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Diffstat (limited to 'Build/source/libs/luajit/LuaJIT-2.1.0-beta1/src/lj_opt_narrow.c')
-rw-r--r-- | Build/source/libs/luajit/LuaJIT-2.1.0-beta1/src/lj_opt_narrow.c | 652 |
1 files changed, 652 insertions, 0 deletions
diff --git a/Build/source/libs/luajit/LuaJIT-2.1.0-beta1/src/lj_opt_narrow.c b/Build/source/libs/luajit/LuaJIT-2.1.0-beta1/src/lj_opt_narrow.c new file mode 100644 index 00000000000..d1993452a6a --- /dev/null +++ b/Build/source/libs/luajit/LuaJIT-2.1.0-beta1/src/lj_opt_narrow.c @@ -0,0 +1,652 @@ +/* +** NARROW: Narrowing of numbers to integers (double to int32_t). +** STRIPOV: Stripping of overflow checks. +** Copyright (C) 2005-2015 Mike Pall. See Copyright Notice in luajit.h +*/ + +#define lj_opt_narrow_c +#define LUA_CORE + +#include "lj_obj.h" + +#if LJ_HASJIT + +#include "lj_bc.h" +#include "lj_ir.h" +#include "lj_jit.h" +#include "lj_iropt.h" +#include "lj_trace.h" +#include "lj_vm.h" +#include "lj_strscan.h" + +/* Rationale for narrowing optimizations: +** +** Lua has only a single number type and this is a FP double by default. +** Narrowing doubles to integers does not pay off for the interpreter on a +** current-generation x86/x64 machine. Most FP operations need the same +** amount of execution resources as their integer counterparts, except +** with slightly longer latencies. Longer latencies are a non-issue for +** the interpreter, since they are usually hidden by other overhead. +** +** The total CPU execution bandwidth is the sum of the bandwidth of the FP +** and the integer units, because they execute in parallel. The FP units +** have an equal or higher bandwidth than the integer units. Not using +** them means losing execution bandwidth. Moving work away from them to +** the already quite busy integer units is a losing proposition. +** +** The situation for JIT-compiled code is a bit different: the higher code +** density makes the extra latencies much more visible. Tight loops expose +** the latencies for updating the induction variables. Array indexing +** requires narrowing conversions with high latencies and additional +** guards (to check that the index is really an integer). And many common +** optimizations only work on integers. +** +** One solution would be speculative, eager narrowing of all number loads. +** This causes many problems, like losing -0 or the need to resolve type +** mismatches between traces. It also effectively forces the integer type +** to have overflow-checking semantics. This impedes many basic +** optimizations and requires adding overflow checks to all integer +** arithmetic operations (whereas FP arithmetics can do without). +** +** Always replacing an FP op with an integer op plus an overflow check is +** counter-productive on a current-generation super-scalar CPU. Although +** the overflow check branches are highly predictable, they will clog the +** execution port for the branch unit and tie up reorder buffers. This is +** turning a pure data-flow dependency into a different data-flow +** dependency (with slightly lower latency) *plus* a control dependency. +** In general, you don't want to do this since latencies due to data-flow +** dependencies