From: Sergey Kaplun via Tarantool-patches <tarantool-patches@dev.tarantool.org> To: Maxim Kokryashkin <m.kokryashkin@tarantool.org>, Sergey Bronnikov <sergeyb@tarantool.org> Cc: tarantool-patches@dev.tarantool.org Subject: [Tarantool-patches] [PATCH luajit 2/5] Remove pow() splitting and cleanup backends. Date: Tue, 15 Aug 2023 12:36:28 +0300 [thread overview] Message-ID: <04224626635ddc4c5bb3341088dddd0d310f7e9f.1692089299.git.skaplun@tarantool.org> (raw) In-Reply-To: <cover.1692089298.git.skaplun@tarantool.org> From: Mike Pall <mike> (cherry-picked from commit b2307c8ad817e350d65cc909a579ca2f77439682) The JIT engine tries to split b^c to exp2(c * log2(b)) with attempt to rejoin them later for some backends. It adds a dependency on C99 exp2() and log2(), which aren't part of some libm implementations. Also, for some cases for IEEE754 we can see, that exp2(log2(x)) != x, due to mathematical functions accuracy and double precision restrictions. So, the values on the JIT slots and Lua stack are inconsistent. This patch removes splitting of pow operator, so IR_POW is emitting for all cases (except power of 0.5 replaced with sqrt operation). Also this patch does some refactoring: * Functions `asm_pow()`, `asm_mod()`, `asm_ldexp()`, `asm_div()` (replaced with `asm_fpdiv()` for CPU architectures) are moved to the <src/lj_asm.c> as far as their implementation is generic for all architectures. * Fusing of IR_HREF + IR_EQ/IR_NE moved to a `asm_fuseequal()`. * Since `lj_vm_exp2()` subroutine and `IRFPM_EXP2` are removed as no longer used. Sergey Kaplun: * added the description and the test for the problem Part of tarantool/tarantool#8825 --- src/lj_arch.h | 3 - src/lj_asm.c | 106 +++++++++++------- src/lj_asm_arm.h | 10 +- src/lj_asm_arm64.h | 39 +------ src/lj_asm_mips.h | 38 +------ src/lj_asm_ppc.h | 9 +- src/lj_asm_x86.h | 37 +----- src/lj_ir.h | 2 +- src/lj_ircall.h | 1 - src/lj_opt_fold.c | 18 ++- src/lj_opt_narrow.c | 20 +--- src/lj_opt_split.c | 21 ---- src/lj_vm.h | 5 - src/lj_vmmath.c | 8 -- .../lj-9-pow-inconsistencies.test.lua | 63 +++++++++++ 15 files changed, 158 insertions(+), 222 deletions(-) create mode 100644 test/tarantool-tests/lj-9-pow-inconsistencies.test.lua diff --git a/src/lj_arch.h b/src/lj_arch.h index cf31a291..3bdbe84e 100644 --- a/src/lj_arch.h +++ b/src/lj_arch.h @@ -607,9 +607,6 @@ #if defined(__ANDROID__) || defined(__symbian__) || LJ_TARGET_XBOX360 || LJ_TARGET_WINDOWS #define LUAJIT_NO_LOG2 #endif -#if defined(__symbian__) || LJ_TARGET_WINDOWS -#define LUAJIT_NO_EXP2 -#endif #if LJ_TARGET_CONSOLE || (LJ_TARGET_IOS && __IPHONE_OS_VERSION_MIN_REQUIRED >= __IPHONE_8_0) #define LJ_NO_SYSTEM 1 #endif diff --git a/src/lj_asm.c b/src/lj_asm.c index b352fd35..a6906b19 100644 --- a/src/lj_asm.c +++ b/src/lj_asm.c @@ -1356,32 +1356,6 @@ static void asm_call(ASMState *as, IRIns *ir) asm_gencall(as, ci, args); } -#if !LJ_SOFTFP32 -static void asm_fppow(ASMState *as, IRIns *ir, IRRef lref, IRRef rref) -{ - const CCallInfo *ci = &lj_ir_callinfo[IRCALL_pow]; - IRRef args[2]; - args[0] = lref; - args[1] = rref; - asm_setupresult(as, ir, ci); - asm_gencall(as, ci, args); -} - -static int asm_fpjoin_pow(ASMState *as, IRIns *ir) -{ - IRIns *irp = IR(ir->op1); - if (irp == ir-1 && irp->o == IR_MUL && !ra_used(irp)) { - IRIns *irpp = IR(irp->op1); - if (irpp == ir-2 && irpp->o == IR_FPMATH && - irpp->op2 == IRFPM_LOG2 && !ra_used(irpp)) { - asm_fppow(as, ir, irpp->op1, irp->op2); - return 1; - } - } - return 0; -} -#endif - /* -- PHI and loop handling ----------------------------------------------- */ /* Break a PHI cycle by renaming to a free register (evict if needed). */ @@ -1652,6 +1626,62 @@ static void asm_loop(ASMState *as) #error "Missing assembler for target CPU" #endif +/* -- Common instruction helpers ------------------------------------------ */ + +#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) +{ +#if LJ_64 && LJ_HASFFI + if (!irt_isnum(ir->t)) + asm_callid(as, ir, irt_isi64(ir->t) ? IRCALL_lj_carith_powi64 : + IRCALL_lj_carith_powu64); + else +#endif + if (irt_isnum(IR(ir->op2)->t)) + asm_callid(as, ir, IRCALL_pow); + else + asm_fppowi(as, ir); +} + +static void asm_div(ASMState *as, IRIns *ir) +{ +#if LJ_64 && LJ_HASFFI + if (!irt_isnum(ir->t)) + asm_callid(as, ir, irt_isi64(ir->t) ? IRCALL_lj_carith_divi64 : + IRCALL_lj_carith_divu64); + else +#endif + asm_fpdiv(as, ir); +} +#endif + +static void asm_mod(ASMState *as, IRIns *ir) +{ +#if LJ_64 && LJ_HASFFI + if (!irt_isint(ir->t)) + asm_callid(as, ir, irt_isi64(ir->t) ? IRCALL_lj_carith_modi64 : + IRCALL_lj_carith_modu64); + else +#endif + asm_callid(as, ir, IRCALL_lj_vm_modi); +} + +static void asm_fuseequal(ASMState *as, IRIns *ir) +{ + /* Fuse HREF + EQ/NE. */ + if ((ir-1)->o == IR_HREF && ir->op1 == as->curins-1) { + as->curins--; + asm_href(as, ir-1, (IROp)ir->o); + } else { + asm_equal(as, ir); + } +} + /* -- Instruction dispatch ------------------------------------------------ */ /* Assemble a single instruction. */ @@ -1674,14 +1704,7 @@ static void asm_ir(ASMState *as, IRIns *ir) case IR_ABC: asm_comp(as, ir); break; - case IR_EQ: case IR_NE: - if ((ir-1)->o == IR_HREF && ir->op1 == as->curins-1) { - as->curins--; - asm_href(as, ir-1, (IROp)ir->o); - } else { - asm_equal(as, ir); - } - break; + case IR_EQ: case IR_NE: asm_fuseequal(as, ir); break; case IR_RETF: asm_retf(as, ir); break; @@ -1750,7 +1773,13 @@ static void asm_ir(ASMState *as, IRIns *ir) case IR_SNEW: case IR_XSNEW: asm_snew(as, ir); break; case IR_TNEW: asm_tnew(as, ir); break; case IR_TDUP: asm_tdup(as, ir); break; - case IR_CNEW: case IR_CNEWI: asm_cnew(as, ir); break; + case IR_CNEW: case IR_CNEWI: +#if LJ_HASFFI + asm_cnew(as, ir); +#else + lua_assert(0); +#endif + break; /* Buffer operations. */ case IR_BUFHDR: asm_bufhdr(as, ir); break; @@ -2215,6 +2244,10 @@ static void asm_setup_regsp(ASMState *as) if (inloop) as->modset |= RSET_SCRATCH; #if LJ_TARGET_X86 + if (irt_isnum(IR(ir->op2)->t)) { + if (as->evenspill < 4) /* Leave room to call