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diff --git a/05/tcc-0.9.25/tcc-doc.texi b/05/tcc-0.9.25/tcc-doc.texi deleted file mode 100644 index 7cc61bb..0000000 --- a/05/tcc-0.9.25/tcc-doc.texi +++ /dev/null @@ -1,1227 +0,0 @@ -\input texinfo @c -*- texinfo -*- -@c %**start of header -@setfilename tcc-doc.info -@settitle Tiny C Compiler Reference Documentation -@c %**end of header - -@include config.texi - -@iftex -@titlepage -@afourpaper -@sp 7 -@center @titlefont{Tiny C Compiler Reference Documentation} -@sp 3 -@end titlepage -@headings double -@end iftex - -@contents - -@node Top, Introduction, (dir), (dir) -@top Tiny C Compiler Reference Documentation - -This manual documents version @value{VERSION} of the Tiny C Compiler. - -@menu -* Introduction:: Introduction to tcc. -* Invoke:: Invocation of tcc (command line, options). -* Clang:: ANSI C and extensions. -* asm:: Assembler syntax. -* linker:: Output file generation and supported targets. -* Bounds:: Automatic bounds-checking of C code. -* Libtcc:: The libtcc library. -* devel:: Guide for Developers. -@end menu - - -@node Introduction -@chapter Introduction - -TinyCC (aka TCC) is a small but hyper fast C compiler. Unlike other C -compilers, it is meant to be self-relying: you do not need an -external assembler or linker because TCC does that for you. - -TCC compiles so @emph{fast} that even for big projects @code{Makefile}s may -not be necessary. - -TCC not only supports ANSI C, but also most of the new ISO C99 -standard and many GNUC extensions including inline assembly. - -TCC can also be used to make @emph{C scripts}, i.e. pieces of C source -that you run as a Perl or Python script. Compilation is so fast that -your script will be as fast as if it was an executable. - -TCC can also automatically generate memory and bound checks -(@pxref{Bounds}) while allowing all C pointers operations. TCC can do -these checks even if non patched libraries are used. - -With @code{libtcc}, you can use TCC as a backend for dynamic code -generation (@pxref{Libtcc}). - -TCC mainly supports the i386 target on Linux and Windows. There are alpha -ports for the ARM (@code{arm-tcc}) and the TMS320C67xx targets -(@code{c67-tcc}). More information about the ARM port is available at -@url{http://lists.gnu.org/archive/html/tinycc-devel/2003-10/msg00044.html}. - -For usage on Windows, see also tcc-win32.txt. - -@node Invoke -@chapter Command line invocation - -@section Quick start - -@example -@c man begin SYNOPSIS -usage: tcc [options] [@var{infile1} @var{infile2}@dots{}] [@option{-run} @var{infile} @var{args}@dots{}] -@c man end -@end example - -@noindent -@c man begin DESCRIPTION -TCC options are a very much like gcc options. The main difference is that TCC -can also execute directly the resulting program and give it runtime -arguments. - -Here are some examples to understand the logic: - -@table @code -@item @samp{tcc -run a.c} -Compile @file{a.c} and execute it directly - -@item @samp{tcc -run a.c arg1} -Compile a.c and execute it directly. arg1 is given as first argument to -the @code{main()} of a.c. - -@item @samp{tcc a.c -run b.c arg1} -Compile @file{a.c} and @file{b.c}, link them together and execute them. arg1 is given -as first argument to the @code{main()} of the resulting program. -@ignore -Because multiple C files are specified, @option{--} are necessary to clearly -separate the program arguments from the TCC options. -@end ignore - -@item @samp{tcc -o myprog a.c b.c} -Compile @file{a.c} and @file{b.c}, link them and generate the executable @file{myprog}. - -@item @samp{tcc -o myprog a.o b.o} -link @file{a.o} and @file{b.o} together and generate the executable @file{myprog}. - -@item @samp{tcc -c a.c} -Compile @file{a.c} and generate object file @file{a.o}. - -@item @samp{tcc -c asmfile.S} -Preprocess with C preprocess and assemble @file{asmfile.S} and generate -object file @file{asmfile.o}. - -@item @samp{tcc -c asmfile.s} -Assemble (but not preprocess) @file{asmfile.s} and generate object file -@file{asmfile.o}. - -@item @samp{tcc -r -o ab.o a.c b.c} -Compile @file{a.c} and @file{b.c}, link them together and generate the object file @file{ab.o}. - -@end table - -Scripting: - -TCC can be invoked from @emph{scripts}, just as shell scripts. You just -need to add @code{#!