1 \input texinfo @c -*- texinfo -*-
3 @setfilename tcc-doc.info
4 @settitle Tiny C Compiler Reference Documentation
13 @center @titlefont{Tiny C Compiler Reference Documentation}
24 @node Top, Introduction, (dir), (dir)
25 @top Tiny C Compiler Reference Documentation
27 This manual documents version @value{VERSION} of the Tiny C Compiler.
30 * Introduction:: Introduction to tcc.
31 * Invoke:: Invocation of tcc (command line, options).
32 * Bounds:: Automatic bounds-checking of C code.
33 * Libtcc:: The libtcc library.
40 TinyCC (aka TCC) is a small but hyper fast C compiler. Unlike other C
41 compilers, it is meant to be self-relying: you do not need an
42 external assembler or linker because TCC does that for you.
44 TCC compiles so @emph{fast} that even for big projects @code{Makefile}s may
47 TCC not only supports ANSI C, but also most of the new ISO C99
48 standard and many GNUC extensions including inline assembly.
50 TCC can also be used to make @emph{C scripts}, i.e. pieces of C source
51 that you run as a Perl or Python script. Compilation is so fast that
52 your script will be as fast as if it was an executable.
54 TCC can also automatically generate memory and bound checks
55 (@pxref{Bounds}) while allowing all C pointers operations. TCC can do
56 these checks even if non patched libraries are used.
58 With @code{libtcc}, you can use TCC as a backend for dynamic code
59 generation (@pxref{Libtcc}).
61 TCC mainly supports the i386 target on Linux and Windows. There are alpha
62 ports for the ARM (@code{arm-tcc}) and the TMS320C67xx targets
63 (@code{c67-tcc}). More information about the ARM port is available at
64 @url{http://lists.gnu.org/archive/html/tinycc-devel/2003-10/msg00044.html}.
67 @chapter Command line invocation
69 [This manual documents version @value{VERSION} of the Tiny C Compiler]
75 usage: tcc [options] [@var{infile1} @var{infile2}@dots{}] [@option{-run} @var{infile} @var{args}@dots{}]
80 @c man begin DESCRIPTION
81 TCC options are a very much like gcc options. The main difference is that TCC
82 can also execute directly the resulting program and give it runtime
85 Here are some examples to understand the logic:
88 @item @samp{tcc -run a.c}
89 Compile @file{a.c} and execute it directly
91 @item @samp{tcc -run a.c arg1}
92 Compile a.c and execute it directly. arg1 is given as first argument to
93 the @code{main()} of a.c.
95 @item @samp{tcc a.c -run b.c arg1}
96 Compile @file{a.c} and @file{b.c}, link them together and execute them. arg1 is given
97 as first argument to the @code{main()} of the resulting program. Because
98 multiple C files are specified, @option{--} are necessary to clearly separate the
99 program arguments from the TCC options.
101 @item @samp{tcc -o myprog a.c b.c}
102 Compile @file{a.c} and @file{b.c}, link them and generate the executable @file{myprog}.
104 @item @samp{tcc -o myprog a.o b.o}
105 link @file{a.o} and @file{b.o} together and generate the executable @file{myprog}.
107 @item @samp{tcc -c a.c}
108 Compile @file{a.c} and generate object file @file{a.o}.
110 @item @samp{tcc -c asmfile.S}
111 Preprocess with C preprocess and assemble @file{asmfile.S} and generate
112 object file @file{asmfile.o}.
114 @item @samp{tcc -c asmfile.s}
115 Assemble (but not preprocess) @file{asmfile.s} and generate object file
118 @item @samp{tcc -r -o ab.o a.c b.c}
119 Compile @file{a.c} and @file{b.c}, link them together and generate the object file @file{ab.o}.
125 TCC can be invoked from @emph{scripts}, just as shell scripts. You just
126 need to add @code{#!/usr/local/bin/tcc -run} at the start of your C source:
129 #!/usr/local/bin/tcc -run
134 printf("Hello World\n");
140 @section Option summary
147 Display current TCC version.
150 Generate an object file (@option{-o} option must also be given).
153 Put object file, executable, or dll into output file @file{outfile}.
156 Set the path where the tcc internal libraries can be found (default is
157 @file{PREFIX/lib/tcc}).