pow(). */ + as->evenspill = 4; + } break; #else ir->prev = REGSP_HINT(RID_FPRET); @@ -2240,9 +2273,6 @@ static void asm_setup_regsp(ASMState *as) continue; } break; - } else if (ir->op2 == IRFPM_EXP2 && !LJ_64) { - if (as->evenspill < 4) /* Leave room to call pow(). */ - as->evenspill = 4; } #endif if (inloop) diff --git a/src/lj_asm_arm.h b/src/lj_asm_arm.h index 2894e5c9..29a07c80 100644 --- a/src/lj_asm_arm.h +++ b/src/lj_asm_arm.h @@ -1275,8 +1275,6 @@ static void asm_cnew(ASMState *as, IRIns *ir) ra_allockreg(as, (int32_t)(sz+sizeof(GCcdata)), ra_releasetmp(as, ASMREF_TMP1)); } -#else -#define asm_cnew(as, ir) ((void)0) #endif /* -- Write barriers ------------------------------------------------------ */ @@ -1371,8 +1369,6 @@ static void asm_callround(ASMState *as, IRIns *ir, int id) static void asm_fpmath(ASMState *as, IRIns *ir) { - if (ir->op2 == IRFPM_EXP2 && asm_fpjoin_pow(as, ir)) - return; if (ir->op2 <= IRFPM_TRUNC) asm_callround(as, ir, ir->op2); else if (ir->op2 == IRFPM_SQRT) @@ -1499,14 +1495,10 @@ static void asm_mul(ASMState *as, IRIns *ir) #define asm_mulov(as, ir) asm_mul(as, ir) #if !LJ_SOFTFP -#define asm_div(as, ir) asm_fparith(as, ir, ARMI_VDIV_D) -#define asm_pow(as, ir) asm_callid(as, ir, IRCALL_lj_vm_powi) +#define asm_fpdiv(as, ir) asm_fparith(as, ir, ARMI_VDIV_D) #define asm_abs(as, ir) asm_fpunary(as, ir, ARMI_VABS_D) -#define asm_ldexp(as, ir) asm_callid(as, ir, IRCALL_ldexp) #endif -#define asm_mod(as, ir) asm_callid(as, ir, IRCALL_lj_vm_modi) - static void asm_neg(ASMState *as, IRIns *ir) { #if !LJ_SOFTFP diff --git a/src/lj_asm_arm64.h b/src/lj_asm_arm64.h index aea251a9..c3d6889e 100644 --- a/src/lj_asm_arm64.h +++ b/src/lj_asm_arm64.h @@ -1249,8 +1249,6 @@ static void asm_cnew(ASMState *as, IRIns *ir) ra_allockreg(as, (int32_t)(sz+sizeof(GCcdata)), ra_releasetmp(as, ASMREF_TMP1)); } -#else -#define asm_cnew(as, ir) ((void)0) #endif /* -- Write barriers ------------------------------------------------------ */ @@ -1327,8 +1325,6 @@ static void asm_fpmath(ASMState *as, IRIns *ir) } else if (fpm <= IRFPM_TRUNC) { asm_fpunary(as, ir, fpm == IRFPM_FLOOR ? A64I_FRINTMd : fpm == IRFPM_CEIL ? A64I_FRINTPd : A64I_FRINTZd); - } else if (fpm == IRFPM_EXP2 && asm_fpjoin_pow(as, ir)) { - return; } else { asm_callid(as, ir, IRCALL_lj_vm_floor + fpm); } @@ -1435,45 +1431,12 @@ static void asm_mul(ASMState *as, IRIns *ir) asm_intmul(as, ir); } -static void asm_div(ASMState *as, IRIns *ir) -{ -#if LJ_HASFFI - if (!irt_isnum(ir->t)) - asm_callid(as, ir, irt_isi64(ir->t) ? IRCALL_lj_carith_divi64 : - IRCALL_lj_carith_divu64); - else -#endif - asm_fparith(as, ir, A64I_FDIVd); -} - -static void asm_pow(ASMState *as, IRIns *ir) -{ -#if LJ_HASFFI - if (!irt_isnum(ir->t)) - asm_callid(as, ir, irt_isi64(ir->t) ? IRCALL_lj_carith_powi64 : - IRCALL_lj_carith_powu64); - else -#endif - asm_callid(as, ir, IRCALL_lj_vm_powi); -} - #define asm_addov(as, ir) asm_add(as, ir) #define asm_subov(as, ir) asm_sub(as, ir) #define asm_mulov(as, ir) asm_mul(as, ir) +#define