ww/test/wcc/739_chained_index.c

/*
 * 739_chained_index — sentinel for #24. Pins wwstage's cgindex to
 * compute the element size of the outer N_INDEX in `arr[i][k]` from
 * the value-type of the inner N_INDEX, instead of defaulting to 8.
 *
 * Pre-fix wwstage cgindex (selfhost/cmd/wcc/cgenexpr.ww) only
 * walked `base.kind == N_IDENT` and `base.kind == N_DOT` for the
 * esz/signed_elem dispatch. When base was the inner N_INDEX of a
 * chained `names[i][k]` shape (names: **u8), esz stayed at the
 * default 8 and the load fell through to MOVQ — an 8-byte load over
 * a 1-byte u8 element, plus a stray `MOVQ $8, CX; IMULQ CX, AX` on
 * the outer index that cstage doesn't emit.
 *
 * Cstage walks `n->lhs->type` directly (cmd/w6c/cgen.c idx_eff +
 * N_INDEX, ~line 6011) — the typed AST already says the post-inner-
 * index value is *u8, so eff->sub->size = 1 lands naturally. Wwstage
 * needed the mirror via indexvaluetnode.
 *
 * Class A wwstage cgen UNDER. Surfaced first time the codebase
 * exercised the **T[i][k] shape — through the dir-enum work in
 * selfhost/cmd/ww/main.ww `expanddir` (task #22, predecessor commit
 * 9e0816e). Workaround there split `names[i][k]` into `let nm: *u8 =
 * names[i]; nm[k]` to route through the bare-pointer index path.
 *
 * Sentinel per row: in the `probe` body, assert the final element
 * load uses the expected narrow MOV mnemonic, the outer-index scale
 * is absent (esz=1) or matches `MOVQ $<esz>, CX`, and the cstage
 * vs wwstage asm is byte-identical.
 */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/wait.h>

static int
runwait(const char *cmd)
{
	int rc = system(cmd);
	if (rc == -1) return -1;
	if (WIFEXITED(rc)) return WEXITSTATUS(rc);
	return -1;
}

/* `loadmov` = expected mnemonic for the trailing `<MOV> (AX), AX`
 * (or similar) load at the outer index. `outerscale` = expected esz
 * for the outer index (1 → no IMULQ; 4 → `MOVQ $4, CX; IMULQ`). */
struct row {
	const char *label;
	const char *src;
	const char *loadmov;
	int outerscale;
};

static const struct row rows[] = {
	/* The load-bearing case: **u8 chained-index that the dir-enum
	 * workaround in selfhost/cmd/ww/main.ww `expanddir` had to dodge. */
	{ "chained_u8",
	  "fn probe(names: **u8) u8 = {\n"
	  "    let i: i32 = 0;\n"
	  "    let k: u64 = 0u64;\n"
	  "    return names[i][k];\n"
	  "};\n"
	  "export fn main() i32 = { return 0; };\n",
	  "MOVZBQ", 1 },
	/* **i32 — 4-byte signed-narrow load on the outer index, IMULQ $4
	 * for the outer scaling, IMULQ $8 for the inner *i32 stride. */
	{ "chained_i32",
	  "fn probe(mat: **i32) i32 = {\n"
	  "    let i: i32 = 0;\n"
	  "    let k: u64 = 0u64;\n"
	  "    return mat[i][k];\n"
	  "};\n"
	  "export fn main() i32 = { return 0; };\n",
	  "MOVSXD", 4 },
};

static int
slurp(const char *path, char *buf, size_t cap)
{
	FILE *f = fopen(path, "rb");
	if (!f) return -1;
	size_t n = fread(buf, 1, cap - 1, f);
	fclose(f);
	buf[n] = '\0';
	return (int)n;
}

static int
emit_s(const char *w6c, const struct row *r, int i, char *out_s, size_t cap)
{
	char src[96], cmd[1024];
	snprintf(src, sizeof src, "/tmp/chidx_%d_%d.ww", getpid(), i);
	snprintf(out_s, cap, "/tmp/chidx_%d_%d_%s.s",
	    getpid(), i, w6c[strlen(w6c) - 1] == 'w' ? "ww" : "c");

	FILE *f = fopen(src, "wb");
	if (!f) return -1;
	fputs(r->src, f);
	fclose(f);

	snprintf(cmd, sizeof cmd, "%s -o %s %s 2>/dev/null", w6c, out_s, src);
	int rc = runwait(cmd);
	unlink(src);
	return rc;
}

/* Inside `TEXT probe`, the final element load must use the
 * expected narrow MOV mnemonic on `(AX), AX`. Pre-fix wwstage
 * emitted plain `MOVQ (AX), AX`. */
static int
check_loadmov(const char *spath, const struct row *r, const char *stage)
{
	char buf[1 << 14];
	if (slurp(spath, buf, sizeof buf) < 0) {
		fprintf(stderr, "row[%s][%s]: cannot read %s\n",
		    r->label, stage, spath);
		return -1;
	}
	const char *fn = strstr(buf, "TEXT probe");
	if (!fn) {
		fprintf(stderr,
		    "row[%s][%s]: no TEXT probe in %s\n",
		    r->label, stage, spath);
		return -1;
	}
	const char *ret = strstr(fn, "\tRET\n");
	char needle[64];
	snprintf(needle, sizeof needle, "\t%s\t(AX), AX\n", r->loadmov);
	const char *m = strstr(fn, needle);
	if (!m || (ret && m > ret)) {
		fprintf(stderr,
		    "row[%s][%s]: expected `%s (AX), AX` in probe body\n",
		    r->label, stage, r->loadmov);
		return -1;
	}
	return 0;
}

