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452 lines
15 KiB
NASM
452 lines
15 KiB
NASM
;
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; MIT License
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; -----------
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;
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; Copyright (c) 2002-2019 Advanced Micro Devices, Inc.
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;
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; Permission is hereby granted, free of charge, to any person obtaining a copy
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; of this Software and associated documentaon files (the "Software"), to deal
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; in the Software without restriction, including without limitation the rights
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; to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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; copies of the Software, and to permit persons to whom the Software is
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; furnished to do so, subject to the following conditions:
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;
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; The above copyright notice and this permission notice shall be included in
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; all copies or substantial portions of the Software.
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;
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; THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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; IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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; FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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; AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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; LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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; OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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; THE SOFTWARE.
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;
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;
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; logf.asm
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;
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; An implementation of the logf libm function.
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;
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; Prototype:
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;
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; float logf(float x);
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;
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;
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; Algorithm:
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; Similar to one presnted in log.asm
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;
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.const
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ALIGN 16
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L_real_one DQ 0000000003f800000h ; 1.0
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DQ 0000000000000000h
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L_real_two DQ 00000000040000000h ; 1.0
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DQ 00000000000000000h
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L_real_ninf DQ 000000000ff800000h ; -inf
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DQ 0000000000000000h
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L_real_inf DQ 0000000007f800000h ; +inf
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DQ 0000000000000000h
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L_real_nan DQ 0000000007fc00000h ; NaN
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DQ 0000000000000000h
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L_real_neg_qnan DQ 000000000ffc00000h
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DQ 0000000000000000h
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L_real_notsign DQ 0000000007ffFFFFFh ; ^sign bit
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DQ 0000000000000000h
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L_real_mant DQ 0007FFFFF007FFFFFh ; mantissa bits
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DQ 0007FFFFF007FFFFFh
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L_mask_127 DQ 00000007f0000007fh ;
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DQ 00000007f0000007fh
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L_mask_253 DQ 000000000000000fdh
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DQ 00000000000000000h
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L_mask_mant_all7 DQ 00000000007f0000h
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DQ 00000000007f0000h
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L_mask_mant8 DQ 0000000000008000h
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DQ 0000000000000000h
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L_real_ca1 DQ 0000000003DAAAAABh ; 8.33333333333317923934e-02
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DQ 00000000000000000h
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L_real_ca2 DQ 0000000003C4CCCCDh ; 1.25000000037717509602e-02
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DQ 00000000000000000h
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L_real_log2_lead DQ 03F3170003F317000h ; 0.693115234375
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DQ 00000000000000000h
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L_real_log2_tail DQ 0000000003805FDF4h ; 0.000031946183
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DQ 00000000000000000h
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L_real_half DQ 0000000003f000000h ; 1/2
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DQ 00000000000000000h
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L_real_1_over_3 DQ 0000000003eaaaaabh
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DQ 00000000000000000h
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L_real_1_over_2 DD 03f000000h
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L_real_neg127 DD 0c2fe0000h
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L_real_qnanbit DD 000400000h ; quiet nan bit
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L_real_threshold DD 03d800000h
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; these codes and the ones in the corresponding .c file have to match
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L_flag_x_zero DD 00000001
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L_flag_x_neg DD 00000002
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L_flag_x_nan DD 00000003
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EXTRN __log_128_lead:DWORD
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EXTRN __log_128_tail:DWORD
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EXTRN __log_F_inv_dword:DWORD
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EXTRN __use_fma3_lib:DWORD
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fname TEXTEQU <logf>
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fname_special TEXTEQU <_logf_special>
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; define local variable storage offsets
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dummy_space EQU 020h
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stack_size EQU 038h
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include fm.inc
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; external function
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EXTERN fname_special:PROC
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.code
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PUBLIC fname
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fname PROC FRAME
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StackAllocate stack_size
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.ENDPROLOG
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cmp DWORD PTR __use_fma3_lib, 0
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jne Llogf_fma3
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; Some of the placement of instructions below iwll be odd.
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; We are attempting to have no more than one branch per 32-byte block.
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Llogf_sse2:
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; Zero the high bits of rax because it will be used as an index later.
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xor rax, rax
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movdqa xmm3, xmm0
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movaps xmm4, xmm0
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; This computation of the expoonent of x will produce nonsenes if x <= 0.,
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; but those cases are eliminated below, so it does no harm.
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psrld xmm3, 23 ; xmm3 <-- biased exp if x > 0.
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; Is x Inf or NaN?
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movd eax, xmm0 ; eax <-- x
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mov ecx, eax
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btr ecx, 31 ; ecx <-- |x|
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cmp ecx, DWORD PTR L_real_inf
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jae Llogf_sse2_x_is_inf_or_nan
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; Finish computing exponent.
