mirror of https://github.com/ctm/syn68k.git
56 lines
2.9 KiB
Plaintext
56 lines
2.9 KiB
Plaintext
6) Fold amodes 6 and 7 together, ignoring the reg field of the amode.
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Some amode 7 (abs short, abs long, imm) should not be folded if the
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amode as a whole is being expanded.
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7) Grab unexpanded regs at the beginning of the case? Saves code iff
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the reg is referred to more than once. Watch out for lvalues and
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aliases...
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14) Table builder should be more aggressive about using OpcodeMappingInfo
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sequences from similar instructions
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20) Look into changing beq et al:
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(if (not ccnz)
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(assign code (deref "uint16 **" code 1))
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(assign code (deref "uint16 **" code 0)))))
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To:
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(assign code (deref "uint16 **" code (not ccnz)))
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22) Handle assigns to dollar registers not in the first instruction word
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(happens now for bitfields, cas2...)
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23) Don't generate switch to correct for postinc/predec when that amode isn't
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possible.
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25) Right now VBR points to a static array in trap.c; make it point
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to real m68k memory.
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27) Rewrite movemw/moveml #ifdef'd for the case where our regs are in an
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array. It should be possible to write it as a nice tight loop.
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33) Expanding two different cc variants of the same instruction won't work.
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Instead, it will only expand bit patterns in the intersection of the two
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bits_to_expand's as it marches along the list, or something like that.
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36) Add a new operand type for 3 bit numbers where 0 is really 8. These
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are common in instructions that specify small constants, and this should
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let us cut down the number of synthetic opcodes we need, thus
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reducing the size of 68k.scm and syn68k.c.
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37) Rewrite parts of byteorder.c to better handle assigning expressions of
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unknown size to memory. As it is, it doesn't know what size of byte
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swapping macro to use when, for example, doing:
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(assign $1.muw (| (<> ccc 0) (<> ccx 0)))
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The current heuristic is to swap based on the size of the smaller of the
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LHS and RHS. This doesn't work in the above example. For now, I've
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worked around this in 68k.scm by inserting native order temp variables of
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the appropriate size, like:
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(assign tmp1.uw (| (<> ccc 0) (<> ccx 0)))
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(assign $1.muw tmp1.uw)
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Here it is straightforward for byteorder.c to figure out what size
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the data to be swapped (tmp1.uw) is. I think this only comes up
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in the ccr/sr instructions.
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38) Test move16
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39) gcc isn't clever about:
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(d0.ub.n = (*(uint8 *) CLEAN ((a0.ul.n - 1) )) ) ;
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a0.ul.n -= 1;
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It computes a0.ul.n - 1 twice! It would be nice to replace this
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with:
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(d0.ub.n = (*(uint8 *) CLEAN ((--a0.ul.n))));
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but it's tricky to do this because, if the dereference of the
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predecremented a0 is used more than once, we want to avoid decrementing
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it more than once.
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40) Separate arrays for the two fields of amode_cleanup_info might be
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faster on the 486; if we are clever, we can possibly get the compiler to
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use the "xlatb" instruction, although perhaps this isn't a win.
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