Hojun-Cho/ww
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

w6c: tagged GLOBAL reassign emits the store

Browse Source 
cstage silently dropped the store on reassigning a module-global
tagged union; mirror the landed wwstage emission (tag+payload to
g(SB) via the widener). Closes the cs half of the F8 #263 pair; the
repro row flips to cs==ww==correct. Task #41.
This commit is contained in:
Hojun-Cho
2026-06-12 22:31:09 +09:00
parent ef7c0c1675
commit 5ff5f4b4fe
2 changed files with 37 additions and 26 deletions
Download Patch File Download Diff File Expand all files Collapse all files

22
cmd/w6c/cgen.c
View File

@@ -6909,7 +6909,27 @@ cgexpr(Cg *c, Node *n, Local *locals)
if (!rhs_sret_call) { if (!rhs_sret_call) {
int off = localfind(locals, int off = localfind(locals,
n->lhs->str); n->lhs->str);
if (off == 0) break; if (off == 0) {
/* #41 (#263): a module-global
* tagged ident has no BP slot —
* LEAQ g(SB),BX then store
* tag+payload off BX (mirror the
* global-struct-field tagged arm
* above + the local arm below).
* Pre-fix this break dropped the
* store entirely; ww half landed
* in F8-c5. */
if (let_islet(n->lhs->str)) {
ins2(c, A_LEAQ,
masym(c, n->lhs->str),
areg(D_BX));
cg_widen_tagged_store(c,
&locals, lu, n->rhs,
D_BX, 0,
(int)lu->size);
}
break;
}
cg_widen_tagged_store(c, &locals, lu, cg_widen_tagged_store(c, &locals, lu,
n->rhs, D_BP, off, (int)lu->size); n->rhs, D_BP, off, (int)lu->size);
break; break;

41
test/wcc/989_globtagreassign_run.c
View File

@@ -3,29 +3,20 @@
* module-GLOBAL tagged-union ident (`g = expr`) must store the new tag and * module-GLOBAL tagged-union ident (`g = expr`) must store the new tag and
* payload, not clobber only one word. * payload, not clobber only one word.
* *
* THE BUG (cat-A silent miscompile, #263 BOTH-WRONG): cgenexpr.ww cgassign's * THE BUG (cat-A silent miscompile, #263 BOTH-WRONG, now CLOSED both stages):
* tagged-union reassignment arm delegated to cgwidentaggedstore ONLY for a * cgassign's tagged-union reassignment arm delegated to the widener ONLY for a
* LOCAL ident (localfindnode != nil). A module-global tagged ident (lc==nil) * LOCAL ident. A module-global tagged ident had no arm and fell through to the
* had no arm and fell through to the generic scalar store, which wrote one * generic scalar store (wwstage clobbered the tag word; cstage dropped the
* word into the tag slot and left the payload stale. cstage is ALSO wrong: * store entirely). The ww half landed in F8-c5; the cstage half (LEAQ g(SB),BX
* it drops the store entirely (the new value never reaches g) — so the repro * then cg_widen_tagged_store off BX) landed in ww-core TASK #41 — both stages
* is cs≠ww residual until the cstage half lands (ww-core TASK #41). * now store the full box and the .s is byte-identical.
* *
* THE WWSTAGE FIX (ww-runtime-correct): add the lc==nil arm — LEAQ g(SB),BX * Rows (cs==ww after the cstage half landed):
* then cgwidentaggedstore stores tag+payload off BX (mirrors the local arm * row | shape | exit
* and the global-struct-field tagged arm). ww now stores the full box. * ----------------+----------------------------------------+-----
* cstage stays wrong → the rows assert ww-correct AND pin cstage's * reassign_i64 | g:(i64|void)=0; g=7; match i64 | 7
* documented-wrong value (store dropped → g keeps its init), so the residual * reassign_str | g:(str|i64)=0; g="hello"; match str→len | 5
* is never misread as a regression. * reassign_union | g:(i64|bool)=0; g=5; match i64 | 5
*
* Rows (per-driver expected — want_cs / want_ww):
* row | shape | cs | ww
* ----------------+----------------------------------------+----+----
* reassign_i64 | g:(i64|void)=0; g=7; match i64 | 0 | 7
* reassign_str | g:(str|i64)=0; g="hello"; match str→len | 88 | 5
* reassign_union | g:(i64|bool)=0; g=5; match i64 | 0 | 5
* (cstage drops the store → g keeps its init → the i64/void/i64-tag arm;
* #41 closes the cs side, at which point these become cs==ww.)
*/ */
#include <stdio.h> #include <stdio.h>
#include <stdlib.h> #include <stdlib.h>
@@ -61,7 +52,7 @@ static const struct row rows[] = {
" case void => return 99;\n" " case void => return 99;\n"
" };\n" " };\n"
"};\n", "};\n",
0, 7 }, 7, 7 },
{ "reassign_str", { "reassign_str",
"package main;\n" "package main;\n"
@@ -73,7 +64,7 @@ static const struct row rows[] = {
" case i64 => return 88;\n" " case i64 => return 88;\n"
" };\n" " };\n"
"};\n", "};\n",
88, 5 }, 5, 5 },
{ "reassign_union", { "reassign_union",
"package main;\n" "package main;\n"
@@ -85,7 +76,7 @@ static const struct row rows[] = {
" case bool => return 77;\n" " case bool => return 77;\n"
" };\n" " };\n"
"};\n", "};\n",
0, 5 }, 5, 5 },
}; };
/* run_build — build+run `src` via `driver`; returns the binary's exit /* run_build — build+run `src` via `driver`; returns the binary's exit