160 Output compilation statistics.
162 @item -run source [args...]
164 Compile file @var{source} and run it with the command line arguments
165 @var{args}. In order to be able to give more than one argument to a
166 script, several TCC options can be given @emph{after} the
167 @option{-run} option, separated by spaces. Example:
170 tcc "-run -L/usr/X11R6/lib -lX11" ex4.c
173 In a script, it gives the following header:
176 #!/usr/local/bin/tcc -run -L/usr/X11R6/lib -lX11
178 int main(int argc, char **argv)
186 Preprocessor options:
190 Specify an additional include path. Include paths are searched in the
191 order they are specified.
193 System include paths are always searched after. The default system
194 include paths are: @file{/usr/local/include}, @file{/usr/include}
195 and @file{PREFIX/lib/tcc/include}. (@file{PREFIX} is usually
196 @file{/usr} or @file{/usr/local}).
199 Define preprocessor symbol @samp{sym} to
200 val. If val is not present, its value is @samp{1}. Function-like macros can
201 also be defined: @option{-DF(a)=a+1}
204 Undefine preprocessor symbol @samp{sym}.
209 Note: each of the following warning options has a negative form beginning with
213 @item -funsigned-char
214 Let the @code{char} type be unsigned.
217 Let the @code{char} type be signed.
220 Do not generate common symbols for uninitialized data.
228 Disable all warnings.
232 Note: each of the following warning options has a negative form beginning with
236 @item -Wimplicit-function-declaration
237 Warn about implicit function declaration.
240 Warn about unsupported GCC features that are ignored by TCC.
242 @item -Wwrite-strings
243 Make string constants be of type @code{const char *} instead of @code{char
247 Abort compilation if warnings are issued.
250 Activate all warnings, except @option{-Werror}, @option{-Wunusupported} and
251 @option{-Wwrite-strings}.
259 Specify an additional static library path for the @option{-l} option. The
260 default library paths are @file{/usr/local/lib}, @file{/usr/lib} and @file{/lib}.
263 Link your program with dynamic library libxxx.so or static library
264 libxxx.a. The library is searched in the paths specified by the
268 Generate a shared library instead of an executable (@option{-o} option
272 Generate a statically linked executable (default is a shared linked
273 executable) (@option{-o} option must also be given).
276 Export global symbols to the dynamic linker. It is useful when a library
277 opened with @code{dlopen()} needs to access executable symbols.
280 Generate an object file combining all input files (@option{-o} option must
283 @item -Wl,-Ttext,address
284 Set the start of the .text section to @var{address}.
286 @item -Wl,--oformat,fmt
287 Use @var{fmt} as output format. The supported output formats are:
290 ELF output format (default)
292 Binary image (only for executable output)
294 COFF output format (only for executable output for TMS320C67xx target)
303 Generate run time debug information so that you get clear run time
304 error messages: @code{ test.c:68: in function 'test5()': dereferencing
305 invalid pointer} instead of the laconic @code{Segmentation
309 Generate additional support code to check
310 memory allocations and array/pointer bounds. @option{-g} is implied. Note
311 that the generated code is slower and bigger in this case.
314 Display N callers in stack traces. This is useful with @option{-g} or
319 Note: GCC options @option{-Ox}, @option{-fx} and @option{-mx} are
326 @settitle Tiny C Compiler
338 @chapter C language support
342 TCC implements all the ANSI C standard, including structure bit fields
343 and floating point numbers (@code{long double}, @code{double}, and
344 @code{float} fully supported).
346 @section ISOC99 extensions
348 TCC implements many features of the new C standard: ISO C99. Currently
349 missing items are: complex and imaginary numbers and variable length
352 Currently implemented ISOC99 features:
356 @item 64 bit @code{long long} types are fully supported.
358 @item The boolean type @code{_Bool} is supported.
360 @item @code{__func__} is a string variable containing the current
363 @item Variadic macros: @code{__VA_ARGS__} can be used for
364 function-like macros:
366 #define dprintf(level, __VA_ARGS__) printf(__VA_ARGS__)
370 @code{dprintf} can then be used with a variable number of parameters.
372 @item Declarations can appear anywhere in a block (as in C++).