/usr/local/bin/tcc -run} at the start of your C source: - -@example -#!/usr/local/bin/tcc -run -#include <stdio.h> - -int main() -@{ - printf("Hello World\n"); - return 0; -@} -@end example - -TCC can read C source code from @emph{standard input} when @option{-} is used in -place of @option{infile}. Example: - -@example -echo 'main()@{puts("hello");@}' | tcc -run - -@end example -@c man end - -@section Option summary - -General Options: - -@c man begin OPTIONS -@table @option -@item -v -Display current TCC version, increase verbosity. - -@item -c -Generate an object file (@option{-o} option must also be given). - -@item -o outfile -Put object file, executable, or dll into output file @file{outfile}. - -@item -Bdir -Set the path where the tcc internal libraries can be found (default is -@file{PREFIX/lib/tcc}). - -@item -bench -Output compilation statistics. - -@item -run source [args...] -Compile file @var{source} and run it with the command line arguments -@var{args}. In order to be able to give more than one argument to a -script, several TCC options can be given @emph{after} the -@option{-run} option, separated by spaces. Example: - -@example -tcc "-run -L/usr/X11R6/lib -lX11" ex4.c -@end example - -In a script, it gives the following header: - -@example -#!/usr/local/bin/tcc -run -L/usr/X11R6/lib -lX11 -#include <stdlib.h> -int main(int argc, char **argv) -@{ - ... -@} -@end example - -@end table - -Preprocessor options: - -@table @option -@item -Idir -Specify an additional include path. Include paths are searched in the -order they are specified. - -System include paths are always searched after. The default system -include paths are: @file{/usr/local/include}, @file{/usr/include} -and @file{PREFIX/lib/tcc/include}. (@file{PREFIX} is usually -@file{/usr} or @file{/usr/local}). - -@item -Dsym[=val] -Define preprocessor symbol @samp{sym} to -val. If val is not present, its value is @samp{1}. Function-like macros can -also be defined: @option{-DF(a)=a+1} - -@item -Usym -Undefine preprocessor symbol @samp{sym}. -@end table - -Compilation flags: - -Note: each of the following warning options has a negative form beginning with -@option{-fno-}. - -@table @option -@item -funsigned-char -Let the @code{char} type be unsigned. - -@item -fsigned-char -Let the @code{char} type be signed. - -@item -fno-common -Do not generate common symbols for uninitialized data. - -@item -fleading-underscore -Add a leading underscore at the beginning of each C symbol. - -@end table - -Warning options: - -@table @option -@item -w -Disable all warnings. - -@end table - -Note: each of the following warning options has a negative form beginning with -@option{-Wno-}. - -@table @option -@item -Wimplicit-function-declaration -Warn about implicit function declaration. - -@item -Wunsupported -Warn about unsupported GCC features that are ignored by TCC. - -@item -Wwrite-strings -Make string constants be of type @code{const char *} instead of @code{char -*}. - -@item -Werror -Abort compilation if warnings are issued. - -@item -Wall -Activate all warnings, except @option{-Werror}, @option{-Wunusupported} and -@option{-Wwrite-strings}. - -@end table - -Linker options: - -@table @option -@item -Ldir -Specify an additional static library path for the @option{-l} option. The -default library paths are @file{/usr/local/lib}, @file{/usr/lib} and @file{/lib}. - -@item -lxxx -Link your program with dynamic library libxxx.so or static library -libxxx.a. The library is searched in the paths specified by the -@option{-L} option. - -@item -shared -Generate a shared library instead of an executable (@option{-o} option -must also be given). - -@item -static -Generate a statically linked executable (default is a shared linked -executable) (@option{-o} option must also be given). - -@item -rdynamic -Export global symbols to the dynamic linker. It is useful when a library -opened with @code{dlopen()} needs to access executable symbols. - -@item -r -Generate an object file combining all input files (@option{-o} option must -also be given). - -@item -Wl,-Ttext,address -Set the start of the .text section to @var{address}. - -@item -Wl,--oformat,fmt -Use @var{fmt} as output format. The supported output formats are: -@table @code -@item elf32-i386 -ELF output