can be well hidden by out-of-order execution. +** +** A better solution is to keep all numbers as FP values and only narrow +** when it's beneficial to do so. LuaJIT uses predictive narrowing for +** induction variables and demand-driven narrowing for index expressions, +** integer arguments and bit operations. Additionally it can eliminate or +** hoist most of the resulting overflow checks. Regular arithmetic +** computations are never narrowed to integers. +** +** The integer type in the IR has convenient wrap-around semantics and +** ignores overflow. Extra operations have been added for +** overflow-checking arithmetic (ADDOV/SUBOV) instead of an extra type. +** Apart from reducing overall complexity of the compiler, this also +** nicely solves the problem where you want to apply algebraic +** simplifications to ADD, but not to ADDOV. And the x86/x64 assembler can +** use lea instead of an add for integer ADD, but not for ADDOV (lea does +** not affect the flags, but it helps to avoid register moves). +** +** +** All of the above has to be reconsidered for architectures with slow FP +** operations or without a hardware FPU. The dual-number mode of LuaJIT +** addresses this issue. Arithmetic operations are performed on integers +** as far as possible and overflow checks are added as needed. +** +** This implies that narrowing for integer arguments and bit operations +** should also strip overflow checks, e.g. replace ADDOV with ADD. The +** original overflow guards are weak and can be eliminated by DCE, if +** there's no other use. +** +** A slight twist is that it's usually beneficial to use overflow-checked +** integer arithmetics if all inputs are already integers. This is the only +** change that affects the single-number mode, too. +*/ + +/* Some local macros to save typing. Undef'd at the end. */ +#define IR(ref) (&J->cur.ir[(ref)]) +#define fins (&J->fold.ins) + +/* Pass IR on to next optimization in chain (FOLD). */ +#define emitir(ot, a, b) (lj_ir_set(J, (ot), (a), (b)), lj_opt_fold(J)) + +#define emitir_raw(ot, a, b) (lj_ir_set(J, (ot), (a), (b)), lj_ir_emit(J)) + +/* -- Elimination of narrowing type conversions --------------------------- */ + +/* Narrowing of index expressions and bit operations is demand-driven. The +** trace recorder emits a narrowing type conversion (CONV.int.num or TOBIT) +** in all of these cases (e.g. array indexing or string indexing). FOLD +** already takes care of eliminating simple redundant conversions like +** CONV.int.num(CONV.num.int(x)) ==> x. +** +** But the surrounding code is FP-heavy and arithmetic operations are +** performed on FP numbers (for the single-number mode). Consider a common +** example such as 'x=t[i+1]', with 'i' already an integer (due to induction +** variable narrowing). The index expression would be recorded as +** CONV.int.num(ADD(CONV.num.int(i), 1)) +** which is clearly suboptimal. +** +** One can do better by recursively backpropagating the narrowing type +** conversion across FP arithmetic operations. This turns FP ops into +** their corresponding integer counterparts. Depending on the semantics of +** the conversion they also need to check for overflow. Currently only ADD +** and SUB are