209 lines
6.8 KiB
ArmAsm
209 lines
6.8 KiB
ArmAsm
.file "libm_frexpf.s"
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// Copyright (c) 2000 - 2003, Intel Corporation
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// All rights reserved.
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//
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//
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// Redistribution and use in source and binary forms, with or without
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// modification, are permitted provided that the following conditions are
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// met:
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//
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// * Redistributions of source code must retain the above copyright
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// notice, this list of conditions and the following disclaimer.
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//
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// * Redistributions in binary form must reproduce the above copyright
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// notice, this list of conditions and the following disclaimer in the
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// documentation and/or other materials provided with the distribution.
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//
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// * The name of Intel Corporation may not be used to endorse or promote
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// products derived from this software without specific prior written
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// permission.
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// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL INTEL OR ITS
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// CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
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// EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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// PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
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// OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY OR TORT (INCLUDING
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// NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
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// SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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//
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// Intel Corporation is the author of this code, and requests that all
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// problem reports or change requests be submitted to it directly at
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// http://www.intel.com/software/products/opensource/libraries/num.htm.
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//
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// History
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//==============================================================
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// 02/02/00 Initial version
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// 03/20/00 Improved speed
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// 06/01/00 Fixed bug when x a double-extended denormal
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// 12/08/00 Corrected label on .endp
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// 01/23/02 Added handling for int 32 or 64 bits
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// 05/20/02 Cleaned up namespace and sf0 syntax
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// 02/10/03 Reordered header: .section, .global, .proc, .align
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//
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// API
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//==============================================================
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// float __libm_frexpf(float x, int* y, int int_type)
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// input floating point f8, pointer to y (r33), int int_type (r34)
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// output floating point f8, returns the fraction of x, 0.5 <= fraction < 1.0
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// output int* y, returns the true exponent of x
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//
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// int_type = 0 if int is 32 bits
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// int_type = 1 if int is 64 bits
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//
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// int* y is returned as a 32 bit integer if int_type = 0
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// int* y is returned as a 64 bit integer if int_type = 1
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//
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// Overview of operation
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//==============================================================
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// break a floating point x number into fraction and an exponent
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// The fraction is returned as a float
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// The exponent is returned as an integer pointed to by y
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// This is a true (not a biased exponent) but 0fffe is subtracted
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// as a bias instead of 0xffff. This is because the fraction returned
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// is between 0.5 and 1.0, not the expected IEEE range.
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//
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// The fraction is 0.5 <= fraction < 1.0
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//
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// Registers used
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//==============================================================
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//
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// general registers:
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// r14 exponent bias for x negative
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// r15 exponent bias for x positive
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// r16 signexp of x
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// r17 exponent mask
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// r18 exponent of x
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// r19 exponent result
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// r20 signexp of 2^64
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// r32 on input contains the 32-bit IEEE float that is in f8
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// r33 on input pointer to 32-bit or 64-bit integer for exponent
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// r34 on input contains 0 if output int is 32 bits, else output int is 64 bits
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//
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// predicate registers:
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// p6 set if x is Nan, zero, or infinity
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// p7 set if x negative
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// p8 set if x positive
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// p9 set if x double-extended denormal
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// p10 set if int_type = 0, 32-bit integer
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// p11 set if int_type = 1, 64-bit integer
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//
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// floating-point registers:
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// f8 input, output
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// f9 normalized x
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// f10 signexp for significand result for x positive
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// f11 signexp for significand result for x negative
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// f12 2^64
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.section .text
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GLOBAL_LIBM_ENTRY(__libm_frexpf)
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// Set signexp for significand result for x>0
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// If x is a NaN, zero, or infinity, return it.
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// Put 0 in the int pointer.
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// x NAN, ZERO, INFINITY?
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// Set signexp for significand result for x<0
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{ .mfi
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mov r15 = 0x0fffe
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fclass.m p6,p7 = f8, 0xe7
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mov r14 = 0x2fffe
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}
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// Form signexp of 2^64 in case x double-extended denormal
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// Save the normalized value of input in f9
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// The normalization also sets fault flags and takes faults if necessary
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{ .mfi
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mov r20 = 0x1003f
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fnorm.s0 f9 = f8
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nop.i 999 ;;
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}
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// Move signexp for significand result for x>0 to FP reg
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// Form 2^64 in case x double-extended denormal
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{ .mmi
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setf.exp f10 = r15
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setf.exp f12 = r20
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nop.i 999 ;;
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}
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// Move signexp for significand result for x<0 to FP reg
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// p7 if x<0, else p8
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// If x=0,nan,inf, set p10 if output int to be 32 bits, or set p11 if 64 bits
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{ .mfi
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setf.exp f11 = r14
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(p7) fcmp.lt.s0 p7,p8 = f8,f0
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(p6) cmp.eq.unc p10,p11 = r34, r0 ;;
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}
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// If x NAN, ZERO, INFINITY, set *y=0 and exit
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{ .mmb
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(p10) st4 [r33] = r0 // Store *y=0 as 32-bit integer
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(p11) st8 [r33] = r0 // Store *y=0 as 64-bit integer
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(p6) br.ret.spnt b0 ;;
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}
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// Form exponent mask
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// Test for fnorm(x) denormal, means x double-extended denormal
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{ .mfi
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mov r17 = 0x1ffff
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fclass.m p9,p0 = f9, 0x0b
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nop.i 999 ;;
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}
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// If x double-extended denormal add 64 to exponent bias for scaling
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// If x double-extended denormal multiply x * 2^64 which is normal
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// Set p10 if output int to be 32 bits, or set p11 if 64 bits
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{ .mfi
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(p9) add r15 = 64, r15
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(p9) fmpy.s0 f9 = f9, f12
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cmp.eq p10,p11 = r34, r0 ;;
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}
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// true exponent stored to int pointer
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// the bias is treated as 0xfffe instead of
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// normal 0xffff because we want the significand
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// to be in the range <=0.5 sig < 1.0
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// Store the value of the exponent at the pointer in r33
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// If x>0 form significand result
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{ .mfi
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nop.m 999
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(p8) fmerge.se f8 = f10,f9
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nop.i 999 ;;
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}
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// Get signexp of normalized x
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// If x<0 form significand result
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{ .mfi
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getf.exp r16 = f9
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(p7) fmerge.se f8 = f11,f9
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nop.i 999 ;;
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}
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// Get exp of normalized x
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// Subtract off bias to get true exponent of x
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{ .mmi
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and r18 = r17,r16 ;;
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sub r19 = r18,r15
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nop.i 999 ;;
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}
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// Store int *y as a 32-bit integer
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// Make the value a float
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{ .mfi
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(p10) st4 [r33] = r19 // Store *y as 32-bit integer
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fnorm.s.s0 f8 = f8
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nop.i 999
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}
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{ .mfb
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(p11) st8 [r33] = r19 // Store *y as 64-bit integer
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nop.f 999
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br.ret.sptk b0 ;;
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}
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GLOBAL_LIBM_END(__libm_frexpf)
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