format (default) -@item binary -Binary image (only for executable output) -@item coff -COFF output format (only for executable output for TMS320C67xx target) -@end table - -@end table - -Debugger options: - -@table @option -@item -g -Generate run time debug information so that you get clear run time -error messages: @code{ test.c:68: in function 'test5()': dereferencing -invalid pointer} instead of the laconic @code{Segmentation -fault}. - -@item -b -Generate additional support code to check -memory allocations and array/pointer bounds. @option{-g} is implied. Note -that the generated code is slower and bigger in this case. - -@item -bt N -Display N callers in stack traces. This is useful with @option{-g} or -@option{-b}. - -@end table - -Note: GCC options @option{-Ox}, @option{-fx} and @option{-mx} are -ignored. -@c man end - -@ignore - -@setfilename tcc -@settitle Tiny C Compiler - -@c man begin SEEALSO -gcc(1) -@c man end - -@c man begin AUTHOR -Fabrice Bellard -@c man end - -@end ignore - -@node Clang -@chapter C language support - -@section ANSI C - -TCC implements all the ANSI C standard, including structure bit fields -and floating point numbers (@code{long double}, @code{double}, and -@code{float} fully supported). - -@section ISOC99 extensions - -TCC implements many features of the new C standard: ISO C99. Currently -missing items are: complex and imaginary numbers and variable length -arrays. - -Currently implemented ISOC99 features: - -@itemize - -@item 64 bit @code{long long} types are fully supported. - -@item The boolean type @code{_Bool} is supported. - -@item @code{__func__} is a string variable containing the current -function name. - -@item Variadic macros: @code{__VA_ARGS__} can be used for - function-like macros: -@example - #define dprintf(level, __VA_ARGS__) printf(__VA_ARGS__) -@end example - -@noindent -@code{dprintf} can then be used with a variable number of parameters. - -@item Declarations can appear anywhere in a block (as in C++). - -@item Array and struct/union elements can be initialized in any order by - using designators: -@example - struct @{ int x, y; @} st[10] = @{ [0].x = 1, [0].y = 2 @}; - - int tab[10] = @{ 1, 2, [5] = 5, [9] = 9@}; -@end example - -@item Compound initializers are supported: -@example - int *p = (int [])@{ 1, 2, 3 @}; -@end example -to initialize a pointer pointing to an initialized array. The same -works for structures and strings. - -@item Hexadecimal floating point constants are supported: -@example - double d = 0x1234p10; -@end example - -@noindent -is the same as writing -@example - double d = 4771840.0; -@end example - -@item @code{inline} keyword is ignored. - -@item @code{restrict} keyword is ignored. -@end itemize - -@section GNU C extensions - -TCC implements some GNU C extensions: - -@itemize - -@item array designators can be used without '=': -@example - int a[10] = @{ [0] 1, [5] 2, 3, 4 @}; -@end example - -@item Structure field designators can be a label: -@example - struct @{ int x, y; @} st = @{ x: 1, y: 1@}; -@end example -instead of -@example - struct @{ int x, y; @} st = @{ .x = 1, .y = 1@}; -@end example - -@item @code{\e} is ASCII character 27. - -@item case ranges : ranges can be used in @code{case}s: -@example - switch(a) @{ - case 1 @dots{} 9: - printf("range 1 to 9\n"); - break; - default: - printf("unexpected\n"); - break; - @} -@end example - -@cindex aligned attribute -@cindex packed attribute -@cindex section attribute -@cindex unused attribute -@cindex cdecl attribute -@cindex stdcall attribute -@cindex regparm attribute -@cindex dllexport attribute - -@item The keyword @code{__attribute__} is handled to specify variable or -function attributes. The following attributes are supported: - @itemize - - @item @code{aligned(n)}: align a variable or a structure field to n bytes -(must be a power of two). - - @item @code{packed}: force alignment of a variable or a structure field to - 1. - - @item @code{section(name)}: generate function or data in assembly section -name (name is a string containing the section name) instead of the default -section. - - @item @code{unused}: specify that the variable or the function is unused. - - @item @code{cdecl}: use standard C calling convention (default). - - @item @code{stdcall}: use Pascal-like