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This is Info file gcc.info, produced by Makeinfo version 1.68 from the input file ./gcc.texi. INFO-DIR-SECTION Programming START-INFO-DIR-ENTRY * gcc: (gcc). The GNU Compiler Collection. END-INFO-DIR-ENTRY 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, 1998, 1999, 2000 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" and "Funding for Free Software" 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" and "Funding for Free Software", 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: Directory Options, Next: Target Options, Prev: Link Options, Up: Invoking GCC Options for Directory Search ============================ These options specify directories to search for header files, for libraries and for parts of the compiler: `-IDIR' Add the directory DIR to the head of the list of directories to be searched for header files. This can be used to override a system header file, substituting your own version, since these directories are searched before the system header file directories. If you use more than one `-I' option, the directories are scanned in left-to-right order; the standard system directories come after. `-I-' Any directories you specify with `-I' options before the `-I-' option are searched only for the case of `#include "FILE"'; they are not searched for `#include <FILE>'. If additional directories are specified with `-I' options after the `-I-', these directories are searched for all `#include' directives. (Ordinarily *all* `-I' directories are used this way.) In addition, the `-I-' option inhibits the use of the current directory (where the current input file came from) as the first search directory for `#include "FILE"'. There is no way to override this effect of `-I-'. With `-I.' you can specify searching the directory which was current when the compiler was invoked. That is not exactly the same as what the preprocessor does by default, but it is often satisfactory. `-I-' does not inhibit the use of the standard system directories for header files. Thus, `-I-' and `-nostdinc' are independent. `-LDIR' Add directory DIR to the list of directories to be searched for `-l'. `-BPREFIX' This option specifies where to find the executables, libraries, include files, and data files of the compiler itself. The compiler driver program runs one or more of the subprograms `cpp', `cc1', `as' and `ld'. It tries PREFIX as a prefix for each program it tries to run, both with and without `MACHINE/VERSION/' (*note Target Options::.). For each subprogram to be run, the compiler driver first tries the `-B' prefix, if any. If that name is not found, or if `-B' was not specified, the driver tries two standard prefixes, which are `/usr/lib/gcc/' and `/usr/local/lib/gcc-lib/'. If neither of those results in a file name that is found, the unmodified program name is searched for using the directories specified in your `PATH' environment variable. `-B' prefixes that effectively specify directory names also apply to libraries in the linker, because the compiler translates these options into `-L' options for the linker. They also apply to includes files in the preprocessor, because the compiler translates these options into `-isystem' options for the preprocessor. In this case, the compiler appends `include' to the prefix. The run-time support file `libgcc.a' can also be searched for using the `-B' prefix, if needed. If it is not found there, the two standard prefixes above are tried, and that is all. The file is left out of the link if it is not found by those means. Another way to specify a prefix much like the `-B' prefix is to use the environment variable `GCC_EXEC_PREFIX'. *Note Environment Variables::. `-specs=FILE' Process FILE after the compiler reads in the standard `specs' file, in order to override the defaults that the `gcc' driver program uses when determining what switches to pass to `cc1', `cc1plus', `as', `ld', etc. More than one `-specs='FILE can be specified on the command line, and they are processed in order, from left to right. File: gcc.info, Node: Target Options, Next: Submodel Options, Prev: Directory Options, Up: Invoking GCC Specifying Target Machine and Compiler Version ============================================== By default, GCC compiles code for the same type of machine that you are using. However, it can also be installed as a cross-compiler, to compile for some other type of machine. In fact, several different configurations of GCC, for different target machines, can be installed side by side. Then you specify which one to use with the `-b' option. In addition, older and newer versions of GCC can be installed side by side. One of them (probably the newest) will be the default, but you may sometimes wish to use another. `-b MACHINE' The argument MACHINE specifies the target machine for compilation. This is useful when you have installed GCC as a cross-compiler. The value to use for MACHINE is the same as was specified as the machine type when configuring GCC as a cross-compiler. For