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diff --git a/gcc/gcc.info-20 b/gcc/gcc.info-20 deleted file mode 100644 index cf674a47b20..00000000000 --- a/gcc/gcc.info-20 +++ /dev/null @@ -1,1207 +0,0 @@ -This is Info file gcc.info, produced by Makeinfo version 1.68 from the -input file gcc.texi. - - This file documents the use and the internals of the GNU compiler. - - Published by the Free Software Foundation 59 Temple Place - Suite 330 -Boston, MA 02111-1307 USA - - Copyright (C) 1988, 1989, 1992, 1993, 1994, 1995, 1996, 1997 Free -Software Foundation, Inc. - - Permission is granted to make and distribute verbatim copies of this -manual provided the copyright notice and this permission notice are -preserved on all copies. - - Permission is granted to copy and distribute modified versions of -this manual under the conditions for verbatim copying, provided also -that the sections entitled "GNU General Public License," "Funding for -Free Software," and "Protect Your Freedom--Fight `Look And Feel'" are -included exactly as in the original, and provided that the entire -resulting derived work is distributed under the terms of a permission -notice identical to this one. - - Permission is granted to copy and distribute translations of this -manual into another language, under the above conditions for modified -versions, except that the sections entitled "GNU General Public -License," "Funding for Free Software," and "Protect Your Freedom--Fight -`Look And Feel'", and this permission notice, may be included in -translations approved by the Free Software Foundation instead of in the -original English. - - -File: gcc.info, Node: Function Units, Prev: Delay Slots, Up: Insn Attributes - -Specifying Function Units -------------------------- - - On most RISC machines, there are instructions whose results are not -available for a specific number of cycles. Common cases are -instructions that load data from memory. On many machines, a pipeline -stall will result if the data is referenced too soon after the load -instruction. - - In addition, many newer microprocessors have multiple function -units, usually one for integer and one for floating point, and often -will incur pipeline stalls when a result that is needed is not yet -ready. - - The descriptions in this section allow the specification of how much -time must elapse between the execution of an instruction and the time -when its result is used. It also allows specification of when the -execution of an instruction will delay execution of similar instructions -due to function unit conflicts. - - For the purposes of the specifications in this section, a machine is -divided into "function units", each of which execute a specific class -of instructions in first-in-first-out order. Function units that -accept one instruction each cycle and allow a result to be used in the -succeeding instruction (usually via forwarding) need not be specified. -Classic RISC microprocessors will normally have a single function unit, -which we can call `memory'. The newer "superscalar" processors will -often have function units for floating point operations, usually at -least a floating point adder and multiplier. - - Each usage of a function units by a class of insns is specified with -a `define_function_unit' expression, which looks like this: - - (define_function_unit NAME MULTIPLICITY SIMULTANEITY - TEST READY-DELAY ISSUE-DELAY - [CONFLICT-LIST]) - - NAME is a string giving the name of the function unit. - - MULTIPLICITY is an integer specifying the number of identical units -in the processor. If more than one unit is specified, they will be -scheduled independently. Only truly independent units should be -counted; a pipelined unit should be specified as a single unit. (The -only common example of a machine that has multiple function units for a -single instruction class that are truly independent and not pipelined -are the two multiply and two increment units of the CDC 6600.) - - SIMULTANEITY specifies the maximum number of insns that can be -executing in each instance of the function unit simultaneously or zero -if the unit is pipelined and has no limit. - - All `define_function_unit' definitions referring to function unit -NAME must have the same name and values for MULTIPLICITY and -SIMULTANEITY. - - TEST is an attribute test that selects the insns we are describing -in this definition. Note that an insn may use more than one function -unit and a function unit may be specified in more than one -`define_function_unit'. - - READY-DELAY is an integer that specifies the number of cycles after -which the result of the instruction can be used without introducing any -stalls. - - ISSUE-DELAY is an integer that specifies the number of cycles after -the instruction matching the TEST expression begins using this unit -until a subsequent instruction can begin. A cost of N indicates an N-1 -cycle delay. A subsequent instruction may also be delayed if an -earlier instruction has a longer READY-DELAY value. This blocking -effect is computed using the SIMULTANEITY, READY-DELAY, ISSUE-DELAY, -and CONFLICT-LIST terms. For a normal non-pipelined function unit, -SIMULTANEITY is one, the unit is taken to block for the READY-DELAY -cycles of the executing insn, and smaller values of ISSUE-DELAY are -ignored. - - CONFLICT-LIST is an optional list giving detailed conflict costs for -this unit. If specified, it is a list of condition test expressions to -be applied to insns chosen to execute in NAME following the particular -insn matching TEST that is already executing in NAME. For each insn in -the list, ISSUE-DELAY specifies the conflict cost; for insns not in the -list, the cost is zero. If not specified, CONFLICT-LIST defaults to -all instructions that use the function unit. - - Typical uses of this vector are where a floating point function unit -can pipeline either single- or double-precision operations, but not -both, or where a memory unit can pipeline loads, but not stores, etc. - - As an example, consider a classic RISC machine where the result of a -load instruction is not available for two cycles (a