calling convention. - - @item @code{regparm(n)}: use fast i386 calling convention. @var{n} must be -between 1 and 3. The first @var{n} function parameters are respectively put in -registers @code{%eax}, @code{%edx} and @code{%ecx}. - - @item @code{dllexport}: export function from dll/executable (win32 only) - - @end itemize - -Here are some examples: -@example - int a __attribute__ ((aligned(8), section(".mysection"))); -@end example - -@noindent -align variable @code{a} to 8 bytes and put it in section @code{.mysection}. - -@example - int my_add(int a, int b) __attribute__ ((section(".mycodesection"))) - @{ - return a + b; - @} -@end example - -@noindent -generate function @code{my_add} in section @code{.mycodesection}. - -@item GNU style variadic macros: -@example - #define dprintf(fmt, args@dots{}) printf(fmt, ## args) - - dprintf("no arg\n"); - dprintf("one arg %d\n", 1); -@end example - -@item @code{__FUNCTION__} is interpreted as C99 @code{__func__} -(so it has not exactly the same semantics as string literal GNUC -where it is a string literal). - -@item The @code{__alignof__} keyword can be used as @code{sizeof} -to get the alignment of a type or an expression. - -@item The @code{typeof(x)} returns the type of @code{x}. -@code{x} is an expression or a type. - -@item Computed gotos: @code{&&label} returns a pointer of type -@code{void *} on the goto label @code{label}. @code{goto *expr} can be -used to jump on the pointer resulting from @code{expr}. - -@item Inline assembly with asm instruction: -@cindex inline assembly -@cindex assembly, inline -@cindex __asm__ -@example -static inline void * my_memcpy(void * to, const void * from, size_t n) -@{ -int d0, d1, d2; -__asm__ __volatile__( - "rep ; movsl\n\t" - "testb $2,%b4\n\t" - "je 1f\n\t" - "movsw\n" - "1:\ttestb $1,%b4\n\t" - "je 2f\n\t" - "movsb\n" - "2:" - : "=&c" (d0), "=&D" (d1), "=&S" (d2) - :"0" (n/4), "q" (n),"1" ((long) to),"2" ((long) from) - : "memory"); -return (to); -@} -@end example - -@noindent -@cindex gas -TCC includes its own x86 inline assembler with a @code{gas}-like (GNU -assembler) syntax. No intermediate files are generated. GCC 3.x named -operands are supported. - -@item @code{__builtin_types_compatible_p()} and @code{__builtin_constant_p()} -are supported. - -@item @code{#pragma pack} is supported for win32 compatibility. - -@end itemize - -@section TinyCC extensions - -@itemize - -@item @code{__TINYC__} is a predefined macro to @code{1} to -indicate that you use TCC. - -@item @code{#!} at the start of a line is ignored to allow scripting. - -@item Binary digits can be entered (@code{0b101} instead of -@code{5}). - -@item @code{__BOUNDS_CHECKING_ON} is defined if bound checking is activated. - -@end itemize - -@node asm -@chapter TinyCC Assembler - -Since version 0.9.16, TinyCC integrates its own assembler. TinyCC -assembler supports a gas-like syntax (GNU assembler). You can -desactivate assembler support if you want a smaller TinyCC executable -(the C compiler does not rely on the assembler). - -TinyCC Assembler is used to handle files with @file{.S} (C -preprocessed assembler) and @file{.s} extensions. It is also used to -handle the GNU inline assembler with the @code{asm} keyword. - -@section Syntax - -TinyCC Assembler supports most of the gas syntax. The tokens are the -same as C. - -@itemize - -@item C and C++ comments are supported. - -@item Identifiers are the same as C, so you cannot use '.' or '$'. - -@item Only 32 bit integer numbers are supported. - -@end itemize - -@section Expressions - -@itemize - -@item Integers in decimal, octal and hexa are supported. - -@item Unary operators: +, -, ~. - -@item Binary operators in decreasing priority order: - -@enumerate -@item *, /, % -@item &, |, ^ -@item +, - -@end enumerate - -@item A value is either an absolute number or a label plus an offset. -All operators accept absolute values except '+' and '-'. '+' or '-' can be -used to add an offset to a label. '-' supports two labels only if they -are the same or if they are both defined and in the same section. - -@end itemize - -@section Labels - -@itemize - -@item All labels are considered as local, except undefined ones. - -@item Numeric labels can be used as local @code{gas}-like labels. -They can be defined several times in the