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annotate lib/Target/MSP430/README.txt @ 0:95c75e76d11b LLVM3.4

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LLVM 3.4
author Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
date Thu, 12 Dec 2013 13:56:28 +0900
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children 60c9769439b8
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1 //===---------------------------------------------------------------------===//
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2 // MSP430 backend.
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3 //===---------------------------------------------------------------------===//
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4
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5 DISCLAIMER: Thid backend should be considered as highly experimental. I never
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6 seen nor worked with this MCU, all information was gathered from datasheet
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7 only. The original intention of making this backend was to write documentation
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8 of form "How to write backend for dummies" :) Thes notes hopefully will be
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9 available pretty soon.
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11 Some things are incomplete / not implemented yet (this list surely is not
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12 complete as well):
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14 1. Verify, how stuff is handling implicit zext with 8 bit operands (this might
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15 be modelled currently in improper way - should we need to mark the superreg as
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16 def for every 8 bit instruction?).
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17
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18 2. Libcalls: multiplication, division, remainder. Note, that calling convention
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19 for libcalls is incomptible with calling convention of libcalls of msp430-gcc
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20 (these cannot be used though due to license restriction).
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22 3. Implement multiplication / division by constant (dag combiner hook?).
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23
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24 4. Implement non-constant shifts.
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25
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26 5. Implement varargs stuff.
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28 6. Verify and fix (if needed) how's stuff playing with i32 / i64.
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29
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30 7. Implement floating point stuff (softfp?)
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31
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32 8. Implement instruction encoding for (possible) direct code emission in the
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33 future.
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34
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35 9. Since almost all instructions set flags - implement brcond / select in better
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36 way (currently they emit explicit comparison).
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37
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38 10. Handle imm in comparisons in better way (see comment in MSP430InstrInfo.td)
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39
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40 11. Implement hooks for better memory op folding, etc.