single "delay" -instruction is required) and where only one load instruction can be -executed simultaneously. This would be specified as: - - (define_function_unit "memory" 1 1 (eq_attr "type" "load") 2 0) - - For the case of a floating point function unit that can pipeline -either single or double precision, but not both, the following could be -specified: - - (define_function_unit - "fp" 1 0 (eq_attr "type" "sp_fp") 4 4 [(eq_attr "type" "dp_fp")]) - (define_function_unit - "fp" 1 0 (eq_attr "type" "dp_fp") 4 4 [(eq_attr "type" "sp_fp")]) - - *Note:* The scheduler attempts to avoid function unit conflicts and -uses all the specifications in the `define_function_unit' expression. -It has recently come to our attention that these specifications may not -allow modeling of some of the newer "superscalar" processors that have -insns using multiple pipelined units. These insns will cause a -potential conflict for the second unit used during their execution and -there is no way of representing that conflict. We welcome any examples -of how function unit conflicts work in such processors and suggestions -for their representation. - - -File: gcc.info, Node: Target Macros, Next: Config, Prev: Machine Desc, Up: Top - -Target Description Macros -************************* - - In addition to the file `MACHINE.md', a machine description includes -a C header file conventionally given the name `MACHINE.h'. This header -file defines numerous macros that convey the information about the -target machine that does not fit into the scheme of the `.md' file. -The file `tm.h' should be a link to `MACHINE.h'. The header file -`config.h' includes `tm.h' and most compiler source files include -`config.h'. - -* Menu: - -* Driver:: Controlling how the driver runs the compilation passes. -* Run-time Target:: Defining `-m' options like `-m68000' and `-m68020'. -* Storage Layout:: Defining sizes and alignments of data. -* Type Layout:: Defining sizes and properties of basic user data types. -* Registers:: Naming and describing the hardware registers. -* Register Classes:: Defining the classes of hardware registers. -* Stack and Calling:: Defining which way the stack grows and by how much. -* Varargs:: Defining the varargs macros. -* Trampolines:: Code set up at run time to enter a nested function. -* Library Calls:: Controlling how library routines are implicitly called. -* Addressing Modes:: Defining addressing modes valid for memory operands. -* Condition Code:: Defining how insns update the condition code. -* Costs:: Defining relative costs of different operations. -* Sections:: Dividing storage into text, data, and other sections. -* PIC:: Macros for position independent code. -* Assembler Format:: Defining how to write insns and pseudo-ops to output. -* Debugging Info:: Defining the format of debugging output. -* Cross-compilation:: Handling floating point for cross-compilers. -* Misc:: Everything else. - - -File: gcc.info, Node: Driver, Next: Run-time Target, Up: Target Macros - -Controlling the Compilation Driver, `gcc' -========================================= - - You can control the compilation driver. - -`SWITCH_TAKES_ARG (CHAR)' - A C expression which determines whether the option `-CHAR' takes - arguments. The value should be the number of arguments that - option takes-zero, for many options. - - By default, this macro is defined as `DEFAULT_SWITCH_TAKES_ARG', - which handles the standard options properly. You need not define - `SWITCH_TAKES_ARG' unless you wish to add additional options which - take arguments. Any redefinition should call - `DEFAULT_SWITCH_TAKES_ARG' and then check for additional options. - -`WORD_SWITCH_TAKES_ARG (NAME)' - A C expression which determines whether the option `-NAME' takes - arguments. The value should be the number of arguments that - option takes-zero, for many options. This macro rather than - `SWITCH_TAKES_ARG' is used for multi-character option names. - - By default, this macro is defined as - `DEFAULT_WORD_SWITCH_TAKES_ARG', which handles the standard options - properly. You need not define `WORD_SWITCH_TAKES_ARG' unless you - wish to add additional options which take arguments. Any - redefinition should call `DEFAULT_WORD_SWITCH_TAKES_ARG' and then - check for additional options. - -`SWITCHES_NEED_SPACES' - A string-valued C expression which enumerates the options for which - the linker needs a space between the option and its argument. - - If this macro is not defined, the default value is `""'. - -`CPP_SPEC' - A C string constant that tells the GNU CC driver program options to - pass to CPP. It can also specify how to translate options you - give to GNU CC into options for GNU CC to pass to the CPP. - - Do not define this macro if it does not need to do anything. - -`NO_BUILTIN_SIZE_TYPE' - If this macro is defined, the preprocessor will not define the - builtin macro `__SIZE_TYPE__'. The macro `__SIZE_TYPE__' must - then be defined by `CPP_SPEC' instead. - - This should be defined if `SIZE_TYPE' depends on target dependent - flags which are not accessible to the preprocessor. Otherwise, it - should not be defined. - -`NO_BUILTIN_PTRDIFF_TYPE' - If this macro is defined, the preprocessor will not define the - builtin macro `__PTRDIFF_TYPE__'. The macro `__PTRDIFF_TYPE__' - must then be defined by `CPP_SPEC' instead. - - This should be defined if `PTRDIFF_TYPE' depends on target - dependent flags which are not accessible to the preprocessor. - Otherwise, it should not be defined. - -`SIGNED_CHAR_SPEC' - A C string constant that tells the GNU CC driver program options to - pass to CPP. By default, this macro is defined to pass the option - `-D__CHAR_UNSIGNED__' to CPP if `char' will be treated as - `unsigned char' by `cc1'. - - Do not define this macro unless you need to override the default - definition. - -`CC1_SPEC' - A C string constant that tells the GNU CC driver program options to - pass to `cc1'. It can also specify how to translate options you - give to GNU CC into options for GNU CC to pass to the `cc1'. - - Do not define this macro if it does not need to do anything. - -`CC1PLUS_SPEC' - A C string