1/*
2** NARROW: Narrowing of numbers to integers (double to int32_t).
3** STRIPOV: Stripping of overflow checks.
4** Copyright (C) 2005-2021 Mike Pall. See Copyright Notice in luajit.h
5*/
6
7#define lj_opt_narrow_c
8#define LUA_CORE
9
10#include "lj_obj.h"
11
12#if LJ_HASJIT
13
14#include "lj_bc.h"
15#include "lj_ir.h"
16#include "lj_jit.h"
17#include "lj_iropt.h"
18#include "lj_trace.h"
19#include "lj_vm.h"
20#include "lj_strscan.h"
21
22/* Rationale for narrowing optimizations:
23**
24** Lua has only a single number type and this is a FP double by default.
25** Narrowing doubles to integers does not pay off for the interpreter on a
26** current-generation x86/x64 machine. Most FP operations need the same
27** amount of execution resources as their integer counterparts, except
28** with slightly longer latencies. Longer latencies are a non-issue for
29** the interpreter, since they are usually hidden by other overhead.
30**
31** The total CPU execution bandwidth is the sum of the bandwidth of the FP
32** and the integer units, because they execute in parallel. The FP units
33** have an equal or higher bandwidth than the integer units. Not using
34** them means losing execution bandwidth. Moving work away from them to
35** the already quite busy integer units is a losing proposition.
36**
37** The situation for JIT-compiled code is a bit different: the higher code
38** density makes the extra latencies much more visible. Tight loops expose
39** the latencies for updating the induction variables. Array indexing
40** requires narrowing conversions with high latencies and additional
41** guards (to check that the index is really an integer). And many common
42** optimizations only work on integers.
43**
44** One solution would be speculative, eager narrowing of all number loads.
45** This causes many problems, like losing -0 or the need to resolve type
46** mismatches between traces. It also effectively forces the integer type
47** to have overflow-checking semantics. This impedes many basic
48** optimizations and requires adding overflow checks to all integer
49** arithmetic operations (whereas FP arithmetics can do without).
50**
51** Always replacing an FP op with an integer op plus an overflow check is
52** counter-productive on a current-generation super-scalar CPU. Although
53** the overflow check branches are highly predictable, they will clog the
54** execution port for the branch unit and tie up reorder buffers. This is
55** turning a pure data-flow dependency into a different data-flow
56** dependency (with slightly lower latency) *plus* a control dependency.
57** In general, you don't want to do this since latencies due to data-flow
58** dependencies can be well hidden by out-of-order execution.
59**
60** A better solution is to keep all numbers as FP values and only narrow
61** when it's beneficial to do so. LuaJIT uses predictive narrowing for
62** induction variables and demand-driven narrowing for index expressions,
63** integer arguments and bit operations. Additionally it can eliminate or
64** hoist most of the resulting overflow checks. Regular arithmetic
65** computations are never narrowed to integers.
66**
67** The integer type in the IR has convenient wrap-around semantics and
68** ignores overflow. Extra operations have been added for
69** overflow-checking arithmetic (ADDOV/SUBOV) instead of an extra type.
70** Apart from reducing overall complexity of the compiler, this also
71** nicely solves the problem where you want to apply algebraic
72** simplifications to ADD, but not to ADDOV. And the x86/x64 assembler can
73** use lea instead of an add for integer ADD, but not for ADDOV (lea does
74** not affect the flags, but it helps to avoid register moves).
75**
76**
77** All of the above has to be reconsidered for architectures with slow FP
78** operations or without a hardware FPU. The dual-number mode of LuaJIT
79** addresses this issue. Arithmetic operations are performed on integers
80** as far as possible and overflow checks are added as needed.
81**
82** This implies that narrowing for integer arguments and bit operations
83** should also strip overflow checks, e.g. replace ADDOV with ADD. The
84** original overflow guards are weak and can be eliminated by DCE, if
85** there's no other use.
86**
87** A slight twist is that it's usually beneficial to use overflow-checked
88** integer arithmetics if all inputs are already integers. This is the only
89** change that affects the single-number mode, too.
