| .file "libm_frexpf.s" |
| |
| |
| // Copyright (c) 2000 - 2003, 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 |
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| // EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, |
| // PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR |
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| // 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 Initial version |
| // 03/20/00 Improved speed |
| // 06/01/00 Fixed bug when x a double-extended denormal |
| // 12/08/00 Corrected label on .endp |
| // 01/23/02 Added handling for int 32 or 64 bits |
| // 05/20/02 Cleaned up namespace and sf0 syntax |
| // 02/10/03 Reordered header: .section, .global, .proc, .align |
| // |
| // API |
| //============================================================== |
| // float __libm_frexpf(float x, int* y, int int_type) |
| // input floating point f8, pointer to y (r33), int int_type (r34) |
| // output floating point f8, returns the fraction of x, 0.5 <= fraction < 1.0 |
| // output int* y, returns the true exponent of x |
| // |
| // int_type = 0 if int is 32 bits |
| // int_type = 1 if int is 64 bits |
| // |
| // int* y is returned as a 32 bit integer if int_type = 0 |
| // int* y is returned as a 64 bit integer if int_type = 1 |
| // |
| // Overview of operation |
| //============================================================== |
| // break a floating point x number into fraction and an exponent |
| // The fraction is returned as a float |
| // The exponent is returned as an integer pointed to by y |
| // This is a true (not a biased exponent) but 0fffe is subtracted |
| // as a bias instead of 0xffff. This is because the fraction returned |
| // is between 0.5 and 1.0, not the expected IEEE range. |
| // |
| // The fraction is 0.5 <= fraction < 1.0 |
| // |
| // Registers used |
| //============================================================== |
| // |
| // general registers: |
| // r14 exponent bias for x negative |
| // r15 exponent bias for x positive |
| // r16 signexp of x |
| // r17 exponent mask |
| // r18 exponent of x |
| // r19 exponent result |
| // r20 signexp of 2^64 |
| // r32 on input contains the 32-bit IEEE float that is in f8 |
| // r33 on input pointer to 32-bit or 64-bit integer for exponent |
| // r34 on input contains 0 if output int is 32 bits, else output int is 64 bits |
| // |
| // predicate registers: |
| // p6 set if x is Nan, zero, or infinity |
| // p7 set if x negative |
| // p8 set if x positive |
| // p9 set if x double-extended denormal |
| // p10 set if int_type = 0, 32-bit integer |
| // p11 set if int_type = 1, 64-bit integer |
| // |
| // floating-point registers: |
| // f8 input, output |
| // f9 normalized x |
| // f10 signexp for significand result for x positive |
| // f11 signexp for significand result for x negative |
| // f12 2^64 |
| |
| .section .text |
| GLOBAL_LIBM_ENTRY(__libm_frexpf) |
| |
| // Set signexp for significand result for x>0 |
| // If x is a NaN, zero, or infinity, return it. |
| // Put 0 in the int pointer. |
| // x NAN, ZERO, INFINITY? |
| // Set signexp for significand result for x<0 |
| { .mfi |
| mov r15 = 0x0fffe |
| fclass.m p6,p7 = f8, 0xe7 |
| mov r14 = 0x2fffe |
| } |
| // Form signexp of 2^64 in case x double-extended denormal |
| // Save the normalized value of input in f9 |
| // The normalization also sets fault flags and takes faults if necessary |
| { .mfi |
| mov r20 = 0x1003f |
| fnorm.s0 f9 = f8 |
| nop.i 999 ;; |
| } |
| |
| // Move signexp for significand result for x>0 to FP reg |
| // Form 2^64 in case x double-extended denormal |
| { .mmi |
| setf.exp f10 = r15 |
| setf.exp f12 = r20 |
| nop.i 999 ;; |
| } |
| |
| // Move signexp for significand result for x<0 to FP reg |
| // p7 if x<0, else p8 |
| // If x=0,nan,inf, set p10 if output int to be 32 bits, or set p11 if 64 bits |
| { .mfi |
| setf.exp f11 = r14 |
| (p7) fcmp.lt.s0 p7,p8 = f8,f0 |
| (p6) cmp.eq.unc p10,p11 = r34, r0 ;; |
| } |
| |
| // If x NAN, ZERO, INFINITY, set *y=0 and exit |
| { .mmb |
| (p10) st4 [r33] = r0 // Store *y=0 as 32-bit integer |
| (p11) st8 [r33] = r0 // Store *y=0 as 64-bit integer |
| (p6) br.ret.spnt b0 ;; |
| } |
| |
| // Form exponent mask |
| // Test for fnorm(x) denormal, means x double-extended denormal |
| { .mfi |
| mov r17 = 0x1ffff |
| fclass.m p9,p0 = f9, 0x0b |
| nop.i 999 ;; |
| } |
| |
| // If x double-extended denormal add 64 to exponent bias for scaling |
| // If x double-extended denormal multiply x * 2^64 which is normal |
| // Set p10 if output int to be 32 bits, or set p11 if 64 bits |
| { .mfi |
| (p9) add r15 = 64, r15 |
| (p9) fmpy.s0 f9 = f9, f12 |
| cmp.eq p10,p11 = r34, r0 ;; |
| } |
| |
| // true exponent stored to int pointer |
| // the bias is treated as 0xfffe instead of |
| // normal 0xffff because we want the significand |
| // to be in the range <=0.5 sig < 1.0 |
| // Store the value of the exponent at the pointer in r33 |
| |
| // If x>0 form significand result |
| { .mfi |
| nop.m 999 |
| (p8) fmerge.se f8 = f10,f9 |
| nop.i 999 ;; |
| } |
| |
| // Get signexp of normalized x |
| // If x<0 form significand result |
| { .mfi |
| getf.exp r16 = f9 |
| (p7) fmerge.se f8 = f11,f9 |
| nop.i 999 ;; |
| } |
| |
| // Get exp of normalized x |
| // Subtract off bias to get true exponent of x |
| { .mmi |
| and r18 = r17,r16 ;; |
| sub r19 = r18,r15 |
| nop.i 999 ;; |
| } |
| |
| // Store int *y as a 32-bit integer |
| // Make the value a float |
| { .mfi |
| (p10) st4 [r33] = r19 // Store *y as 32-bit integer |
| fnorm.s.s0 f8 = f8 |
| nop.i 999 |
| } |
| { .mfb |
| (p11) st8 [r33] = r19 // Store *y as 64-bit integer |
| nop.f 999 |
| br.ret.sptk b0 ;; |
| } |
| |
| GLOBAL_LIBM_END(__libm_frexpf) |