same source. Use 'b' -(backward) or 'f' (forward) as suffix to reference them: - -@example - 1: - jmp 1b /* jump to '1' label before */ - jmp 1f /* jump to '1' label after */ - 1: -@end example - -@end itemize - -@section Directives -@cindex assembler directives -@cindex directives, assembler -@cindex align directive -@cindex skip directive -@cindex space directive -@cindex byte directive -@cindex word directive -@cindex short directive -@cindex int directive -@cindex long directive -@cindex quad directive -@cindex globl directive -@cindex global directive -@cindex section directive -@cindex text directive -@cindex data directive -@cindex bss directive -@cindex fill directive -@cindex org directive -@cindex previous directive -@cindex string directive -@cindex asciz directive -@cindex ascii directive - -All directives are preceeded by a '.'. The following directives are -supported: - -@itemize -@item .align n[,value] -@item .skip n[,value] -@item .space n[,value] -@item .byte value1[,...] -@item .word value1[,...] -@item .short value1[,...] -@item .int value1[,...] -@item .long value1[,...] -@item .quad immediate_value1[,...] -@item .globl symbol -@item .global symbol -@item .section section -@item .text -@item .data -@item .bss -@item .fill repeat[,size[,value]] -@item .org n -@item .previous -@item .string string[,...] -@item .asciz string[,...] -@item .ascii string[,...] -@end itemize - -@section X86 Assembler -@cindex assembler - -All X86 opcodes are supported. Only ATT syntax is supported (source -then destination operand order). If no size suffix is given, TinyCC -tries to guess it from the operand sizes. - -Currently, MMX opcodes are supported but not SSE ones. - -@node linker -@chapter TinyCC Linker -@cindex linker - -@section ELF file generation -@cindex ELF - -TCC can directly output relocatable ELF files (object files), -executable ELF files and dynamic ELF libraries without relying on an -external linker. - -Dynamic ELF libraries can be output but the C compiler does not generate -position independent code (PIC). It means that the dynamic library -code generated by TCC cannot be factorized among processes yet. - -TCC linker eliminates unreferenced object code in libraries. A single pass is -done on the object and library list, so the order in which object files and -libraries are specified is important (same constraint as GNU ld). No grouping -options (@option{--start-group} and @option{--end-group}) are supported. - -@section ELF file loader - -TCC can load ELF object files, archives (.a files) and dynamic -libraries (.so). - -@section PE-i386 file generation -@cindex PE-i386 - -TCC for Windows supports the native Win32 executable file format (PE-i386). It -generates EXE files (console and gui) and DLL files. - -For usage on Windows, see also tcc-win32.txt. - -@section GNU Linker Scripts -@cindex scripts, linker -@cindex linker scripts -@cindex GROUP, linker command -@cindex FILE, linker command -@cindex OUTPUT_FORMAT, linker command -@cindex TARGET, linker command - -Because on many Linux systems some dynamic libraries (such as -@file{/usr/lib/libc.so}) are in fact GNU ld link scripts (horrible!), -the TCC linker also supports a subset of GNU ld scripts. - -The @code{GROUP} and @code{FILE} commands are supported. @code{OUTPUT_FORMAT} -and @code{TARGET} are ignored. - -Example from @file{/usr/lib/libc.so}: -@example -/* GNU ld script - Use the shared library, but some functions are only in - the static library, so try that secondarily. */ -GROUP ( /lib/libc.so.6 /usr/lib/libc_nonshared.a ) -@end example - -@node Bounds -@chapter TinyCC Memory and Bound checks -@cindex bound checks -@cindex memory checks - -This feature is activated with the @option{-b} (@pxref{Invoke}). - -Note that pointer size is @emph{unchanged} and that code generated -with bound checks is @emph{fully compatible} with unchecked -code. When a pointer comes from unchecked code, it is assumed to be -valid. Even very obscure C code with casts should work correctly. - -For more information about the ideas behind this method, see -@url{http://www.doc.ic.ac.uk/~phjk/BoundsChecking.html}. - -Here are some examples of caught errors: - -@table @asis - -@item Invalid range with standard string function: -@example -@{ - char tab[10]; - memset(tab, 