90*/
91
92/* Some local macros to save typing. Undef'd at the end. */
93#define IR(ref) (&J->cur.ir[(ref)])
94#define fins (&J->fold.ins)
95
96/* Pass IR on to next optimization in chain (FOLD). */
97#define emitir(ot, a, b) (lj_ir_set(J, (ot), (a), (b)), lj_opt_fold(J))
98
99#define emitir_raw(ot, a, b) (lj_ir_set(J, (ot), (a), (b)), lj_ir_emit(J))
100
101/* -- Elimination of narrowing type conversions --------------------------- */
102
103/* Narrowing of index expressions and bit operations is demand-driven. The
104** trace recorder emits a narrowing type conversion (CONV.int.num or TOBIT)
105** in all of these cases (e.g. array indexing or string indexing). FOLD
106** already takes care of eliminating simple redundant conversions like
107** CONV.int.num(CONV.num.int(x)) ==> x.
108**
109** But the surrounding code is FP-heavy and arithmetic operations are
110** performed on FP numbers (for the single-number mode). Consider a common
111** example such as 'x=t[i+1]', with 'i' already an integer (due to induction
112** variable narrowing). The index expression would be recorded as
113** CONV.int.num(ADD(CONV.num.int(i), 1))
114** which is clearly suboptimal.
115**
116** One can do better by recursively backpropagating the narrowing type
117** conversion across FP arithmetic operations. This turns FP ops into
118** their corresponding integer counterparts. Depending on the semantics of
119** the conversion they also need to check for overflow. Currently only ADD
120** and SUB are supported.
121**
122** The above example can be rewritten as
123** ADDOV(CONV.int.num(CONV.num.int(i)), 1)
124** and then into ADDOV(i, 1) after folding of the conversions. The original
125** FP ops remain in the IR and are eliminated by DCE since all references to
126** them are gone.
127**
128** [In dual-number mode the trace recorder already emits ADDOV etc., but
129** this can be further reduced. See below.]
130**
131** Special care has to be taken to avoid narrowing across an operation
132** which is potentially operating on non-integral operands. One obvious
133** case is when an expression contains a non-integral constant, but ends
134** up as an integer index at runtime (like t[x+1.5] with x=0.5).
135**
136** Operations with two non-constant operands illustrate a similar problem
137** (like t[a+b] with a=1.5 and b=2.5). Backpropagation has to stop there,
138** unless it can be proven that either operand is integral (e.g. by CSEing
139** a previous conversion). As a not-so-obvious corollary this logic also
140** applies for a whole expression tree (e.g. t[(a+1)+(b+1)]).
141**
142** Correctness of the transformation is guaranteed by avoiding to expand
143** the tree by adding more conversions than the one we would need to emit
144** if not backpropagating. TOBIT employs a more optimistic rule, because
145** the conversion has special semantics, designed to make the life of the
146** compiler writer easier. ;-)
147**
148** Using on-the-fly backpropagation of an expression tree doesn't work
149** because it's unknown whether the transform is correct until the end.
150** This either requires IR rollback and cache invalidation for every
151** subtree or a two-pass algorithm. The former didn't work out too well,
152** so the code now combines a recursive collector with a stack-based
153** emitter.
154**
155** [A recursive backpropagation algorithm with backtracking, employing
156** skip-list lookup and round-robin caching, emitting stack operations
157** on-the-fly for a stack-based interpreter -- and all of that in a meager
158** kilobyte? Yep, compilers are a great treasure chest. Throw away your
159** textbooks and read the codebase of a compiler today!]
160**
161** There's another optimization opportunity for array indexing: it's
162** always accompanied by an array bounds-check. The outermost overflow
163** check may be delegated to the ABC operation. This works because ABC is
164** an unsigned comparison and wrap-around due to overflow creates negative
165** numbers.
166**
167** But this optimization is only valid for constants that cannot overflow
168** an int32_t into the range of valid array indexes [0..2^27+1). A check
169** for +-2^30 is safe since -2^31 - 2^30 wraps to 2^30 and 2^31-1 + 2^30
170** wraps to -2^30-1.
171**
172** It's also good enough in practice, since e.g. t[i+1] or t[i-10] are
173** quite common. So the above example finally ends up as ADD(i, 1)!
