[Tarantool-patches] [PATCH luajit 4/5] Fix pow() optimization inconsistencies.
Sergey Kaplun
skaplun at tarantool.org
Tue Aug 15 12:36:30 MSK 2023
From: Mike Pall <mike>
(cherry-picked from commit 9512d5c1aced61e13e7be2d3208ec7ae3516b458)
This patch fixes different misbehaviour between JIT-compiled code and
the interpreter for power operator with the following ways:
* Drop folding optimizations for base ^ 0.5 => sqrt(base), as far as
pow(base, 0.5) isn't interchangeable and depends on the <math.h>
implementation.
* Drop folding optimizations for 2 ^ int_pow => ldexp(1.0, int_pow), to
avoid dependcy on the <math.h> implementation.
* Now `asm_pow()` always assemble a call to the `lj_vm_powi()` function,
that is general now for all CPU architectures. Using this internal
function instead of toolchain-provided `pow()` guarantees consistency
between interpreter and JIT results. Also, it drops custom
implementation for the `vm_powi_sse()` on x86_64.
* `math_extern2` macro in the VM may take the second argument, that is
used as the target function to call. The first argument is still the
name for `func_nnsse` macro.
* Narrowing for power operation avoids range guard for non-constant base
IR. This leads to invalid result if value on trace is out of range.
Now it is done unconditionally.
Be aware, that [220/502] lib/string/format/num.lua test [1] from
LuaJIT-test suite fails after this commit.
[1]: https://www.exploringbinary.com/incorrect-floating-point-to-decimal-conversions/
Sergey Kaplun:
* added the description and the test for the problem
Part of tarantool/tarantool#8825
---
src/lj_asm.c | 7 +-
src/lj_asm_x86.h | 13 ---
src/lj_dispatch.h | 2 +-
src/lj_ircall.h | 2 +-
src/lj_opt_fold.c | 27 ------
src/lj_opt_narrow.c | 12 +--
src/lj_vm.h | 7 +-
src/lj_vmmath.c | 82 +++++++++--------
src/vm_arm.dasc | 13 +--
src/vm_arm64.dasc | 11 ++-
src/vm_mips.dasc | 11 ++-
src/vm_mips64.dasc | 11 ++-
src/vm_ppc.dasc | 11 ++-
src/vm_x64.dasc | 44 ++-------
src/vm_x86.dasc | 46 ++--------
.../lj-684-pow-inconsistencies.test.lua | 89 +++++++++++++++++++
.../lj-9-pow-inconsistencies.test.lua | 2 +
17 files changed, 195 insertions(+), 195 deletions(-)
create mode 100644 test/tarantool-tests/lj-684-pow-inconsistencies.test.lua
diff --git a/src/lj_asm.c b/src/lj_asm.c
index d71fa8c8..65261d50 100644
--- a/src/lj_asm.c
+++ b/src/lj_asm.c
@@ -1650,7 +1650,6 @@ static void asm_loop(ASMState *as)
#if !LJ_SOFTFP32
#if !LJ_TARGET_X86ORX64
#define asm_ldexp(as, ir) asm_callid(as, ir, IRCALL_ldexp)
-#define asm_fppowi(as, ir) asm_callid(as, ir, IRCALL_lj_vm_powi)
#endif
static void asm_pow(ASMState *as, IRIns *ir)
@@ -1661,10 +1660,8 @@ static void asm_pow(ASMState *as, IRIns *ir)
IRCALL_lj_carith_powu64);
else
#endif
- if (irt_isnum(IR(ir->op2)->t))
- asm_callid(as, ir, IRCALL_pow);
- else
- asm_fppowi(as, ir);