constant that tells the GNU CC driver program options to - pass to `cc1plus'. It can also specify how to translate options - you give to GNU CC into options for GNU CC to pass to the - `cc1plus'. - - Do not define this macro if it does not need to do anything. - -`ASM_SPEC' - A C string constant that tells the GNU CC driver program options to - pass to the assembler. It can also specify how to translate - options you give to GNU CC into options for GNU CC to pass to the - assembler. See the file `sun3.h' for an example of this. - - Do not define this macro if it does not need to do anything. - -`ASM_FINAL_SPEC' - A C string constant that tells the GNU CC driver program how to - run any programs which cleanup after the normal assembler. - Normally, this is not needed. See the file `mips.h' for an - example of this. - - Do not define this macro if it does not need to do anything. - -`LINK_SPEC' - A C string constant that tells the GNU CC driver program options to - pass to the linker. It can also specify how to translate options - you give to GNU CC into options for GNU CC to pass to the linker. - - Do not define this macro if it does not need to do anything. - -`LIB_SPEC' - Another C string constant used much like `LINK_SPEC'. The - difference between the two is that `LIB_SPEC' is used at the end - of the command given to the linker. - - If this macro is not defined, a default is provided that loads the - standard C library from the usual place. See `gcc.c'. - -`LIBGCC_SPEC' - Another C string constant that tells the GNU CC driver program how - and when to place a reference to `libgcc.a' into the linker - command line. This constant is placed both before and after the - value of `LIB_SPEC'. - - If this macro is not defined, the GNU CC driver provides a default - that passes the string `-lgcc' to the linker unless the `-shared' - option is specified. - -`STARTFILE_SPEC' - Another C string constant used much like `LINK_SPEC'. The - difference between the two is that `STARTFILE_SPEC' is used at the - very beginning of the command given to the linker. - - If this macro is not defined, a default is provided that loads the - standard C startup file from the usual place. See `gcc.c'. - -`ENDFILE_SPEC' - Another C string constant used much like `LINK_SPEC'. The - difference between the two is that `ENDFILE_SPEC' is used at the - very end of the command given to the linker. - - Do not define this macro if it does not need to do anything. - -`EXTRA_SPECS' - Define this macro to provide additional specifications to put in - the `specs' file that can be used in various specifications like - `CC1_SPEC'. - - The definition should be an initializer for an array of structures, - containing a string constant, that defines the specification name, - and a string constant that provides the specification. - - Do not define this macro if it does not need to do anything. - - `EXTRA_SPECS' is useful when an architecture contains several - related targets, which have various `..._SPECS' which are similar - to each other, and the maintainer would like one central place to - keep these definitions. - - For example, the PowerPC System V.4 targets use `EXTRA_SPECS' to - define either `_CALL_SYSV' when the System V calling sequence is - used or `_CALL_AIX' when the older AIX-based calling sequence is - used. - - The `config/rs6000/rs6000.h' target file defines: - - #define EXTRA_SPECS \ - { "cpp_sysv_default", CPP_SYSV_DEFAULT }, - - #define CPP_SYS_DEFAULT "" - - The `config/rs6000/sysv.h' target file defines: - #undef CPP_SPEC - #define CPP_SPEC \ - "%{posix: -D_POSIX_SOURCE } \ - %{mcall-sysv: -D_CALL_SYSV } %{mcall-aix: -D_CALL_AIX } \ - %{!mcall-sysv: %{!mcall-aix: %(cpp_sysv_default) }} \ - %{msoft-float: -D_SOFT_FLOAT} %{mcpu=403: -D_SOFT_FLOAT}" - - #undef CPP_SYSV_DEFAULT - #define CPP_SYSV_DEFAULT "-D_CALL_SYSV" - - while the `config/rs6000/eabiaix.h' target file defines - `CPP_SYSV_DEFAULT' as: - - #undef CPP_SYSV_DEFAULT - #define CPP_SYSV_DEFAULT "-D_CALL_AIX" - -`LINK_LIBGCC_SPECIAL' - Define this macro if the driver program should find the library - `libgcc.a' itself and should not pass `-L' options to the linker. - If you do not define this macro, the driver program will pass the - argument `-lgcc' to tell the linker to do the search and will pass - `-L' options to it. - -`LINK_LIBGCC_SPECIAL_1' - Define this macro if the driver program should find the library - `libgcc.a'. If you do not define this macro, the driver program - will pass the argument `-lgcc' to tell the linker to do the search. - This macro is similar to `LINK_LIBGCC_SPECIAL', except that it does - not affect `-L' options. - -`MULTILIB_DEFAULTS' - Define this macro as a C expression for the initializer of an - array of string to tell the driver program which options are - defaults for this target and thus do not need to be handled - specially when using `MULTILIB_OPTIONS'. - - Do not define this macro if `MULTILIB_OPTIONS' is not defined in - the target makefile fragment or if none of the options listed in - `MULTILIB_OPTIONS' are set by default. *Note Target Fragment::. - -`RELATIVE_PREFIX_NOT_LINKDIR' - Define this macro to tell `gcc' that it should only translate a - `-B' prefix into a `-L' linker option if the prefix indicates an - absolute file name. - -`STANDARD_EXEC_PREFIX' - Define this macro as a C string constant if you wish to override - the standard choice of `/usr/local/lib/gcc-lib/' as the default - prefix to try when searching for the executable files of the - compiler. - -`MD_EXEC_PREFIX' - If defined, this macro is an additional prefix to try after - `STANDARD_EXEC_PREFIX'. `MD_EXEC_PREFIX' is not searched when the - `-b' option is used, or the compiler is built as a cross compiler. - -`STANDARD_STARTFILE_PREFIX' - Define this macro as a C string constant if you wish to override - the standard choice of `/usr/local/lib/' as the default prefix to - try when searching for startup files such as `crt0.o'. - -`MD_STARTFILE_PREFIX' - If defined, this macro supplies an additional prefix to try after - the standard prefixes. `MD_EXEC_PREFIX' is not searched when