174**
175** Later on, the assembler is able to fuse the whole array reference and
176** the ADD into the memory operands of loads and other instructions. This
177** is why LuaJIT is able to generate very pretty (and fast) machine code
178** for array indexing. And that, my dear, concludes another story about
179** one of the hidden secrets of LuaJIT ...
180*/
181
182/* Maximum backpropagation depth and maximum stack size. */
183#define NARROW_MAX_BACKPROP 100
184#define NARROW_MAX_STACK 256
185
186/* The stack machine has a 32 bit instruction format: [IROpT | IRRef1]
187** The lower 16 bits hold a reference (or 0). The upper 16 bits hold
188** the IR opcode + type or one of the following special opcodes:
189*/
190enum {
191 NARROW_REF, /* Push ref. */
192 NARROW_CONV, /* Push conversion of ref. */
193 NARROW_SEXT, /* Push sign-extension of ref. */
194 NARROW_INT /* Push KINT ref. The next code holds an int32_t. */
195};
196
197typedef uint32_t NarrowIns;
198
199#define NARROWINS(op, ref) (((op) << 16) + (ref))
200#define narrow_op(ins) ((IROpT)((ins) >> 16))
201#define narrow_ref(ins) ((IRRef1)(ins))
202
203/* Context used for narrowing of type conversions. */
204typedef struct NarrowConv {
205 jit_State *J; /* JIT compiler state. */
206 NarrowIns *sp; /* Current stack pointer. */
207 NarrowIns *maxsp; /* Maximum stack pointer minus redzone. */
208 IRRef mode; /* Conversion mode (IRCONV_*). */
209 IRType t; /* Destination type: IRT_INT or IRT_I64. */
210 NarrowIns stack[NARROW_MAX_STACK]; /* Stack holding stack-machine code. */
211} NarrowConv;
212
213/* Lookup a reference in the backpropagation cache. */
214static BPropEntry *narrow_bpc_get(jit_State *J, IRRef1 key, IRRef mode)
215{
216 ptrdiff_t i;
217 for (i = 0; i < BPROP_SLOTS; i++) {
218 BPropEntry *bp = &J->bpropcache[i];
219 /* Stronger checks are ok, too. */
220 if (bp->key == key && bp->mode >= mode &&
221 ((bp->mode ^ mode) & IRCONV_MODEMASK) == 0)
222 return bp;
223 }
224 return NULL;
225}
226
227/* Add an entry to the backpropagation cache. */
228static void narrow_bpc_set(jit_State *J, IRRef1 key, IRRef1 val, IRRef mode)
229{
230 uint32_t slot = J->bpropslot;
231 BPropEntry *bp = &J->bpropcache[slot];
232 J->bpropslot = (slot + 1) & (BPROP_SLOTS-1);
233 bp->key = key;
234 bp->val = val;
235 bp->mode = mode;
236}
237
238/* Backpropagate overflow stripping. */
239static void narrow_stripov_backprop(NarrowConv *nc, IRRef ref, int depth)
240{
241 jit_State *J = nc->J;
242 IRIns *ir = IR(ref);
243 if (ir->o == IR_ADDOV || ir->o == IR_SUBOV ||
244 (ir->o == IR_MULOV && (nc->mode & IRCONV_CONVMASK) == IRCONV_ANY)) {
245 BPropEntry *bp = narrow_bpc_get(nc->J, ref, IRCONV_TOBIT);
246 if (bp) {
247 ref = bp->val;
248 } else if (++depth < NARROW_MAX_BACKPROP && nc->sp < nc->maxsp) {
249 NarrowIns *savesp = nc->sp;
250 narrow_stripov_backprop(nc, ir->op1, depth);
251 if (nc->sp < nc->maxsp) {
252 narrow_stripov_backprop(nc, ir->op2, depth);
