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cgen: key the tagged-widen struct copy on natural size, not slot size

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cgwidentaggedstorebp's struct-ident arms (local and module-global)
counted copy bytes from structinfo.totsize, the round-8 slot width, so
a struct whose natural size is not a multiple of 8 took the MOVQ word
loop and copied the source slot's dirty pad bytes over the zero-fill
the arm itself just established; the width-true tail emitter beneath
was dead code. cstage keys the same copy on su->size. Route both arms
through copysrcnatsize (the stamped-tinfo natural size, #71).
Graduates r71_tagged_return_scratch_mixed.
This commit is contained in:
Hojun-Cho
2026-08-07 23:51:07 +09:00
parent 4559b52950
commit c717facf78
2 changed files with 8 additions and 4 deletions
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9
selfhost/cmd/wcc/cgenutil.ww
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@@ -4842,7 +4842,9 @@ fn cgwidentaggedstorebp(c: *cgen, dst: *syntax.tinfo, src: *syntax.node, slot_of
let gtag: i32 = taggedvariantindext(c, dt, src);
if (gtag < 0) { gtag = 0; };
if (aggargsrcaddr(c, src, "SI")) {
let gtot: i32 = gsi.totsize;
// Natural size, not slot-padded (see the
// local-ident twin below; cstage su->size).
let gtot: i32 = copysrcnatsize(c, src);
let gk: i32 = 0;
for (gk + 8 <= gtot) {
emitline("\tMOVQ\t");
@@ -4913,7 +4915,10 @@ fn cgwidentaggedstorebp(c: *cgen, dst: *syntax.tinfo, src: *syntax.node, slot_of
let lc: *local = localfindnode(c, src.str);
let soff: i32 = 0;
if (lc != nil) { soff = lc.off; };
let stotal: i32 = si.totsize;
// Copy the NATURAL size (cstage su->size): the slot-
// padded totsize would MOVQ the source slot's dirty
// pad bytes over the zero-fill just established.
let stotal: i32 = copysrcnatsize(c, src);
let ki: i32 = 0;
for (ki + 8 <= stotal) {
emitline("\tMOVQ\t");