
TEXT/SUBQ + flush); localadd @-prefix dedups against atlocals +
fail-louds on size-grow (rule 7 — no silent truncate); cgreturn-tagged
routes through @retscr (was colliding with @tagscr on arg-widen sizes);
variadic gather esz uses raw primsize (rune->4) not slotsize (rune->8)
— matches cstage and fixes the #36 sibling runtime miscompile in
non-leaf variadic+iter+match-prev callees.

cmd/w6c/cgen.c: drop the over-allocation hack ("for byte-id with
wwstage scanlocals reservation") since wwstage no longer over-reserves;
add fail-loud on @sretscr size-grow; @tagscr sites pass actual slot_sz
instead of stale c.tagscrsz.

748_size_strategy_convergence: table-driven 4 rows x 2 stages
(tag_variadic_runearm, trim_iter_match_prev, variadic_gather_rune_stride,
leaf_baseline). Each exercises a #36 surface shape; 8/8 ok.

Net -1565 lines. Sister latents filed as cosmetic (cs/ws frame size
drift on multiple-variadic-call fns): labelseq drift + varargseq
stuck at 0 — both bootstrap-byte-id safe (ww2==ww3==ww4 holds since
both ww2 and ww3 are wwstage outputs).

make test 122/122; ww2==ww3==ww4 byte-id holds via 995_self_rebuild.
This commit is contained in:
Hojun-Cho
2026-05-19 02:13:58 +09:00
parent 7a278c1a2d
commit 5609d0456f
10 changed files with 1197 additions and 2469 deletions
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31
selfhost/cmd/wcc/cgenstmt.ww
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@@ -193,13 +193,19 @@ fn cgreturn(c: *cgen, n: *node) void = {
};
if (needswiden) {
let rsz: i32 = slotsize(c, c.fnret);
// Use c.tagscrsz so the first @tagscr allocation in
// the fn lands a slot sized to the *max* across all
// uses (scanlocals bumped to rsz here). Hardcoding 24
// truncated 32B-slot returns and overwrote adjacent
// locals during the pre-zero loop (#38).
let scroff: i32 = localadd(c, "@tagscr",
c.tagscrsz, nil);
// @retscr (not @tagscr) for the return materialise
// path. Cstage cmd/w6c/cgen.c cgreturn uses
// `@retscr` here and reserves the @tagscr SSoT
// for arg-widen / non-BP-base store / N_INDEX
// tagged-element write. Sharing the name in a fn
// that BOTH returns a 32B tagged AND pushes a
// smaller tagged arg fatals localadd's @-prefix
// size-grow guard (rule 7); routing returns
// through their own slot keeps each cache
// monotonic. Hardcoding 24 truncated 32B-slot
// returns and overwrote adjacent locals during
// the pre-zero loop (#38).
let scroff: i32 = localadd(c, "@retscr", rsz, nil);
emitline("\tXORQ\tAX, AX\n");
let zz: i32 = 0;
for (zz < rsz) {
@@ -299,7 +305,8 @@ fn cgreturn(c: *cgen, n: *node) void = {
// the SysV "return the pointer" discipline. Two rhs shapes
// are wired: N_IDENT (word-copy from rhs slot to *(dest))
// and N_STRUCTLIT (cgstructlitfill with mode=1 PTR_LOCAL).
if (c.sretargoff != 0) {
let sretargoff: i32 = localfind(c, "@sretarg");
if (sretargoff != 0) {
let scs: i32 = sretretsize(c, c.fnret);
if (scs > 0) {
// sret return-forwarding (task #9 follow-up to
@@ -317,7 +324,7 @@ fn cgreturn(c: *cgen, n: *node) void = {
c.sretforward = 1;
cgexpr(c, rhs);
emitline("\tMOVQ\t");
emitoff(c.sretargoff: i64);
emitoff(sretargoff: i64);
emitline("(BP), AX\n");
emitline("\tMOVQ\tBP, SP\n");
emitline("\tPOPQ\tBP\n");
@@ -346,14 +353,14 @@ fn cgreturn(c: *cgen, n: *node) void = {
// each field store. disp = 0 because
// the dest pointer IS the struct base.
cgstructlitfill(c, sret_si, rhs,
1, c.sretargoff, emptys,
1, sretargoff, emptys,
0, scs);
};
} else {
let rl: *local = localfindnode(c, rhs.str);
if (rl != nil) {
emitline("\tMOVQ\t");
emitoff(c.sretargoff: i64);
emitoff(sretargoff: i64);
emitline("(BP), BX\n");
let k: i32 = 0;
for (k + 8 <= scs) {
@@ -387,7 +394,7 @@ fn cgreturn(c: *cgen, n: *node) void = {
};
// sret return: RAX = dest pointer.
emitline("\tMOVQ\t");
emitoff(c.sretargoff: i64);
emitoff(sretargoff: i64);
emitline("(BP), AX\n");
emitline("\tMOVQ\tBP, SP\n");
emitline("\tPOPQ\tBP\n");