+ asm_callid(as, ir, irt_isnum(IR(ir->op2)->t) ? IRCALL_lj_vm_pow :
+ IRCALL_lj_vm_powi);
}
static void asm_div(ASMState *as, IRIns *ir)
diff --git a/src/lj_asm_x86.h b/src/lj_asm_x86.h
index 74f2d853..2b810c8d 100644
--- a/src/lj_asm_x86.h
+++ b/src/lj_asm_x86.h
@@ -2005,19 +2005,6 @@ static void asm_ldexp(ASMState *as, IRIns *ir)
asm_x87load(as, ir->op2);
}
-static void asm_fppowi(ASMState *as, IRIns *ir)
-{
- /* The modified regs must match with the *.dasc implementation. */
- RegSet drop = RSET_RANGE(RID_XMM0, RID_XMM1+1)|RID2RSET(RID_EAX);
- if (ra_hasreg(ir->r))
- rset_clear(drop, ir->r); /* Dest reg handled below. */
- ra_evictset(as, drop);
- ra_destreg(as, ir, RID_XMM0);
- emit_call(as, lj_vm_powi_sse);
- ra_left(as, RID_XMM0, ir->op1);
- ra_left(as, RID_EAX, ir->op2);
-}
-
static int asm_swapops(ASMState *as, IRIns *ir)
{
IRIns *irl = IR(ir->op1);
diff --git a/src/lj_dispatch.h b/src/lj_dispatch.h
index b8bc2594..af870a75 100644
--- a/src/lj_dispatch.h
+++ b/src/lj_dispatch.h
@@ -44,7 +44,7 @@ extern double __divdf3(double a, double b);
#define GOTDEF(_) \
_(floor) _(ceil) _(trunc) _(log) _(log10) _(exp) _(sin) _(cos) _(tan) \
_(asin) _(acos) _(atan) _(sinh) _(cosh) _(tanh) _(frexp) _(modf) _(atan2) \
- _(pow) _(fmod) _(ldexp) _(lj_vm_modi) \
+ _(lj_vm_pow) _(fmod) _(ldexp) _(lj_vm_modi) \
_(lj_dispatch_call) _(lj_dispatch_ins) _(lj_dispatch_stitch) \
_(lj_dispatch_profile) _(lj_err_throw) \
_(lj_ffh_coroutine_wrap_err) _(lj_func_closeuv) _(lj_func_newL_gc) \
diff --git a/src/lj_ircall.h b/src/lj_ircall.h
index af064a6f..ac0888a0 100644
--- a/src/lj_ircall.h
+++ b/src/lj_ircall.h
@@ -195,7 +195,7 @@ typedef struct CCallInfo {
_(ANY, log, 1, N, NUM, XA_FP) \
_(ANY, lj_vm_log2, 1, N, NUM, XA_FP) \
_(ANY, lj_vm_powi, 2, N, NUM, XA_FP) \
- _(ANY, pow, 2, N, NUM, XA2_FP) \
+ _(ANY, lj_vm_pow, 2, N, NUM, XA2_FP) \
_(ANY, atan2, 2, N, NUM, XA2_FP) \
_(ANY, ldexp, 2, N, NUM, XA_FP) \
_(SOFTFP, lj_vm_tobit, 1, N, INT, XA_FP32) \
diff --git a/src/lj_opt_fold.c b/src/lj_opt_fold.c
index 0007107b..7d7cc9d1 100644
--- a/src/lj_opt_fold.c
+++ b/src/lj_opt_fold.c
@@ -1114,33 +1114,6 @@ LJFOLDF(simplify_numpow_xkint)
return ref;
}
-LJFOLD(POW any KNUM)
-LJFOLDF(simplify_numpow_xknum)
-{
- if (knumright == 0.5) /* x ^ 0.5 ==> sqrt(x) */
- return emitir(IRTN(IR_FPMATH), fins->op1, IRFPM_SQRT);
- return NEXTFOLD;
-}
-
-LJFOLD(POW KNUM any)
-LJFOLDF(simplify_numpow_kx)
-{
- lua_Number n = knumleft;
- if (n == 2.0 && irt_isint(fright->t)) { /* 2.0 ^ i ==> ldexp(1.0, i) */
-#if LJ_TARGET_X86ORX64
- /* Different IR_LDEXP calling convention on x86/x64 requires conversion. */
- fins->o = IR_CONV;
- fins->op1 = fins->op2;
- fins->op2 = IRCONV_NUM_INT;
- fins->op2 = (IRRef1)lj_opt_fold(J);
-#endif
- fins->op1 = (IRRef1)lj_ir_knum_one(J);
- fins->o = IR_LDEXP;
- return RETRYFOLD;
- }
- return NEXTFOLD;
-}
-
