fpu.h

Go to the documentation of this file.

#ifndef __ASM_ALPHA_FPU_H
#define __ASM_ALPHA_FPU_H

#ifdef __KERNEL__
#include <asm/special_insns.h>
#endif

/*
 * Alpha floating-point control register defines:
 */
#define FPCR_DNOD   (1UL<<47)   /* denorm INV trap disable */
#define FPCR_DNZ    (1UL<<48)   /* denorms to zero */
#define FPCR_INVD   (1UL<<49)   /* invalid op disable (opt.) */
#define FPCR_DZED   (1UL<<50)   /* division by zero disable (opt.) */
#define FPCR_OVFD   (1UL<<51)   /* overflow disable (optional) */
#define FPCR_INV    (1UL<<52)   /* invalid operation */
#define FPCR_DZE    (1UL<<53)   /* division by zero */
#define FPCR_OVF    (1UL<<54)   /* overflow */
#define FPCR_UNF    (1UL<<55)   /* underflow */
#define FPCR_INE    (1UL<<56)   /* inexact */
#define FPCR_IOV    (1UL<<57)   /* integer overflow */
#define FPCR_UNDZ   (1UL<<60)   /* underflow to zero (opt.) */
#define FPCR_UNFD   (1UL<<61)   /* underflow disable (opt.) */
#define FPCR_INED   (1UL<<62)   /* inexact disable (opt.) */
#define FPCR_SUM    (1UL<<63)   /* summary bit */

#define FPCR_DYN_SHIFT  58      /* first dynamic rounding mode bit */
#define FPCR_DYN_CHOPPED (0x0UL << FPCR_DYN_SHIFT)  /* towards 0 */
#define FPCR_DYN_MINUS   (0x1UL << FPCR_DYN_SHIFT)  /* towards -INF */
#define FPCR_DYN_NORMAL  (0x2UL << FPCR_DYN_SHIFT)  /* towards nearest */
#define FPCR_DYN_PLUS    (0x3UL << FPCR_DYN_SHIFT)  /* towards +INF */
#define FPCR_DYN_MASK    (0x3UL << FPCR_DYN_SHIFT)

#define FPCR_MASK   0xffff800000000000L

/*
 * IEEE trap enables are implemented in software.  These per-thread
 * bits are stored in the "ieee_state" field of "struct thread_info".
 * Thus, the bits are defined so as not to conflict with the
 * floating-point enable bit (which is architected).  On top of that,
 * we want to make these bits compatible with OSF/1 so
 * ieee_set_fp_control() etc. can be implemented easily and
 * compatibly.  The corresponding definitions are in
 * /usr/include/machine/fpu.h under OSF/1.
 */
#define IEEE_TRAP_ENABLE_INV    (1UL<<1)    /* invalid op */
#define IEEE_TRAP_ENABLE_DZE    (1UL<<2)    /* division by zero */
#define IEEE_TRAP_ENABLE_OVF    (1UL<<3)    /* overflow */
#define IEEE_TRAP_ENABLE_UNF    (1UL<<4)    /* underflow */
#define IEEE_TRAP_ENABLE_INE    (1UL<<5)    /* inexact */
#define IEEE_TRAP_ENABLE_DNO    (1UL<<6)    /* denorm */
#define IEEE_TRAP_ENABLE_MASK   (IEEE_TRAP_ENABLE_INV | IEEE_TRAP_ENABLE_DZE |\
                 IEEE_TRAP_ENABLE_OVF | IEEE_TRAP_ENABLE_UNF |\
                 IEEE_TRAP_ENABLE_INE | IEEE_TRAP_ENABLE_DNO)

/* Denorm and Underflow flushing */
#define IEEE_MAP_DMZ        (1UL<<12)   /* Map denorm inputs to zero */
#define IEEE_MAP_UMZ        (1UL<<13)   /* Map underflowed outputs to zero */

#define IEEE_MAP_MASK       (IEEE_MAP_DMZ | IEEE_MAP_UMZ)

/* status bits coming from fpcr: */
#define IEEE_STATUS_INV     (1UL<<17)
#define IEEE_STATUS_DZE     (1UL<<18)
#define IEEE_STATUS_OVF     (1UL<<19)
#define IEEE_STATUS_UNF     (1UL<<20)
#define IEEE_STATUS_INE     (1UL<<21)
#define IEEE_STATUS_DNO     (1UL<<22)

#define IEEE_STATUS_MASK    (IEEE_STATUS_INV | IEEE_STATUS_DZE |    \
                 IEEE_STATUS_OVF | IEEE_STATUS_UNF |    \
                 IEEE_STATUS_INE | IEEE_STATUS_DNO)

#define IEEE_SW_MASK        (IEEE_TRAP_ENABLE_MASK |        \
                 IEEE_STATUS_MASK | IEEE_MAP_MASK)