asm_fpdiv(as, ir) asm_fparith(as, ir, A64I_FDIVd) #define asm_abs(as, ir) asm_fpunary(as, ir, A64I_FABS) -#define asm_ldexp(as, ir) asm_callid(as, ir, IRCALL_ldexp) - -static void asm_mod(ASMState *as, IRIns *ir) -{ -#if LJ_HASFFI - if (!irt_isint(ir->t)) - asm_callid(as, ir, irt_isi64(ir->t) ? IRCALL_lj_carith_modi64 : - IRCALL_lj_carith_modu64); - else -#endif - asm_callid(as, ir, IRCALL_lj_vm_modi); -} static void asm_neg(ASMState *as, IRIns *ir) { diff --git a/src/lj_asm_mips.h b/src/lj_asm_mips.h index 4626507b..0f92959b 100644 --- a/src/lj_asm_mips.h +++ b/src/lj_asm_mips.h @@ -1613,8 +1613,6 @@ static void asm_cnew(ASMState *as, IRIns *ir) ra_allockreg(as, (int32_t)(sz+sizeof(GCcdata)), ra_releasetmp(as, ASMREF_TMP1)); } -#else -#define asm_cnew(as, ir) ((void)0) #endif /* -- Write barriers ------------------------------------------------------ */ @@ -1683,8 +1681,6 @@ static void asm_fpunary(ASMState *as, IRIns *ir, MIPSIns mi) #if !LJ_SOFTFP32 static void asm_fpmath(ASMState *as, IRIns *ir) { - if (ir->op2 == IRFPM_EXP2 && asm_fpjoin_pow(as, ir)) - return; #if !LJ_SOFTFP if (ir->op2 <= IRFPM_TRUNC) asm_callround(as, ir, IRCALL_lj_vm_floor + ir->op2); @@ -1772,41 +1768,13 @@ static void asm_mul(ASMState *as, IRIns *ir) } } -static void asm_mod(ASMState *as, IRIns *ir) -{ -#if LJ_64 && LJ_HASFFI - if (!irt_isint(ir->t)) - asm_callid(as, ir, irt_isi64(ir->t) ? IRCALL_lj_carith_modi64 : - IRCALL_lj_carith_modu64); - else -#endif - asm_callid(as, ir, IRCALL_lj_vm_modi); -} - #if !LJ_SOFTFP32 -static void asm_pow(ASMState *as, IRIns *ir) -{ -#if LJ_64 && LJ_HASFFI - if (!irt_isnum(ir->t)) - asm_callid(as, ir, irt_isi64(ir->t) ? IRCALL_lj_carith_powi64 : - IRCALL_lj_carith_powu64); - else -#endif - asm_callid(as, ir, IRCALL_lj_vm_powi); -} - -static void asm_div(ASMState *as, IRIns *ir) +static void asm_fpdiv(ASMState *as, IRIns *ir) { -#if LJ_64 && LJ_HASFFI - if (!irt_isnum(ir->t)) - asm_callid(as, ir, irt_isi64(ir->t) ? IRCALL_lj_carith_divi64 : - IRCALL_lj_carith_divu64); - else -#endif #if !LJ_SOFTFP asm_fparith(as, ir, MIPSI_DIV_D); #else - asm_callid(as, ir, IRCALL_softfp_div); + asm_callid(as, ir, IRCALL_softfp_div); #endif } #endif @@ -1844,8 +1812,6 @@ static void asm_abs(ASMState *as, IRIns *ir) } #endif -#define asm_ldexp(as, ir) asm_callid(as, ir, IRCALL_ldexp) - static void asm_arithov(ASMState *as, IRIns *ir) { /* TODO MIPSR6: bovc/bnvc. Caveat: no delay slot to load RID_TMP. */ diff --git a/src/lj_asm_ppc.h b/src/lj_asm_ppc.h index 6aaed058..62a5c3e2 100644 --- a/src/lj_asm_ppc.h +++ b/src/lj_asm_ppc.h @@ -1177,8 +1177,6 @@ static void asm_cnew(ASMState *as, IRIns *ir) ra_allockreg(as, (int32_t)(sz+sizeof(GCcdata)), ra_releasetmp(as, ASMREF_TMP1)); } -#else -#define asm_cnew(as, ir) ((void)0) #endif /* -- Write barriers ------------------------------------------------------ */ @@ -1249,8 +1247,6 @@ static void asm_fpunary(ASMState *as, IRIns *ir, PPCIns pi) static void asm_fpmath(ASMState *as, IRIns *ir) { - if (ir->op2 == IRFPM_EXP2 && asm_fpjoin_pow(as, ir)) - return; if (ir->op2 == IRFPM_SQRT && (as->flags & JIT_F_SQRT)) asm_fpunary(as, ir, PPCI_FSQRT); else @@ -1364,9 +1360,7 @@ static void asm_mul(ASMState *as, IRIns *ir) } } -#define asm_div(as, ir) asm_fparith(as, ir, PPCI_FDIV) -#define asm_mod(as, ir) asm_callid(as, ir, IRCALL_lj_vm_modi) -#define asm_pow(as, ir) asm_callid(as, ir, IRCALL_lj_vm_powi) +#define asm_fpdiv(as, ir) asm_fparith(as, ir, PPCI_FDIV) static void asm_neg(ASMState *as, IRIns *ir) { @@ -1390,7 +1384,6 @@ static void asm_neg(ASMState *as, IRIns *ir) } #define asm_abs(as, ir) asm_fpunary(as, ir, PPCI_FABS) -#define asm_ldexp(as, ir) asm_callid(as, ir, IRCALL_ldexp) static void asm_arithov(ASMState *as, IRIns *ir, PPCIns pi) { diff --git a/src/lj_asm_x86.h b/src/lj_asm_x86.h index 63d332ca..5f5fe3cf 100644 --- a/src/lj_asm_x86.h +++ b/src/lj_asm_x86.h @@ -1857,8 +1857,6 @@ static void asm_cnew(ASMState *as, IRIns *ir) asm_gencall(as, ci, args); emit_loadi(as, ra_releasetmp(as, ASMREF_TMP1), (int32_t)(sz+sizeof(GCcdata))); } -#else -#define asm_cnew(as, ir) ((void)0) #endif /* -- Write barriers ------------------------------------------------------ */ @@ -1964,8 +1962,6 @@ static void asm_fpmath(ASMState *as, IRIns *ir) fpm == IRFPM_CEIL ? lj_vm_ceil_sse : lj_vm_trunc_sse); ra_left(as, RID_XMM0, ir->op1); } - } else if (fpm == IRFPM_EXP2 && asm_fpjoin_pow(as, ir)) { - /* Rejoined to pow(). */ } else { asm_callid(as, ir, IRCALL_lj_vm_floor + fpm); } @@ -2000,17 +1996,6 @@ static void asm_fppowi(ASMState *as, IRIns *ir) ra_left(as, RID_EAX, ir->op2); } -static void asm_pow(ASMState *as, IRIns *ir) -{ -#if LJ_64 && LJ_HASFFI - if (!irt_isnum(ir->t)) - asm_callid(as, ir, irt_isi64(ir->t) ? IRCALL_lj_carith_powi64 : - IRCALL_lj_carith_powu64); - else -#endif - asm_fppowi(as, ir); -} - static int asm_swapops(ASMState *as, IRIns *ir) { IRIns *irl = IR(ir->op1); @@ -2208,27 +2193,7 @@ static void asm_mul(ASMState *as, IRIns *ir) asm_intarith(as, ir, XOg_X_IMUL); } -static void asm_div(ASMState *as, IRIns *ir) -{ -#if LJ_64 && LJ_HASFFI - if (!irt_isnum(ir->t)) - asm_callid(as, ir, irt_isi64(ir->t) ? IRCALL_lj_carith_divi64 : - IRCALL_lj_carith_divu64); - else -#endif - asm_fparith(as, ir, XO_DIVSD); -} - -static void asm_mod(ASMState *as, IRIns *ir) -{ -#if LJ_64 && LJ_HASFFI - if (!irt_isint(ir->t)) - asm_callid(as, ir, irt_isi64(ir->t) ? IRCALL_lj_carith_modi64 : - IRCALL_lj_carith_modu64); - else -#endif - asm_callid(as, ir, IRCALL_lj_vm_modi); -} +#define asm_fpdiv(as, ir) asm_fparith(as, ir, XO_DIVSD) static void asm_neg_not(ASMState *as, IRIns *ir, x86Group3 xg) { diff --git a/src/lj_ir.h b/src/lj_ir.h index e8bca275..43e55069 100644 --- a/src/lj_ir.h +++ b/src/lj_ir.h @@ -177,7 +177,7 @@ LJ_STATIC_ASSERT((int)IR_XLOAD + IRDELTA_L2S == (int)IR_XSTORE); /* FPMATH sub-functions. ORDER FPM. */ #define IRFPMDEF(_) \ _(FLOOR) _(CEIL) _(TRUNC) /* Must be first and in this order. */ \ - _(SQRT) _(EXP2) _(LOG) _(LOG2) \ + _(SQRT) _(LOG) _(LOG2) \ _(OTHER) typedef enum { diff --git a/src/lj_ircall.h b/src/lj_ircall.h index bbad35b1..af064a6f 100644 --- a/src/lj_ircall.h +++ b/src/lj_ircall.h @@ -192,7 +192,6 @@ typedef struct CCallInfo { _(FPMATH, lj_vm_ceil, 1, N, NUM, XA_FP) \ _(FPMATH, lj_vm_trunc, 1, N, NUM, XA_FP) \ _(FPMATH, sqrt, 1, N, NUM, XA_FP) \ - _(ANY, lj_vm_exp2, 1, N, NUM, XA_FP) \ _(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) \ diff --git a/src/lj_opt_fold.c b/src/lj_opt_fold.c index 27e489af..cd803d87 100644 --- a/src/lj_opt_fold.c +++ b/src/lj_opt_fold.c @@ -237,10 +237,11 @@ LJFOLDF(kfold_fpcall2) } LJFOLD(POW KNUM KINT) +LJFOLD(POW KNUM KNUM) LJFOLDF(kfold_numpow) { lua_Number a = knumleft; - lua_Number b = (lua_Number)fright->i; + lua_Number b = fright->o == IR_KINT ? (lua_Number)fright->i : knumright; lua_Number y = lj_vm_foldarith(a, b, IR_POW - IR_ADD); return lj_ir_knum(J, y); } @@ -1077,7 +1078,7 @@ LJFOLDF(simplify_nummuldiv_negneg) } LJFOLD(POW any KINT) -LJFOLDF(simplify_numpow_xk) +LJFOLDF(simplify_numpow_xkint) { int32_t k = fright->i; TRef ref = fins->op1; @@ -1106,13 +1107,22 @@ LJFOLDF(simplify_numpow_xk) 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) { /* 2.0 ^ i ==> ldexp(1.0, tonum(i)) */ - fins->o = IR_CONV; + 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); diff --git a/src/lj_opt_narrow.c b/src/lj_opt_narrow.c index bb61f97b..4f285334 100644 --- a/src/lj_opt_narrow.c +++ b/src/lj_opt_narrow.c @@ -593,10 +593,10 @@ TRef lj_opt_narrow_pow(jit_State *J, TRef rb, TRef rc, TValue *vb, TValue *vc) /* 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. */ + /* 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; + if (!(k >= -65536 && k <= 65536)) goto force_pow_num; checkrange = 1; } if (!tref_isinteger(rc)) { @@ -607,19 +607,11 @@ TRef lj_opt_narrow_pow(jit_State *J, TRef rb, TRef rc, TValue *vb, TValue *vc) 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); + } else { +force_pow_num: + rc = lj_ir_tonum(J, rc); /* Want POW(num, num), not POW(num, int). */ } -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); + return emitir(IRTN(IR_POW), rb, rc); } /* -- Predictive narrowing of induction variables ------------------------- */ diff --git a/src/lj_opt_split.c b/src/lj_opt_split.c index 2fc36b8d..c10a85cb 100644 --- a/src/lj_opt_split.c +++ b/src/lj_opt_split.c @@ -403,27 +403,6 @@ static void split_ir(jit_State *J) hi = split_call_li(J, hisubst, oir, ir, IRCALL_lj_vm_powi); break; case IR_FPMATH: - /* Try to rejoin pow from EXP2, MUL and LOG2. */ - if (nir->op2 == IRFPM_EXP2 && nir->op1 > J->loopref) { - IRIns *irp = IR(nir->op1); - if (irp->o == IR_CALLN && irp->op2 == IRCALL_softfp_mul) { - IRIns *irm4 = IR(irp->op1); - IRIns *irm3 = IR(irm4->op1); - IRIns *irm12 = IR(irm3->op1); - IRIns *irl1 = IR(irm12->op1); - if (irm12->op1 > J->loopref && irl1->o == IR_CALLN && - irl1->op2 == IRCALL_lj_vm_log2) { - IRRef tmp = irl1->op1; /* Recycle first two args from LOG2. */ - IRRef arg3 = irm3->op2, arg4 = irm4->op2; - J->cur.nins--; - tmp = split_emit(J, IRT(IR_CARG, IRT_NIL), tmp, arg3); - tmp = split_emit(J, IRT(IR_CARG, IRT_NIL), tmp, arg4); - ir->prev = tmp = split_emit(J, IRTI(IR_CALLN), tmp, IRCALL_pow); - hi = split_emit(J, IRT(IR_HIOP, IRT_SOFTFP), tmp, tmp); - break; - } - } - } hi = split_call_l(J, hisubst, oir, ir, IRCALL_lj_vm_floor + ir->op2); break; case IR_LDEXP: diff --git a/src/lj_vm.h b/src/lj_vm.h index 411caafa..abaa7c52 100644 --- a/src/lj_vm.h +++ b/src/lj_vm.h @@ -95,11 +95,6 @@ LJ_ASMF double lj_vm_trunc(double); LJ_ASMF double lj_vm_trunc_sf(double); #endif #endif -#ifdef LUAJIT_NO_EXP2 -LJ_ASMF double lj_vm_exp2(double); -#else -#define lj_vm_exp2 exp2 -#endif #if LJ_HASFFI LJ_ASMF int lj_vm_errno(void); #endif diff --git a/src/lj_vmmath.c b/src/lj_vmmath.c index ae4e0f15..9c0d3fde 100644 --- a/src/lj_vmmath.c +++ b/src/lj_vmmath.c @@ -79,13 +79,6 @@ double lj_vm_log2(double a) } #endif -#ifdef LUAJIT_NO_EXP2 -double lj_vm_exp2(double a) -{ - return exp(a * 0.6931471805599453); -} -#endif - #if !LJ_TARGET_X86ORX64 /* Unsigned x^k. */ static double lj_vm_powui(double x, uint32_t k) @@ -128,7 +121,6 @@ double lj_vm_foldfpm(double x, int fpm) case IRFPM_CEIL: return lj_vm_ceil(x); case IRFPM_TRUNC: return lj_vm_trunc(x); case IRFPM_SQRT: return sqrt(x); - case IRFPM_EXP2: return lj_vm_exp2(x); case IRFPM_LOG: return log(x); case IRFPM_LOG2: return lj_vm_log2(x); default: lua_assert(0); diff --git a/test/tarantool-tests/lj-9-pow-inconsistencies.test.lua b/test/tarantool-tests/lj-9-pow-inconsistencies.test.lua new file mode 100644 index 00000000..21b3a0d9 --- /dev/null +++ b/test/tarantool-tests/lj-9-pow-inconsistencies.test.lua @@ -0,0 +1,63 @@ +local tap = require('tap') +-- Test to demonstrate the incorrect JIT behaviour when splitting +-- IR_POW. +-- See also https://github.com/LuaJIT/LuaJIT/issues/9. +local test = tap.test('lj-9-pow-inconsistencies'):skipcond({ + ['Test requires JIT enabled'] = not jit.status(), +}) + +local nan = 0 / 0 +local inf = math.huge + +-- Table with some corner cases to check: +local INTERESTING_VALUES = { + -- 0, -0, 1, -1 special cases with nan, inf, etc.. + 0, -0, 1, -1, nan, inf, -inf, + -- 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:plan(1 + (#INTERESTING_VALUES) ^ 2) + +jit.opt.start('hotloop=1') + +-- The JIT engine tries to split b^c to exp2(c * log2(b)). +-- For some cases for IEEE754 we can see, that +-- (double)exp2((double)log2(x)) != x, due to mathematical +-- functions accuracy and double precision restrictions. +-- Just use some numbers to observe this misbehaviour. +local res = {} +local cnt = 1 +while cnt < 4 do + -- XXX: use local variable to prevent folding via parser. + local b = -0.90000000001 + res[cnt] = 1000 ^ b + cnt = cnt + 1 +end + +test:samevalues(res, 'consistent pow operator behaviour for corner case') + +-- Prevent JIT side effects for parent loops. +jit.off() +for i = 1, #INTERESTING_VALUES do + for j = 1, #INTERESTING_VALUES do + local b = INTERESTING_VALUES[i] + local c = INTERESTING_VALUES[j] + local results = {} + local counter = 1 + jit.on() + while counter < 4 do + results[counter] = b ^ c + counter = counter + 1 + end + -- Prevent JIT side effects. + jit.off() + jit.flush() + test:samevalues( + results, + ('consistent pow operator behaviour for (%s)^(%s)'):format(b, c) + ) + end +end + +test:done(true) -- 2.41.0