/* -- Simplify conversions ------------------------------------------------ */
LJFOLD(CONV CONV IRCONV_NUM_INT) /* _NUM */
diff --git a/src/lj_opt_narrow.c b/src/lj_opt_narrow.c
index 2cfb775b..d6601f4c 100644
--- a/src/lj_opt_narrow.c
+++ b/src/lj_opt_narrow.c
@@ -590,20 +590,14 @@ TRef lj_opt_narrow_pow(jit_State *J, TRef rb, TRef rc, TValue *vb, TValue *vc)
rb = conv_str_tonum(J, rb, vb);
rb = lj_ir_tonum(J, rb); /* Left arg is always treated as an FP number. */
rc = conv_str_tonum(J, rc, vc);
- /* Narrowing must be unconditional to preserve (-x)^i semantics. */
if (tvisint(vc) || numisint(numV(vc))) {
- int checkrange = 0;
- /* 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 force_pow_num;
- checkrange = 1;
- }
+ int32_t k = numberVint(vc);
+ if (!(k >= -65536 && k <= 65536)) goto force_pow_num;
if (!tref_isinteger(rc)) {
/* 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 */
+ if (!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));
}
diff --git a/src/lj_vm.h b/src/lj_vm.h
index abaa7c52..f6f28a08 100644
--- a/src/lj_vm.h
+++ b/src/lj_vm.h
@@ -82,10 +82,6 @@ LJ_ASMF int32_t LJ_FASTCALL lj_vm_modi(int32_t, int32_t);
LJ_ASMF void lj_vm_floor_sse(void);
LJ_ASMF void lj_vm_ceil_sse(void);
LJ_ASMF void lj_vm_trunc_sse(void);
-LJ_ASMF void lj_vm_powi_sse(void);
-#define lj_vm_powi NULL
-#else
-LJ_ASMF double lj_vm_powi(double, int32_t);
#endif
#if LJ_TARGET_PPC || LJ_TARGET_ARM64
#define lj_vm_trunc trunc
@@ -100,6 +96,9 @@ LJ_ASMF int lj_vm_errno(void);
#endif
#endif
+LJ_ASMF double lj_vm_powi(double, int32_t);
+LJ_ASMF double lj_vm_pow(double, double);
+
/* Continuations for metamethods. */
LJ_ASMF void lj_cont_cat(void); /* Continue with concatenation. */
LJ_ASMF void lj_cont_ra(void); /* Store result in RA from instruction. */
diff --git a/src/lj_vmmath.c b/src/lj_vmmath.c
index 14e66687..539f955b 100644
--- a/src/lj_vmmath.c
+++ b/src/lj_vmmath.c
@@ -30,11 +30,51 @@ LJ_FUNCA double lj_wrap_sinh(double x) { return sinh(x); }
LJ_FUNCA double lj_wrap_cosh(double x) { return cosh(x); }
LJ_FUNCA double lj_wrap_tanh(double x) { return tanh(x); }
LJ_FUNCA double lj_wrap_atan2(double x, double y) { return atan2(x, y); }
-LJ_FUNCA double lj_wrap_pow(double x, double y) { return pow(x, y); }
LJ_FUNCA double lj_wrap_fmod(double x, double y) { return fmod(x, y); }
#endif
-/* -- Helper functions for generated machine code ------------------------- */
+/* -- Helper functions ---------------------------------------------------- */
+
+/* Unsigned x^k. */
+static double lj_vm_powui(double x, uint32_t k)
+{
+ double y;
+ lj_assertX(k != 0, "pow with zero exponent");
+ for (; (k & 1) == 0; k >>= 1) x *= x;
+ y = x;
+ if ((k >>= 1) != 0) {
+ for (;;) {
+ x *= x;
+ if (k == 1) break;
+ if (k & 1) y *= x;
+ k >>= 1;
+ }
+ y *= x;
+ }
+ return y;
+}
+
+/* Signed x^k. */
+double lj_vm_powi(double x, int32_t k)
+{
+ if (k > 1)