the - `-b' option is used, or when the compiler is built as a cross - compiler. - -`MD_STARTFILE_PREFIX_1' - If defined, this macro supplies yet another prefix to try after the - standard prefixes. It is not searched when the `-b' option is - used, or when the compiler is built as a cross compiler. - -`INIT_ENVIRONMENT' - Define this macro as a C string constant if you wish to set - environment variables for programs called by the driver, such as - the assembler and loader. The driver passes the value of this - macro to `putenv' to initialize the necessary environment - variables. - -`LOCAL_INCLUDE_DIR' - Define this macro as a C string constant if you wish to override - the standard choice of `/usr/local/include' as the default prefix - to try when searching for local header files. `LOCAL_INCLUDE_DIR' - comes before `SYSTEM_INCLUDE_DIR' in the search order. - - Cross compilers do not use this macro and do not search either - `/usr/local/include' or its replacement. - -`SYSTEM_INCLUDE_DIR' - Define this macro as a C string constant if you wish to specify a - system-specific directory to search for header files before the - standard directory. `SYSTEM_INCLUDE_DIR' comes before - `STANDARD_INCLUDE_DIR' in the search order. - - Cross compilers do not use this macro and do not search the - directory specified. - -`STANDARD_INCLUDE_DIR' - Define this macro as a C string constant if you wish to override - the standard choice of `/usr/include' as the default prefix to try - when searching for header files. - - Cross compilers do not use this macro and do not search either - `/usr/include' or its replacement. - -`STANDARD_INCLUDE_COMPONENT' - The "component" corresponding to `STANDARD_INCLUDE_DIR'. See - `INCLUDE_DEFAULTS', below, for the description of components. If - you do not define this macro, no component is used. - -`INCLUDE_DEFAULTS' - Define this macro if you wish to override the entire default - search path for include files. For a native compiler, the default - search path usually consists of `GCC_INCLUDE_DIR', - `LOCAL_INCLUDE_DIR', `SYSTEM_INCLUDE_DIR', - `GPLUSPLUS_INCLUDE_DIR', and `STANDARD_INCLUDE_DIR'. In addition, - `GPLUSPLUS_INCLUDE_DIR' and `GCC_INCLUDE_DIR' are defined - automatically by `Makefile', and specify private search areas for - GCC. The directory `GPLUSPLUS_INCLUDE_DIR' is used only for C++ - programs. - - The definition should be an initializer for an array of structures. - Each array element should have four elements: the directory name (a - string constant), the component name, and flag for C++-only - directories, and a flag showing that the includes in the directory - don't need to be wrapped in `extern `C'' when compiling C++. Mark - the end of the array with a null element. - - The component name denotes what GNU package the include file is - part of, if any, in all upper-case letters. For example, it might - be `GCC' or `BINUTILS'. If the package is part of the a - vendor-supplied operating system, code the component name as `0'. - - For example, here is the definition used for VAX/VMS: - - #define INCLUDE_DEFAULTS \ - { \ - { "GNU_GXX_INCLUDE:", "G++", 1, 1}, \ - { "GNU_CC_INCLUDE:", "GCC", 0, 0}, \ - { "SYS$SYSROOT:[SYSLIB.]", 0, 0, 0}, \ - { ".", 0, 0, 0}, \ - { 0, 0, 0, 0} \ - } - - Here is the order of prefixes tried for exec files: - - 1. Any prefixes specified by the user with `-B'. - - 2. The environment variable `GCC_EXEC_PREFIX', if any. - - 3. The directories specified by the environment variable - `COMPILER_PATH'. - - 4. The macro `STANDARD_EXEC_PREFIX'. - - 5. `/usr/lib/gcc/'. - - 6. The macro `MD_EXEC_PREFIX', if any. - - Here is the order of prefixes tried for startfiles: - - 1. Any prefixes specified by the user with `-B'. - - 2. The environment variable `GCC_EXEC_PREFIX', if any. - - 3. The directories specified by the environment variable - `LIBRARY_PATH' (native only, cross compilers do not use this). - - 4. The macro `STANDARD_EXEC_PREFIX'. - - 5. `/usr/lib/gcc/'. - - 6. The macro `MD_EXEC_PREFIX', if any. - - 7. The macro `MD_STARTFILE_PREFIX', if any. - - 8. The macro `STANDARD_STARTFILE_PREFIX'. - - 9. `/lib/'. - - 10. `/usr/lib/'. - - -File: gcc.info, Node: Run-time Target, Next: Storage Layout, Prev: Driver, Up: Target Macros - -Run-time Target Specification -============================= - - Here are run-time target specifications. - -`CPP_PREDEFINES' - Define this to be a string constant containing `-D' options to - define the predefined macros that identify this machine and system. - These macros will be predefined unless the `-ansi' option is - specified. - - In addition, a parallel set of macros are predefined, whose names - are made by appending `__' at the beginning and at the end. These - `__' macros are permitted by the ANSI standard, so they are - predefined regardless of whether `-ansi' is specified. - - For example, on the Sun, one can use the following value: - - "-Dmc68000 -Dsun -Dunix" - - The result is to define the macros `__mc68000__', `__sun__' and - `__unix__' unconditionally, and the macros `mc68000', `sun' and - `unix' provided `-ansi' is not specified. - -`extern int target_flags;' - This declaration should be present. - -`TARGET_...' - This series of macros is to allow compiler command arguments to - enable or disable the use of optional features of the target - machine. For example, one machine description serves both the - 68000 and the 68020; a command argument tells the compiler whether - it should use 68020-only instructions or not. This command - argument works by means of a macro `TARGET_68020' that tests a bit - in `target_flags'. - - Define a macro `TARGET_FEATURENAME' for each such option. Its - definition should test a bit in `target_flags'; for example: - - #define TARGET_68020 (target_flags & 1) - - One place where these macros are used is in the - condition-expressions of instruction patterns. Note how - `TARGET_68020' appears frequently in the 68000 machine description - file, `m68k.md'. Another place they are used is in the - definitions of the other macros in the `MACHINE.h' file. - -`TARGET_SWITCHES' - This macro defines names