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Taking a second parse, prefer non-lookup-table solutions.

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This commit is contained in:
Thomas Harte 2022-06-17 11:55:38 -04:00
parent b0ab5b7b62
commit a0bc332fe6
1 changed files with 19 additions and 20 deletions
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39
Processors/68000Mk2/68000Mk2.hpp
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@ -141,11 +141,12 @@ struct Microcycle {
} }
/*! /*!
@returns 0 if this byte access wants the low part of a 16-bit word; 8 if it wants the high part. @returns 0 if this byte access wants the low part of a 16-bit word; 8 if it wants the high part,
i.e. take a word quantity and shift it right by this amount to get the quantity being
accessed into the lowest value byte.
*/ */
forceinline unsigned int byte_shift() const { forceinline unsigned int byte_shift() const {
static constexpr unsigned int shifts[] = {8, 0}; return ~(*address << 3) & 8;
return shifts[*address & 1];
} }
/*! /*!
@ -154,8 +155,7 @@ struct Microcycle {
@returns 0x00ff if this byte access wants the low part of a 16-bit word; 0xff00 if it wants the high part. @returns 0x00ff if this byte access wants the low part of a 16-bit word; 0xff00 if it wants the high part.
*/ */
forceinline uint16_t byte_mask() const { forceinline uint16_t byte_mask() const {
static constexpr uint16_t masks[] = {0xff00, 0x00ff}; return uint16_t(0xff00 >> ((*address << 3) & 8));
return masks[*address & 1];
} }
/*! /*!
@ -165,8 +165,7 @@ struct Microcycle {
@returns 0xff00 if this byte access wants the low part of a 16-bit word; 0x00ff if it wants the high part. @returns 0xff00 if this byte access wants the low part of a 16-bit word; 0x00ff if it wants the high part.
*/ */
forceinline uint16_t untouched_byte_mask() const { forceinline uint16_t untouched_byte_mask() const {
static constexpr uint16_t masks[] = {0x00ff, 0xff00}; return uint16_t(0x00ff << ((*address << 3) & 8));
return masks[*address & 1];
} }
/*! /*!
@ -181,14 +180,14 @@ struct Microcycle {
@returns non-zero if the 68000 LDS is asserted; zero otherwise. @returns non-zero if the 68000 LDS is asserted; zero otherwise.
*/ */
forceinline int lower_data_select() const { forceinline int lower_data_select() const {
return ((operation & SelectByte) & (*address & 1)) | (operation & SelectWord); return (operation & SelectByte & *address) | (operation & SelectWord);
} }
/*! /*!
@returns non-zero if the 68000 UDS is asserted; zero otherwise. @returns non-zero if the 68000 UDS is asserted; zero otherwise.
*/ */
forceinline int upper_data_select() const { forceinline int upper_data_select() const {
return ((operation & SelectByte) & ~(*address & 1)) | (operation & SelectWord); return (operation & SelectByte & ~*address) | (operation & SelectWord);
} }
/*! /*!
@ -199,7 +198,15 @@ struct Microcycle {
the address space, etc. the address space, etc.
*/ */
forceinline uint32_t word_address() const { forceinline uint32_t word_address() const {
return (address ? (*address) & 0x00fffffe : 0) >> 1; return (address ? *address & 0x00fffffe : 0) >> 1;
}
/*!
@returns the same value as word_address() for any Microcycle with the NewAddress or
SameAddress flags set; undefined behaviour otherwise.
*/
forceinline uint32_t active_operation_word_address() const {
return (*address & 0x00fffffe) >> 1;
} }
/*! /*!
@ -217,7 +224,7 @@ struct Microcycle {
#if TARGET_RT_BIG_ENDIAN #if TARGET_RT_BIG_ENDIAN
return *address & 0xffffff; return *address & 0xffffff;
#else #else
return (*address ^ (1 & operation & SelectByte)) & 0xffffff; return (*address ^ (operation & SelectByte)) & 0xffffff;
#endif #endif
} }
@ -272,7 +279,7 @@ struct Microcycle {
} }
/*! /*!
Equivalent to set_value16((v) | 0xff00). Equivalent to set_value16(v | 0xff00).
*/ */
forceinline void set_value8_low(uint8_t v) const { forceinline void set_value8_low(uint8_t v) const {
assert(operation & Microcycle::Read); assert(operation & Microcycle::Read);
@ -283,14 +290,6 @@ struct Microcycle {
} }
} }
/*!
@returns the same value as word_address() for any Microcycle with the NewAddress or
SameAddress flags set; undefined behaviour otherwise.
*/
forceinline uint32_t active_operation_word_address() const {
return ((*address) & 0x00fffffe) >> 1;
}
// PermitRead and PermitWrite are used as part of the read/write mask // PermitRead and PermitWrite are used as part of the read/write mask
// supplied to @c apply; they are picked to be small enough values that // supplied to @c apply; they are picked to be small enough values that
// a byte can be used for storage. // a byte can be used for storage.