374 @item Array and struct/union elements can be initialized in any order by
377 struct @{ int x, y; @} st[10] = @{ [0].x = 1, [0].y = 2 @};
379 int tab[10] = @{ 1, 2, [5] = 5, [9] = 9@};
382 @item Compound initializers are supported:
384 int *p = (int [])@{ 1, 2, 3 @};
386 to initialize a pointer pointing to an initialized array. The same
387 works for structures and strings.
389 @item Hexadecimal floating point constants are supported:
391 double d = 0x1234p10;
395 is the same as writing
397 double d = 4771840.0;
400 @item @code{inline} keyword is ignored.
402 @item @code{restrict} keyword is ignored.
405 @section GNU C extensions
406 @cindex aligned attribute
407 @cindex packed attribute
408 @cindex section attribute
409 @cindex unused attribute
410 @cindex cdecl attribute
411 @cindex stdcall attribute
412 @cindex regparm attribute
414 TCC implements some GNU C extensions:
418 @item array designators can be used without '=':
420 int a[10] = @{ [0] 1, [5] 2, 3, 4 @};
423 @item Structure field designators can be a label:
425 struct @{ int x, y; @} st = @{ x: 1, y: 1@};
429 struct @{ int x, y; @} st = @{ .x = 1, .y = 1@};
432 @item @code{\e} is ASCII character 27.
434 @item case ranges : ranges can be used in @code{case}s:
438 printf("range 1 to 9\n");
441 printf("unexpected\n");
446 @item The keyword @code{__attribute__} is handled to specify variable or
447 function attributes. The following attributes are supported:
450 @item @code{aligned(n)}: align a variable or a structure field to n bytes
451 (must be a power of two).
453 @item @code{packed}: force alignment of a variable or a structure field to
456 @item @code{section(name)}: generate function or data in assembly section
457 name (name is a string containing the section name) instead of the default
460 @item @code{unused}: specify that the variable or the function is unused.
462 @item @code{cdecl}: use standard C calling convention (default).
464 @item @code{stdcall}: use Pascal-like calling convention.
466 @item @code{regparm(n)}: use fast i386 calling convention. @var{n} must be
467 between 1 and 3. The first @var{n} function parameters are respectively put in
468 registers @code{%eax}, @code{%edx} and @code{%ecx}.
472 Here are some examples:
474 int a __attribute__ ((aligned(8), section(".mysection")));
478 align variable @code{a} to 8 bytes and put it in section @code{.mysection}.
481 int my_add(int a, int b) __attribute__ ((section(".mycodesection")))
488 generate function @code{my_add} in section @code{.mycodesection}.
490 @item GNU style variadic macros:
492 #define dprintf(fmt, args@dots{}) printf(fmt, ## args)
495 dprintf("one arg %d\n", 1);
498 @item @code{__FUNCTION__} is interpreted as C99 @code{__func__}
499 (so it has not exactly the same semantics as string literal GNUC
500 where it is a string literal).
502 @item The @code{__alignof__} keyword can be used as @code{sizeof}
503 to get the alignment of a type or an expression.
505 @item The @code{typeof(x)} returns the type of @code{x}.
506 @code{x} is an expression or a type.
508 @item Computed gotos: @code{&&label} returns a pointer of type
509 @code{void *} on the goto label @code{label}. @code{goto *expr} can be
510 used to jump on the pointer resulting from @code{expr}.
512 @item Inline assembly with asm instruction:
513 @cindex inline assembly
514 @cindex assembly, inline
517 static inline void * my_memcpy(void * to, const void * from, size_t n)
520 __asm__ __volatile__(
525 "1:\ttestb $1,%b4\n\t"
529 : "=&c" (d0), "=&D" (d1), "=&S" (d2)
530 :"0" (n/4), "q" (n),"1" ((long) to),"2" ((long) from)
538 TCC includes its own x86 inline assembler with a @code{gas}-like (GNU
539 assembler) syntax. No intermediate files are generated. GCC 3.x named
540 operands are supported.
542 @item @code{__builtin_types_compatible_p()} and @code{__builtin_constant_p()}
547 @section TinyCC extensions
551 @item @code{__TINYC__} is a predefined macro to @code{1} to
552 indicate that you use TCC.
554 @item @code{#!} at the start of a line is ignored to allow scripting.