+ return lj_vm_powui(x, (uint32_t)k);
+ else if (k == 1)
+ return x;
+ else if (k == 0)
+ return 1.0;
+ else
+ return 1.0 / lj_vm_powui(x, (uint32_t)-k);
+}
+
+double lj_vm_pow(double x, double y)
+{
+ int32_t k = lj_num2int(y);
+ if ((k >= -65536 && k <= 65536) && y == (double)k)
+ return lj_vm_powi(x, k);
+ else
+ return pow(x, y);
+}
double lj_vm_foldarith(double x, double y, int op)
{
@@ -44,7 +84,7 @@ double lj_vm_foldarith(double x, double y, int op)
case IR_MUL - IR_ADD: return x*y; break;
case IR_DIV - IR_ADD: return x/y; break;
case IR_MOD - IR_ADD: return x-lj_vm_floor(x/y)*y; break;
- case IR_POW - IR_ADD: return pow(x, y); break;
+ case IR_POW - IR_ADD: return lj_vm_pow(x, y); break;
case IR_NEG - IR_ADD: return -x; break;
case IR_ABS - IR_ADD: return fabs(x); break;
#if LJ_HASJIT
@@ -56,6 +96,8 @@ double lj_vm_foldarith(double x, double y, int op)
}
}
+/* -- Helper functions for generated machine code ------------------------- */
+
#if (LJ_HASJIT && !(LJ_TARGET_ARM || LJ_TARGET_ARM64 || LJ_TARGET_PPC)) || LJ_TARGET_MIPS
int32_t LJ_FASTCALL lj_vm_modi(int32_t a, int32_t b)
{
@@ -80,40 +122,6 @@ double lj_vm_log2(double a)
}
#endif
-#if !LJ_TARGET_X86ORX64
-/* Unsigned x^k. */
-static double lj_vm_powui(double x, uint32_t k)
-{
- double y;
- lj_assertX(k != 0, "pow with zero exponent");
- for (; (k & 1) == 0; k >>= 1) x *= x;
- y = x;
- if ((k >>= 1) != 0) {
- for (;;) {
- x *= x;
- if (k == 1) break;
- if (k & 1) y *= x;
- k >>= 1;
- }
- y *= x;
- }
- return y;
-}
-
-/* Signed x^k. */
-double lj_vm_powi(double x, int32_t k)
-{
- if (k > 1)
- return lj_vm_powui(x, (uint32_t)k);
- else if (k == 1)
- return x;
- else if (k == 0)
- return 1.0;
- else
- return 1.0 / lj_vm_powui(x, (uint32_t)-k);
-}
-#endif
-
/* Computes fpm(x) for extended math functions. */
double lj_vm_foldfpm(double x, int fpm)
{
diff --git a/src/vm_arm.dasc b/src/vm_arm.dasc
index 767d31f9..792f0363 100644
--- a/src/vm_arm.dasc
+++ b/src/vm_arm.dasc
@@ -1485,11 +1485,11 @@ static void build_subroutines(BuildCtx *ctx)
|.endif
|.endmacro
|
- |.macro math_extern2, func
+ |.macro math_extern2, name, func
|.if HFABI
- | .ffunc_dd math_ .. func
+ | .ffunc_dd math_ .. name
|.else
- | .ffunc_nn math_ .. func
+ | .ffunc_nn math_ .. name
|.endif
| .IOS mov RA, BASE
| bl extern func
@@ -1500,6 +1500,9 @@ static void build_subroutines(BuildCtx *ctx)
| b ->fff_restv
|.endif
|.endmacro
+ |.macro math_extern2, func
+ | math_extern2 func, func
+ |.endmacro
|
|.if FPU
| .ffunc_d math_sqrt
@@ -1545,7 +1548,7 @@ static void build_subroutines(BuildCtx *ctx)
| math_extern sinh
| math_extern cosh
| math_extern tanh
- | math_extern2 pow
+ | math_extern2 pow, lj_vm_pow
| math_extern2 atan2
| math_extern2 fmod
|
@@ -3153,7 +3156,7 @@ static void build_ins(BuildCtx *ctx, BCOp op, int defop)
break;
case BC_POW:
| // NYI: (partial) integer arithmetic.
