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6733782381
These comments should make it easier to see the (small) diff introduced in cf8e3f8757. Without these comments, the diff may get list on a future upstream merge.
126 lines
3.9 KiB
Awk
126 lines
3.9 KiB
Awk
# Script to generate constants for Python pretty printers.
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#
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# Copyright (C) 2016-2018 Free Software Foundation, Inc.
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# This file is part of the GNU C Library.
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#
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# The GNU C Library is free software; you can redistribute it and/or
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# modify it under the terms of the GNU Lesser General Public
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# License as published by the Free Software Foundation; either
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# version 2.1 of the License, or (at your option) any later version.
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#
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# The GNU C Library is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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# Lesser General Public License for more details.
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#
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# You should have received a copy of the GNU Lesser General Public
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# License along with the GNU C Library; if not, see
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# <http://www.gnu.org/licenses/>.
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# This script is a smaller version of the clever gen-asm-const.awk hack used to
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# generate ASM constants from .sym files. We'll use this to generate constants
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# for Python pretty printers.
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#
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# The input to this script are .pysym files that look like:
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# #C_Preprocessor_Directive...
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# NAME1
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# NAME2 expression...
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#
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# A line giving just a name implies an expression consisting of just that name.
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# Comments start with '--'.
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#
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# The output of this script is a 'dummy' function containing 'asm' declarations
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# for each non-preprocessor line in the .pysym file. The expression values
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# will appear as input operands to the 'asm' declaration. For example, if we
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# have:
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#
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# /* header.h */
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# #define MACRO 42
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#
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# struct S {
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# char c1;
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# char c2;
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# char c3;
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# };
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#
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# enum E {
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# ZERO,
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# ONE
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# };
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#
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# /* symbols.pysym */
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# #include <stddef.h>
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# #include "header.h"
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# -- This is a comment
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# MACRO
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# C3_OFFSET offsetof(struct S, c3)
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# E_ONE ONE
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#
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# the output will be:
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#
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# #include <stddef.h>
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# #include "header.h"
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# void dummy(void)
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# {
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# asm ("@name@MACRO@value@%0@" : : "i" (MACRO));
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# asm ("@name@C3_OFFSET@value@%0@" : : "i" (offsetof(struct S, c3)));
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# asm ("@name@E_ONE@value@%0@" : : "i" (ONE));
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# }
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#
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# We'll later feed this output to gcc -S. Since '-S' tells gcc to compile but
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# not assemble, gcc will output something like:
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#
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# dummy:
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# ...
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# @name@MACRO@value@$42@
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# @name@C3_OFFSET@value@$2@
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# @name@E_ONE@value@$1@
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#
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# Finally, we can process that output to extract the constant values.
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# Notice gcc may prepend a special character such as '$' to each value.
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# found_symbol indicates whether we found a non-comment, non-preprocessor line.
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BEGIN { found_symbol = 0 }
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# C preprocessor directives go straight through.
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/^#/ { print; next; }
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# Skip comments.
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/--/ { next; }
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# Trim leading whitespace.
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{ sub(/^[[:blank:]]*/, ""); }
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# If we found a non-comment, non-preprocessor line, print the 'dummy' function
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# header.
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NF > 0 && !found_symbol {
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print "void dummy(void)\n{";
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found_symbol = 1;
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}
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# If the line contains just a name, duplicate it so we can use that name
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# as the value of the expression.
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NF == 1 { sub(/^.*$/, "& &"); }
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# If a line contains a name and an expression...
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NF > 1 {
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name = $1;
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# Remove any characters before the second field.
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sub(/^[^[:blank:]]+[[:blank:]]+/, "");
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# The `.ascii` directive here is needed for LLVM/clang support. LLVM will
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# validate every `asm(...)` directive before emitting it, whereas GCC will
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# literally emit the directive without validation. Without `.ascii` the
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# directives emitted by this generator are not valid assembler statements,
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# and the LLVM assembler will fail to assemble the file. The `.ascii` here
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# has no functional affect, because string parsing is used to extract the
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# integer constant from the assembly file built from the generated file.
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# '$0' ends up being everything that appeared after the first field
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# separator.
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printf " asm (\".ascii \\\"@name@%s@value@%0@\\\"\" : : \"i\" (%s));\n", name, $0;
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}
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# Close the 'dummy' function.
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END { if (found_symbol) print "}"; }
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