556 @item Binary digits can be entered (@code{0b101} instead of
559 @item @code{__BOUNDS_CHECKING_ON} is defined if bound checking is activated.
563 @chapter TinyCC Assembler
565 Since version 0.9.16, TinyCC integrates its own assembler. TinyCC
566 assembler supports a gas-like syntax (GNU assembler). You can
567 desactivate assembler support if you want a smaller TinyCC executable
568 (the C compiler does not rely on the assembler).
570 TinyCC Assembler is used to handle files with @file{.S} (C
571 preprocessed assembler) and @file{.s} extensions. It is also used to
572 handle the GNU inline assembler with the @code{asm} keyword.
576 TinyCC Assembler supports most of the gas syntax. The tokens are the
581 @item C and C++ comments are supported.
583 @item Identifiers are the same as C, so you cannot use '.' or '$'.
585 @item Only 32 bit integer numbers are supported.
593 @item Integers in decimal, octal and hexa are supported.
595 @item Unary operators: +, -, ~.
597 @item Binary operators in decreasing priority order:
605 @item A value is either an absolute number or a label plus an offset.
606 All operators accept absolute values except '+' and '-'. '+' or '-' can be
607 used to add an offset to a label. '-' supports two labels only if they
608 are the same or if they are both defined and in the same section.
616 @item All labels are considered as local, except undefined ones.
618 @item Numeric labels can be used as local @code{gas}-like labels.
619 They can be defined several times in the same source. Use 'b'
620 (backward) or 'f' (forward) as suffix to reference them:
624 jmp 1b /* jump to '1' label before */
625 jmp 1f /* jump to '1' label after */
632 @cindex assembler directives
633 @cindex directives, assembler
634 @cindex align directive
635 @cindex skip directive
636 @cindex space directive
637 @cindex byte directive
638 @cindex word directive
639 @cindex short directive
640 @cindex int directive
641 @cindex long directive
642 @cindex quad directive
643 @cindex globl directive
644 @cindex global directive
645 @cindex section directive
646 @cindex text directive
647 @cindex data directive
648 @cindex bss directive
649 @cindex fill directive
650 @cindex org directive
651 @cindex previous directive
652 @cindex string directive
653 @cindex asciz directive
654 @cindex ascii directive
656 All directives are preceeded by a '.'. The following directives are
660 @item .align n[,value]
661 @item .skip n[,value]
662 @item .space n[,value]
663 @item .byte value1[,...]
664 @item .word value1[,...]
665 @item .short value1[,...]
666 @item .int value1[,...]
667 @item .long value1[,...]
668 @item .quad immediate_value1[,...]
671 @item .section section
675 @item .fill repeat[,size[,value]]
678 @item .string string[,...]
679 @item .asciz string[,...]
680 @item .ascii string[,...]
683 @section X86 Assembler
686 All X86 opcodes are supported. Only ATT syntax is supported (source
687 then destination operand order). If no size suffix is given, TinyCC
688 tries to guess it from the operand sizes.
690 Currently, MMX opcodes are supported but not SSE ones.
692 @chapter TinyCC Linker
695 @section ELF file generation
698 TCC can directly output relocatable ELF files (object files),
699 executable ELF files and dynamic ELF libraries without relying on an
702 Dynamic ELF libraries can be output but the C compiler does not generate
703 position independent code (PIC). It means that the dynamic library
704 code generated by TCC cannot be factorized among processes yet.
706 TCC linker eliminates unreferenced object code in libraries. A single pass is
707 done on the object and library list, so the order in which object files and
708 libraries are specified is important (same constraint as GNU ld). No grouping
709 options (@option{--start-group} and @option{--end-group}) are supported.
711 @section ELF file loader
713 TCC can load ELF object files, archives (.a files) and dynamic
716 @section GNU Linker Scripts
717 @cindex scripts, linker
718 @cindex linker scripts
719 @cindex GROUP, linker command
720 @cindex FILE, linker command
721 @cindex OUTPUT_FORMAT, linker command
722 @cindex TARGET, linker command
724 Because on many Linux systems some dynamic libraries (such as
725 @file{/usr/lib/libc.so}) are in fact GNU ld link scripts (horrible!),
726 the TCC linker also supports a subset of GNU ld scripts.