of command options to set and clear bits - in `target_flags'. Its definition is an initializer with a - subgrouping for each command option. - - Each subgrouping contains a string constant, that defines the - option name, and a number, which contains the bits to set in - `target_flags'. A negative number says to clear bits instead; the - negative of the number is which bits to clear. The actual option - name is made by appending `-m' to the specified name. - - One of the subgroupings should have a null string. The number in - this grouping is the default value for `target_flags'. Any target - options act starting with that value. - - Here is an example which defines `-m68000' and `-m68020' with - opposite meanings, and picks the latter as the default: - - #define TARGET_SWITCHES \ - { { "68020", 1}, \ - { "68000", -1}, \ - { "", 1}} - -`TARGET_OPTIONS' - This macro is similar to `TARGET_SWITCHES' but defines names of - command options that have values. Its definition is an - initializer with a subgrouping for each command option. - - Each subgrouping contains a string constant, that defines the - fixed part of the option name, and the address of a variable. The - variable, type `char *', is set to the variable part of the given - option if the fixed part matches. The actual option name is made - by appending `-m' to the specified name. - - Here is an example which defines `-mshort-data-NUMBER'. If the - given option is `-mshort-data-512', the variable `m88k_short_data' - will be set to the string `"512"'. - - extern char *m88k_short_data; - #define TARGET_OPTIONS \ - { { "short-data-", &m88k_short_data } } - -`TARGET_VERSION' - This macro is a C statement to print on `stderr' a string - describing the particular machine description choice. Every - machine description should define `TARGET_VERSION'. For example: - - #ifdef MOTOROLA - #define TARGET_VERSION \ - fprintf (stderr, " (68k, Motorola syntax)"); - #else - #define TARGET_VERSION \ - fprintf (stderr, " (68k, MIT syntax)"); - #endif - -`OVERRIDE_OPTIONS' - Sometimes certain combinations of command options do not make - sense on a particular target machine. You can define a macro - `OVERRIDE_OPTIONS' to take account of this. This macro, if - defined, is executed once just after all the command options have - been parsed. - - Don't use this macro to turn on various extra optimizations for - `-O'. That is what `OPTIMIZATION_OPTIONS' is for. - -`OPTIMIZATION_OPTIONS (LEVEL)' - Some machines may desire to change what optimizations are - performed for various optimization levels. This macro, if - defined, is executed once just after the optimization level is - determined and before the remainder of the command options have - been parsed. Values set in this macro are used as the default - values for the other command line options. - - LEVEL is the optimization level specified; 2 if `-O2' is - specified, 1 if `-O' is specified, and 0 if neither is specified. - - You should not use this macro to change options that are not - machine-specific. These should uniformly selected by the same - optimization level on all supported machines. Use this macro to - enable machine-specific optimizations. - - *Do not examine `write_symbols' in this macro!* The debugging - options are not supposed to alter the generated code. - -`CAN_DEBUG_WITHOUT_FP' - Define this macro if debugging can be performed even without a - frame pointer. If this macro is defined, GNU CC will turn on the - `-fomit-frame-pointer' option whenever `-O' is specified. - - -File: gcc.info, Node: Storage Layout, Next: Type Layout, Prev: Run-time Target, Up: Target Macros - -Storage Layout -============== - - Note that the definitions of the macros in this table which are -sizes or alignments measured in bits do not need to be constant. They -can be C expressions that refer to static variables, such as the -`target_flags'. *Note Run-time Target::. - -`BITS_BIG_ENDIAN' - Define this macro to have the value 1 if the most significant bit - in a byte has the lowest number; otherwise define it to have the - value zero. This means that bit-field instructions count from the - most significant bit. If the machine has no bit-field - instructions, then this must still be defined, but it doesn't - matter which value it is defined to. This macro need not be a - constant. - - This macro does not affect the way structure fields are packed into - bytes or words; that is controlled by `BYTES_BIG_ENDIAN'. - -`BYTES_BIG_ENDIAN' - Define this macro to have the value 1 if the most significant byte - in a word has the lowest number. This macro need not be a - constant. - -`WORDS_BIG_ENDIAN' - Define this macro to have the value 1 if, in a multiword object, - the most significant word has the lowest number. This applies to - both memory locations and registers; GNU CC fundamentally assumes - that the order of words in memory is the same as the order in - registers. This macro need not be a constant. - -`LIBGCC2_WORDS_BIG_ENDIAN' - Define this macro if WORDS_BIG_ENDIAN is not constant. This must - be a constant value with the same meaning as WORDS_BIG_ENDIAN, - which will be used only when compiling libgcc2.c. Typically the - value will be set based on preprocessor defines. - -`FLOAT_WORDS_BIG_ENDIAN' - Define this macro to have the value 1 if `DFmode', `XFmode' or - `TFmode' floating point numbers are stored in memory with the word - containing the sign bit at the lowest address; otherwise define it - to have the value 0. This macro need not be a constant. - - You need not define this macro if the ordering is the same as for - multi-word integers. - -`BITS_PER_UNIT' - Define this macro to be the number of bits in an addressable - storage unit (byte); normally 8. - -`BITS_PER_WORD' - Number of bits in a word; normally 32. - -`MAX_BITS_PER_WORD' - Maximum number of bits in a word. If this is undefined, the - default is `BITS_PER_WORD'. Otherwise, it is the constant value - that is the largest value that `BITS_PER_WORD' can have at - run-time. - -`UNITS_PER_WORD' - Number of storage units in a word; normally 4. - -`MIN_UNITS_PER_WORD' - Minimum number