- | ins_arithfp extern, extern pow
+ | ins_arithfp extern, extern lj_vm_pow
break;
case BC_CAT:
diff --git a/src/vm_arm64.dasc b/src/vm_arm64.dasc
index de33bde4..fb267a76 100644
--- a/src/vm_arm64.dasc
+++ b/src/vm_arm64.dasc
@@ -1391,11 +1391,14 @@ static void build_subroutines(BuildCtx *ctx)
| b ->fff_resn
|.endmacro
|
- |.macro math_extern2, func
- | .ffunc_nn math_ .. func
+ |.macro math_extern2, name, func
+ | .ffunc_nn math_ .. name
| bl extern func
| b ->fff_resn
|.endmacro
+ |.macro math_extern2, func
+ | math_extern2 func, func
+ |.endmacro
|
|.ffunc_n math_sqrt
| fsqrt d0, d0
@@ -1424,7 +1427,7 @@ static void build_subroutines(BuildCtx *ctx)
| math_extern sinh
| math_extern cosh
| math_extern tanh
- | math_extern2 pow
+ | math_extern2 pow, lj_vm_pow
| math_extern2 atan2
| math_extern2 fmod
|
@@ -2621,7 +2624,7 @@ static void build_ins(BuildCtx *ctx, BCOp op, int defop)
| ins_arithload FARG1, FARG2
| ins_arithfallback ins_arithcheck_num
|.if "fpins" == "fpow"
- | bl extern pow
+ | bl extern lj_vm_pow
|.else
| fpins FARG1, FARG1, FARG2
|.endif
diff --git a/src/vm_mips.dasc b/src/vm_mips.dasc
index 32caabf7..5664f503 100644
--- a/src/vm_mips.dasc
+++ b/src/vm_mips.dasc
@@ -1631,14 +1631,17 @@ static void build_subroutines(BuildCtx *ctx)
|. nop
|.endmacro
|
- |.macro math_extern2, func
- | .ffunc_nn math_ .. func
+ |.macro math_extern2, name, func
+ | .ffunc_nn math_ .. name
|. load_got func
| call_extern
|. nop
| b ->fff_resn
|. nop
|.endmacro
+ |.macro math_extern2, func
+ | math_extern2 func, func
+ |.endmacro
|
|// TODO: Return integer type if result is integer (own sf implementation).
|.macro math_round, func
@@ -1692,7 +1695,7 @@ static void build_subroutines(BuildCtx *ctx)
| math_extern sinh
| math_extern cosh
| math_extern tanh
- | math_extern2 pow
+ | math_extern2 pow, lj_vm_pow
| math_extern2 atan2
| math_extern2 fmod
|
@@ -3585,7 +3588,7 @@ static void build_ins(BuildCtx *ctx, BCOp op, int defop)
| sltiu AT, SFARG1HI, LJ_TISNUM
| sltiu TMP0, SFARG2HI, LJ_TISNUM
| and AT, AT, TMP0
- | load_got pow
+ | load_got lj_vm_pow
| beqz AT, ->vmeta_arith
|. addu RA, BASE, RA
|.if FPU
diff --git a/src/vm_mips64.dasc b/src/vm_mips64.dasc
index 44fba36c..249605d4 100644
--- a/src/vm_mips64.dasc
+++ b/src/vm_mips64.dasc
@@ -1669,14 +1669,17 @@ static void build_subroutines(BuildCtx *ctx)
|. nop
|.endmacro
|
- |.macro math_extern2, func
- | .ffunc_nn math_ .. func
+ |.macro math_extern2, name, func
+ | .ffunc_nn math_ .. name
|. load_got func
| call_extern
|. nop
| b ->fff_resn
|. nop
|.endmacro
+ |.macro math_extern2, func
+ | math_extern2 func, func
+ |.endmacro
|
|// TODO: Return integer type if result is integer (own sf implementation).
