.file "expf.s" // Copyright (c) 2000 - 2005, Intel Corporation // All rights reserved. // // Contributed 2000 by the Intel Numerics Group, Intel Corporation // // Redistribution and use in source and binary forms, with or without // modification, are permitted provided that the following conditions are // met: // // * Redistributions of source code must retain the above copyright // notice, this list of conditions and the following disclaimer. // // * Redistributions in binary form must reproduce the above copyright // notice, this list of conditions and the following disclaimer in the // documentation and/or other materials provided with the distribution. // // * The name of Intel Corporation may not be used to endorse or promote // products derived from this software without specific prior written // permission. // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL INTEL OR ITS // CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, // EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, // PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR // PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY // OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY OR TORT (INCLUDING // NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS // SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. // // Intel Corporation is the author of this code, and requests that all // problem reports or change requests be submitted to it directly at // http://www.intel.com/software/products/opensource/libraries/num.htm. // History //********************************************************************* // 02/02/00 Original version // 04/04/00 Unwind support added // 08/15/00 Bundle added after call to __libm_error_support to properly // set [the previously overwritten] GR_Parameter_RESULT. // 08/21/00 Improvements to save 2 cycles on main path, and shorten x=0 case // 12/07/00 Widen main path, shorten x=inf, nan paths // 03/15/01 Fix monotonicity problem around x=0 for round to +inf // 02/05/02 Corrected uninitialize predicate in POSSIBLE_UNDERFLOW path // 05/20/02 Cleaned up namespace and sf0 syntax // 07/26/02 Algorithm changed, accuracy improved // 09/26/02 support of higher precision inputs added, underflow threshold // corrected // 11/15/02 Improved performance on Itanium 2, added possible over/under paths // 05/30/03 Set inexact flag on unmasked overflow/underflow // 03/31/05 Reformatted delimiters between data tables // // // API //********************************************************************* // float expf(float) // // Overview of operation //********************************************************************* // Take the input x. w is "how many log2/128 in x?" // w = x * 64/log2 // NJ = int(w) // x = NJ*log2/64 + R // NJ = 64*n + j // x = n*log2 + (log2/64)*j + R // // So, exp(x) = 2^n * 2^(j/64)* exp(R) // // T = 2^n * 2^(j/64) // Construct 2^n // Get 2^(j/64) table // actually all the entries of 2^(j/64) table are stored in DP and // with exponent bits set to 0 -> multiplication on 2^n can be // performed by doing logical "or" operation with bits presenting 2^n // exp(R) = 1 + (exp(R) - 1) // P = exp(R) - 1 approximated by Taylor series of 3rd degree // P = A3*R^3 + A2*R^2 + R, A3 = 1/6, A2 = 1/2 // // The final result is reconstructed as follows // exp(x) = T + T*P // Special