of units in a word. If this is undefined, the - default is `UNITS_PER_WORD'. Otherwise, it is the constant value - that is the smallest value that `UNITS_PER_WORD' can have at - run-time. - -`POINTER_SIZE' - Width of a pointer, in bits. You must specify a value no wider - than the width of `Pmode'. If it is not equal to the width of - `Pmode', you must define `POINTERS_EXTEND_UNSIGNED'. - -`POINTERS_EXTEND_UNSIGNED' - A C expression whose value is nonzero if pointers that need to be - extended from being `POINTER_SIZE' bits wide to `Pmode' are - sign-extended and zero if they are zero-extended. - - You need not define this macro if the `POINTER_SIZE' is equal to - the width of `Pmode'. - -`PROMOTE_MODE (M, UNSIGNEDP, TYPE)' - A macro to update M and UNSIGNEDP when an object whose type is - TYPE and which has the specified mode and signedness is to be - stored in a register. This macro is only called when TYPE is a - scalar type. - - On most RISC machines, which only have operations that operate on - a full register, define this macro to set M to `word_mode' if M is - an integer mode narrower than `BITS_PER_WORD'. In most cases, - only integer modes should be widened because wider-precision - floating-point operations are usually more expensive than their - narrower counterparts. - - For most machines, the macro definition does not change UNSIGNEDP. - However, some machines, have instructions that preferentially - handle either signed or unsigned quantities of certain modes. For - example, on the DEC Alpha, 32-bit loads from memory and 32-bit add - instructions sign-extend the result to 64 bits. On such machines, - set UNSIGNEDP according to which kind of extension is more - efficient. - - Do not define this macro if it would never modify M. - -`PROMOTE_FUNCTION_ARGS' - Define this macro if the promotion described by `PROMOTE_MODE' - should also be done for outgoing function arguments. - -`PROMOTE_FUNCTION_RETURN' - Define this macro if the promotion described by `PROMOTE_MODE' - should also be done for the return value of functions. - - If this macro is defined, `FUNCTION_VALUE' must perform the same - promotions done by `PROMOTE_MODE'. - -`PROMOTE_FOR_CALL_ONLY' - Define this macro if the promotion described by `PROMOTE_MODE' - should *only* be performed for outgoing function arguments or - function return values, as specified by `PROMOTE_FUNCTION_ARGS' - and `PROMOTE_FUNCTION_RETURN', respectively. - -`PARM_BOUNDARY' - Normal alignment required for function parameters on the stack, in - bits. All stack parameters receive at least this much alignment - regardless of data type. On most machines, this is the same as the - size of an integer. - -`STACK_BOUNDARY' - Define this macro if you wish to preserve a certain alignment for - the stack pointer. The definition is a C expression for the - desired alignment (measured in bits). - - If `PUSH_ROUNDING' is not defined, the stack will always be aligned - to the specified boundary. If `PUSH_ROUNDING' is defined and - specifies a less strict alignment than `STACK_BOUNDARY', the stack - may be momentarily unaligned while pushing arguments. - -`FUNCTION_BOUNDARY' - Alignment required for a function entry point, in bits. - -`BIGGEST_ALIGNMENT' - Biggest alignment that any data type can require on this machine, - in bits. - -`MINIMUM_ATOMIC_ALIGNMENT' - If defined, the smallest alignment, in bits, that can be given to - an object that can be referenced in one operation, without - disturbing any nearby object. Normally, this is `BITS_PER_UNIT', - but may be larger on machines that don't have byte or half-word - store operations. - -`BIGGEST_FIELD_ALIGNMENT' - Biggest alignment that any structure field can require on this - machine, in bits. If defined, this overrides `BIGGEST_ALIGNMENT' - for structure fields only. - -`ADJUST_FIELD_ALIGN (FIELD, COMPUTED)' - An expression for the alignment of a structure field FIELD if the - alignment computed in the usual way is COMPUTED. GNU CC uses this - value instead of the value in `BIGGEST_ALIGNMENT' or - `BIGGEST_FIELD_ALIGNMENT', if defined, for structure fields only. - -`MAX_OFILE_ALIGNMENT' - Biggest alignment supported by the object file format of this - machine. Use this macro to limit the alignment which can be - specified using the `__attribute__ ((aligned (N)))' construct. If - not defined, the default value is `BIGGEST_ALIGNMENT'. - -`DATA_ALIGNMENT (TYPE, BASIC-ALIGN)' - If defined, a C expression to compute the alignment for a static - variable. TYPE is the data type, and BASIC-ALIGN is the alignment - that the object would ordinarily have. The value of this macro is - used instead of that alignment to align the object. - - If this macro is not defined, then BASIC-ALIGN is used. - - One use of this macro is to increase alignment of medium-size data - to make it all fit in fewer cache lines. Another is to cause - character arrays to be word-aligned so that `strcpy' calls that - copy constants to character arrays can be done inline. - -`CONSTANT_ALIGNMENT (CONSTANT, BASIC-ALIGN)' - If defined, a C expression to compute the alignment given to a - constant that is being placed in memory. CONSTANT is the constant - and BASIC-ALIGN is the alignment that the object would ordinarily - have. The value of this macro is used instead of that alignment to - align the object. - - If this macro is not defined, then BASIC-ALIGN is used. - - The typical use of this macro is to increase alignment for string - constants to be word aligned so that `strcpy' calls that copy - constants can be done inline. - -`EMPTY_FIELD_BOUNDARY' - Alignment in bits to be given to a structure bit field that - follows an empty field such as `int : 0;'. - - Note that `PCC_BITFIELD_TYPE_MATTERS' also affects the alignment - that results from an empty field. - -`STRUCTURE_SIZE_BOUNDARY' - Number of bits which any structure or union's size must be a - multiple of. Each structure or union's size is rounded up to a - multiple of this. - - If you do not define this macro, the default is the same as - `BITS_PER_UNIT'. - -`STRICT_ALIGNMENT' - Define this macro to be the value 1 