253 if (nc->sp < nc->maxsp) {
254 *nc->sp++ = NARROWINS(IRT(ir->o - IR_ADDOV + IR_ADD, IRT_INT), ref);
255 return;
256 }
257 }
258 nc->sp = savesp; /* Path too deep, need to backtrack. */
259 }
260 }
261 *nc->sp++ = NARROWINS(NARROW_REF, ref);
262}
263
264/* Backpropagate narrowing conversion. Return number of needed conversions. */
265static int narrow_conv_backprop(NarrowConv *nc, IRRef ref, int depth)
266{
267 jit_State *J = nc->J;
268 IRIns *ir = IR(ref);
269 IRRef cref;
270
271 if (nc->sp >= nc->maxsp) return 10; /* Path too deep. */
272
273 /* Check the easy cases first. */
274 if (ir->o == IR_CONV && (ir->op2 & IRCONV_SRCMASK) == IRT_INT) {
275 if ((nc->mode & IRCONV_CONVMASK) <= IRCONV_ANY)
276 narrow_stripov_backprop(nc, ir->op1, depth+1);
277 else
278 *nc->sp++ = NARROWINS(NARROW_REF, ir->op1); /* Undo conversion. */
279 if (nc->t == IRT_I64)
280 *nc->sp++ = NARROWINS(NARROW_SEXT, 0); /* Sign-extend integer. */
281 return 0;
282 } else if (ir->o == IR_KNUM) { /* Narrow FP constant. */
283 lua_Number n = ir_knum(ir)->n;
284 if ((nc->mode & IRCONV_CONVMASK) == IRCONV_TOBIT) {
285 /* Allows a wider range of constants. */
286 int64_t k64 = (int64_t)n;
287 if (n == (lua_Number)k64) { /* Only if const doesn't lose precision. */
288 *nc->sp++ = NARROWINS(NARROW_INT, 0);
289 *nc->sp++ = (NarrowIns)k64; /* But always truncate to 32 bits. */
290 return 0;
291 }
292 } else {
293 int32_t k = lj_num2int(n);
294 /* Only if constant is a small integer. */
295 if (checki16(k) && n == (lua_Number)k) {
296 *nc->sp++ = NARROWINS(NARROW_INT, 0);
297 *nc->sp++ = (NarrowIns)k;
298 return 0;
299 }
300 }
301 return 10; /* Never narrow other FP constants (this is rare). */
302 }
303
304 /* Try to CSE the conversion. Stronger checks are ok, too. */
305 cref = J->chain[fins->o];
306 while (cref > ref) {
307 IRIns *cr = IR(cref);
308 if (cr->op1 == ref &&
309 (fins->o == IR_TOBIT ||
310 ((cr->op2 & IRCONV_MODEMASK) == (nc->mode & IRCONV_MODEMASK) &&
311 irt_isguard(cr->t) >= irt_isguard(fins->t)))) {
312 *nc->sp++ = NARROWINS(NARROW_REF, cref);
313 return 0; /* Already there, no additional conversion needed. */
314 }
315 cref = cr->prev;
316 }
317
318 /* Backpropagate across ADD/SUB. */
319 if (ir->o == IR_ADD || ir->o == IR_SUB) {
320 /* Try cache lookup first. */
321 IRRef mode = nc->mode;
322 BPropEntry *bp;
323 /* Inner conversions need a stronger check. */
324 if ((mode & IRCONV_CONVMASK) == IRCONV_INDEX && depth > 0)
325 mode += IRCONV_CHECK-IRCONV_INDEX;
326 bp = narrow_bpc_get(nc->J, (IRRef1)ref, mode);
327 if (bp) {
328 *nc->sp++ = NARROWINS(NARROW_REF, bp->val);
329 return 0;
330 } else if (nc->t == IRT_I64) {
331 /* Try sign-extending from an existing (checked) conversion to int. */
332 mode = (IRT_INT<<5)|IRT_NUM|IRCONV_INDEX;
333 bp = narrow_bpc_get(nc->J, (IRRef1)ref, mode);
334 if (bp) {
335 *nc->sp++ = NARROWINS(NARROW_REF, bp->val);
336 *nc->sp++ = NARROWINS(NARROW_SEXT, 0);
337 return 0;
338 }
339 }