values //********************************************************************* // expf(+0) = 1.0 // expf(-0) = 1.0 // expf(+qnan) = +qnan // expf(-qnan) = -qnan // expf(+snan) = +qnan // expf(-snan) = -qnan // expf(-inf) = +0 // expf(+inf) = +inf // Overflow and Underflow //********************************************************************* // expf(x) = largest single normal when // x = 88.72283 = 0x42b17217 // expf(x) = smallest single normal when // x = -87.33654 = 0xc2aeac4f // expf(x) = largest round-to-nearest single zero when // x = -103.97208 = 0xc2cff1b5 // Registers used //********************************************************************* // Floating Point registers used: // f8, input // f6,f7, f9 -> f15, f32 -> f40 // General registers used: // r3, r23 -> r38 // Predicate registers used: // p10 -> p15 // Assembly macros //********************************************************************* // integer registers used // scratch rNJ = r3 rTmp = r23 rJ = r23 rN = r24 rTblAddr = r25 rA3 = r26 rExpHalf = r27 rLn2Div64 = r28 r17ones_m1 = r29 rGt_ln = r29 rRightShifter = r30 r64DivLn2 = r31 // stacked GR_SAVE_PFS = r32 GR_SAVE_B0 = r33 GR_SAVE_GP = r34 GR_Parameter_X = r35 GR_Parameter_Y = r36 GR_Parameter_RESULT = r37 GR_Parameter_TAG = r38 // floating point registers used FR_X = f10 FR_Y = f1 FR_RESULT = f8 // scratch fRightShifter = f6 f64DivLn2 = f7 fNormX = f9 fNint = f10 fN = f11 fR = f12 fLn2Div64 = f13 fA2 = f14 fA3 = f15 // stacked fP = f32 fT = f33 fMIN_SGL_OFLOW_ARG = f34 fMAX_SGL_ZERO_ARG = f35 fMAX_SGL_NORM_ARG = f36 fMIN_SGL_NORM_ARG = f37 fRSqr = f38 fTmp = f39 fGt_pln = f39 fWre_urm_f8 = f40 fFtz_urm_f8 = f40 RODATA .align 16 LOCAL_OBJECT_START(_expf_table) data4 0x42b17218 // Smallest sgl arg to overflow sgl result, +88.7228 data4 0xc2cff1b5 // Largest sgl for rnd-to-nearest 0 result, -103.9720 data4 0x42b17217 // Largest sgl arg to give normal sgl result, +88.7228 data4 0xc2aeac4f // Smallest sgl arg to give normal sgl result, -87.3365 // // 2^(j/64) table, j goes from 0 to 63 data8 0x0000000000000000 // 2^(0/64) data8 0x00002C9A3E778061 // 2^(1/64) data8 0x000059B0D3158574 // 2^(2/64) data8 0x0000874518759BC8 // 2^(3/64) data8 0x0000B5586CF9890F // 2^(4/64) data8 0x0000E3EC32D3D1A2 // 2^(5/64) data8 0x00011301D0125B51 // 2^(6/64) data8 0x0001429AAEA92DE0 // 2^(7/64) data8 0x000172B83C7D517B // 2^(8/64) data8 0x0001A35BEB6FCB75 // 2^(9/64) data8 0x0001D4873168B9AA // 2^(10/64) data8 0x0002063B88628CD6 // 2^(11/64) data8 0x0002387A6E756238 // 2^(12/64) data8 0x00026B4565E27CDD // 2^(13/64) data8 0x00029E9DF51FDEE1 // 2^(14/64) data8 0x0002D285A6E4030B // 2^(15/64) data8 0x000306FE0A31B715 // 2^(16/64) data8 0x00033C08B26416FF // 2^(17/64) data8 0x000371A7373AA9CB // 2^(18/64) data8 0x0003A7DB34E59FF7 // 2^(19/64) data8 0x0003DEA64C123422 // 2^(20/64) data8 0x0004160A21F72E2A // 2^(21/64) data8 0x00044E086061892D // 2^(22/64) data8 0x000486A2B5C13CD0 // 2^(23/64) data8 0x0004BFDAD5362A27 // 2^(24/64) data8 0x0004F9B2769D2CA7 // 2^(25/64) data8 0x0005342B569D4F82 // 2^(26/64) data8 0x00056F4736B527DA // 2^(27/64) data8 0x0005AB07DD485429 // 2^(28/64) data8 0x0005E76F15AD2148 // 2^(29/64) data8 0x0006247EB03A5585 // 2^(30/64) data8 0x0006623882552225 // 2^(31/64) data8 0x0006A09E667F3BCD // 2^(32/64) data8 0x0006DFB23C651A2F // 2^(33/64) data8 0x00071F75E8EC5F74 // 