Alien-TinyCC

 view release on metacpan or  search on metacpan

src/tcc-doc.texi  view on Meta::CPAN

@c man begin OPTIONS
@table @option
@item -c
Generate an object file.

@item -o outfile
Put object file, executable, or dll into output file @file{outfile}.

@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
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
@end example

@item -dumpversion
Print only the compiler version and nothing else.

@item -v
Display TCC version.

@item -vv
Show included files.  As sole argument, print search dirs (as below).

@item -bench
Display compilation statistics.

@item -print-search-dirs
Print the configured installation directory and a list of library
and include directories tcc will search.

@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

src/tcc-doc.texi  view on Meta::CPAN

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 chosen 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_VLA        0x20000 /* VLA type (also has VT_PTR and VT_ARRAY) */
#define VT_BITFIELD   0x0040  /* bitfield modifier */
#define VT_CONSTANT   0x0800  /* const modifier */
#define VT_VOLATILE   0x1000  /* volatile modifier */
#define VT_SIGNED     0x2000  /* signed type */

#define VT_STRUCT_SHIFT 18   /* structure/enum name shift (14 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. Variable length arrays are considered as special
arrays and have flag @code{VT_VLA} set instead of @code{VT_ARRAY}.

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 */
#define VT_INLINE  0x00000400  /* inline definition */
#define VT_IMPORT  0x00004000  /* win32: extern data imported from dll */
#define VT_EXPORT  0x00008000  /* win32: data exported from dll */
#define VT_WEAK    0x00010000  /* win32: data exported from dll */
@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 like its address for normal
symbols, and the number of entries for symbols representing arrays.
Variable length array types use @code{Sym.c} as a location on the stack
which holds the runtime sizeof for the type.

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

src/tcc-doc.texi  view on Meta::CPAN

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: