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ww/cmd/w6c/txt.c
Hojun-Cho 13441c5e2e w6a, wcc: add A_SARQ for signed arithmetic right-shift (#136) 
Add SAR/SARQ to both assemblers' opcode tables (cstage cmd/w6a +
wwstage selfhost/cmd/w6a) — REX.W + D3 /7, parallel to SHR's D3 /5.
Encoding is the unary-on-CL form (SAR r/m64, CL), the only variant
the cgen emits today. cstage cgen + wwstage cgen sweep all 12 SHRQ
emission sites (6 per stage) so signed RSHIFT and signed RSHIFTEQ
route through SARQ (arithmetic, sign-extends MSB) instead of SHRQ
(logical, zero-fill). Pre-fix `let i: i32 = -200; i >>= 2;`
produced 0x3FFFFFCE (1073741774) instead of -50; cs==ww held because
BOTH stages emitted SHRQ, so the 990-997 byte-id gates were
gate-blind to this silent miscompile.

Sites covered (per stage 6, same shape in both):
  - plain TK_RSHIFT (cgbin / N_BIN ordered binop) — derives unsignd
    from operand types via type_isunsigned / nodeisunsigned, picks
    SHRQ vs SARQ at emit
  - chained-ptr-field compound RSHIFTEQ (cgen.c:3281-3317 area)
  - N_INDEX-lhs compound RSHIFTEQ (#133-expanded N_INDEX site)
  - deref-target compound RSHIFTEQ
  - top-level let compound RSHIFTEQ
  - IDENT-local compound RSHIFTEQ
All sites reuse the in-scope unsignd variable from the surrounding
SLASHEQ block (or derive one locally when not available). LSHIFTEQ
unchanged — SHL == SAL at the encoder, no signedness dispatch needed.

912_sar_shr_run: 5 rows. i32_neg_rshifteq (lead's repro, was wrong
1073741774 → now -50), i64_neg_rshifteq (wider type), i32_pos_
rshifteq (positive control, SARQ ≡ SHRQ on positives, no regression),
u32_rshifteq (unsigned control, still SHRQ), i32_neg_rshift_binop
(plain >> not compound, cgbin TK_RSHIFT site). Exit codes use small
absolute values with u8 wrap (-50 = 206) per Unix 8-bit exit.

Bootstrap-NEUTRAL — `grep -rE '>>=|>>\b'` in lib/+selfhost/ (excl.
combined.ww) returned zero callers of signed RSHIFT today; the only
asm shifts are on previously-broken paths. 990-997 + combined_ww_
fresh stay green. Closes the silent-misbehavior class on signed
right-shift across all 12 cgen emission paths in one fold per
rule-11. Foundation for Eisel-Lemire (strconv fold-4) big-int signed
shifts.
2026-05-27 01:29:24 +09:00