0, 11); -@} -@end example - -@item Out of bounds-error in global or local arrays: -@example -@{ - int tab[10]; - for(i=0;i<11;i++) @{ - sum += tab[i]; - @} -@} -@end example - -@item Out of bounds-error in malloc'ed data: -@example -@{ - int *tab; - tab = malloc(20 * sizeof(int)); - for(i=0;i<21;i++) @{ - sum += tab4[i]; - @} - free(tab); -@} -@end example - -@item Access of freed memory: -@example -@{ - int *tab; - tab = malloc(20 * sizeof(int)); - free(tab); - for(i=0;i<20;i++) @{ - sum += tab4[i]; - @} -@} -@end example - -@item Double free: -@example -@{ - int *tab; - tab = malloc(20 * sizeof(int)); - free(tab); - free(tab); -@} -@end example - -@end table - -@node Libtcc -@chapter The @code{libtcc} library - -The @code{libtcc} library enables you to use TCC as a backend for -dynamic code generation. - -Read the @file{libtcc.h} to have an overview of the API. Read -@file{libtcc_test.c} to have a very simple example. - -The idea consists in giving a C string containing the program you want -to compile directly to @code{libtcc}. Then you can access to any global -symbol (function or variable) defined. - -@node devel -@chapter Developer's guide - -This chapter gives some hints to understand how TCC works. You can skip -it if you do not intend to modify the TCC code. - -@section File reading - -The @code{BufferedFile} structure contains the context needed to read a -file, including the current line number. @code{tcc_open()} opens a new -file and @code{tcc_close()} closes it. @code{inp()} returns the next -character. - -@section Lexer - -@code{next()} reads the next token in the current -file. @code{next_nomacro()} reads the next token without macro -expansion. - -@code{tok} contains the current token (see @code{TOK_xxx}) -constants. Identifiers and keywords are also keywords. @code{tokc} -contains additional infos about the token (for example a constant value -if number or string token). - -@section Parser - -The parser is hardcoded (yacc is not necessary). It does only one pass, -except: - -@itemize - -@item For initialized arrays with unknown size, a first pass -is done to count the number of elements. - -@item For architectures where arguments are evaluated in -reverse order, a first pass is done to reverse the argument order. - -@end itemize - -@section Types - -The types are stored in a single 'int' variable. It was choosen in the -first stages of development when tcc was much simpler. Now, it may not -be the best solution. - -@example -#define VT_INT 0 /* integer type */ -#define VT_BYTE 1 /* signed byte type */ -#define VT_SHORT 2 /* short type */ -#define VT_VOID 3 /* void type */ -#define VT_PTR 4 /* pointer */ -#define VT_ENUM 5 /* enum definition */ -#define VT_FUNC 6 /* function type */ -#define VT_STRUCT 7 /* struct/union definition */ -#define VT_FLOAT 8 /* IEEE float */ -#define VT_DOUBLE 9 /* IEEE double */ -#define VT_LDOUBLE 10 /* IEEE long double */ -#define VT_BOOL 11 /* ISOC99 boolean type */ -#define VT_LLONG 12 /* 64 bit integer */ -#define VT_LONG 13 /* long integer (NEVER USED as type, only - during parsing) */ -#define VT_BTYPE 0x000f /* mask for basic type */ -#define VT_UNSIGNED 0x0010 /* unsigned type */ -#define VT_ARRAY 0x0020 /* array type (also has VT_PTR) */ -#define VT_BITFIELD 0x0040 /* bitfield modifier */ - -#define VT_STRUCT_SHIFT 16 /* structure/enum name shift (16 bits left) */ -@end example - -When a reference to another type is needed (for pointers, functions and -structures), the @code{32 - VT_STRUCT_SHIFT} high order bits are used to -store an identifier reference. - -The @code{VT_UNSIGNED} flag can be set for chars, shorts, ints and long -longs. - -Arrays are considered as pointers @code{VT_PTR} with the flag -@code{VT_ARRAY} set. - -The @code{VT_BITFIELD} flag can be set for chars, shorts, ints and long -longs. If it is set, then the bitfield position is stored from bits -VT_STRUCT_SHIFT to VT_STRUCT_SHIFT + 5 and the bit field size is stored -from bits VT_STRUCT_SHIFT + 6 to VT_STRUCT_SHIFT + 11. - -@code{VT_LONG} is never used except during parsing. - -During parsing, the storage of an object is also stored in the type -integer: - -@example -#define VT_EXTERN 0x00000080 /* extern definition */ -#define VT_STATIC 0x00000100 /* static variable */ -#define