728 The @code{GROUP} and @code{FILE} commands are supported. @code{OUTPUT_FORMAT}
729 and @code{TARGET} are ignored.
731 Example from @file{/usr/lib/libc.so}:
734 Use the shared library, but some functions are only in
735 the static library, so try that secondarily. */
736 GROUP ( /lib/libc.so.6 /usr/lib/libc_nonshared.a )
740 @chapter TinyCC Memory and Bound checks
742 @cindex memory checks
744 This feature is activated with the @option{-b} (@pxref{Invoke}).
746 Note that pointer size is @emph{unchanged} and that code generated
747 with bound checks is @emph{fully compatible} with unchecked
748 code. When a pointer comes from unchecked code, it is assumed to be
749 valid. Even very obscure C code with casts should work correctly.
751 For more information about the ideas behind this method, see
752 @url{http://www.doc.ic.ac.uk/~phjk/BoundsChecking.html}.
754 Here are some examples of caught errors:
758 @item Invalid range with standard string function:
766 @item Out of bounds-error in global or local arrays:
776 @item Out of bounds-error in malloc'ed data:
780 tab = malloc(20 * sizeof(int));
788 @item Access of freed memory:
792 tab = malloc(20 * sizeof(int));
804 tab = malloc(20 * sizeof(int));
813 @chapter The @code{libtcc} library
815 The @code{libtcc} library enables you to use TCC as a backend for
816 dynamic code generation.
818 Read the @file{libtcc.h} to have an overview of the API. Read
819 @file{libtcc_test.c} to have a very simple example.
821 The idea consists in giving a C string containing the program you want
822 to compile directly to @code{libtcc}. Then you can access to any global
823 symbol (function or variable) defined.
825 @chapter Developer's guide
827 This chapter gives some hints to understand how TCC works. You can skip
828 it if you do not intend to modify the TCC code.
830 @section File reading
832 The @code{BufferedFile} structure contains the context needed to read a
833 file, including the current line number. @code{tcc_open()} opens a new
834 file and @code{tcc_close()} closes it. @code{inp()} returns the next
839 @code{next()} reads the next token in the current
840 file. @code{next_nomacro()} reads the next token without macro
843 @code{tok} contains the current token (see @code{TOK_xxx})
844 constants. Identifiers and keywords are also keywords. @code{tokc}
845 contains additional infos about the token (for example a constant value
846 if number or string token).
850 The parser is hardcoded (yacc is not necessary). It does only one pass,
855 @item For initialized arrays with unknown size, a first pass
856 is done to count the number of elements.
858 @item For architectures where arguments are evaluated in
859 reverse order, a first pass is done to reverse the argument order.
865 The types are stored in a single 'int' variable. It was choosen in the
866 first stages of development when tcc was much simpler. Now, it may not
867 be the best solution.
870 #define VT_INT 0 /* integer type */
871 #define VT_BYTE 1 /* signed byte type */
872 #define VT_SHORT 2 /* short type */
873 #define VT_VOID 3 /* void type */
874 #define VT_PTR 4 /* pointer */
875 #define VT_ENUM 5 /* enum definition */
876 #define VT_FUNC 6 /* function type */
877 #define VT_STRUCT 7 /* struct/union definition */
878 #define VT_FLOAT 8 /* IEEE float */
879 #define VT_DOUBLE 9 /* IEEE double */
880 #define VT_LDOUBLE 10 /* IEEE long double */
881 #define VT_BOOL 11 /* ISOC99 boolean type */
882 #define VT_LLONG 12 /* 64 bit integer */
883 #define VT_LONG 13 /* long integer (NEVER USED as type, only
885 #define VT_BTYPE 0x000f /* mask for basic type */
886 #define VT_UNSIGNED 0x0010 /* unsigned type */
887 #define VT_ARRAY 0x0020 /* array type (also has VT_PTR) */
888 #define VT_BITFIELD 0x0040 /* bitfield modifier */
890 #define VT_STRUCT_SHIFT 16 /* structure/enum name shift (16 bits left) */
893 When a reference to another type is needed (for pointers, functions and
894 structures), the @code{32 - VT_STRUCT_SHIFT} high order bits are used to
895 store an identifier reference.