340 if (++depth < NARROW_MAX_BACKPROP && nc->sp < nc->maxsp) {
341 NarrowIns *savesp = nc->sp;
342 int count = narrow_conv_backprop(nc, ir->op1, depth);
343 count += narrow_conv_backprop(nc, ir->op2, depth);
344 if (count <= 1) { /* Limit total number of conversions. */
345 *nc->sp++ = NARROWINS(IRT(ir->o, nc->t), ref);
346 return count;
347 }
348 nc->sp = savesp; /* Too many conversions, need to backtrack. */
349 }
350 }
351
352 /* Otherwise add a conversion. */
353 *nc->sp++ = NARROWINS(NARROW_CONV, ref);
354 return 1;
355}
356
357/* Emit the conversions collected during backpropagation. */
358static IRRef narrow_conv_emit(jit_State *J, NarrowConv *nc)
359{
360 /* The fins fields must be saved now -- emitir() overwrites them. */
361 IROpT guardot = irt_isguard(fins->t) ? IRTG(IR_ADDOV-IR_ADD, 0) : 0;
362 IROpT convot = fins->ot;
363 IRRef1 convop2 = fins->op2;
364 NarrowIns *next = nc->stack; /* List of instructions from backpropagation. */
365 NarrowIns *last = nc->sp;
366 NarrowIns *sp = nc->stack; /* Recycle the stack to store operands. */
367 while (next < last) { /* Simple stack machine to process the ins. list. */
368 NarrowIns ref = *next++;
369 IROpT op = narrow_op(ref);
370 if (op == NARROW_REF) {
371 *sp++ = ref;
372 } else if (op == NARROW_CONV) {
373 *sp++ = emitir_raw(convot, ref, convop2); /* Raw emit avoids a loop. */
374 } else if (op == NARROW_SEXT) {
375 lj_assertJ(sp >= nc->stack+1, "stack underflow");
376 sp[-1] = emitir(IRT(IR_CONV, IRT_I64), sp[-1],
377 (IRT_I64<<5)|IRT_INT|IRCONV_SEXT);
378 } else if (op == NARROW_INT) {
379 lj_assertJ(next < last, "missing arg to NARROW_INT");
380 *sp++ = nc->t == IRT_I64 ?
381 lj_ir_kint64(J, (int64_t)(int32_t)*next++) :
382 lj_ir_kint(J, *next++);
383 } else { /* Regular IROpT. Pops two operands and pushes one result. */
384 IRRef mode = nc->mode;
385 lj_assertJ(sp >= nc->stack+2, "stack underflow");
386 sp--;
387 /* Omit some overflow checks for array indexing. See comments above. */
388 if ((mode & IRCONV_CONVMASK) == IRCONV_INDEX) {
389 if (next == last && irref_isk(narrow_ref(sp[0])) &&
390 (uint32_t)IR(narrow_ref(sp[0]))->i + 0x40000000u < 0x80000000u)
391 guardot = 0;
392 else /* Otherwise cache a stronger check. */
393 mode += IRCONV_CHECK-IRCONV_INDEX;
394 }
395 sp[-1] = emitir(op+guardot, sp[-1], sp[0]);
396 /* Add to cache. */
397 if (narrow_ref(ref))
398 narrow_bpc_set(J, narrow_ref(ref), narrow_ref(sp[-1]), mode);
399 }
400 }
401 lj_assertJ(sp == nc->stack+1, "stack misalignment");
402 return nc->stack[0];
403}
404
405/* Narrow a type conversion of an arithmetic operation. */
406TRef LJ_FASTCALL lj_opt_narrow_convert(jit_State *J)
407{
408 if ((J->flags & JIT_F_OPT_NARROW)) {
409 NarrowConv nc;
410 nc.J = J;
411 nc.sp = nc.stack;
412 nc.maxsp = &nc.stack[NARROW_MAX_STACK-4];
413 nc.t = irt_type(fins->t);
414 if (fins->o == IR_TOBIT) {
415 nc.mode = IRCONV_TOBIT; /* Used only in the backpropagation cache. */
416 } else {