|.macro math_round, func
@@ -1730,7 +1733,7 @@ static void build_subroutines(BuildCtx *ctx)
| math_extern sinh
| math_extern cosh
| math_extern tanh
- | math_extern2 pow
+ | math_extern2 pow, lj_vm_pow
| math_extern2 atan2
| math_extern2 fmod
|
@@ -3823,7 +3826,7 @@ static void build_ins(BuildCtx *ctx, BCOp op, int defop)
| sltiu TMP0, TMP0, LJ_TISNUM
| sltiu TMP1, TMP1, LJ_TISNUM
| and AT, TMP0, TMP1
- | load_got pow
+ | load_got lj_vm_pow
| beqz AT, ->vmeta_arith
|. daddu RA, BASE, RA
|.if FPU
diff --git a/src/vm_ppc.dasc b/src/vm_ppc.dasc
index 980ad897..94af63e6 100644
--- a/src/vm_ppc.dasc
+++ b/src/vm_ppc.dasc
@@ -2032,11 +2032,14 @@ static void build_subroutines(BuildCtx *ctx)
| b ->fff_resn
|.endmacro
|
- |.macro math_extern2, func
- | .ffunc_nn math_ .. func
+ |.macro math_extern2, name, func
+ | .ffunc_nn math_ .. name
| blex func
| b ->fff_resn
|.endmacro
+ |.macro math_extern2, func
+ | math_extern2 func, func
+ |.endmacro
|
|.macro math_round, func
| .ffunc_1 math_ .. func
@@ -2161,7 +2164,7 @@ static void build_subroutines(BuildCtx *ctx)
| math_extern sinh
| math_extern cosh
| math_extern tanh
- | math_extern2 pow
+ | math_extern2 pow, lj_vm_pow
| math_extern2 atan2
| math_extern2 fmod
|
@@ -4154,7 +4157,7 @@ static void build_ins(BuildCtx *ctx, BCOp op, int defop)
| checknum cr1, CARG3
| crand 4*cr0+lt, 4*cr0+lt, 4*cr1+lt
| bge ->vmeta_arith_vv
- | blex pow
+ | blex lj_vm_pow
| ins_next1
|.if FPU
| stfdx FARG1, BASE, RA
diff --git a/src/vm_x64.dasc b/src/vm_x64.dasc
index 7b04b928..acbe8dc2 100644
--- a/src/vm_x64.dasc
+++ b/src/vm_x64.dasc
@@ -1825,13 +1825,16 @@ static void build_subroutines(BuildCtx *ctx)
| jmp ->fff_resxmm0
|.endmacro
|
- |.macro math_extern2, func
- | .ffunc_nn math_ .. func
+ |.macro math_extern2, name, func
+ | .ffunc_nn math_ .. name
| mov RB, BASE
| call extern func
| mov BASE, RB
| jmp ->fff_resxmm0
|.endmacro
+ |.macro math_extern2, func
+ | math_extern2 func, func
+ |.endmacro
|
| math_extern log10
| math_extern exp
@@ -1844,7 +1847,7 @@ static void build_subroutines(BuildCtx *ctx)
| math_extern sinh
| math_extern cosh
| math_extern tanh
- | math_extern2 pow
+ | math_extern2 pow, lj_vm_pow
| math_extern2 atan2
| math_extern2 fmod
|
@@ -2649,41 +2652,6 @@ static void build_subroutines(BuildCtx *ctx)
| subsd xmm0, xmm1
| ret
|
- |// Args in xmm0/eax. Ret in xmm0. xmm0-xmm1 and eax modified.