VT_TYPEDEF 0x00000200 /* typedef definition */ -@end example - -@section Symbols - -All symbols are stored in hashed symbol stacks. Each symbol stack -contains @code{Sym} structures. - -@code{Sym.v} contains the symbol name (remember -an idenfier is also a token, so a string is never necessary to store -it). @code{Sym.t} gives the type of the symbol. @code{Sym.r} is usually -the register in which the corresponding variable is stored. @code{Sym.c} is -usually a constant associated to the symbol. - -Four main symbol stacks are defined: - -@table @code - -@item define_stack -for the macros (@code{#define}s). - -@item global_stack -for the global variables, functions and types. - -@item local_stack -for the local variables, functions and types. - -@item global_label_stack -for the local labels (for @code{goto}). - -@item label_stack -for GCC block local labels (see the @code{__label__} keyword). - -@end table - -@code{sym_push()} is used to add a new symbol in the local symbol -stack. If no local symbol stack is active, it is added in the global -symbol stack. - -@code{sym_pop(st,b)} pops symbols from the symbol stack @var{st} until -the symbol @var{b} is on the top of stack. If @var{b} is NULL, the stack -is emptied. - -@code{sym_find(v)} return the symbol associated to the identifier -@var{v}. The local stack is searched first from top to bottom, then the -global stack. - -@section Sections - -The generated code and datas are written in sections. The structure -@code{Section} contains all the necessary information for a given -section. @code{new_section()} creates a new section. ELF file semantics -is assumed for each section. - -The following sections are predefined: - -@table @code - -@item text_section -is the section containing the generated code. @var{ind} contains the -current position in the code section. - -@item data_section -contains initialized data - -@item bss_section -contains uninitialized data - -@item bounds_section -@itemx lbounds_section -are used when bound checking is activated - -@item stab_section -@itemx stabstr_section -are used when debugging is actived to store debug information - -@item symtab_section -@itemx strtab_section -contain the exported symbols (currently only used for debugging). - -@end table - -@section Code generation -@cindex code generation - -@subsection Introduction - -The TCC code generator directly generates linked binary code in one -pass. It is rather unusual these days (see gcc for example which -generates text assembly), but it can be very fast and surprisingly -little complicated. - -The TCC code generator is register based. Optimization is only done at -the expression level. No intermediate representation of expression is -kept except the current values stored in the @emph{value stack}. - -On x86, three temporary registers are used. When more registers are -needed, one register is spilled into a new temporary variable on the stack. - -@subsection The value stack -@cindex value stack, introduction - -When an expression is parsed, its value is pushed on the value stack -(@var{vstack}). The top of the value stack is @var{vtop}. Each value -stack entry is the structure @code{SValue}. - -@code{SValue.t} is the type. @code{SValue.r} indicates how the value is -currently stored in the generated code. It is usually a CPU register -index (@code{REG_xxx} constants), but additional values and flags are -defined: - -@example -#define VT_CONST 0x00f0 -#define VT_LLOCAL 0x00f1 -#define VT_LOCAL 0x00f2 -#define VT_CMP 0x00f3 -#define VT_JMP 0x00f4 -#define VT_JMPI 0x00f5 -#define VT_LVAL 0x0100 -#define VT_SYM 0x0200 -#define VT_MUSTCAST 0x0400 -#define VT_MUSTBOUND 0x0800 -#define VT_BOUNDED 0x8000 -#define VT_LVAL_BYTE 0x1000 -#define VT_LVAL_SHORT 0x2000 -#define VT_LVAL_UNSIGNED 0x4000 -#define VT_LVAL_TYPE (VT_LVAL_BYTE | VT_LVAL_SHORT | VT_LVAL_UNSIGNED) -@end example - -@table @code - -@item VT_CONST -indicates that the value is a constant. It is stored in the union -@code{SValue.c}, depending on its type. - -@item VT_LOCAL -indicates a local variable pointer at offset @code{SValue.c.i} in the -stack. - -@item VT_CMP -indicates that the value is actually stored in the CPU flags (i.e. the -value is the consequence of a test). The value is either 0 or 1. The -actual CPU flags