src/arch/x86/utility.hh

/*
 * Copyright (c) 2007 The Hewlett-Packard Development Company
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 *
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 * property including but not limited to intellectual property relating
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 * met: redistributions of source code must retain the above copyright
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#ifndef __ARCH_X86_UTILITY_HH__
#define __ARCH_X86_UTILITY_HH__

#include "cpu/static_inst.hh"
#include "cpu/thread_context.hh"
#include "sim/full_system.hh"

namespace gem5
{

namespace X86ISA
{
    /**
     * Reconstruct the rflags register from the internal gem5 register
     * state.
     *
     * gem5 stores rflags in several different registers to avoid
     * pipeline dependencies. In order to get the true rflags value,
     * we can't simply read the value of misc_reg::Rflags. Instead, we
     * need to read out various state from microcode registers and
     * merge that with misc_reg::Rflags.
     *
     * @param tc Thread context to read rflags from.
     * @return rflags as seen by the guest.
     */
    uint64_t getRFlags(ThreadContext *tc);

    /**
     * Set update the rflags register and internal gem5 state.
     *
     * @note This function does not update misc_reg::M5Reg. You might
     * need to update this register by writing anything to
     * misc_reg::M5Reg with side-effects.
     *
     * @see X86ISA::getRFlags()
     *
     * @param tc Thread context to update
     * @param val New rflags value to store in TC
     */
    void setRFlags(ThreadContext *tc, uint64_t val);

    /**
     * Convert an x87 tag word to abridged tag format.
     *
     * Convert from the x87 tag representation to the tag abridged
     * representation used in the FXSAVE area. The classic format uses
     * 2 bits per stack position to indicate if a position is valid,
     * zero, special, or empty. The abridged format only stores
     * whether a position is empty or not.
     *
     * @param ftw Tag word in classic x87 format.
     * @return Tag word in the abridged format.
     */
    uint8_t convX87TagsToXTags(uint16_t ftw);

    /**
     * Convert an x87 xtag word to normal tags format.
     *
     * Convert from the abridged x87 tag representation used in the
     * FXSAVE area to a full x87 tag. The classic format uses 2 bits
     * per stack position to indicate if a position is valid, zero,
     * special, or empty. The abridged format only stores whether a
     * position is empty or not.
     *
     * @todo Reconstruct the correct state of stack positions instead
     * of just valid/invalid.
     *
     * @param ftwx Tag word in the abridged format.
     * @return Tag word in classic x87 format.
     */
    uint16_t convX87XTagsToTags(uint8_t ftwx);

    /**
     * Generate and updated x87 tag register after a push/pop
     * operation.
     *
     * @note There is currently no support for setting other tags than
     * valid and invalid. A real x87 will set the tag value to zero or
     * special for some special floating point values.
     *
     * @param ftw Current value of the FTW register.
     * @param top Current x87 TOP value.
     * @param spm Stack displacement.
     * @return New value of the FTW register.
     */
    uint16_t genX87Tags(uint16_t ftw, uint8_t top, int8_t spm);

    /**
     * Load an 80-bit float from memory and convert it to double.
     *
     * @param mem Pointer to an 80-bit float.
     * @return double representation of the 80-bit float.
     */
    double loadFloat80(const void *mem);

    /**
     * Convert and store a double as an 80-bit float.
     *
     * @param mem Pointer to destination for the 80-bit float.
     * @param value Double precision float to store.
     */
    void storeFloat80(void *mem, double value);

} // namespace X86ISA
} // namespace gem5

#endif // __ARCH_X86_UTILITY_HH__