supported. +** +** The above example can be rewritten as +** ADDOV(CONV.int.num(CONV.num.int(i)), 1) +** and then into ADDOV(i, 1) after folding of the conversions. The original +** FP ops remain in the IR and are eliminated by DCE since all references to +** them are gone. +** +** [In dual-number mode the trace recorder already emits ADDOV etc., but +** this can be further reduced. See below.] +** +** Special care has to be taken to avoid narrowing across an operation +** which is potentially operating on non-integral operands. One obvious +** case is when an expression contains a non-integral constant, but ends +** up as an integer index at runtime (like t[x+1.5] with x=0.5). +** +** Operations with two non-constant operands illustrate a similar problem +** (like t[a+b] with a=1.5 and b=2.5). Backpropagation has to stop there, +** unless it can be proven that either operand is integral (e.g. by CSEing +** a previous conversion). As a not-so-obvious corollary this logic also +** applies for a whole expression tree (e.g. t[(a+1)+(b+1)]). +** +** Correctness of the transformation is guaranteed by avoiding to expand +** the tree by adding more conversions than the one we would need to emit +** if not backpropagating. TOBIT employs a more optimistic rule, because +** the conversion has special semantics, designed to make the life of the +** compiler writer easier. ;-) +** +** Using on-the-fly backpropagation of an expression tree doesn't work +** because it's unknown whether the transform is correct until the end. +** This either requires IR rollback and cache invalidation for every +** subtree or a two-pass algorithm. The former didn't work out too well, +** so the code now combines a recursive collector with a stack-based +** emitter. +** +** [A recursive backpropagation algorithm with backtracking, employing +** skip-list lookup and round-robin caching, emitting stack operations +** on-the-fly for a stack-based interpreter -- and all of that in a meager +** kilobyte? Yep, compilers are a great treasure chest. Throw away your +** textbooks and read the codebase of a compiler today!] +** +** There's another optimization opportunity for array indexing: it's +** always accompanied by an array bounds-check. The outermost overflow +** check may be delegated to the ABC operation. This works because ABC is +** an unsigned comparison and wrap-around due to overflow creates negative +** numbers. +** +** But this optimization is only valid for constants that cannot overflow +** an int32_t into the range of valid array indexes [0..2^27+1). A check +** for +-2^30 is safe since -2^31 - 2^30 wraps to 2^30 and 2^31-1 + 2^30 +** wraps to -2^30-1. +** +** It's also good enough in practice, since e.g. t[i+1] or t[i-10] are +** quite common. So the above example finally ends up as ADD(i, 1)! +** +** Later on, the assembler is able to fuse the whole array reference and +** the ADD into the memory operands of loads and other instructions. This +** is why LuaJIT is able to generate very pretty (and fast) machine code +** for array indexing. And that, my dear, concludes another story about +** one of the hidden secrets of LuaJIT ... +*/ + +/* Maximum backpropagation depth and maximum stack