- |->vm_powi_sse:
- | cmp eax, 1; jle >6 // i<=1?
- | // Now 1 < (unsigned)i <= 0x80000000.
- |1: // Handle leading zeros.
- | test eax, 1; jnz >2
- | mulsd xmm0, xmm0
- | shr eax, 1
- | jmp <1
- |2:
- | shr eax, 1; jz >5
- | movaps xmm1, xmm0
- |3: // Handle trailing bits.
- | mulsd xmm0, xmm0
- | shr eax, 1; jz >4
- | jnc <3
- | mulsd xmm1, xmm0
- | jmp <3
- |4:
- | mulsd xmm0, xmm1
- |5:
- | ret
- |6:
- | je <5 // x^1 ==> x
- | jb >7 // x^0 ==> 1
- | neg eax
- | call <1
- | sseconst_1 xmm1, RD
- | divsd xmm1, xmm0
- | movaps xmm0, xmm1
- | ret
- |7:
- | sseconst_1 xmm0, RD
- | ret
- |
|//-----------------------------------------------------------------------
|//-- Miscellaneous functions --------------------------------------------
|//-----------------------------------------------------------------------
diff --git a/src/vm_x86.dasc b/src/vm_x86.dasc
index bd1e940e..bf30cce6 100644
--- a/src/vm_x86.dasc
+++ b/src/vm_x86.dasc
@@ -2240,8 +2240,8 @@ static void build_subroutines(BuildCtx *ctx)
| jmp ->fff_resfp
|.endmacro
|
- |.macro math_extern2, func
- | .ffunc_nnsse math_ .. func
+ |.macro math_extern2, name, func
+ | .ffunc_nnsse math_ .. name
|.if not X64
| movsd FPARG1, xmm0
| movsd FPARG3, xmm1
@@ -2251,6 +2251,9 @@ static void build_subroutines(BuildCtx *ctx)
| mov BASE, RB
| jmp ->fff_resfp
|.endmacro
+ |.macro math_extern2, func
+ | math_extern2 func, func
+ |.endmacro
|
| math_extern log10
| math_extern exp
@@ -2263,7 +2266,7 @@ static void build_subroutines(BuildCtx *ctx)
| math_extern sinh
| math_extern cosh
| math_extern tanh
- | math_extern2 pow
+ | math_extern2 pow, lj_vm_pow
| math_extern2 atan2
| math_extern2 fmod
|
@@ -3140,41 +3143,6 @@ static void build_subroutines(BuildCtx *ctx)
| subsd xmm0, xmm1
| ret
|
- |// Args in xmm0/eax. Ret in xmm0. xmm0-xmm1 and eax modified.
- |->vm_powi_sse:
- | cmp eax, 1; jle >6 // i<=1?
- | // Now 1 < (unsigned)i <= 0x80000000.
- |1: // Handle leading zeros.
- | test eax, 1; jnz >2
- | mulsd xmm0, xmm0
- | shr eax, 1
- | jmp <1
- |2:
- | shr eax, 1; jz >5
- | movaps xmm1, xmm0
- |3: // Handle trailing bits.
- | mulsd xmm0, xmm0
- | shr eax, 1; jz >4
- | jnc <3
- | mulsd xmm1, xmm0
- | jmp <3
- |4:
- | mulsd xmm0, xmm1
- |5:
- | ret
- |6:
- | je <5 // x^1 ==> x
- | jb >7 // x^0 ==> 1
- | neg eax
- | call <1
- | sseconst_1 xmm1, RDa
- | divsd xmm1, xmm0
- | movaps xmm0, xmm1
- | ret
- |7:
- | sseconst_1 xmm0, RDa
- | ret
- |
|//-----------------------------------------------------------------------
|//-- Miscellaneous functions --------------------------------------------
|//-----------------------------------------------------------------------
@@ -3976,7 +3944,7 @@ static void build_ins(BuildCtx *ctx, BCOp op, int defop)
| movsd FPARG1, xmm0
| movsd FPARG3, xmm1
|.endif
- | call extern pow
+ | call extern lj_vm_pow
| movzx RA, PC_RA
| mov BASE, RB
|.if X64
diff --git a/test/tarantool-tests/lj-684-pow-inconsistencies.test.lua b/test/tarantool-tests/lj-684-pow-inconsistencies.test.lua
new file mode 100644
index 00000000..5129fc45
--- /dev/null
+++ b/test/tarantool-tests/lj-684-pow-inconsistencies.test.lua
@@ -0,0 +1,89 @@
+local tap = require('tap')
+-- Test to demonstrate the incorrect JIT behaviour for different
+-- power operation optimizations.