897 The @code{VT_UNSIGNED} flag can be set for chars, shorts, ints and long
900 Arrays are considered as pointers @code{VT_PTR} with the flag
903 The @code{VT_BITFIELD} flag can be set for chars, shorts, ints and long
904 longs. If it is set, then the bitfield position is stored from bits
905 VT_STRUCT_SHIFT to VT_STRUCT_SHIFT + 5 and the bit field size is stored
906 from bits VT_STRUCT_SHIFT + 6 to VT_STRUCT_SHIFT + 11.
908 @code{VT_LONG} is never used except during parsing.
910 During parsing, the storage of an object is also stored in the type
914 #define VT_EXTERN 0x00000080 /* extern definition */
915 #define VT_STATIC 0x00000100 /* static variable */
916 #define VT_TYPEDEF 0x00000200 /* typedef definition */
921 All symbols are stored in hashed symbol stacks. Each symbol stack
922 contains @code{Sym} structures.
924 @code{Sym.v} contains the symbol name (remember
925 an idenfier is also a token, so a string is never necessary to store
926 it). @code{Sym.t} gives the type of the symbol. @code{Sym.r} is usually
927 the register in which the corresponding variable is stored. @code{Sym.c} is
928 usually a constant associated to the symbol.
930 Four main symbol stacks are defined:
935 for the macros (@code{#define}s).
938 for the global variables, functions and types.
941 for the local variables, functions and types.
943 @item global_label_stack
944 for the local labels (for @code{goto}).
947 for GCC block local labels (see the @code{__label__} keyword).
951 @code{sym_push()} is used to add a new symbol in the local symbol
952 stack. If no local symbol stack is active, it is added in the global
955 @code{sym_pop(st,b)} pops symbols from the symbol stack @var{st} until
956 the symbol @var{b} is on the top of stack. If @var{b} is NULL, the stack
959 @code{sym_find(v)} return the symbol associated to the identifier
960 @var{v}. The local stack is searched first from top to bottom, then the
965 The generated code and datas are written in sections. The structure
966 @code{Section} contains all the necessary information for a given
967 section. @code{new_section()} creates a new section. ELF file semantics
968 is assumed for each section.
970 The following sections are predefined:
975 is the section containing the generated code. @var{ind} contains the
976 current position in the code section.
979 contains initialized data
982 contains uninitialized data
985 @itemx lbounds_section
986 are used when bound checking is activated
989 @itemx stabstr_section
990 are used when debugging is actived to store debug information
993 @itemx strtab_section
994 contain the exported symbols (currently only used for debugging).
998 @section Code generation
999 @cindex code generation
1001 @subsection Introduction
1003 The TCC code generator directly generates linked binary code in one
1004 pass. It is rather unusual these days (see gcc for example which
1005 generates text assembly), but it can be very fast and surprisingly
1008 The TCC code generator is register based. Optimization is only done at
1009 the expression level. No intermediate representation of expression is
1010 kept except the current values stored in the @emph{value stack}.
1012 On x86, three temporary registers are used. When more registers are
1013 needed, one register is spilled into a new temporary variable on the stack.
1015 @subsection The value stack
1016 @cindex value stack, introduction
1018 When an expression is parsed, its value is pushed on the value stack
1019 (@var{vstack}). The top of the value stack is @var{vtop}. Each value
1020 stack entry is the structure @code{SValue}.
1022 @code{SValue.t} is the type. @code{SValue.r} indicates how the value is
1023 currently stored in the generated code. It is usually a CPU register
1024 index (@code{REG_xxx} constants), but additional values and flags are
1028 #define VT_CONST 0x00f0
1029 #define VT_LLOCAL 0x00f1
1030 #define VT_LOCAL 0x00f2
1031 #define VT_CMP 0x00f3
1032 #define VT_JMP 0x00f4
1033 #define VT_JMPI 0x00f5
1034 #define VT_LVAL 0x0100
1035 #define VT_SYM 0x0200
1036 #define VT_MUSTCAST 0x0400
1037 #define VT_MUSTBOUND 0x0800
1038 #define VT_BOUNDED 0x8000
1039 #define VT_LVAL_BYTE 0x1000
1040 #define VT_LVAL_SHORT 0x2000
1041 #define VT_LVAL_UNSIGNED 0x4000
1042 #define VT_LVAL_TYPE (VT_LVAL_BYTE | VT_LVAL_SHORT | VT_LVAL_UNSIGNED)
1048 indicates that the value is a constant. It is stored in the union
1049 @code{SValue.c}, depending on its type.