size. */ +#define NARROW_MAX_BACKPROP 100 +#define NARROW_MAX_STACK 256 + +/* The stack machine has a 32 bit instruction format: [IROpT | IRRef1] +** The lower 16 bits hold a reference (or 0). The upper 16 bits hold +** the IR opcode + type or one of the following special opcodes: +*/ +enum { + NARROW_REF, /* Push ref. */ + NARROW_CONV, /* Push conversion of ref. */ + NARROW_SEXT, /* Push sign-extension of ref. */ + NARROW_INT /* Push KINT ref. The next code holds an int32_t. */ +}; + +typedef uint32_t NarrowIns; + +#define NARROWINS(op, ref) (((op) << 16) + (ref)) +#define narrow_op(ins) ((IROpT)((ins) >> 16)) +#define narrow_ref(ins) ((IRRef1)(ins)) + +/* Context used for narrowing of type conversions. */ +typedef struct NarrowConv { + jit_State *J; /* JIT compiler state. */ + NarrowIns *sp; /* Current stack pointer. */ + NarrowIns *maxsp; /* Maximum stack pointer minus redzone. */ + IRRef mode; /* Conversion mode (IRCONV_*). */ + IRType t; /* Destination type: IRT_INT or IRT_I64. */ + NarrowIns stack[NARROW_MAX_STACK]; /* Stack holding stack-machine code. */ +} NarrowConv; + +/* Lookup a reference in the backpropagation cache. */ +static BPropEntry *narrow_bpc_get(jit_State *J, IRRef1 key, IRRef mode) +{ + ptrdiff_t i; + for (i = 0; i < BPROP_SLOTS; i++) { + BPropEntry *bp = &J->bpropcache[i]; + /* Stronger checks are ok, too. */ + if (bp->key == key && bp->mode >= mode && + ((bp->mode ^ mode) & IRCONV_MODEMASK) == 0) + return bp; + } + return NULL; +} + +/* Add an entry to the backpropagation cache. */ +static void narrow_bpc_set(jit_State *J, IRRef1 key, IRRef1 val, IRRef mode) +{ + uint32_t slot = J->bpropslot; + BPropEntry *bp = &J->bpropcache[slot]; + J->bpropslot = (slot + 1) & (BPROP_SLOTS-1); + bp->key = key; + bp->val = val; + bp->mode = mode; +} + +/* Backpropagate overflow stripping. */ +static void narrow_stripov_backprop(NarrowConv *nc, IRRef ref, int depth) +{ + jit_State *J = nc->J; + IRIns *ir = IR(ref); + if (ir->o == IR_ADDOV || ir->o == IR_SUBOV || + (ir->o == IR_MULOV && (nc->mode & IRCONV_CONVMASK) == IRCONV_ANY)) { + BPropEntry *bp = narrow_bpc_get(nc->J, ref, IRCONV_TOBIT); + if (bp) { + ref = bp->val; + } else if (++depth < NARROW_MAX_BACKPROP && nc->sp < nc->maxsp) { + NarrowIns *savesp = nc->sp; + narrow_stripov_backprop(nc, ir->op1, depth); + if (nc->sp < nc->maxsp) { + narrow_stripov_backprop(nc, ir->op2, depth); + if (nc->sp < nc->maxsp) { + *nc->sp++ = NARROWINS(IRT(ir->o - IR_ADDOV + IR_ADD, IRT_INT), ref); + return; + } + } + nc->sp = savesp; /* Path too deep, need to backtrack. */ + } + } + *nc->sp++ = NARROWINS(NARROW_REF, ref); +} + +/* Backpropagate narrowing conversion. Return number of needed conversions. */ +static int narrow_conv_backprop(NarrowConv *nc, IRRef ref, int depth) +{ + jit_State *J = nc->J; + IRIns *ir = IR(ref); + IRRef cref; + + if (nc->sp >= nc->maxsp) return 10; /* Path too deep. */ + + /* Check the easy cases first. */ + if (ir->o == IR_CONV && (ir->op2 & IRCONV_SRCMASK) == IRT_INT) { + if ((nc->mode & IRCONV_CONVMASK) <= IRCONV_ANY) + narrow_stripov_backprop(nc, ir->op1, depth+1); + else + *nc->sp++ = NARROWINS(NARROW_REF, ir->op1); /* Undo conversion. */ + if (nc->t == IRT_I64) + *nc->sp++ = NARROWINS(NARROW_SEXT, 