2^(34/64) data8 0x00075FEB564267C9 // 2^(35/64) data8 0x0007A11473EB0187 // 2^(36/64) data8 0x0007E2F336CF4E62 // 2^(37/64) data8 0x00082589994CCE13 // 2^(38/64) data8 0x000868D99B4492ED // 2^(39/64) data8 0x0008ACE5422AA0DB // 2^(40/64) data8 0x0008F1AE99157736 // 2^(41/64) data8 0x00093737B0CDC5E5 // 2^(42/64) data8 0x00097D829FDE4E50 // 2^(43/64) data8 0x0009C49182A3F090 // 2^(44/64) data8 0x000A0C667B5DE565 // 2^(45/64) data8 0x000A5503B23E255D // 2^(46/64) data8 0x000A9E6B5579FDBF // 2^(47/64) data8 0x000AE89F995AD3AD // 2^(48/64) data8 0x000B33A2B84F15FB // 2^(49/64) data8 0x000B7F76F2FB5E47 // 2^(50/64) data8 0x000BCC1E904BC1D2 // 2^(51/64) data8 0x000C199BDD85529C // 2^(52/64) data8 0x000C67F12E57D14B // 2^(53/64) data8 0x000CB720DCEF9069 // 2^(54/64) data8 0x000D072D4A07897C // 2^(55/64) data8 0x000D5818DCFBA487 // 2^(56/64) data8 0x000DA9E603DB3285 // 2^(57/64) data8 0x000DFC97337B9B5F // 2^(58/64) data8 0x000E502EE78B3FF6 // 2^(59/64) data8 0x000EA4AFA2A490DA // 2^(60/64) data8 0x000EFA1BEE615A27 // 2^(61/64) data8 0x000F50765B6E4540 // 2^(62/64) data8 0x000FA7C1819E90D8 // 2^(63/64) LOCAL_OBJECT_END(_expf_table) .section .text GLOBAL_IEEE754_ENTRY(expf) { .mlx addl rTblAddr = @ltoff(_expf_table),gp movl r64DivLn2 = 0x40571547652B82FE // 64/ln(2) } { .mlx addl rA3 = 0x3E2AA, r0 // high bits of 1.0/6.0 rounded to SP movl rRightShifter = 0x43E8000000000000 // DP Right Shifter } ;; { .mfi // point to the beginning of the table ld8 rTblAddr = [rTblAddr] fclass.m p14, p0 = f8, 0x22 // test for -INF shl rA3 = rA3, 12 // 0x3E2AA000, approx to 1.0/6.0 in SP } { .mfi nop.m 0 fnorm.s1 fNormX = f8 // normalized x addl rExpHalf = 0xFFFE, r0 // exponent of 1/2 } ;; { .mfi setf.d f64DivLn2 = r64DivLn2 // load 64/ln(2) to FP reg fclass.m p15, p0 = f8, 0x1e1 // test for NaT,NaN,+Inf nop.i 0 } { .mlx // load Right Shifter to FP reg setf.d fRightShifter = rRightShifter movl rLn2Div64 = 0x3F862E42FEFA39EF // DP ln(2)/64 in GR } ;; { .mfi nop.m 0 fcmp.eq.s1 p13, p0 = f0, f8 // test for x = 0.0 nop.i 0 } { .mfb setf.s fA3 = rA3 // load A3 to FP reg (p14) fma.s.s0 f8 = f0, f1, f0 // result if x = -inf (p14) br.ret.spnt b0 // exit here if x = -inf } ;; { .mfi setf.exp fA2 = rExpHalf // load A2 to FP reg fcmp.eq.s0 p6, p0 = f8, f0 // Dummy to flag denorm nop.i 0 } { .mfb setf.d fLn2Div64 = rLn2Div64 // load ln(2)/64 to FP reg (p15) fma.s.s0 f8 = f8, f1, f0 // result if x = NaT,NaN,+Inf (p15) br.ret.spnt b0 // exit here if x = NaT,NaN,+Inf } ;; { .mfb // overflow and underflow_zero threshold ldfps fMIN_SGL_OFLOW_ARG, fMAX_SGL_ZERO_ARG = [rTblAddr], 8 (p13) fma.s.s0 f8 = f1, f1, f0 // result if x = 0.0 (p13) br.ret.spnt b0 // exit here if x =0.0 } ;; // max normal and underflow_denorm threshold { .mfi ldfps fMAX_SGL_NORM_ARG, fMIN_SGL_NORM_ARG = [rTblAddr], 8 nop.f 0 nop.i 0 } ;; { .mfi nop.m 0 // x*(64/ln(2)) + Right Shifter fma.s1 fNint = fNormX, f64DivLn2, fRightShifter nop.i 0 } ;; // Divide arguments into the following categories: // Certain Underflow p11 - -inf < x <= MAX_SGL_ZERO_ARG // Possible Underflow p13 - MAX_SGL_ZERO_ARG < x < MIN_SGL_NORM_ARG // Certain Safe - MIN_SGL_NORM_ARG <= x <= MAX_SGL_NORM_ARG // Possible Overflow p14 - MAX_SGL_NORM_ARG < x < MIN_SGL_OFLOW_ARG // Certain Overflow p15 - MIN_SGL_OFLOW_ARG <= x < +inf // // If the input is really a single arg, then there will never be // "Possible