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.file "logb.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//==============================================================// 2/02/00 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 = r34GR_SAVE_GP = r35GR_SAVE_PFS = r32
GR_Parameter_X = r38GR_Parameter_Y = r39GR_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 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 getf.exp r35 = f8 fnorm f10=f8 nop.i 999 ;;
}
// qnan snan inf norm unorm 0 -+// 1 1 1 0 0 0 11// e 3{ .mmf mov r33 = 0xffff mov r34 = 0x1ffff fclass.m.unc p6,p0 = f8, 0xe3 ;;
}
{ .mfb and r36 = r35, r34 fclass.m.unc p7,p0 = f8, 0x07(p8) br.cond.spnt LOGB_DENORM ;;
}
{ .mib sub r37 = r36, r33 nop.i 999(p6) br.cond.spnt LOGB_NAN_INF ;;
}
{ .mib setf.sig f9 = r37 nop.i 999(p7) br.cond.spnt LOGB_ZERO ;;
}
{ .mfi nop.m 999 fcvt.xf f10 = f9 nop.i 999 ;;
}
{ .mfb nop.m 999 fnorm.d f8 = f10 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 mov r38 = 0x1003f fclass.m.unc p8,p0 = f10, 0x0b nop.i 999 ;;
}
// Form 2^64 in case need to scale denormal{ .mfi 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 getf.exp r35 = f10 ;;
nop.m 999 nop.i 999 ;;
}
{ .mmi and r36 = r35, r34 ;;
sub r37 = r36, r33 nop.i 999 ;;
}
{ .mmi setf.sig f9 = r37 nop.m 999 nop.i 999 ;;
}
{ .mfi nop.m 999 fcvt.xf f10 = f9 nop.i 999 ;;
}
{ .mfb nop.m 999 fnorm.d f8 = f10 br.ret.sptk b0 ;;
}
LOGB_NAN_INF:
// X NAN or INFINITY, return f8 * f8{ .mfb nop.m 999 fma.d f8= f8,f8,f0 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 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#
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