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psubd xmm3, XMMWORD PTR L_mask_127 ; xmm3 <-- xexp (unbiased)
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movdqa xmm2, xmm0
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cvtdq2ps xmm5, xmm3 ; (float)xexp, unless x <= 0.
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; Is x negative or zero?
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xorps xmm1, xmm1
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comiss xmm0, xmm1
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jbe Llogf_sse2_x_is_zero_or_neg
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pand xmm2, XMMWORD PTR L_real_mant ; xmm2 <-- x mantissa for later
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subss xmm4, DWORD PTR L_real_one ; xmm4 <-- x - 1. for later
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comiss xmm5, DWORD PTR L_real_neg127 ; x!=0, xexp==0 ==> subnormal
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je Llogf_sse2_subnormal_adjust
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Llogf_sse2_continue_common:
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; At this point we need |x| (possibly adjusted) in eax
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; and m = xexpx (possibly adjusted) in xmm5
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; We also need the value of x - 1. computed above.
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; compute the index into the log tables
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mov r9d, eax
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and eax, DWORD PTR L_mask_mant_all7 ; eax <-- 7 bits of x mantissa
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and r9d, DWORD PTR L_mask_mant8 ; r9d <-- 8th bit
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shl r9d, 1
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add eax, r9d ; use 8th bit to round up
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movd xmm1, eax
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; Is x near 1.0 ?
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; Note that if x is subnormal it is perforce not near one.
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andps xmm4, XMMWORD PTR L_real_notsign ; xmm4 <-- |x-1|
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comiss xmm4, DWORD PTR L_real_threshold ; is |x-1| < 1/16?
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jb Llogf_sse2_near_one ; if so, handle elsewhere
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; F, Y
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; F is a number in [.5,1) scaled from the rounded mantissa bits computed
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; above by oring in the exponent of .5.
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; Y is all of the mantissa bits of X scaled to [.5,1.) similarly
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shr eax, 16 ; shift eax to use as index
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por xmm2, XMMWORD PTR L_real_half ; xmm2 <-- Y
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por xmm1, XMMWORD PTR L_real_half ; xmm2 <-- F
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lea r9, QWORD PTR __log_F_inv_dword
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; f = F - Y, r = f * inv
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subss xmm1, xmm2 ; xmm1 <-- f
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mulss xmm1, DWORD PTR [r9+rax*4] ; xmm1 <-- r = f*inv (tabled)
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movaps xmm2, xmm1
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movaps xmm0, xmm1
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; poly
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mulss xmm2, DWORD PTR L_real_1_over_3 ; xmm2 <-- r/3
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mulss xmm0, xmm1 ; xmm0 <-- r^2
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addss xmm2, DWORD PTR L_real_1_over_2
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movaps xmm3, XMMWORD PTR L_real_log2_tail
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lea r9, QWORD PTR __log_128_tail
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lea r10, QWORD PTR __log_128_lead
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mulss xmm2, xmm0 ; xmm2 <-- r^2 * (r/3 + 1/2)
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mulss xmm3, xmm5 ; xmm3 <-- (m=xexp)*log2_tail
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addss xmm1, xmm2 ; xmm1 <-- poly
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; m*log(2) + log(G) - poly, where G is just 2*F
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; log(G) is precomputed to extra precision.
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; small pieces and large pieces are separated until the final add,
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; to preserve accuracy
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movaps xmm0, XMMWORD PTR L_real_log2_lead
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subss xmm3, xmm1 ; xmm3 <-- m*log2_tail - poly
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mulss xmm0, xmm5 ; xmm0 <-- m*log1_lead
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addss xmm3, DWORD PTR [r9+rax*4] ; xmm3 += log(G) tail
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addss xmm0, DWORD PTR [r10+rax*4] ; xmm0 += log(G) lead
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addss xmm0, xmm3 ; xmm0 <-- m*log(2)+log(G)-poly
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StackDeallocate stack_size
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ret
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ALIGN 16
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Llogf_sse2_near_one:
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; Computation of the log for x near one requires special techniques.
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movaps xmm2, DWORD PTR L_real_two
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subss xmm0, DWORD PTR L_real_one ; xmm0 <-- r = x - 1.0
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addss xmm2, xmm0
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movaps xmm1, xmm0
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divss xmm1, xmm2 ; xmm1 <-- u = r/(2.0+r)
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movaps xmm4, xmm0
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mulss xmm4, xmm1 ; xmm4 <-- correction = r*u
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addss xmm1, xmm1 ; xmm1 <-- u = 2.*u
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movaps xmm2, xmm1
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mulss xmm2, xmm2 ; xmm2 <-- u^2
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; r2 = (u^3 * (ca_1 + u^2 * ca_2) - correction)
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movaps xmm3, xmm1
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mulss xmm3, xmm2 ; xmm3 <-- u^3
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mulss xmm2, DWORD PTR L_real_ca2 ; xmm2 <-- ca2*u^2
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addss xmm2, DWORD PTR L_real_ca1 ; xmm2 <-- ca2*u^2 + ca1
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mulss xmm2, xmm3 ; xmm2 <-- u^3*(ca1+u^2*ca2)
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subss xmm2, xmm4 ; xmm2 <-- r2
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; return r + r2
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addss xmm0, xmm2
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StackDeallocate stack_size
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ret
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ALIGN 16
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Llogf_sse2_subnormal_adjust:
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; This code adjusts eax and xmm5.