1052 indicates a local variable pointer at offset @code{SValue.c.i} in the
1056 indicates that the value is actually stored in the CPU flags (i.e. the
1057 value is the consequence of a test). The value is either 0 or 1. The
1058 actual CPU flags used is indicated in @code{SValue.c.i}.
1060 If any code is generated which destroys the CPU flags, this value MUST be
1061 put in a normal register.
1065 indicates that the value is the consequence of a conditional jump. For VT_JMP,
1066 it is 1 if the jump is taken, 0 otherwise. For VT_JMPI it is inverted.
1068 These values are used to compile the @code{||} and @code{&&} logical
1071 If any code is generated, this value MUST be put in a normal
1072 register. Otherwise, the generated code won't be executed if the jump is
1076 is a flag indicating that the value is actually an lvalue (left value of
1077 an assignment). It means that the value stored is actually a pointer to
1080 Understanding the use @code{VT_LVAL} is very important if you want to
1081 understand how TCC works.
1084 @itemx VT_LVAL_SHORT
1085 @itemx VT_LVAL_UNSIGNED
1086 if the lvalue has an integer type, then these flags give its real
1087 type. The type alone is not enough in case of cast optimisations.
1090 is a saved lvalue on the stack. @code{VT_LLOCAL} should be eliminated
1091 ASAP because its semantics are rather complicated.
1094 indicates that a cast to the value type must be performed if the value
1095 is used (lazy casting).
1098 indicates that the symbol @code{SValue.sym} must be added to the constant.
1102 are only used for optional bound checking.
1106 @subsection Manipulating the value stack
1109 @code{vsetc()} and @code{vset()} pushes a new value on the value
1110 stack. If the previous @var{vtop} was stored in a very unsafe place(for
1111 example in the CPU flags), then some code is generated to put the
1112 previous @var{vtop} in a safe storage.
1114 @code{vpop()} pops @var{vtop}. In some cases, it also generates cleanup
1115 code (for example if stacked floating point registers are used as on
1118 The @code{gv(rc)} function generates code to evaluate @var{vtop} (the
1119 top value of the stack) into registers. @var{rc} selects in which
1120 register class the value should be put. @code{gv()} is the @emph{most
1121 important function} of the code generator.
1123 @code{gv2()} is the same as @code{gv()} but for the top two stack
1126 @subsection CPU dependent code generation
1127 @cindex CPU dependent
1128 See the @file{i386-gen.c} file to have an example.
1133 must generate the code needed to load a stack value into a register.
1136 must generate the code needed to store a register into a stack value
1140 @itemx gfunc_param()
1142 should generate a function call
1144 @item gfunc_prolog()
1145 @itemx gfunc_epilog()
1146 should generate a function prolog/epilog.
1149 must generate the binary integer operation @var{op} on the two top
1150 entries of the stack which are guaranted to contain integer types.
1152 The result value should be put on the stack.
1155 same as @code{gen_opi()} for floating point operations. The two top
1156 entries of the stack are guaranted to contain floating point values of
1159 @item gen_cvt_itof()
1160 integer to floating point conversion.
1162 @item gen_cvt_ftoi()
1163 floating point to integer conversion.
1165 @item gen_cvt_ftof()
1166 floating point to floating point of different size conversion.
1168 @item gen_bounded_ptr_add()
1169 @item gen_bounded_ptr_deref()
1170 are only used for bounds checking.
1174 @section Optimizations done
1175 @cindex optimizations
1176 @cindex constant propagation
1177 @cindex strength reduction
1178 @cindex comparison operators
1179 @cindex caching processor flags
1180 @cindex flags, caching
1181 @cindex jump optimization
1182 Constant propagation is done for all operations. Multiplications and
1183 divisions are optimized to shifts when appropriate. Comparison
1184 operators are optimized by maintaining a special cache for the
1185 processor flags. &&, || and ! are optimized by maintaining a special
1186 'jump target' value. No other jump optimization is currently performed
1187 because it would require to store the code in a more abstract fashion.
1189 @unnumbered Concept Index
1196 @c texinfo-column-for-description: 32