Overflow" arguments. // { .mfi nop.m 0 // check for overflow fcmp.ge.s1 p15, p0 = fNormX, fMIN_SGL_OFLOW_ARG nop.i 0 } ;; { .mfi nop.m 0 // check for underflow and tiny (+0) result fcmp.le.s1 p11, p0 = fNormX, fMAX_SGL_ZERO_ARG nop.i 0 } { .mfb nop.m 0 fms.s1 fN = fNint, f1, fRightShifter // n in FP register // branch out if overflow (p15) br.cond.spnt EXP_CERTAIN_OVERFLOW } ;; { .mfb getf.sig rNJ = fNint // bits of n, j // check for underflow and deno result fcmp.lt.s1 p13, p0 = fNormX, fMIN_SGL_NORM_ARG // branch out if underflow and tiny (+0) result (p11) br.cond.spnt EXP_CERTAIN_UNDERFLOW } ;; { .mfi nop.m 0 // check for possible overflow fcmp.gt.s1 p14, p0 = fNormX, fMAX_SGL_NORM_ARG extr.u rJ = rNJ, 0, 6 // bits of j } { .mfi addl rN = 0xFFFF - 63, rNJ // biased and shifted n fnma.s1 fR = fLn2Div64, fN, fNormX // R = x - N*ln(2)/64 nop.i 0 } ;; { .mfi shladd rJ = rJ, 3, rTblAddr // address in the 2^(j/64) table nop.f 0 shr rN = rN, 6 // biased n } ;; { .mfi ld8 rJ = [rJ] nop.f 0 shl rN = rN, 52 // 2^n bits in DP format } ;; { .mfi or rN = rN, rJ // bits of 2^n * 2^(j/64) in DP format nop.f 0 nop.i 0 } ;; { .mfi setf.d fT = rN // 2^n * 2^(j/64) fma.s1 fP = fA3, fR, fA2 // A3*R + A2 nop.i 0 } { .mfi nop.m 0 fma.s1 fRSqr = fR, fR, f0 // R^2 nop.i 0 } ;; { .mfi nop.m 0 fma.s1 fP = fP, fRSqr, fR // P = (A3*R + A2)*R^2 + R nop.i 0 } ;; { .mbb nop.m 0 // branch out if possible underflow (p13) br.cond.spnt EXP_POSSIBLE_UNDERFLOW // branch out if possible overflow result (p14) br.cond.spnt EXP_POSSIBLE_OVERFLOW } ;; { .mfb nop.m 0 // final result in the absence of over- and underflow fma.s.s0 f8 = fP, fT, fT // exit here in the absence of over- and underflow br.ret.sptk b0 } ;; EXP_POSSIBLE_OVERFLOW: // Here if fMAX_SGL_NORM_ARG < x < fMIN_SGL_OFLOW_ARG // This cannot happen if input is a single, only if input higher precision. // Overflow is a possibility, not a certainty. // Recompute result using status field 2 with user's rounding mode, // and wre set. If result is larger than largest single, then we have // overflow { .mfi mov rGt_ln = 0x1007f // Exponent for largest single + 1 ulp fsetc.s2 0x7F,0x42 // Get user's round mode, set wre nop.i 0 } ;; { .mfi setf.exp fGt_pln = rGt_ln // Create largest single + 1 ulp fma.s.s2 fWre_urm_f8 = fP, fT, fT // Result with wre set nop.i 0 } ;; { .mfi nop.m 0 fsetc.s2 0x7F,0x40 // Turn off wre in sf2 nop.i 0 } ;; { .mfi nop.m 0 fcmp.ge.s1 p6, p0 = fWre_urm_f8, fGt_pln // Test for overflow nop.i 0 } ;; { .mfb nop.m 0 nop.f 0 (p6) br.cond.spnt EXP_CERTAIN_OVERFLOW // Branch if overflow } ;; { .mfb nop.m 0 fma.s.s0 f8 = fP, fT, fT br.ret.sptk b0 // Exit if really no overflow } ;; // here if overflow EXP_CERTAIN_OVERFLOW: { .mmi addl r17ones_m1 = 0x1FFFE, r0 ;; setf.exp fTmp = r17ones_m1 nop.i 0 } ;; { .mfi alloc r32=ar.pfs,0,3,4,0 fmerge.s FR_X = f8,f8 nop.i 0 } { .mfb mov GR_Parameter_TAG = 16 fma.s.s0 FR_RESULT = fTmp, fTmp, fTmp // Set I,O and +INF result br.cond.sptk __libm_error_region } ;; EXP_POSSIBLE_UNDERFLOW: // Here if fMAX_SGL_ZERO_ARG < x < fMIN_SGL_NORM_ARG // Underflow is a possibility, not a certainty // We define an underflow when the answer with // ftz set // is zero (tiny numbers become zero) // Notice (from below) that if we have an unlimited exponent range, // then there is an extra machine number E between the largest denormal and // the smallest normal. // So if with unbounded exponent we round to E or below, then we are // tiny and underflow has occurred. // But notice that you can be in a situation where we are tiny, namely // rounded to E, but when the exponent is bounded we round to smallest // normal. So the answer can be the smallest normal with underflow. // E // -----+--------------------+--------------------+----- // | | | // 1.1...10 2^-3fff 1.1...11 2^-3fff 1.0...00 2^-3ffe // 0.1...11 2^-3ffe (biased, 1) // largest dn smallest normal { .mfi nop.m 0 fsetc.s2 0x7F,0x41 // Get user's round mode, set ftz nop.i 0 } ;; { .mfi nop.m 0 fma.s.s2 fFtz_urm_f8 = fP, fT, fT // Result with ftz set nop.i 0 } ;; { .mfi nop.m 0 fsetc.s2 0x7F,0x40 // Turn off ftz in sf2 nop.i 0 } ;; { .mfi nop.m 0 fcmp.eq.s1 p6, p7 = fFtz_urm_f8, f0 // Test for underflow nop.i 0 } { .mfi nop.m 0 fma.s.s0 f8 = fP, fT, fT // Compute result, set I, maybe U nop.i 0 } ;; { .mbb nop.m 0 (p6) br.cond.spnt EXP_UNDERFLOW_COMMON // Branch if really underflow (p7) br.ret.sptk b0 // Exit if really no underflow } ;; EXP_CERTAIN_UNDERFLOW: // Here if x < fMAX_SGL_ZERO_ARG // Result will be zero (or smallest denorm if round to +inf) with I, U set { .mmi mov rTmp = 1 ;; setf.exp fTmp = rTmp // Form small normal nop.i 0 } ;; { .mfi nop.m 0 fmerge.se fTmp = fTmp, f64DivLn2 // Small with non-trial signif nop.i 0 } ;; { .mfb nop.m 0 fma.s.s0 f8 = fTmp, fTmp, f0 // Set I,U, tiny (+0.0) result br.cond.sptk EXP_UNDERFLOW_COMMON } ;; EXP_UNDERFLOW_COMMON: // Determine if underflow result is zero or nonzero { .mfi alloc r32=ar.pfs,0,3,4,0 fcmp.eq.s1 p6, p0 = f8, f0 nop.i 0 } ;; { .mfb nop.m 0 fmerge.s FR_X = fNormX,fNormX (p6) br.cond.spnt EXP_UNDERFLOW_ZERO } ;; EXP_UNDERFLOW_NONZERO: // Here if x < fMIN_SGL_NORM_ARG and result nonzero; // I, U are set { .mfb mov GR_Parameter_TAG = 17 nop.f 0 // FR_RESULT already set br.cond.sptk __libm_error_region } ;; EXP_UNDERFLOW_ZERO: // Here if x < fMIN_SGL_NORM_ARG and result zero; // I, U are set { .mfb mov GR_Parameter_TAG = 17 nop.f 0 // FR_RESULT already set br.cond.sptk __libm_error_region } ;; GLOBAL_IEEE754_END(expf) LOCAL_LIBM_ENTRY(__libm_error_region) .prologue { .mfi add GR_Parameter_Y=-32,sp // Parameter 2 value nop.f 0 .save ar.pfs,GR_SAVE_PFS mov GR_SAVE_PFS=ar.pfs // Save ar.pfs } { .mfi .fframe 64 add sp=-64,sp // Create new stack nop.f 0 mov GR_SAVE_GP=gp // Save gp };; { .mmi stfs [GR_Parameter_Y] = FR_Y,16 // Store Parameter 2 on stack add GR_Parameter_X = 16,sp // Parameter 1 address .save b0, GR_SAVE_B0 mov GR_SAVE_B0=b0 // Save b0 };; .body { .mfi stfs [GR_Parameter_X] = FR_X // Store Parameter 1 on stack nop.f 0 add GR_Parameter_RESULT = 0,GR_Parameter_Y // Parameter 3 address } { .mib stfs [GR_Parameter_Y] = FR_RESULT // Store Parameter 3 on stack add GR_Parameter_Y = -16,GR_Parameter_Y br.call.sptk b0=__libm_error_support# // Call error handling function };; { .mmi add GR_Parameter_RESULT = 48,sp nop.m 0 nop.i 0 };; { .mmi ldfs f8 = [GR_Parameter_RESULT] // Get return result off stack .restore sp add sp = 64,sp // Restore stack pointer mov b0 = GR_SAVE_B0 // Restore return address };; { .mib mov gp = GR_SAVE_GP // Restore gp mov ar.pfs = GR_SAVE_PFS // Restore ar.pfs br.ret.sptk b0 // Return };; LOCAL_LIBM_END(__libm_error_region) .type __libm_error_support#,@function .global __libm_error_support#