FPI(3)              RISC/os Reference Manual               FPI(3)



NAME
     fpi - floating-point interrupt analysis

SYNOPSIS
     #include <fpi.h>

     void fpi()

     void printfpicounts()
     int fpicounts[];

     char *fpilist[];

DESCRIPTION
     MIPS floating-point units generate floating-point interrupts
     for some classes of operations that occur with low fre-
     quency.  In these cases the system software then emulates
     the operation in software.  As a program takes floating-
     point interrupts its performance degrades since the opera-
     tions are emulated in software.  The routines and counters
     described here are used to analyze the causes of floating-
     point interrupts.

     The routine fpi makes a sysmips(2) [MIPS_FPSIGINT] system
     call to causes floating-point interrupts to generate a
     SIGFPE. It also sets up a special signal handler for
     SIGFPE's.  On a floating-point interrupt that signal handler
     determines the precise cause of the interrupt and increments
     the appropriate counter in fpi_counts[].

     The routine printfpi_counts prints out the value of the
     counters and their description on stderr as in the following
     example:


          source signaling NaN = 0
          source quiet NaN = 10
          source denormalized value = 23
          move of zero = 83
          negate of zero = 84
          implemented only in software = 5
          invalid operation = 96
          divide by zero = 3837
          destination overflow = 398
          destination underflow = 489

     The constants in the file <fpi.h> along the counters,
     fpi_counts[], and the descriptive strings, fpi_list[], can
     also be used to format messages.

LIMITATIONS




                        Printed 11/19/92                   Page 1

FPI(3)              RISC/os Reference Manual               FPI(3)



     fpi can't be used with programs that normally generate
     SIGFPE's.

SEE ALSO
     R2010 Floating Point Coprocessor Architecture
     R2360 Floating Point Board Product Description
     sysmips(2).
















































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