if instructions will fail to - work if given data not on the nominal alignment. If instructions - will merely go slower in that case, define this macro as 0. - -`PCC_BITFIELD_TYPE_MATTERS' - Define this if you wish to imitate the way many other C compilers - handle alignment of bitfields and the structures that contain them. - - The behavior is that the type written for a bitfield (`int', - `short', or other integer type) imposes an alignment for the - entire structure, as if the structure really did contain an - ordinary field of that type. In addition, the bitfield is placed - within the structure so that it would fit within such a field, not - crossing a boundary for it. - - Thus, on most machines, a bitfield whose type is written as `int' - would not cross a four-byte boundary, and would force four-byte - alignment for the whole structure. (The alignment used may not be - four bytes; it is controlled by the other alignment parameters.) - - If the macro is defined, its definition should be a C expression; - a nonzero value for the expression enables this behavior. - - Note that if this macro is not defined, or its value is zero, some - bitfields may cross more than one alignment boundary. The - compiler can support such references if there are `insv', `extv', - and `extzv' insns that can directly reference memory. - - The other known way of making bitfields work is to define - `STRUCTURE_SIZE_BOUNDARY' as large as `BIGGEST_ALIGNMENT'. Then - every structure can be accessed with fullwords. - - Unless the machine has bitfield instructions or you define - `STRUCTURE_SIZE_BOUNDARY' that way, you must define - `PCC_BITFIELD_TYPE_MATTERS' to have a nonzero value. - - If your aim is to make GNU CC use the same conventions for laying - out bitfields as are used by another compiler, here is how to - investigate what the other compiler does. Compile and run this - program: - - struct foo1 - { - char x; - char :0; - char y; - }; - - struct foo2 - { - char x; - int :0; - char y; - }; - - main () - { - printf ("Size of foo1 is %d\n", - sizeof (struct foo1)); - printf ("Size of foo2 is %d\n", - sizeof (struct foo2)); - exit (0); - } - - If this prints 2 and 5, then the compiler's behavior is what you - would get from `PCC_BITFIELD_TYPE_MATTERS'. - -`BITFIELD_NBYTES_LIMITED' - Like PCC_BITFIELD_TYPE_MATTERS except that its effect is limited to - aligning a bitfield within the structure. - -`ROUND_TYPE_SIZE (STRUCT, SIZE, ALIGN)' - Define this macro as an expression for the overall size of a - structure (given by STRUCT as a tree node) when the size computed - from the fields is SIZE and the alignment is ALIGN. - - The default is to round SIZE up to a multiple of ALIGN. - -`ROUND_TYPE_ALIGN (STRUCT, COMPUTED, SPECIFIED)' - Define this macro as an expression for the alignment of a structure - (given by STRUCT as a tree node) if the alignment computed in the - usual way is COMPUTED and the alignment explicitly specified was - SPECIFIED. - - The default is to use SPECIFIED if it is larger; otherwise, use - the smaller of COMPUTED and `BIGGEST_ALIGNMENT' - -`MAX_FIXED_MODE_SIZE' - An integer expression for the size in bits of the largest integer - machine mode that should actually be used. All integer machine - modes of this size or smaller can be used for structures and - unions with the appropriate sizes. If this macro is undefined, - `GET_MODE_BITSIZE (DImode)' is assumed. - -`CHECK_FLOAT_VALUE (MODE, VALUE, OVERFLOW)' - A C statement to validate the value VALUE (of type `double') for - mode MODE. This means that you check whether VALUE fits within - the possible range of values for mode MODE on this target machine. - The mode MODE is always a mode of class `MODE_FLOAT'. OVERFLOW - is nonzero if the value is already known to be out of range. - - If VALUE is not valid or if OVERFLOW is nonzero, you should set - OVERFLOW to 1 and then assign some valid value to VALUE. Allowing - an invalid value to go through the compiler can produce incorrect - assembler code which may even cause Unix assemblers to crash. - - This macro need not be defined if there is no work for it to do. - -`TARGET_FLOAT_FORMAT' - A code distinguishing the floating point format of the target - machine. There are three defined values: - - `IEEE_FLOAT_FORMAT' - This code indicates IEEE floating point. It is the default; - there is no need to define this macro when the format is IEEE. - - `VAX_FLOAT_FORMAT' - This code indicates the peculiar format used on the Vax. - - `UNKNOWN_FLOAT_FORMAT' - This code indicates any other format. - - The value of this macro is compared with `HOST_FLOAT_FORMAT' - (*note Config::.) to determine whether the target machine has the - same format as the host machine. If any other formats are - actually in use on supported machines, new codes should be defined - for them. - - The ordering of the component words of floating point values - stored in memory is controlled by `FLOAT_WORDS_BIG_ENDIAN' for the - target machine and `HOST_FLOAT_WORDS_BIG_ENDIAN' for the host. - -`DEFAULT_VTABLE_THUNKS' - GNU CC supports two ways of implementing C++ vtables: traditional - or with so-called "thunks". The flag `-fvtable-thunk' chooses - between them. Define this macro to be a C expression for the - default value of that flag. If `DEFAULT_VTABLE_THUNKS' is 0, GNU - CC uses the traditional implementation by default. The "thunk" - implementation is more efficient (especially if you have provided - an implementation of `ASM_OUTPUT_MI_THUNK', see *Note Function - Entry::), but is not binary compatible with code compiled using - the traditional implementation. If you are writing a new ports, - define `DEFAULT_VTABLE_THUNKS' to 1. - - If you do not define this macro, the default for `-fvtable-thunk' - is 0. - - -File: gcc.info, Node: Type Layout, Next: Registers, Prev: Storage Layout, Up: Target Macros - -Layout of Source Language Data Types -==================================== - - These macros define the sizes and other characteristics of the -standard basic data types used in programs being compiled. Unlike the -macros in the previous section, these apply to specific