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1 Right now there is no documentation for the GCC tree -> rtl interfaces
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2 (or more generally the interfaces for adding new languages).
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3
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4 Such documentation would be of great benefit to the project. Until such
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5 time as we can formally start documenting the interface this file will
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6 serve as a repository for information on these interface and any incompatable
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7 changes we've made.
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8
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9 2004-09-09:
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10 In an effort to decrease execution time, single char tree code
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11 classes were changed to enumerated values.
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12
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13 Old way:
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14
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15 DEFTREECODE (CLASS_METHOD_DECL, "class_method_decl", 'd', 0)
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16
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17 New way:
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18
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19 DEFTREECODE (CLASS_METHOD_DECL, "class_method_decl", tcc_declaration, 0)
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20
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21 2001-02-26:
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22 A DECL_INITIAL of NULL_TREE or error_mark_node in a VAR_DECL is no longer
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23 taken to signify a tentative definition which should not be emitted until
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24 end-of-file. Frontends which want that behavior should set
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25 DECL_DEFER_OUTPUT before calling rest_of_decl_compilation.
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26
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27 Feb 1, 1998:
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28
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29 GCC used to store structure sizes & offsets to elements as bitsize
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30 quantities. This causes problems because a structure can only be
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31 (target memsize / 8) bytes long (this may effect arrays too). This
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32 is particularly problematical on machines with small address spaces.
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33
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34 So:
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35
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36 All trees that represent sizes in bits should have a TREE_TYPE of
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37 bitsizetype (rather than sizetype).
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38
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39 Accordingly, when such values are computed / initialized, care has to
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40 be takes to use / compute the proper type.
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41
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42 When a size in bits is converted into a size in bytes, which is expressed
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43 in trees, care should be taken to change the tree's type again to sizetype.
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44
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45 ?? 1997:
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46
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47 In an effort to decrease cache thrashing and useless loads we've changed the
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48 third argument to the DEFTREECODE macro to be a single char. This will
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49 affect languages that defined their own tree codes (usually in a .def file).
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50
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51 Old way:
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52
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53 DEFTREECODE (CLASS_METHOD_DECL, "class_method_decl", "d", 0)
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54
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55 New way:
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56
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57 DEFTREECODE (CLASS_METHOD_DECL, "class_method_decl", 'd', 0)
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