.file "logb.s"
// Copyright (c) 2000, 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
//==============================================================
// 2/02/00 Initial version
// 2/16/00 Modified to conform to C9X
// 3/16/00 Improved speed
// 4/04/00 Unwind support added
// 5/30/00 Fixed bug when x double-extended denormal
// 8/15/00 Bundle added after call to __libm_error_support to properly
// set [the previously overwritten] GR_Parameter_RESULT.
//
// API
//==============================================================
// double _logb( double x);
//
// Overview of operation
//==============================================================
// The logb function extracts the exponent of x as an integer in
// floating-point format.
// logb computes log2 of x as a double
//
// logb is similar to ilogb but differs in the following ways:
// +-inf
// ilogb: returns INT_MAX
// logb: returns +inf
// Nan returns FP_LOGBNAN (which is either INT_MAX or INT_MIN)
// ilogb: returns INT_MAX (7fffffff)
// logb: returns QNAN (quietized SNAN)
// 0 returns FP_ILOGB0 (which is either INT_MIN or -INT_MAX)
// ilogb: returns -INT_MAX (80000001)
// logb: returns -inf, raises the divide-by-zero exception,
// and calls libm_error_support to set domain error
//
// Registers used
//==============================================================
// general registers used:
// ar.pfs r32
// r33 -> r37
// r38 -> r41 used as parameters to error path
//
// predicate registers used:
// p6, p7, p8
// floating-point registers used:
// f9, f10, f11
// f8, input
GR_SAVE_B0 = r34
GR_SAVE_GP = r35
GR_SAVE_PFS = r32
GR_Parameter_X = r38
GR_Parameter_Y = r39
GR_Parameter_RESULT = r40
.align 32
.global _logb#
.section .text
.proc _logb#
.align 32
_logb:
// qnan snan inf norm unorm 0 -+
// 0 0 0 0 1 0 11
// 0 b
{ .mfi
alloc r32=ar.pfs,1,5,4,0
(p0) fclass.m.unc p8,p0 = f8, 0x0b
nop.i 999
}
// X NORMAL
// r37 = exp(f8) - - 0xffff
// sig(f8) = r37
// f8 = convert_to_fp (sig))
{ .mfi
(p0) getf.exp r35 = f8
(p0) fnorm f10=f8
nop.i 999 ;;
}
// qnan snan inf norm unorm 0 -+
// 1 1 1 0 0 0 11
// e 3
{ .mmf
(p0) mov r33 = 0xffff
(p0) mov r34 = 0x1ffff
(p0) fclass.m.unc p6,p0 = f8, 0xe3 ;;
}
{ .mfb
(p0) and r36 = r35, r34
(p0) fclass.m.unc p7,p0 = f8, 0x07
(p8) br.cond.spnt LOGB_DENORM ;;
}
{ .mib
(p0) sub r37 = r36, r33
nop.i 999
(p6) br.cond.spnt LOGB_NAN_INF ;;
}
{ .mib
(p0) setf.sig f9 = r37
nop.i 999
(p7) br.cond.spnt LOGB_ZERO ;;
}
{ .mfi
nop.m 999
(p0) fcvt.xf f10 = f9
nop.i 999 ;;
}
{ .mfb
nop.m 999
(p0) fnorm.d f8 = f10
(p0) br.ret.sptk b0 ;;
}
LOGB_DENORM:
// Form signexp of 2^64 in case need to scale denormal
// Check to see if double-extended denormal
{ .mfi
(p0) mov r38 = 0x1003f
(p0) fclass.m.unc p8,p0 = f10, 0x0b
nop.i 999 ;;
}
// Form 2^64 in case need to scale denormal
{ .mfi
(p0) setf.exp f11 = r38
nop.f 999
nop.i 999 ;;
}
// If double-extended denormal add 64 to exponent bias for scaling
// If double-extended denormal form x * 2^64 which is normal
{ .mfi
(p8) add r33 = 64, r33
(p8) fmpy f10 = f10, f11
nop.i 999 ;;
}
// Logic is the same as normal path but use normalized input
{ .mmi
(p0) getf.exp r35 = f10 ;;
nop.m 999
nop.i 999 ;;
}
{ .mmi
(p0) and r36 = r35, r34 ;;
(p0) sub r37 = r36, r33
nop.i 999 ;;
}
{ .mmi
(p0) setf.sig f9 = r37
nop.m 999
nop.i 999 ;;
}
{ .mfi
nop.m 999
(p0) fcvt.xf f10 = f9
nop.i 999 ;;
}
{ .mfb
nop.m 999
(p0) fnorm.d f8 = f10
(p0) br.ret.sptk b0 ;;
}
LOGB_NAN_INF:
// X NAN or INFINITY, return f8 * f8
{ .mfb
nop.m 999
(p0) fma.d f8= f8,f8,f0
(p0) br.ret.sptk b0 ;;
}
.endp _logb#
// Stack operations when calling error support.
// (1) (2) (3) (call) (4)
// sp -> + psp -> + psp -> + sp -> +
// | | | |
// | | <- GR_Y R3 ->| <- GR_RESULT | -> f8
// | | | |
// | <-GR_Y Y2->| Y2 ->| <- GR_Y |
// | | | |
// | | <- GR_X X1 ->| |
// | | | |
// sp-64 -> + sp -> + sp -> + +
// save ar.pfs save b0 restore gp
// save gp restore ar.pfs
.proc __libm_error_region
__libm_error_region:
LOGB_ZERO:
.prologue
// f9 = |f8|
// f10 = -f9 = -|f8|
// f9 = 1.0/f10 = -1.0/-|f8|
{ .mfi
mov r41 = 151 // Error code
(p0) fmerge.s f9 = f0,f8
nop.i 999
}
;;
{ .mfi
nop.m 999
fmerge.ns f10 = f0,f9
nop.i 999
}
;;
// (1)
{ .mfi
add GR_Parameter_Y=-32,sp // Parameter 2 value
frcpa f9,p6 = f1,f10
.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
};;
// (2)
{ .mmi
stfd [GR_Parameter_Y] = f0,16 // 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
// (3)
{ .mib
stfd [GR_Parameter_X] = f8 // STORE Parameter 1 on stack
add GR_Parameter_RESULT = 0,GR_Parameter_Y // Parameter 3 address
nop.b 0
}
{ .mib
stfd [GR_Parameter_Y] = f9 // 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
};;
// (4)
{ .mmi
ldfd f8 = [GR_Parameter_RESULT] // Get return result off stack
.restore
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
};;
.endp __libm_error_region
.type __libm_error_support#,@function
.global __libm_error_support#