+-- See also:
+-- https://github.com/LuaJIT/LuaJIT/issues/684.
+local test = tap.test('lj-684-pow-inconsistencies'):skipcond({
+ ['Test requires JIT enabled'] = not jit.status(),
+})
+
+local tostring = tostring
+
+test:plan(4)
+
+jit.opt.start('hotloop=1')
+
+-- XXX: Prevent hotcount side effects.
+jit.off()
+jit.flush()
+
+local res = {}
+-- -0 ^ 0.5 = 0. Test sign with `tostring()`.
+-- XXX: use local variable to prevent folding via parser.
+-- XXX: use stack slot out of trace to prevent constant folding.
+local minus_zero = -0
+jit.on()
+for i = 1, 4 do
+ res[i] = tostring(minus_zero ^ 0.5)
+end
+
+-- XXX: Prevent hotcount side effects.
+jit.off()
+jit.flush()
+
+test:samevalues(res, ('consistent results for folding (-0) ^ 0.5'))
+
+jit.on()
+-- -inf ^ 0.5 = inf.
+res = {}
+local minus_inf = -math.huge
+jit.on()
+for i = 1, 4 do
+ res[i] = minus_inf ^ 0.5
+end
+
+-- XXX: Prevent hotcount side effects.
+jit.off()
+jit.flush()
+
+test:samevalues(res, ('consistent results for folding (-inf) ^ 0.5'))
+
+-- 2921 ^ 0.5 = 0x1.b05ec632536fap+5.
+res = {}
+-- XXX: use local variable to prevent folding via parser.
+-- XXX: use stack slot out of trace to prevent constant folding.
+local corner_case_05 = 2921
+jit.on()
+for i = 1, 4 do
+ res[i] = corner_case_05 ^ 0.5
+end
+
+-- XXX: Prevent hotcount side effects.
+jit.off()
+jit.flush()
+
+test:samevalues(res, ('consistent results for folding 2921 ^ 0.5'))
+
+-- Narrowing for non-constant base of power operation.
+local function pow(base, power)
+ return base ^ power
+end
+
+jit.on()
+
+-- Compile function first.
+pow(1, 2)
+pow(1, 2)
+
+-- Need some value near 1, to avoid infinite result.
+local base = 1.0000000001
+local power = 65536 * 3
+local resulting_value = pow(base, power)
+
+-- XXX: Prevent hotcount side effects.
+jit.off()
+jit.flush()
+
+test:is(resulting_value, base ^ power, 'guard for narrowing of power operation')
+
+test:done(true)
diff --git a/test/tarantool-tests/lj-9-pow-inconsistencies.test.lua b/test/tarantool-tests/lj-9-pow-inconsistencies.test.lua
index 21b3a0d9..1f7f65c5 100644
--- a/test/tarantool-tests/lj-9-pow-inconsistencies.test.lua
+++ b/test/tarantool-tests/lj-9-pow-inconsistencies.test.lua
@@ -16,6 +16,8 @@ local INTERESTING_VALUES = {
-- x ^ inf = 0 (inf), if |x| < 1 (|x| > 1).
-- x ^ -inf = inf (0), if |x| < 1 (|x| > 1).
0.999999, 1.000001, -0.999999, -1.000001,
+ -- Test power of even numbers optimizations.
+ 2, -2, 0.5, -0.5,
}
test:plan(1 + (#INTERESTING_VALUES) ^ 2)
--
2.41.0
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