417 nc.mode = fins->op2;
418 }
419 if (narrow_conv_backprop(&nc, fins->op1, 0) <= 1)
420 return narrow_conv_emit(J, &nc);
421 }
422 return NEXTFOLD;
423}
424
425/* -- Narrowing of implicit conversions ----------------------------------- */
426
427/* Recursively strip overflow checks. */
428static TRef narrow_stripov(jit_State *J, TRef tr, int lastop, IRRef mode)
429{
430 IRRef ref = tref_ref(tr);
431 IRIns *ir = IR(ref);
432 int op = ir->o;
433 if (op >= IR_ADDOV && op <= lastop) {
434 BPropEntry *bp = narrow_bpc_get(J, ref, mode);
435 if (bp) {
436 return TREF(bp->val, irt_t(IR(bp->val)->t));
437 } else {
438 IRRef op1 = ir->op1, op2 = ir->op2; /* The IR may be reallocated. */
439 op1 = narrow_stripov(J, op1, lastop, mode);
440 op2 = narrow_stripov(J, op2, lastop, mode);
441 tr = emitir(IRT(op - IR_ADDOV + IR_ADD,
442 ((mode & IRCONV_DSTMASK) >> IRCONV_DSH)), op1, op2);
443 narrow_bpc_set(J, ref, tref_ref(tr), mode);
444 }
445 } else if (LJ_64 && (mode & IRCONV_SEXT) && !irt_is64(ir->t)) {
446 tr = emitir(IRT(IR_CONV, IRT_INTP), tr, mode);
447 }
448 return tr;
449}
450
451/* Narrow array index. */
452TRef LJ_FASTCALL lj_opt_narrow_index(jit_State *J, TRef tr)
453{
454 IRIns *ir;
455 lj_assertJ(tref_isnumber(tr), "expected number type");
456 if (tref_isnum(tr)) /* Conversion may be narrowed, too. See above. */
457 return emitir(IRTGI(IR_CONV), tr, IRCONV_INT_NUM|IRCONV_INDEX);
458 /* Omit some overflow checks for array indexing. See comments above. */
459 ir = IR(tref_ref(tr));
460 if ((ir->o == IR_ADDOV || ir->o == IR_SUBOV) && irref_isk(ir->op2) &&
461 (uint32_t)IR(ir->op2)->i + 0x40000000u < 0x80000000u)
462 return emitir(IRTI(ir->o - IR_ADDOV + IR_ADD), ir->op1, ir->op2);
463 return tr;
464}
465
466/* Narrow conversion to integer operand (overflow undefined). */
467TRef LJ_FASTCALL lj_opt_narrow_toint(jit_State *J, TRef tr)
468{
469 if (tref_isstr(tr))
470 tr = emitir(IRTG(IR_STRTO, IRT_NUM), tr, 0);
471 if (tref_isnum(tr)) /* Conversion may be narrowed, too. See above. */
472 return emitir(IRTI(IR_CONV), tr, IRCONV_INT_NUM|IRCONV_ANY);
473 if (!tref_isinteger(tr))
474 lj_trace_err(J, LJ_TRERR_BADTYPE);
475 /*
476 ** Undefined overflow semantics allow stripping of ADDOV, SUBOV and MULOV.
477 ** Use IRCONV_TOBIT for the cache entries, since the semantics are the same.
478 */
479 return narrow_stripov(J, tr, IR_MULOV, (IRT_INT<<5)|IRT_INT|IRCONV_TOBIT);
480}
481
482/* Narrow conversion to bitop operand (overflow wrapped). */
483TRef LJ_FASTCALL lj_opt_narrow_tobit(jit_State *J, TRef tr)
484{
485 if (tref_isstr(tr))
486 tr = emitir(IRTG(IR_STRTO, IRT_NUM), tr, 0);
487 if (tref_isnum(tr)) /* Conversion may be narrowed, too. See above. */
488 return emitir(IRTI(IR_TOBIT), tr, lj_ir_knum_tobit(J));
489 if (!tref_isinteger(tr))
490 lj_trace_err(J, LJ_TRERR_BADTYPE);
491 /*
492 ** Wrapped overflow semantics allow stripping of ADDOV and SUBOV.
493 ** MULOV cannot be stripped due to precision widening.