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; It must preserve xmm4.
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por xmm2, XMMWORD PTR L_real_one
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subss xmm2, DWORD PTR L_real_one
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movdqa xmm5, xmm2
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pand xmm2, XMMWORD PTR L_real_mant
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movd eax, xmm2
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psrld xmm5, 23
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psubd xmm5, XMMWORD PTR L_mask_253
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cvtdq2ps xmm5, xmm5
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jmp Llogf_sse2_continue_common
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; Until we get to the FMA3 code, the rest of this is special case handling.
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Llogf_sse2_x_is_zero_or_neg:
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jne Llogf_sse2_x_is_neg
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movaps xmm1, XMMWORD PTR L_real_ninf
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mov r8d, DWORD PTR L_flag_x_zero
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call fname_special
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jmp Llogf_sse2_finish
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Llogf_sse2_x_is_neg:
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movaps xmm1, XMMWORD PTR L_real_neg_qnan
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mov r8d, DWORD PTR L_flag_x_neg
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call fname_special
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jmp Llogf_sse2_finish
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Llogf_sse2_x_is_inf_or_nan:
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cmp eax, DWORD PTR L_real_inf
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je Llogf_sse2_finish
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cmp eax, DWORD PTR L_real_ninf
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je Llogf_sse2_x_is_neg
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or eax, DWORD PTR L_real_qnanbit
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movd xmm1, eax
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mov r8d, DWORD PTR L_flag_x_nan
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call fname_special
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jmp Llogf_sse2_finish
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Llogf_sse2_finish:
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StackDeallocate stack_size
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ret
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ALIGN 16
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Llogf_fma3:
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; compute exponent part
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vmovaps xmm4,XMMWORD PTR L_real_inf ; preload for inf/nan test
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xor rax,rax
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vpsrld xmm3,xmm0,23 ; xmm3 <-- (ux>>23)
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vmovd eax,xmm0 ;eax = x
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vpsubd xmm3,xmm3,DWORD PTR L_mask_127 ; xmm3 <-- (ux>>23) - 127
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vcvtdq2ps xmm5,xmm3 ; xmm5 <-- float((ux>>23)-127) = xexp
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; NaN or inf
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vpand xmm1,xmm0,xmm4 ; xmm1 <-- (ux & 07f800000h)
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vcomiss xmm1,xmm4
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je Llogf_fma3_x_is_inf_or_nan
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; check for negative numbers or zero
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vpxor xmm1,xmm1,xmm1
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vcomiss xmm0,xmm1
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jbe Llogf_fma3_x_is_zero_or_neg
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vpand xmm2,xmm0,DWORD PTR L_real_mant ; xmm2 <-- ux & 0007FFFFFh
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vsubss xmm4,xmm0,DWORD PTR L_real_one ; xmm4 <-- x - 1.0
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vcomiss xmm5,DWORD PTR L_real_neg127
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je Llogf_fma3_subnormal_adjust
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Llogf_fma3_continue_common:
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; compute the index into the log tables
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vpand xmm1,xmm0,DWORD PTR L_mask_mant_all7 ; xmm1 = ux & 0007f0000h
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vpand xmm3,xmm0,DWORD PTR L_mask_mant8 ; xmm3 = ux & 000008000h
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vpslld xmm3,xmm3,1 ; xmm3 = (ux & 000008000h) << 1
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vpaddd xmm1,xmm3,xmm1
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; eax = (ux & 0007f0000h) + ((ux & 000008000h) << 1)
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; eax <-- x/127., rounded to nearest
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vmovd eax,xmm1
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; near one codepath
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vandps xmm4,xmm4,DWORD PTR L_real_notsign ; xmm4 <-- fabs (x - 1.0)
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vcomiss xmm4,DWORD PTR L_real_threshold
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jb Llogf_fma3_near_one
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; F,Y
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shr eax,16
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vpor xmm2,xmm2,DWORD PTR L_real_half ; xmm2 <-- Y
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vpor xmm1,xmm1,DWORD PTR L_real_half ; xmm1 <-- F
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lea r9,QWORD PTR __log_F_inv_dword
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; f = F - Y