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/*
* txt.c — print a Prog list as Plan 9-flavoured amd64 asm text.
*
* Format we emit (and that w6a expects):
* TEXT name<framesize>
* MOVQ $1, AX
* MOVQ AX, name(SB) ; extern symbol
* MOVQ off(BP), AX ; local
* CMPQ AX, $0
* JE label
* RET
* label:
*
* Operand order is Plan 9-ish: source first, dest second. (Same as
* AT&T; the convention diverges from Plan 9 only on a few items we
* don't yet emit.)
*/
#include "gc.h"
#include <string.h>
const char *
anames(int op)
{
switch (op) {
case A_NOP: return "NOP";
case A_TEXT: return "TEXT";
case A_DATA: return "DATA";
case A_DATAW: return "DATAW";
case A_DATAR: return "DATAR";
case A_GLOBL: return "GLOBL";
case A_END: return "END";
case A_MOVQ: return "MOVQ";
case A_MOVL: return "MOVL";
case A_MOVW: return "MOVW";
case A_MOVB: return "MOVB";
case A_MOVZBQ: return "MOVZBQ";
case A_MOVZWQ: return "MOVZWQ";
case A_MOVSXD: return "MOVSXD";
case A_MOVSWQ: return "MOVSWQ";
case A_MOVSBQ: return "MOVSBQ";
case A_MOVSD: return "MOVSD";
case A_ADDSD: return "ADDSD";
case A_SUBSD: return "SUBSD";
case A_MULSD: return "MULSD";
case A_DIVSD: return "DIVSD";
case A_UCOMISD: return "UCOMISD";
case A_CVTTSD2SI: return "CVTTSD2SI";
case A_CVTSI2SD:return "CVTSI2SD";
case A_MOVSS: return "MOVSS";
case A_ADDSS: return "ADDSS";
case A_SUBSS: return "SUBSS";
case A_MULSS: return "MULSS";
case A_DIVSS: return "DIVSS";
case A_UCOMISS: return "UCOMISS";
case A_CVTTSS2SI: return "CVTTSS2SI";
case A_CVTSI2SS:return "CVTSI2SS";
case A_CVTSD2SS:return "CVTSD2SS";
case A_CVTSS2SD:return "CVTSS2SD";
case A_ADDQ: return "ADDQ";
case A_SUBQ: return "SUBQ";
case A_IMULQ: return "IMULQ";
case A_IDIVQ: return "IDIVQ";
case A_DIVQ: return "DIVQ";
case A_CQO: return "CQO";
case A_NEGQ: return "NEGQ";
case A_NOTQ: return "NOTQ";
case A_ANDQ: return "ANDQ";
case A_ORQ: return "ORQ";
case A_XORQ: return "XORQ";
case A_SHLQ: return "SHLQ";
case A_SHRQ: return "SHRQ";
case A_SARQ: return "SARQ";
case A_CMPQ: return "CMPQ";
case A_PUSHQ: return "PUSHQ";
case A_POPQ: return "POPQ";
case A_LEAQ: return "LEAQ";
case A_CALL: return "CALL";
case A_RET: return "RET";
case A_JMP: return "JMP";
case A_JE: return "JE";
case A_JNE: return "JNE";
case A_JL: return "JL";
case A_JLE: return "JLE";
case A_JG: return "JG";
case A_JGE: return "JGE";
case A_JB: return "JB";
case A_JBE: return "JBE";
case A_JA: return "JA";
case A_JAE: return "JAE";
case A_JZ: return "JZ";
case A_JNZ: return "JNZ";
case A_JP: return "JP";
case A_SYSCALL: return "SYSCALL";
}
return "??";
}
const char *
rnames(int r)
{
switch (r) {
case D_AX: return "AX"; case D_CX: return "CX";
case D_DX: return "DX"; case D_BX: return "BX";
case D_SP: return "SP"; case D_BP: return "BP";
case D_SI: return "SI"; case D_DI: return "DI";
case D_R8: return "R8"; case D_R9: return "R9";
case D_R10: return "R10"; case D_R11: return "R11";
case D_R12: return "R12"; case D_R13: return "R13";
case D_R14: return "R14"; case D_R15: return "R15";
case D_X0: return "X0"; case D_X1: return "X1";
case D_X2: return "X2"; case D_X3: return "X3";
case D_X4: return "X4"; case D_X5: return "X5";
case D_X6: return "X6"; case D_X7: return "X7";
case D_X8: return "X8"; case D_X9: return "X9";
case D_X10: return "X10"; case D_X11: return "X11";
case D_X12: return "X12"; case D_X13: return "X13";
case D_X14: return "X14"; case D_X15: return "X15";
case D_PSP: return "SP"; case D_PFP: return "FP"; case D_PSB: return "SB";
}
return "?";
}
static void
prAdr(FILE *f, Adr a)
{
switch (a.type) {
case D_NONE: fputs("?", f); break;
case D_CONST:
fprintf(f, "$%lld", a.offset);
break;
case D_INDIR:
if (a.offset)
fprintf(f, "%lld(%s)", a.offset, rnames(a.reg));
else
fprintf(f, "(%s)", rnames(a.reg));
break;
case D_BRANCH:
fputs(a.sym ? a.sym : "?", f);
break;
case D_EXTERN:
fprintf(f, "%s(SB)", a.sym ? a.sym : "?");
break;
default:
fputs(rnames(a.type), f);
}
}
void
txt_emit(FILE *f, Prog *head)
{
for (Prog *p = head; p; p = p->link) {
if (p->label) {
fprintf(f, "%s:\n", p->label);
if (p->as == A_NOP) continue;
}
switch (p->as) {
case A_NOP:
break;
case A_TEXT:
fprintf(f, "TEXT %s,$%lld\n",
p->to.sym ? p->to.sym : "?",
p->from.offset);
break;
case A_RET:
fputs("\tRET\n", f);
break;
case A_SYSCALL:
fputs("\tSYSCALL\n", f);
break;
case A_CQO:
fputs("\tCQO\n", f);
break;
case A_NEGQ:
case A_NOTQ:
case A_PUSHQ:
case A_POPQ:
case A_IDIVQ:
case A_DIVQ:
fprintf(f, "\t%s\t", anames(p->as));
prAdr(f, p->to);
fputc('\n', f);
break;
case A_CALL:
case A_JMP:
case A_JE: case A_JNE:
case A_JL: case A_JLE: case A_JG: case A_JGE:
case A_JB: case A_JBE: case A_JA: case A_JAE:
case A_JZ: case A_JNZ:
case A_JP:
fprintf(f, "\t%s\t", anames(p->as));
prAdr(f, p->to);
fputc('\n', f);
break;
default:
fprintf(f, "\t%s\t", anames(p->as));
prAdr(f, p->from);
fputs(", ", f);
prAdr(f, p->to);
fputc('\n', f);
}
}
}
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