0); /* Sign-extend integer. */ + return 0; + } else if (ir->o == IR_KNUM) { /* Narrow FP constant. */ + lua_Number n = ir_knum(ir)->n; + if ((nc->mode & IRCONV_CONVMASK) == IRCONV_TOBIT) { + /* Allows a wider range of constants. */ + int64_t k64 = (int64_t)n; + if (n == (lua_Number)k64) { /* Only if const doesn't lose precision. */ + *nc->sp++ = NARROWINS(NARROW_INT, 0); + *nc->sp++ = (NarrowIns)k64; /* But always truncate to 32 bits. */ + return 0; + } + } else { + int32_t k = lj_num2int(n); + /* Only if constant is a small integer. */ + if (checki16(k) && n == (lua_Number)k) { + *nc->sp++ = NARROWINS(NARROW_INT, 0); + *nc->sp++ = (NarrowIns)k; + return 0; + } + } + return 10; /* Never narrow other FP constants (this is rare). */ + } + + /* Try to CSE the conversion. Stronger checks are ok, too. */ + cref = J->chain[fins->o]; + while (cref > ref) { + IRIns *cr = IR(cref); + if (cr->op1 == ref && + (fins->o == IR_TOBIT || + ((cr->op2 & IRCONV_MODEMASK) == (nc->mode & IRCONV_MODEMASK) && + irt_isguard(cr->t) >= irt_isguard(fins->t)))) { + *nc->sp++ = NARROWINS(NARROW_REF, cref); + return 0; /* Already there, no additional conversion needed. */ + } + cref = cr->prev; + } + + /* Backpropagate across ADD/SUB. */ + if (ir->o == IR_ADD || ir->o == IR_SUB) { + /* Try cache lookup first. */ + IRRef mode = nc->mode; + BPropEntry *bp; + /* Inner conversions need a stronger check. */ + if ((mode & IRCONV_CONVMASK) == IRCONV_INDEX && depth > 0) + mode += IRCONV_CHECK-IRCONV_INDEX; + bp = narrow_bpc_get(nc->J, (IRRef1)ref, mode); + if (bp) { + *nc->sp++ = NARROWINS(NARROW_REF, bp->val); + return 0; + } else if (nc->t == IRT_I64) { + /* Try sign-extending from an existing (checked) conversion to int. */ + mode = (IRT_INT<<5)|IRT_NUM|IRCONV_INDEX; + bp = narrow_bpc_get(nc->J, (IRRef1)ref, mode); + if (bp) { + *nc->sp++ = NARROWINS(NARROW_REF, bp->val); + *nc->sp++ = NARROWINS(NARROW_SEXT, 0); + return 0; + } + } + if (++depth < NARROW_MAX_BACKPROP && nc->sp < nc->maxsp) { + NarrowIns *savesp = nc->sp; + int count = narrow_conv_backprop(nc, ir->op1, depth); + count += narrow_conv_backprop(nc, ir->op2, depth); + if (count <= 1) { /* Limit total number of conversions. */ + *nc->sp++ = NARROWINS(IRT(ir->o, nc->t), ref); + return count; + } + nc->sp = savesp; /* Too many conversions, need to backtrack. */ + } + } + + /* Otherwise add a conversion. */ + *nc->sp++ = NARROWINS(NARROW_CONV, ref); + return 1; +} + +/* Emit the conversions collected during backpropagation. */ +static IRRef narrow_conv_emit(jit_State *J, NarrowConv *nc) +{ + /* The fins fields must be saved now -- emitir() overwrites them. */ + IROpT guardot = irt_isguard(fins->t) ? IRTG(IR_ADDOV-IR_ADD, 0) : 0; + IROpT convot = fins->ot; + IRRef1 convop2 = fins->op2; + NarrowIns *next = nc->stack; /* List of instructions from backpropagation. */ + NarrowIns *last = nc->sp; + NarrowIns *sp = nc->stack; /* Recycle the stack to store operands. */ + while (next < last) { /* Simple stack machine to process the ins. list. */ + NarrowIns ref = *next++; + IROpT op = narrow_op(ref); + if (op == NARROW_REF) { + *sp++ = ref; + } else if (op == NARROW_CONV) { + *sp++ = emitir_raw(convot, ref, convop2); /* Raw emit avoids a loop. */ + } else if (op == NARROW_SEXT) { + lua_assert(sp >= nc->stack+1); + sp[-1] = emitir(IRT(IR_CONV, IRT_I64), sp[-1], + (IRT_I64<<5)|IRT_INT|IRCONV_SEXT); + } else if (op == NARROW_INT) { + lua_assert(next < last); + *sp++ = nc->t == IRT_I64 ? + lj_ir_kint64(J, (int64_t)(int32_t)*next++) : + lj_ir_kint(J, *next++); + } else { /* Regular IROpT. Pops two operands and pushes one result. */ + IRRef mode = nc->mode; + lua_assert(sp >= nc->stack+2); + sp--; + /* Omit some overflow checks for array indexing. See comments above. */ + if ((mode & IRCONV_CONVMASK) == IRCONV_INDEX) { + if (next == last && irref_isk(narrow_ref(sp[0])) && + (uint32_t)IR(narrow_ref(sp[0]))->i + 0x40000000u < 0x80000000u) + guardot = 0; + else /* Otherwise cache a stronger check. */ + mode += IRCONV_CHECK-IRCONV_INDEX; + } + sp[-1] = emitir(op+guardot, sp[-1], sp[0]); + /* Add to cache. */ + if (narrow_ref(ref)) + narrow_bpc_set(J, narrow_ref(ref), narrow_ref(sp[-1]), mode); + } + } + lua_assert(sp == nc->stack+1); + return nc->stack[0]; +} + +/* Narrow a type conversion of an arithmetic operation. */ +TRef LJ_FASTCALL lj_opt_narrow_convert(jit_State *J) +{ + if ((J->flags & JIT_F_OPT_NARROW)) { + NarrowConv nc; + nc.J = J; + nc.sp = nc.stack; + nc.maxsp = &nc.stack[NARROW_MAX_STACK-4]; + nc.t = irt_type(fins->t); + if (fins->o == IR_TOBIT) { + nc.mode = IRCONV_TOBIT; /* Used only in the backpropagation cache. */ + } else { + nc.mode = fins->op2; + } + if (narrow_conv_backprop(&nc, fins->op1, 0) <= 1) + return narrow_conv_emit(J, &nc); + } + return NEXTFOLD; +} + +/* -- Narrowing of implicit conversions ----------------------------------- */ + +/* Recursively strip overflow checks. */ +static TRef narrow_stripov(jit_State *J, TRef tr, int lastop, IRRef mode) +{ + IRRef ref = tref_ref(tr); + IRIns *ir = IR(ref); + int op = ir->o; + if (op >= IR_ADDOV && op <= lastop) { + BPropEntry *bp = narrow_bpc_get(J, ref, mode); + if (bp) { + return TREF(bp->val, irt_t(IR(bp->val)->t)); + } else { + IRRef op1 = ir->op1, op2 = ir->op2; /* The IR may be reallocated. */ + op1 = narrow_stripov(J, op1, lastop, mode); + op2 = narrow_stripov(J, op2, lastop, mode); + tr = emitir(IRT(op - IR_ADDOV + IR_ADD, + ((mode & IRCONV_DSTMASK) >> IRCONV_DSH)), op1, op2); + narrow_bpc_set(J, ref, tref_ref(tr), mode); + } + } else if (LJ_64 && (mode & IRCONV_SEXT) && !irt_is64(ir->t)) { + tr = emitir(IRT(IR_CONV, IRT_INTP), tr, mode); + } + return tr; +} + +/* Narrow array index. */ +TRef LJ_FASTCALL lj_opt_narrow_index(jit_State *J, TRef tr) +{ + IRIns *ir; + lua_assert(tref_isnumber(tr)); + if (tref_isnum(tr)) /* Conversion may be narrowed, too. See above. */ + return emitir(IRTGI(IR_CONV), tr, IRCONV_INT_NUM|IRCONV_INDEX); + /* Omit some overflow checks for array indexing. See comments above. */ + ir = IR(tref_ref(tr)); + if ((ir->o == IR_ADDOV || ir->o == IR_SUBOV) && irref_isk(ir->op2) && + (uint32_t)IR(ir->op2)->i + 0x40000000u < 0x80000000u) + return emitir(IRTI(ir->o - IR_ADDOV + IR_ADD), ir->op1, ir->op2); + return tr; +} + +/* Narrow conversion to integer operand (overflow undefined). */ +TRef LJ_FASTCALL lj_opt_narrow_toint(jit_State *J, TRef tr) +{ + if (tref_isstr(tr)) + tr = emitir(IRTG(IR_STRTO, IRT_NUM), tr, 0); + if (tref_isnum(tr)) /* Conversion may be narrowed, too. See above. */ + return emitir(IRTI(IR_CONV), tr, IRCONV_INT_NUM|IRCONV_ANY); + if (!tref_isinteger(tr)) + lj_trace_err(J, LJ_TRERR_BADTYPE); + /* + ** Undefined overflow semantics allow stripping of ADDOV, SUBOV and MULOV. + ** Use IRCONV_TOBIT for the cache entries, since the semantics are the same. + */ + return narrow_stripov(J, tr, IR_MULOV, (IRT_INT<<5)|IRT_INT|IRCONV_TOBIT); +} + +/* Narrow conversion to bitop operand (overflow wrapped). */ +TRef LJ_FASTCALL lj_opt_narrow_tobit(jit_State *J, TRef tr) +{ + if (tref_isstr(tr)) + tr = emitir(IRTG(IR_STRTO, IRT_NUM), tr, 0); + if (tref_isnum(tr)) /* Conversion may be narrowed, too. See above. */ + return emitir(IRTI(IR_TOBIT), tr, lj_ir_knum_tobit(J)); + if (!tref_isinteger(tr)) + lj_trace_err(J, LJ_TRERR_BADTYPE); + /* + ** Wrapped overflow semantics allow stripping of ADDOV and SUBOV. + ** MULOV cannot be stripped due to precision widening. + */ + return narrow_stripov(J, tr, IR_SUBOV, (IRT_INT<<5)|IRT_INT|IRCONV_TOBIT); +} + +#if LJ_HASFFI +/* Narrow C array index (overflow undefined). */ +TRef LJ_FASTCALL lj_opt_narrow_cindex(jit_State *J, TRef tr) +{ + lua_assert(tref_isnumber(tr)); + if (tref_isnum(tr)) + return emitir(IRT(IR_CONV, IRT_INTP), tr, (IRT_INTP<<5)|IRT_NUM|IRCONV_ANY); + /* Undefined overflow semantics allow stripping of ADDOV, SUBOV and MULOV. */ + return narrow_stripov(J, tr, IR_MULOV, + LJ_64 ? ((IRT_INTP<<5)|IRT_INT|IRCONV_SEXT) : + ((IRT_INTP<<5)|IRT_INT|IRCONV_TOBIT)); +} +#endif + +/* -- Narrowing of arithmetic operators ----------------------------------- */ + +/* Check whether a number fits into an int32_t (-0 is ok, too). */ +static int numisint(lua_Number n) +{ + return (n == (lua_Number)lj_num2int(n)); +} + +/* Narrowing of arithmetic operations. */ +TRef lj_opt_narrow_arith(jit_State *J, TRef rb, TRef rc, + TValue *vb, TValue *vc, IROp op) +{ + if (tref_isstr(rb)) { + rb = emitir(IRTG(IR_STRTO, IRT_NUM), rb, 0); + lj_strscan_num(strV(vb), vb); + } + if (tref_isstr(rc)) { + rc = emitir(IRTG(IR_STRTO, IRT_NUM), rc, 0); + lj_strscan_num(strV(vc), vc); + } + /* Must not narrow MUL in non-DUALNUM variant, because it loses -0. */ + if ((op >= IR_ADD && op <= (LJ_DUALNUM ? IR_MUL : IR_SUB)) && + tref_isinteger(rb) && tref_isinteger(rc) && + numisint(lj_vm_foldarith(numberVnum(vb), numberVnum(vc), + (int)op - (int)IR_ADD))) + return emitir(IRTGI((int)op - (int)IR_ADD + (int)IR_ADDOV), rb, rc); + if (!tref_isnum(rb)) rb = emitir(IRTN(IR_CONV), rb, IRCONV_NUM_INT); + if (!tref_isnum(rc)) rc = emitir(IRTN(IR_CONV), rc, IRCONV_NUM_INT); + return emitir(IRTN(op), rb, rc); +} + +/* Narrowing of unary minus operator. */ +TRef lj_opt_narrow_unm(jit_State *J, TRef rc, TValue *vc) +{ + if (tref_isstr(rc)) { + rc = emitir(IRTG(IR_STRTO, IRT_NUM), rc, 0); + lj_strscan_num(strV(vc), vc); + } + if (tref_isinteger(rc)) { + if ((uint32_t)numberVint(vc) != 0x80000000u) + return emitir(IRTGI(IR_SUBOV), lj_ir_kint(J, 0), rc); + rc = emitir(IRTN(IR_CONV), rc, IRCONV_NUM_INT); + } + return emitir(IRTN(IR_NEG), rc, lj_ir_knum_neg(J)); +} + +/* Narrowing of modulo operator. */ +TRef lj_opt_narrow_mod(jit_State *J, TRef rb, TRef rc, TValue *vc) +{ + TRef tmp; + if (tvisstr(vc) && !lj_strscan_num(strV(vc), vc)) + lj_trace_err(J, LJ_TRERR_BADTYPE); + if ((LJ_DUALNUM || (J->flags & JIT_F_OPT_NARROW)) && + tref_isinteger(rb) && tref_isinteger(rc) && + (tvisint(vc) ? intV(vc) != 0 : !tviszero(vc))) { + emitir(IRTGI(IR_NE), rc, lj_ir_kint(J, 0)); + return emitir(IRTI(IR_MOD), rb, rc); + } + /* b % c ==> b - floor(b/c)*c */ + rb = lj_ir_tonum(J, rb); + rc = lj_ir_tonum(J, rc); + tmp = emitir(IRTN(IR_DIV), rb, rc); + tmp = emitir(IRTN(IR_FPMATH), tmp, IRFPM_FLOOR); + tmp = emitir(IRTN(IR_MUL), tmp, rc); + return emitir(IRTN(IR_SUB), rb, tmp); +} + +/* Narrowing of power operator or math.pow. */ +TRef lj_opt_narrow_pow(jit_State *J, TRef rb, TRef rc, TValue *vc) +{ + if (tvisstr(vc) && !lj_strscan_num(strV(vc), vc)) + lj_trace_err(J, LJ_TRERR_BADTYPE); + /* Narrowing must be unconditional to preserve (-x)^i semantics. */ + if (tvisint(vc) || numisint(numV(vc))) { + int checkrange = 0; + /* Split pow is faster for bigger exponents. But do this only for (+k)^i. */ + if (tref_isk(rb) && (int32_t)ir_knum(IR(tref_ref(rb)))->u32.hi >= 0) { + int32_t k = numberVint(vc); + if (!(k >= -65536 && k <= 65536)) goto split_pow; + checkrange = 1; + } + if (!tref_isinteger(rc)) { + if (tref_isstr(rc)) + rc = emitir(IRTG(IR_STRTO, IRT_NUM), rc, 0); + /* Guarded conversion to integer! */ + rc = emitir(IRTGI(IR_CONV), rc, IRCONV_INT_NUM|IRCONV_CHECK); + } + if (checkrange && !tref_isk(rc)) { /* Range guard: -65536 <= i <= 65536 */ + TRef tmp = emitir(IRTI(IR_ADD), rc, lj_ir_kint(J, 65536)); + emitir(IRTGI(IR_ULE), tmp, lj_ir_kint(J, 2*65536)); + } + return emitir(IRTN(IR_POW), rb, rc); + } +split_pow: + /* FOLD covers most cases, but some are easier to do here. */ + if (tref_isk(rb) && tvispone(ir_knum(IR(tref_ref(rb))))) + return rb; /* 1 ^ x ==> 1 */ + rc = lj_ir_tonum(J, rc); + if (tref_isk(rc) && ir_knum(IR(tref_ref(rc)))->n == 0.5) + return emitir(IRTN(IR_FPMATH), rb, IRFPM_SQRT); /* x ^ 0.5 ==> sqrt(x) */ + /* Split up b^c into exp2(c*log2(b)). Assembler may rejoin later. */ + rb = emitir(IRTN(IR_FPMATH), rb, IRFPM_LOG2); + rc = emitir(IRTN(IR_MUL), rb, rc); + return emitir(IRTN(IR_FPMATH), rc, IRFPM_EXP2); +} + +/* -- Predictive narrowing of induction variables ------------------------- */ + +/* Narrow a single runtime value. */ +static int narrow_forl(jit_State *J, cTValue *o) +{ + if (tvisint(o)) return 1; + if (LJ_DUALNUM || (J->flags & JIT_F_OPT_NARROW)) return numisint(numV(o)); + return 0; +} + +/* Narrow the FORL index type by looking at the runtime values. */ +IRType lj_opt_narrow_forl(jit_State *J, cTValue *tv) +{ + lua_assert(tvisnumber(&tv[FORL_IDX]) && + tvisnumber(&tv[FORL_STOP]) && + tvisnumber(&tv[FORL_STEP])); + /* Narrow only if the runtime values of start/stop/step are all integers. */ + if (narrow_forl(J, &tv[FORL_IDX]) && + narrow_forl(J, &tv[FORL_STOP]) && + narrow_forl(J, &tv[FORL_STEP])) { + /* And if the loop index can't possibly overflow. */ + lua_Number step = numberVnum(&tv[FORL_STEP]); + lua_Number sum = numberVnum(&tv[FORL_STOP]) + step; + if (0 <= step ? (sum <= 2147483647.0) : (sum >= -2147483648.0)) + return IRT_INT; + } + return IRT_NUM; +} + +#undef IR +#undef fins +#undef emitir +#undef emitir_raw + +#endif |