#define IEEE_CURRENT_RM_SHIFT   32
#define IEEE_CURRENT_RM_MASK    (3UL<<IEEE_CURRENT_RM_SHIFT)

#define IEEE_STATUS_TO_EXCSUM_SHIFT 16

#define IEEE_INHERIT    (1UL<<63)   /* inherit on thread create? */

/*
 * Convert the software IEEE trap enable and status bits into the
 * hardware fpcr format. 
 *
 * Digital Unix engineers receive my thanks for not defining the
 * software bits identical to the hardware bits.  The chip designers
 * receive my thanks for making all the not-implemented fpcr bits
 * RAZ forcing us to use system calls to read/write this value.
 */

static inline unsigned long
ieee_swcr_to_fpcr(unsigned long sw)
{
    unsigned long fp;
    fp = (sw & IEEE_STATUS_MASK) << 35;
    fp |= (sw & IEEE_MAP_DMZ) << 36;
    fp |= (sw & IEEE_STATUS_MASK ? FPCR_SUM : 0);
    fp |= (~sw & (IEEE_TRAP_ENABLE_INV
              | IEEE_TRAP_ENABLE_DZE
              | IEEE_TRAP_ENABLE_OVF)) << 48;
    fp |= (~sw & (IEEE_TRAP_ENABLE_UNF | IEEE_TRAP_ENABLE_INE)) << 57;
    fp |= (sw & IEEE_MAP_UMZ ? FPCR_UNDZ | FPCR_UNFD : 0);
    fp |= (~sw & IEEE_TRAP_ENABLE_DNO) << 41;
    return fp;
}

static inline unsigned long
ieee_fpcr_to_swcr(unsigned long fp)
{
    unsigned long sw;
    sw = (fp >> 35) & IEEE_STATUS_MASK;
    sw |= (fp >> 36) & IEEE_MAP_DMZ;
    sw |= (~fp >> 48) & (IEEE_TRAP_ENABLE_INV
                 | IEEE_TRAP_ENABLE_DZE
                 | IEEE_TRAP_ENABLE_OVF);
    sw |= (~fp >> 57) & (IEEE_TRAP_ENABLE_UNF | IEEE_TRAP_ENABLE_INE);
    sw |= (fp >> 47) & IEEE_MAP_UMZ;
    sw |= (~fp >> 41) & IEEE_TRAP_ENABLE_DNO;
    return sw;
}

#ifdef __KERNEL__

/* The following two functions don't need trapb/excb instructions
   around the mf_fpcr/mt_fpcr instructions because (a) the kernel
   never generates arithmetic faults and (b) call_pal instructions
   are implied trap barriers.  */

static inline unsigned long
rdfpcr(void)
{
    unsigned long tmp, ret;

#if defined(CONFIG_ALPHA_EV6) || defined(CONFIG_ALPHA_EV67)
    __asm__ __volatile__ (
        "ftoit $f0,%0\n\t"
        "mf_fpcr $f0\n\t"
        "ftoit $f0,%1\n\t"
        "itoft %0,$f0"
        : "=r"(tmp), "=r"(ret));
#else
    __asm__ __volatile__ (
        "stt $f0,%0\n\t"
        "mf_fpcr $f0\n\t"
        "stt $f0,%1\n\t"
        "ldt $f0,%0"
        : "=m"(tmp), "=m"(ret));
#endif

    return ret;
}

static inline void
wrfpcr(unsigned long val)
{
    unsigned long tmp;

#if defined(CONFIG_ALPHA_EV6) || defined(CONFIG_ALPHA_EV67)
    __asm__ __volatile__ (
        "ftoit $f0,%0\n\t"
        "itoft %1,$f0\n\t"
        "mt_fpcr $f0\n\t"
        "itoft %0,$f0"
        : "=&r"(tmp) : "r"(val));
#else
    __asm__ __volatile__ (
        "stt $f0,%0\n\t"
        "ldt $f0,%1\n\t"
        "mt_fpcr $f0\n\t"
        "ldt $f0,%0"
        : "=m"(tmp) : "m"(val));
#endif
}

static inline unsigned long
swcr_update_status(unsigned long swcr, unsigned long fpcr)
{
    /* EV6 implements most of the bits in hardware.  Collect
       the acrued exception bits from the real fpcr.  */
    if (implver() == IMPLVER_EV6) {
        swcr &= ~IEEE_STATUS_MASK;
        swcr |= (fpcr >> 35) & IEEE_STATUS_MASK;
    }
    return swcr;
}

extern unsigned long alpha_read_fp_reg (unsigned long reg);
extern void alpha_write_fp_reg (unsigned long reg, unsigned long val);
extern unsigned long alpha_read_fp_reg_s (unsigned long reg);
extern void alpha_write_fp_reg_s (unsigned long reg, unsigned long val);

#endif /* __KERNEL__ */

#endif /* __ASM_ALPHA_FPU_H */