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vsubss xmm1,xmm1,xmm2 ; f = F - Y
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; r = f * log_F_inv_dword[index]
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vmulss xmm1,xmm1,DWORD PTR [r9 + rax * 4]
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; poly
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vmovaps xmm2,XMMWORD PTR L_real_1_over_3
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vfmadd213ss xmm2,xmm1,DWORD PTR L_real_1_over_2 ; 1/3*r + 1/2
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vmulss xmm0,xmm1,xmm1 ; r*r
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vmovaps xmm3,DWORD PTR L_real_log2_tail;
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lea r9,DWORD PTR __log_128_tail
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lea r10,DWORD PTR __log_128_lead
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vfmadd231ss xmm1,xmm2,xmm0 ; poly = r + 1/2*r*r + 1/3*r*r*r
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vfmsub213ss xmm3,xmm5,xmm1 ; (xexp * log2_tail) - poly
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; m*log(2) + log(G) - poly
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vmovaps xmm0,DWORD PTR L_real_log2_lead
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vfmadd213ss xmm0,xmm5,[r10 + rax * 4]
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; z2 = (xexp * log2_tail) - poly + log_128_tail[index]
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vaddss xmm3,xmm3,DWORD PTR [r9 + rax * 4]
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vaddss xmm0,xmm0,xmm3 ; return z1 + z2
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StackDeallocate stack_size
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ret
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ALIGN 16
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Llogf_fma3_near_one:
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; r = x - 1.0;
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vmovaps xmm2,DWORD PTR L_real_two
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vsubss xmm0,xmm0,DWORD PTR L_real_one ; xmm0 = r = = x - 1.0
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; u = r / (2.0 + r)
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vaddss xmm2,xmm2,xmm0 ; (r+2.0)
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vdivss xmm1,xmm0,xmm2 ; u = r / (2.0 + r)
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; correction = r * u
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vmulss xmm4,xmm0,xmm1 ; correction = u*r
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; u = u + u;
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vaddss xmm1,xmm1,xmm1 ; u = u+u
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vmulss xmm2,xmm1,xmm1 ; v = u^2
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; r2 = (u * v * (ca_1 + v * ca_2) - correction)
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vmulss xmm3,xmm1,xmm2 ; u^3
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vmovaps xmm5,DWORD PTR L_real_ca2
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vfmadd213ss xmm2,xmm5,DWORD PTR L_real_ca1
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vfmsub213ss xmm2,xmm3,xmm4 ; r2 = (ca1 + ca2 * v) * u^3 - correction
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; r + r2
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vaddss xmm0,xmm0,xmm2
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StackDeallocate stack_size
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ret
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ALIGN 16
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Llogf_fma3_subnormal_adjust:
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vmovaps xmm3,DWORD PTR L_real_one
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vpor xmm2,xmm2,xmm3 ; xmm2 = temp = ((ux &0007FFFFFh) | 03f800000h)
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vsubss xmm2,xmm2,xmm3 ; xmm2 = temp -1.0
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vpsrld xmm5,xmm2,23 ; xmm5 = (utemp >> 23)
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vpand xmm2,xmm2,DWORD PTR L_real_mant ; xmm2 = (utemp & 0007FFFFFh)
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vmovaps xmm0,xmm2
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vpsubd xmm5,xmm5,DWORD PTR L_mask_253 ; xmm5 = (utemp >> 23) - 253
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vcvtdq2ps xmm5,xmm5 ; xmm5 = (float) ((utemp >> 23) - 253)
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jmp Llogf_fma3_continue_common
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Llogf_fma3_x_is_zero_or_neg:
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jne Llogf_fma3_x_is_neg
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vmovaps xmm1,DWORD PTR L_real_ninf
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mov r8d,DWORD PTR L_flag_x_zero
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call fname_special
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StackDeallocate stack_size
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ret
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Llogf_fma3_x_is_neg:
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vmovaps xmm1,DWORD PTR L_real_neg_qnan
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mov r8d,DWORD PTR L_flag_x_neg
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call fname_special
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StackDeallocate stack_size
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ret
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Llogf_fma3_x_is_inf_or_nan:
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cmp eax,DWORD PTR L_real_inf
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je Llogf_fma3_finish
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cmp eax,DWORD PTR L_real_ninf
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je Llogf_fma3_x_is_neg
|
|
|
|
or eax,DWORD PTR L_real_qnanbit
|
|
vmovd xmm1,eax
|
|
mov r8d,DWORD PTR L_flag_x_nan
|
|
call fname_special
|
|
|
|
StackDeallocate stack_size
|
|
ret
|
|
|
|
Llogf_fma3_finish:
|
|
|
|
StackDeallocate stack_size
|
|
ret
|
|
|
|
|
|
fname endp
|
|
END
|