494 */
495 return narrow_stripov(J, tr, IR_SUBOV, (IRT_INT<<5)|IRT_INT|IRCONV_TOBIT);
496}
497
498#if LJ_HASFFI
499/* Narrow C array index (overflow undefined). */
500TRef LJ_FASTCALL lj_opt_narrow_cindex(jit_State *J, TRef tr)
501{
502 lj_assertJ(tref_isnumber(tr), "expected number type");
503 if (tref_isnum(tr))
504 return emitir(IRT(IR_CONV, IRT_INTP), tr, (IRT_INTP<<5)|IRT_NUM|IRCONV_ANY);
505 /* Undefined overflow semantics allow stripping of ADDOV, SUBOV and MULOV. */
506 return narrow_stripov(J, tr, IR_MULOV,
507 LJ_64 ? ((IRT_INTP<<5)|IRT_INT|IRCONV_SEXT) :
508 ((IRT_INTP<<5)|IRT_INT|IRCONV_TOBIT));
509}
510#endif
511
512/* -- Narrowing of arithmetic operators ----------------------------------- */
513
514/* Check whether a number fits into an int32_t (-0 is ok, too). */
515static int numisint(lua_Number n)
516{
517 return (n == (lua_Number)lj_num2int(n));
518}
519
520/* Convert string to number. Error out for non-numeric string values. */
521static TRef conv_str_tonum(jit_State *J, TRef tr, TValue *o)
522{
523 if (tref_isstr(tr)) {
524 tr = emitir(IRTG(IR_STRTO, IRT_NUM), tr, 0);
525 /* Would need an inverted STRTO for this rare and useless case. */
526 if (!lj_strscan_num(strV(o), o)) /* Convert in-place. Value used below. */
527 lj_trace_err(J, LJ_TRERR_BADTYPE); /* Punt if non-numeric. */
528 }
529 return tr;
530}
531
532/* Narrowing of arithmetic operations. */
533TRef lj_opt_narrow_arith(jit_State *J, TRef rb, TRef rc,
534 TValue *vb, TValue *vc, IROp op)
535{
536 rb = conv_str_tonum(J, rb, vb);
537 rc = conv_str_tonum(J, rc, vc);
538 /* Must not narrow MUL in non-DUALNUM variant, because it loses -0. */
539 if ((op >= IR_ADD && op <= (LJ_DUALNUM ? IR_MUL : IR_SUB)) &&
540 tref_isinteger(rb) && tref_isinteger(rc) &&
541 numisint(lj_vm_foldarith(numberVnum(vb), numberVnum(vc),
542 (int)op - (int)IR_ADD)))
543 return emitir(IRTGI((int)op - (int)IR_ADD + (int)IR_ADDOV), rb, rc);
544 if (!tref_isnum(rb)) rb = emitir(IRTN(IR_CONV), rb, IRCONV_NUM_INT);
545 if (!tref_isnum(rc)) rc = emitir(IRTN(IR_CONV), rc, IRCONV_NUM_INT);
546 return emitir(IRTN(op), rb, rc);
547}
548
549/* Narrowing of unary minus operator. */
550TRef lj_opt_narrow_unm(jit_State *J, TRef rc, TValue *vc)
551{
552 rc = conv_str_tonum(J, rc, vc);
553 if (tref_isinteger(rc)) {
554 uint32_t k = (uint32_t)numberVint(vc);
555 if ((LJ_DUALNUM || k != 0) && k != 0x80000000u) {
556 TRef zero = lj_ir_kint(J, 0);
557 if (!LJ_DUALNUM)
558 emitir(IRTGI(IR_NE), rc, zero);
559 return emitir(IRTGI(IR_SUBOV), zero, rc);
560 }
561 rc = emitir(IRTN(IR_CONV), rc, IRCONV_NUM_INT);
562 }
563 return emitir(IRTN(IR_NEG), rc, lj_ir_ksimd(J, LJ_KSIMD_NEG));
564}
565
566/* Narrowing of modulo operator. */
567TRef lj_opt_narrow_mod(jit_State *J, TRef rb, TRef rc, TValue *vb, TValue *vc)
568{
569 TRef tmp;
570 rb = conv_str_tonum(J, rb, vb);
571 rc = conv_str_tonum(J, rc, vc);