/* Negative: pre-fix wwstage emitted a stray `MOVQ $8, CX; IMULQ CX,
 * AX` for the OUTER index of a **u8 chain (because esz defaulted to
 * 8). For a u8 outer the correct emit is no scaling at all. Assert
 * the count of `MOVQ $8, CX` followed by `IMULQ CX, AX` pairs in the
 * probe body matches the expected inner-only count (= 1 for **T;
 * the inner index of *T elements always scales by 8). */
static int
check_inner_scale_only(const char *spath, const struct row *r,
    const char *stage)
{
	char buf[1 << 14];
	if (slurp(spath, buf, sizeof buf) < 0) return -1;
	const char *fn = strstr(buf, "TEXT probe");
	if (!fn) return -1;
	const char *ret = strstr(fn, "\tRET\n");
	if (!ret) ret = fn + strlen(fn);

	int n_inner = 0, n_outer = 0;
	const char *p = fn;
	while (p < ret) {
		const char *inner = strstr(p, "\tMOVQ\t$8, CX\n");
		if (!inner || inner >= ret) break;
		const char *next = strstr(inner, "\tIMULQ\tCX, AX\n");
		if (!next || next >= ret) { p = inner + 1; continue; }
		n_inner++;
		p = next + 1;
	}
	if (r->outerscale == 1) {
		/* Pre-fix wwstage had two `MOVQ $8, CX; IMULQ` pairs (one
		 * for the outer index that shouldn't scale at all). Cstage
		 * has one — for the inner *u8 stride only. */
		if (n_inner != 1) {
			fprintf(stderr,
			    "row[%s][%s]: expected exactly 1 inner `MOVQ $8, "
			    "CX; IMULQ CX, AX` pair (no outer scaling for u8), "
			    "got %d\n", r->label, stage, n_inner);
			return -1;
		}
	} else {
		/* For **i32: inner stride is 8 (sizeof *i32), outer scale is
		 * 4 (sizeof i32). Assert one `MOVQ $8, CX` for inner and one
		 * `MOVQ $4, CX` for outer. */
		p = fn;
		while (p < ret) {
			const char *outer = strstr(p, "\tMOVQ\t$4, CX\n");
			if (!outer || outer >= ret) break;
			const char *next = strstr(outer, "\tIMULQ\tCX, AX\n");
			if (!next || next >= ret) { p = outer + 1; continue; }
			n_outer++;
			p = next + 1;
		}
		if (n_inner != 1 || n_outer != 1) {
			fprintf(stderr,
			    "row[%s][%s]: expected 1 inner `MOVQ $8` + 1 outer "
			    "`MOVQ $4` IMULQ pair, got inner=%d outer=%d\n",
			    r->label, stage, n_inner, n_outer);
			return -1;
		}
	}
	return 0;
}

int
main(void)
{
	const char *bin = getenv("BIN");
	if (!bin) bin = "out/bin";
	char absbin[512];
	if (bin[0] != '/') {
		char cwd[256];
		if (getcwd(cwd, sizeof cwd) == NULL) return 1;
		snprintf(absbin, sizeof absbin, "%s/%s", cwd, bin);
		bin = absbin;
	}

	char w6c[640], w6c_ww[640];
	snprintf(w6c, sizeof w6c, "%s/w6c", bin);
	snprintf(w6c_ww, sizeof w6c_ww, "%s/w6c_ww", bin);

	int have_ww = (access(w6c_ww, X_OK) == 0);
	int n = (int)(sizeof rows / sizeof rows[0]);
	int total = 0, fail = 0;

	for (int i = 0; i < n; i++) {
		char cs_path[128], ws_path[128];

		if (emit_s(w6c, &rows[i], i, cs_path, sizeof cs_path) != 0) {
			fprintf(stderr,
			    "chained_index[cstage][%s]: w6c failed\n",
			    rows[i].label);
			fail++; total++; continue;
		}
		total += 2;
		if (check_loadmov(cs_path, &rows[i], "cstage") != 0) fail++;
		if (check_inner_scale_only(cs_path, &rows[i], "cstage") != 0)
			fail++;

		if (!have_ww) { unlink(cs_path); continue; }

		if (emit_s(w6c_ww, &rows[i], i, ws_path, sizeof ws_path) != 0) {
			fprintf(stderr,
			    "chained_index[wwstage][%s]: w6c_ww failed\n",
			    rows[i].label);
			fail++; total++;
			unlink(cs_path); continue;
		}
		total += 2;
		if (check_loadmov(ws_path, &rows[i], "wwstage") != 0) fail++;
		if (check_inner_scale_only(ws_path, &rows[i], "wwstage") != 0)
			fail++;

		total++;
		char cmd[512];
		snprintf(cmd, sizeof cmd, "cmp -s %s %s", cs_path, ws_path);
		if (runwait(cmd) != 0) {
			fprintf(stderr,
			    "chained_index[%s]: cstage vs wwstage asm differs\n",
			    rows[i].label);
			fail++;
		}

		unlink(cs_path); unlink(ws_path);
	}

	if (fail) {
		fprintf(stderr,
		    "chained_index: %d/%d fixtures failed\n", fail, total);
		return 1;
	}
	printf("chained_index: %d/%d ok\n", total, total);
	return 0;
}