used is indicated in @code{SValue.c.i}. - -If any code is generated which destroys the CPU flags, this value MUST be -put in a normal register. - -@item VT_JMP -@itemx VT_JMPI -indicates that the value is the consequence of a conditional jump. For VT_JMP, -it is 1 if the jump is taken, 0 otherwise. For VT_JMPI it is inverted. - -These values are used to compile the @code{||} and @code{&&} logical -operators. - -If any code is generated, this value MUST be put in a normal -register. Otherwise, the generated code won't be executed if the jump is -taken. - -@item VT_LVAL -is a flag indicating that the value is actually an lvalue (left value of -an assignment). It means that the value stored is actually a pointer to -the wanted value. - -Understanding the use @code{VT_LVAL} is very important if you want to -understand how TCC works. - -@item VT_LVAL_BYTE -@itemx VT_LVAL_SHORT -@itemx VT_LVAL_UNSIGNED -if the lvalue has an integer type, then these flags give its real -type. The type alone is not enough in case of cast optimisations. - -@item VT_LLOCAL -is a saved lvalue on the stack. @code{VT_LLOCAL} should be eliminated -ASAP because its semantics are rather complicated. - -@item VT_MUSTCAST -indicates that a cast to the value type must be performed if the value -is used (lazy casting). - -@item VT_SYM -indicates that the symbol @code{SValue.sym} must be added to the constant. - -@item VT_MUSTBOUND -@itemx VT_BOUNDED -are only used for optional bound checking. - -@end table - -@subsection Manipulating the value stack -@cindex value stack - -@code{vsetc()} and @code{vset()} pushes a new value on the value -stack. If the previous @var{vtop} was stored in a very unsafe place(for -example in the CPU flags), then some code is generated to put the -previous @var{vtop} in a safe storage. - -@code{vpop()} pops @var{vtop}. In some cases, it also generates cleanup -code (for example if stacked floating point registers are used as on -x86). - -The @code{gv(rc)} function generates code to evaluate @var{vtop} (the -top value of the stack) into registers. @var{rc} selects in which -register class the value should be put. @code{gv()} is the @emph{most -important function} of the code generator. - -@code{gv2()} is the same as @code{gv()} but for the top two stack -entries. - -@subsection CPU dependent code generation -@cindex CPU dependent -See the @file{i386-gen.c} file to have an example. - -@table @code - -@item load() -must generate the code needed to load a stack value into a register. - -@item store() -must generate the code needed to store a register into a stack value -lvalue. - -@item gfunc_start() -@itemx gfunc_param() -@itemx gfunc_call() -should generate a function call - -@item gfunc_prolog() -@itemx gfunc_epilog() -should generate a function prolog/epilog. - -@item gen_opi(op) -must generate the binary integer operation @var{op} on the two top -entries of the stack which are guaranted to contain integer types. - -The result value should be put on the stack. - -@item gen_opf(op) -same as @code{gen_opi()} for floating point operations. The two top -entries of the stack are guaranted to contain floating point values of -same types. - -@item gen_cvt_itof() -integer to floating point conversion. - -@item gen_cvt_ftoi() -floating point to integer conversion. - -@item gen_cvt_ftof() -floating point to floating point of different size conversion. - -@item gen_bounded_ptr_add() -@item gen_bounded_ptr_deref() -are only used for bounds checking. - -@end table - -@section Optimizations done -@cindex optimizations -@cindex constant propagation -@cindex strength reduction -@cindex comparison operators -@cindex caching processor flags -@cindex flags, caching -@cindex jump optimization -Constant propagation is done for all operations. Multiplications and -divisions are optimized to shifts when appropriate. Comparison -operators are optimized by maintaining a special cache for the -processor flags. &&, || and ! are optimized by maintaining a special -'jump target' value. No other jump optimization is currently performed -because it would require to store the code in a more abstract fashion. - -@unnumbered Concept Index -@printindex cp - -@bye - -@c Local variables: -@c fill-column: 78 -@c texinfo-column-for-description: 32 -@c End: |