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DUALNUM: Handle integer type in JIT compiler.

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This commit is contained in:
Mike Pall
2011-03-10 01:57:24 +01:00
parent 3f26e3a89d
commit bfce3c1127
16 changed files with 486 additions and 278 deletions
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235
src/lj_opt_narrow.c
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@@ -1,5 +1,6 @@
/*
** NARROW: Narrowing of numbers to integers (double to int32_t).
** STRIPOV: Stripping of overflow checks.
** Copyright (C) 2005-2011 Mike Pall. See Copyright Notice in luajit.h
*/
@@ -16,6 +17,7 @@
#include "lj_jit.h"
#include "lj_iropt.h"
#include "lj_trace.h"
#include "lj_vm.h"
/* Rationale for narrowing optimizations:
**
@@ -57,24 +59,34 @@
**
** 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
** and bit operations. Additionally it can eliminate or hoists most of the
** resulting overflow checks. Regular arithmetic computations are never
** narrowed to integers.
** 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 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).
** 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).
**
** Note that all of the above has to be reconsidered if LuaJIT is to be
** ported to architectures with slow FP operations or with no hardware FPU
** at all. In the latter case an integer-only port may be the best overall
** solution (if this still meets user demands).
**
** 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. */
@@ -94,10 +106,10 @@
** 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 all arithmetic operations are
** performed on FP numbers. 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
** 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.
**
@@ -113,6 +125,9 @@
** 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
@@ -221,6 +236,26 @@ static void narrow_bpc_set(jit_State *J, IRRef1 key, IRRef1 val, IRRef mode)
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) {
narrow_stripov_backprop(nc, ir->op1, depth);
narrow_stripov_backprop(nc, ir->op2, depth);
*nc->sp++ = NARROWINS(IRT(ir->o - IR_ADDOV + IR_ADD, IRT_INT), ref);
return;
}
}
*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)
{
@@ -230,24 +265,26 @@ static int narrow_conv_backprop(NarrowConv *nc, IRRef ref, int depth)
/* Check the easy cases first. */
if (ir->o == IR_CONV && (ir->op2 & IRCONV_SRCMASK) == IRT_INT) {
if (nc->t == IRT_I64)
*nc->sp++ = NARROWINS(NARROW_SEXT, ir->op1); /* Reduce to sign-ext. */
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 == cast_num(k64)) { /* Only if constant doesn't lose precision. */
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);
if (n == cast_num(k)) { /* Only if constant is really an integer. */
if (n == (lua_Number)k) { /* Only if constant is really an integer. */
*nc->sp++ = NARROWINS(NARROW_INT, 0);
*nc->sp++ = (NarrowIns)k;
return 0;
@@ -287,7 +324,8 @@ static int narrow_conv_backprop(NarrowConv *nc, IRRef ref, int depth)
mode = (IRT_INT<<5)|IRT_NUM|IRCONV_INDEX;
bp = narrow_bpc_get(nc->J, (IRRef1)ref, mode);
if (bp) {
*nc->sp++ = NARROWINS(NARROW_SEXT, bp->val);
*nc->sp++ = NARROWINS(NARROW_REF, bp->val);
*nc->sp++ = NARROWINS(NARROW_SEXT, 0);
return 0;
}
}
@@ -326,8 +364,9 @@ static IRRef narrow_conv_emit(jit_State *J, NarrowConv *nc)
} else if (op == NARROW_CONV) {
*sp++ = emitir_raw(convot, ref, convop2); /* Raw emit avoids a loop. */
} else if (op == NARROW_SEXT) {
*sp++ = emitir(IRT(IR_CONV, IRT_I64), ref,
(IRT_I64<<5)|IRT_INT|IRCONV_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 ?
@@ -340,7 +379,7 @@ static IRRef narrow_conv_emit(jit_State *J, NarrowConv *nc)
/* 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 + 0x40000000 < 0x80000000)
(uint32_t)IR(narrow_ref(sp[0]))->i + 0x40000000u < 0x80000000u)
guardot = 0;
else /* Otherwise cache a stronger check. */
mode += IRCONV_CHECK-IRCONV_INDEX;
@@ -377,12 +416,123 @@ TRef LJ_FASTCALL lj_opt_narrow_convert(jit_State *J)
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(IRTI(IR_CONV), tr,
(IRT_INTP<<5)|IRT_NUM|IRCONV_TRUNC|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 == cast_num(lj_num2int(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_str_tonum(strV(vb), vb);
}
if (tref_isstr(rc)) {
rc = emitir(IRTG(IR_STRTO, IRT_NUM), rc, 0);
lj_str_tonum(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 modulo operator. */
@@ -409,16 +559,15 @@ TRef lj_opt_narrow_mod(jit_State *J, TRef rb, TRef rc)
/* Narrowing of power operator or math.pow. */
TRef lj_opt_narrow_pow(jit_State *J, TRef rb, TRef rc, TValue *vc)
{
lua_Number n;
if (tvisstr(vc) && !lj_str_tonum(strV(vc), vc))
lj_trace_err(J, LJ_TRERR_BADTYPE);
n = numV(vc);
/* Narrowing must be unconditional to preserve (-x)^i semantics. */
if (numisint(n)) {
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) {
if (!(n >= -65536.0 && n <= 65536.0)) goto split_pow;
int32_t k = numberVint(vc);
if (!(k >= -65536 && k <= 65536)) goto split_pow;
checkrange = 1;
}
if (!tref_isinteger(rc)) {
@@ -448,20 +597,28 @@ split_pow:
/* -- Predictive narrowing of induction variables ------------------------- */
/* Narrow the FORL index type by looking at the runtime values. */
IRType lj_opt_narrow_forl(cTValue *forbase)
/* Narrow a single runtime value. */
static int narrow_forl(jit_State *J, cTValue *o)
{
lua_assert(tvisnum(&forbase[FORL_IDX]) &&
tvisnum(&forbase[FORL_STOP]) &&
tvisnum(&forbase[FORL_STEP]));
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 (numisint(numV(&forbase[FORL_IDX])) &&
numisint(numV(&forbase[FORL_STOP])) &&
numisint(numV(&forbase[FORL_STEP]))) {
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 = numV(&forbase[FORL_STEP]);
lua_Number sum = numV(&forbase[FORL_STOP]) + step;
if (0 <= step ? sum <= 2147483647.0 : sum >= -2147483648.0)
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;