572 if ((LJ_DUALNUM || (J->flags & JIT_F_OPT_NARROW)) &&
573 tref_isinteger(rb) && tref_isinteger(rc) &&
574 (tvisint(vc) ? intV(vc) != 0 : !tviszero(vc))) {
575 emitir(IRTGI(IR_NE), rc, lj_ir_kint(J, 0));
576 return emitir(IRTI(IR_MOD), rb, rc);
577 }
578 /* b % c ==> b - floor(b/c)*c */
579 rb = lj_ir_tonum(J, rb);
580 rc = lj_ir_tonum(J, rc);
581 tmp = emitir(IRTN(IR_DIV), rb, rc);
582 tmp = emitir(IRTN(IR_FPMATH), tmp, IRFPM_FLOOR);
583 tmp = emitir(IRTN(IR_MUL), tmp, rc);
584 return emitir(IRTN(IR_SUB), rb, tmp);
585}
586
587/* Narrowing of power operator or math.pow. */
588TRef lj_opt_narrow_pow(jit_State *J, TRef rb, TRef rc, TValue *vb, TValue *vc)
589{
590 rb = conv_str_tonum(J, rb, vb);
591 rb = lj_ir_tonum(J, rb); /* Left arg is always treated as an FP number. */
592 rc = conv_str_tonum(J, rc, vc);
593 /* Narrowing must be unconditional to preserve (-x)^i semantics. */
594 if (tvisint(vc) || numisint(numV(vc))) {
595 int checkrange = 0;
596 /* pow() is faster for bigger exponents. But do this only for (+k)^i. */
597 if (tref_isk(rb) && (int32_t)ir_knum(IR(tref_ref(rb)))->u32.hi >= 0) {
598 int32_t k = numberVint(vc);
599 if (!(k >= -65536 && k <= 65536)) goto force_pow_num;
600 checkrange = 1;
601 }
602 if (!tref_isinteger(rc)) {
603 /* Guarded conversion to integer! */
604 rc = emitir(IRTGI(IR_CONV), rc, IRCONV_INT_NUM|IRCONV_CHECK);
605 }
606 if (checkrange && !tref_isk(rc)) { /* Range guard: -65536 <= i <= 65536 */
607 TRef tmp = emitir(IRTI(IR_ADD), rc, lj_ir_kint(J, 65536));
608 emitir(IRTGI(IR_ULE), tmp, lj_ir_kint(J, 2*65536));
609 }
610 } else {
611force_pow_num:
612 rc = lj_ir_tonum(J, rc); /* Want POW(num, num), not POW(num, int). */
613 }
614 return emitir(IRTN(IR_POW), rb, rc);
615}
616
617/* -- Predictive narrowing of induction variables ------------------------- */
618
619/* Narrow a single runtime value. */
620static int narrow_forl(jit_State *J, cTValue *o)
621{
622 if (tvisint(o)) return 1;
623 if (LJ_DUALNUM || (J->flags & JIT_F_OPT_NARROW)) return numisint(numV(o));
624 return 0;
625}
626
627/* Narrow the FORL index type by looking at the runtime values. */
628IRType lj_opt_narrow_forl(jit_State *J, cTValue *tv)
629{
630 lj_assertJ(tvisnumber(&tv[FORL_IDX]) &&
631 tvisnumber(&tv[FORL_STOP]) &&
632 tvisnumber(&tv[FORL_STEP]),
633 "expected number types");
634 /* Narrow only if the runtime values of start/stop/step are all integers. */
635 if (narrow_forl(J, &tv[FORL_IDX]) &&
636 narrow_forl(J, &tv[FORL_STOP]) &&
637 narrow_forl(J, &tv[FORL_STEP])) {
638 /* And if the loop index can't possibly overflow. */
639 lua_Number step = numberVnum(&tv[FORL_STEP]);
640 lua_Number sum = numberVnum(&tv[FORL_STOP]) + step;
641 if (0 <= step ? (sum <= 2147483647.0) : (sum >= -2147483648.0))
642 return IRT_INT;
643 }
644 return IRT_NUM;
645}
646
647#undef IR
648#undef fins
649#undef emitir
650#undef emitir_raw
651
652#endif
653