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.file "ilogbf.s"
// Copyright (c) 2000, 2001, Intel Corporation
// All rights reserved.
//
// Contributed 2/2/2000 by John Harrison, Ted Kubaska, Bob Norin, Shane Story,
// and Ping Tak Peter Tang of the Computational Software Lab, Intel Corporation.
//
// WARRANTY DISCLAIMER
//
// 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://developer.intel.com/opensource.
//
// History
//==============================================================
// 2/03/00 Initial version
// 5/26/00 Fix bug when x a double-extended denormal;
// if x=0 call error routine, per C9X
// 8/15/00 Bundle added after call to __libm_error_support to properly
// set [the previously overwritten] GR_Parameter_RESULT.
// 1/20/01 Fixed result for x=0
.align 32
.global ilogbf#
.section .text
.proc ilogbf#
.align 32
// API
//==============================================================
// int = ilogbf(float)
// Overview of operation
//==============================================================
// ilogbf computes log2(x) as an int
// and returns it in r8
// ilogbf is similar to logbf but differs in the following ways:
// +-inf
// ilogbf: returns INT_MAX
// logbf: returns +inf
// Nan returns FP_ILOGBNAN (which is either INT_MAX or INT_MIN)
// ilogbf: returns INT_MAX (7fffffff)
// logbf: returns QNAN (quieted SNAN)
// 0 returns FP_ILOGB0 (which is either INT_MIN or -INT_MAX)
// ilogbf: returns INT_MIN (80000000)
// logbf: returns -inf
// Registers used
//==============================================================
// general local registers:
// ar.pfs r32
// r33 -> r37
// r38 -> r41 used as parameters to error path
// predicate registers used:
// p6 - x nan, inf
// p7 - x 0
// p8 - x norm, unorm
// p9 - x unorm
// floating-point registers used:
// f8 - f10
#include "libm_support.h"
GR_SAVE_PFS = r32
GR_SAVE_B0 = r34
GR_SAVE_GP = r35
GR_Parameter_X = r38
GR_Parameter_Y = r39
GR_Parameter_RESULT = r40
GR_Parameter_TAG = r41
FR_X = f8
FR_Y = f0
FR_RESULT = f0
ilogbf:
// Form signexp of 2^64 in case need to scale denormal
{ .mmf
alloc r32=ar.pfs,1,5,4,0
(p0) mov r37 = 0x1003f
(p0) fnorm f9 = f8 ;;
}
// Form 2^64 in case need to scale denormal
{ .mfi
(p0) setf.exp f10 = r37
(p0) fclass.m.unc p7, p8 = f8, 0xe3
(p0) mov r34 = 0xffff ;;
}
// qnan snan inf norm unorm 0 -+
// 1 1 1 0 0 0 11
// e 3
// X ZERO, returns INT_MIN
// X INF or NAN, returns INT_MAX
{ .mfi
(p0) mov r35 = 0x1ffff
(p8) fclass.m.unc p6, p8 = f8, 0x07
nop.i 999 ;;
}
{ .mlx
nop.m 999
(p7) movl r8 = 0x000000007fffffff ;;
}
{ .mib
nop.m 999
nop.i 999
(p6) br.cond.spnt L(ILOGB_ZERO) ;;
}
// Test for denormal
{ .mfi
nop.m 999
(p8) fclass.m.unc p9, p0 = f9, 0x0b
nop.i 999 ;;
}
L(ILOGB_COMMON):
// X NORMAL returns true exponent
{ .mmi
nop.m 999
(p8) getf.exp r33 = f9
nop.i 999 ;;
}
// If denormal add 64 to exponent bias for scaling
{ .mfb
(p9) add r34 = 64, r34
nop.f 999
(p9) br.cond.spnt L(ILOGB_DENORM) ;;
}
{ .mmi
(p8) and r36 = r35, r33
nop.m 999
nop.i 999 ;;
}
{ .mib
(p8) sub r8 = r36, r34
nop.i 999
(p0) br.ret.sptk b0 ;;
}
L(ILOGB_DENORM):
// Here if x denormal
// Form x * 2^64 which is normal
// Return to common code
{ .mfb
cmp.eq p8,p9 = r0,r0
fmpy f9 = f9, f10
br.cond.sptk L(ILOGB_COMMON) ;;
}
// X ZERO
// return INT_MIN, call error support
L(ILOGB_ZERO):
{.mlx
mov GR_Parameter_TAG = 158
(p6) movl r33 = 0x0000000080000000 ;;
};;
.endp ilogbf
ASM_SIZE_DIRECTIVE(ilogbf)
.proc __libm_error_region
__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 // Save 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
{ .mib
stfs [GR_Parameter_X] = FR_X // Store Parameter 1 on stack
add GR_Parameter_RESULT = 0,GR_Parameter_Y
nop.b 0 // 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
nop.m 0
nop.m 0
add GR_Parameter_RESULT = 48,sp
};;
{ .mmi
mov r8 = r33 // Store result
.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
};;
.endp __libm_error_region
ASM_SIZE_DIRECTIVE(__libm_error_region)
.type __libm_error_support#,@function
.global __libm_error_support#
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