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annotate lwlib/lw_win.c @ 418:3832a68d83ef
Fix internal compiler error on "var2 = var1 + 1" patterns
This appears to be the correct fix. It was provided by Tormod Volden
(debian.tormod@gmail.com). The final commit is substantially different from
Tormod's submission mostly due to housecleaning (removing the old patches
and updating the README). Tormod's comments follow.
The original addhi_mem_1 "insn" instruction pattern /matches/ two
memory operands, just with the /constraint/ that these are the same
location. A pattern match tells the compiler "you should be able to use
this, but you might have to work on it to meet the constraints". For
typical constraints on registers the compiler can add "reloads", moving
stuff between registers or from memory, until the constraints are met
and the instruction can be used. However, in this case, no amount of
reloads can make two memory locations the same if they already weren't,
so the compiler breaks down and cries "unable to generate reloads".
It seems this issue only appears if optimization is enabled. The proof
is in gcc's reload.c and is left as an exercise to the reader.
Limiting the matching pattern to identical memory operands avoids
these situations, while allowing the common "var++" cases.
References:
The pattern/constraints difference is explained in
https://gcc.gnu.org/onlinedocs/gccint/Simple-Constraints.html#index-other-register-constraints-3335
author | William Astle <lost@l-w.ca> |
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date | Tue, 29 Mar 2016 21:21:49 -0600 |
parents | 4130ffdeb5c8 |
children | 33e37b3d98cf |
rev | line source |
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1 /* |
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2 lw_win.c |
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3 |
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4 Copyright © 2015 William Astle |
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5 |
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6 This file is part of LWTOOLS. |
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7 |
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8 LWTOOLS is free software: you can redistribute it and/or modify it under the |
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9 terms of the GNU General Public License as published by the Free Software |
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10 Foundation, either version 3 of the License, or (at your option) any later |
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11 version. |
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12 |
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13 This program is distributed in the hope that it will be useful, but WITHOUT |
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14 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
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15 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for |
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16 more details. |
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17 |
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18 You should have received a copy of the GNU General Public License along with |
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19 this program. If not, see <http://www.gnu.org/licenses/>. |
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20 */ |
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21 |
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22 #include "lw_win.h" |
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23 |
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24 #include <stdio.h> |
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25 #include <stdarg.h> |
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26 |
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27 int c99_vsnprintf(char* str, size_t size, const char* format, va_list ap) |
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28 { |
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29 int count = -1; |
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30 |
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31 if (size != 0) |
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32 count = _vsnprintf_s(str, size, _TRUNCATE, format, ap); |
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33 if (count == -1) |
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34 count = _vscprintf(format, ap); |
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35 |
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36 return count; |
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37 } |
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38 |
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39 int c99_snprintf(char* str, size_t size, const char* format, ...) |
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40 { |
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41 int count; |
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42 va_list ap; |
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43 |
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44 va_start(ap, format); |
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45 count = c99_vsnprintf(str, size, format, ap); |
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46 va_end(ap); |
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47 |
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48 return count; |
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49 } |