next prev parent reply other threads:[~2023-08-15 9:42 UTC|newest] Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top 2023-08-15 9:36 [Tarantool-patches] [PATCH luajit 0/5] Fix pow inconsistencies and improve asserts Sergey Kaplun via Tarantool-patches 2023-08-15 9:36 ` [Tarantool-patches] [PATCH luajit 1/5] test: introduce `samevalues()` TAP checker Sergey Kaplun via Tarantool-patches 2023-08-17 14:03 ` Maxim Kokryashkin via Tarantool-patches 2023-08-17 15:03 ` Sergey Kaplun via Tarantool-patches 2023-08-18 10:43 ` Sergey Bronnikov via Tarantool-patches 2023-08-18 10:58 ` Sergey Kaplun via Tarantool-patches 2023-08-18 11:12 ` Sergey Bronnikov via Tarantool-patches 2023-08-21 10:47 ` Igor Munkin via Tarantool-patches 2023-08-24 7:44 ` Sergey Bronnikov via Tarantool-patches 2023-08-15 9:36 ` Sergey Kaplun via Tarantool-patches [this message] 2023-08-17 14:52 ` [Tarantool-patches] [PATCH luajit 2/5] Remove pow() splitting and cleanup backends Maxim Kokryashkin via Tarantool-patches 2023-08-17 15:33 ` Sergey Kaplun via Tarantool-patches 2023-08-20 9:48 ` Maxim Kokryashkin via Tarantool-patches 2023-08-18 11:08 ` Sergey Bronnikov via Tarantool-patches 2023-08-15 9:36 ` [Tarantool-patches] [PATCH luajit 3/5] Improve assertions Sergey Kaplun via Tarantool-patches 2023-08-17 14:58 ` Maxim Kokryashkin via Tarantool-patches 2023-08-18 7:56 ` Sergey Kaplun via Tarantool-patches 2023-08-18 11:20 ` Sergey Bronnikov via Tarantool-patches 2023-08-15 9:36 ` [Tarantool-patches] [PATCH luajit 4/5] Fix pow() optimization inconsistencies Sergey Kaplun via Tarantool-patches 2023-08-18 12:45 ` Sergey Bronnikov via Tarantool-patches 2023-08-21 8:07 ` Sergey Kaplun via Tarantool-patches 2023-08-20 9:26 ` Maxim Kokryashkin via Tarantool-patches 2023-08-21 8:06 ` Sergey Kaplun via Tarantool-patches 2023-08-21 9:00 ` Maxim Kokryashkin via Tarantool-patches 2023-08-21 9:31 ` Sergey Kaplun via Tarantool-patches 2023-08-15 9:36 ` [Tarantool-patches] [PATCH luajit 5/5] Revert to trival pow() optimizations to prevent inaccuracies Sergey Kaplun via Tarantool-patches 2023-08-18 12:49 ` Sergey Bronnikov via Tarantool-patches 2023-08-21 8:16 ` Sergey Kaplun via Tarantool-patches 2023-08-20 9:37 ` Maxim Kokryashkin via Tarantool-patches 2023-08-21 8:15 ` Sergey Kaplun via Tarantool-patches 2023-08-21 9:06 ` Maxim Kokryashkin via Tarantool-patches 2023-08-21 9:36 ` Sergey Kaplun via Tarantool-patches 2023-08-24 7:47 ` [Tarantool-patches] [PATCH luajit 0/5] Fix pow inconsistencies and improve asserts Sergey Bronnikov via Tarantool-patches 2023-08-31 15:18 ` Igor Munkin via Tarantool-patches
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