features of C -and related languages, rather than to fundamental aspects of storage -layout. - -`INT_TYPE_SIZE' - A C expression for the size in bits of the type `int' on the - target machine. If you don't define this, the default is one word. - -`MAX_INT_TYPE_SIZE' - Maximum number for the size in bits of the type `int' on the target - machine. If this is undefined, the default is `INT_TYPE_SIZE'. - Otherwise, it is the constant value that is the largest value that - `INT_TYPE_SIZE' can have at run-time. This is used in `cpp'. - -`SHORT_TYPE_SIZE' - A C expression for the size in bits of the type `short' on the - target machine. If you don't define this, the default is half a - word. (If this would be less than one storage unit, it is rounded - up to one unit.) - -`LONG_TYPE_SIZE' - A C expression for the size in bits of the type `long' on the - target machine. If you don't define this, the default is one word. - -`MAX_LONG_TYPE_SIZE' - Maximum number for the size in bits of the type `long' on the - target machine. If this is undefined, the default is - `LONG_TYPE_SIZE'. Otherwise, it is the constant value that is the - largest value that `LONG_TYPE_SIZE' can have at run-time. This is - used in `cpp'. - -`LONG_LONG_TYPE_SIZE' - A C expression for the size in bits of the type `long long' on the - target machine. If you don't define this, the default is two - words. If you want to support GNU Ada on your machine, the value - of macro must be at least 64. - -`CHAR_TYPE_SIZE' - A C expression for the size in bits of the type `char' on the - target machine. If you don't define this, the default is one - quarter of a word. (If this would be less than one storage unit, - it is rounded up to one unit.) - -`MAX_CHAR_TYPE_SIZE' - Maximum number for the size in bits of the type `char' on the - target machine. If this is undefined, the default is - `CHAR_TYPE_SIZE'. Otherwise, it is the constant value that is the - largest value that `CHAR_TYPE_SIZE' can have at run-time. This is - used in `cpp'. - -`FLOAT_TYPE_SIZE' - A C expression for the size in bits of the type `float' on the - target machine. If you don't define this, the default is one word. - -`DOUBLE_TYPE_SIZE' - A C expression for the size in bits of the type `double' on the - target machine. If you don't define this, the default is two - words. - -`LONG_DOUBLE_TYPE_SIZE' - A C expression for the size in bits of the type `long double' on - the target machine. If you don't define this, the default is two - words. - -`WIDEST_HARDWARE_FP_SIZE' - A C expression for the size in bits of the widest floating-point - format supported by the hardware. If you define this macro, you - must specify a value less than or equal to the value of - `LONG_DOUBLE_TYPE_SIZE'. If you do not define this macro, the - value of `LONG_DOUBLE_TYPE_SIZE' is the default. - -`DEFAULT_SIGNED_CHAR' - An expression whose value is 1 or 0, according to whether the type - `char' should be signed or unsigned by default. The user can - always override this default with the options `-fsigned-char' and - `-funsigned-char'. - -`DEFAULT_SHORT_ENUMS' - A C expression to determine whether to give an `enum' type only as - many bytes as it takes to represent the range of possible values - of that type. A nonzero value means to do that; a zero value - means all `enum' types should be allocated like `int'. - - If you don't define the macro, the default is 0. - -`SIZE_TYPE' - A C expression for a string describing the name of the data type - to use for size values. The typedef name `size_t' is defined - using the contents of the string. - - The string can contain more than one keyword. If so, separate - them with spaces, and write first any length keyword, then - `unsigned' if appropriate, and finally `int'. The string must - exactly match one of the data type names defined in the function - `init_decl_processing' in the file `c-decl.c'. You may not omit - `int' or change the order--that would cause the compiler to crash - on startup. - - If you don't define this macro, the default is `"long unsigned - int"'. - -`PTRDIFF_TYPE' - A C expression for a string describing the name of the data type - to use for the result of subtracting two pointers. The typedef - name `ptrdiff_t' is defined using the contents of the string. See - `SIZE_TYPE' above for more information. - - If you don't define this macro, the default is `"long int"'. - -`WCHAR_TYPE' - A C expression for a string describing the name of the data type - to use for wide characters. The typedef name `wchar_t' is defined - using the contents of the string. See `SIZE_TYPE' above for more - information. - - If you don't define this macro, the default is `"int"'. - -`WCHAR_TYPE_SIZE' - A C expression for the size in bits of the data type for wide - characters. This is used in `cpp', which cannot make use of - `WCHAR_TYPE'. - -`MAX_WCHAR_TYPE_SIZE' - Maximum number for the size in bits of the data type for wide - characters. If this is undefined, the default is - `WCHAR_TYPE_SIZE'. Otherwise, it is the constant value that is the - largest value that `WCHAR_TYPE_SIZE' can have at run-time. This is - used in `cpp'. - -`OBJC_INT_SELECTORS' - Define this macro if the type of Objective C selectors should be - `int'. - - If this macro is not defined, then selectors should have the type - `struct objc_selector *'. - -`OBJC_SELECTORS_WITHOUT_LABELS' - Define this macro if the compiler can group all the selectors - together into a vector and use just one label at the beginning of - the vector. Otherwise, the compiler must give each selector its - own assembler label. - - On certain machines, it is important to have a separate label for - each selector because this enables the linker to eliminate - duplicate selectors. - -`TARGET_BELL' - A C constant expression for the integer value for escape sequence - `\a'. - -`TARGET_BS' -`TARGET_TAB' -`TARGET_NEWLINE' - C constant expressions for the integer values for escape sequences - `\b', `\t' and `\n'. - -`TARGET_VT' -`TARGET_FF' -`TARGET_CR' - C constant expressions for the integer values for escape sequences - `\v', `\f' and `\r'. - |