example, if a cross-compiler was configured with `configure i386v', meaning to compile for an 80386 running System V, then you would specify `-b i386v' to run that cross compiler. When you do not specify `-b', it normally means to compile for the same type of machine that you are using. `-V VERSION' The argument VERSION specifies which version of GCC to run. This is useful when multiple versions are installed. For example, VERSION might be `2.0', meaning to run GCC version 2.0. The default version, when you do not specify `-V', is the last version of GCC that you installed. The `-b' and `-V' options actually work by controlling part of the file name used for the executable files and libraries used for compilation. A given version of GCC, for a given target machine, is normally kept in the directory `/usr/local/lib/gcc-lib/MACHINE/VERSION'. Thus, sites can customize the effect of `-b' or `-V' either by changing the names of these directories or adding alternate names (or symbolic links). If in directory `/usr/local/lib/gcc-lib/' the file `80386' is a link to the file `i386v', then `-b 80386' becomes an alias for `-b i386v'. In one respect, the `-b' or `-V' do not completely change to a different compiler: the top-level driver program `gcc' that you originally invoked continues to run and invoke the other executables (preprocessor, compiler per se, assembler and linker) that do the real work. However, since no real work is done in the driver program, it usually does not matter that the driver program in use is not the one for the specified target and version. The only way that the driver program depends on the target machine is in the parsing and handling of special machine-specific options. However, this is controlled by a file which is found, along with the other executables, in the directory for the specified version and target machine. As a result, a single installed driver program adapts to any specified target machine and compiler version. The driver program executable does control one significant thing, however: the default version and target machine. Therefore, you can install different instances of the driver program, compiled for different targets or versions, under different names. For example, if the driver for version 2.0 is installed as `ogcc' and that for version 2.1 is installed as `gcc', then the command `gcc' will use version 2.1 by default, while `ogcc' will use 2.0 by default. However, you can choose either version with either command with the `-V' option. File: gcc.info, Node: Submodel Options, Next: Code Gen Options, Prev: Target Options, Up: Invoking GCC Hardware Models and Configurations ================================== Earlier we discussed the standard option `-b' which chooses among different installed compilers for completely different target machines, such as Vax vs. 68000 vs. 80386. In addition, each of these target machine types can have its own special options, starting with `-m', to choose among various hardware models or configurations--for example, 68010 vs 68020, floating coprocessor or none. A single installed version of the compiler can compile for any model or configuration, according to the options specified. Some configurations of the compiler also support additional special options, usually for compatibility with other compilers on the same platform. These options are defined by the macro `TARGET_SWITCHES' in the machine description. The default for the options is also defined by that macro, which enables you to change the defaults. * Menu: * M680x0 Options:: * VAX Options:: * SPARC Options:: * Convex Options:: * AMD29K Options:: * ARM Options:: * Thumb Options:: * MN10200 Options:: * MN10300 Options:: * M32R/D Options:: * M88K Options:: * RS/6000 and PowerPC Options:: * RT Options:: * MIPS Options:: * i386 Options:: * HPPA Options:: * Intel 960 Options:: * DEC Alpha Options:: * Clipper Options:: * H8/300 Options:: * SH Options:: * System V Options:: * TMS320C3x/C4x Options:: * V850 Options:: * ARC Options:: * NS32K Options:: File: gcc.info, Node: M680x0 Options, Next: VAX Options, Up: Submodel Options M680x0 Options -------------- These are the `-m' options defined for the 68000 series. The default values for these options depends on which style of 68000 was selected when the compiler was configured; the defaults for the most common choices are given below. `-m68000' `-mc68000' Generate output for a 68000. This is the default when the compiler is configured for 68000-based systems. Use this option for microcontrollers with a 68000 or EC000 core, including the 68008, 68302, 68306, 68307, 68322, 68328 and 68356. `-m68020' `-mc68020' Generate output for a 68020. This is the default when the compiler is configured for 68020-based systems. `-m68881' Generate output containing 68881 instructions for floating point. This is the default for most 68020 systems unless `-nfp' was specified when the compiler was configured. `-m68030' Generate output for a 68030. This is the default when the compiler is configured for 68030-based systems. `-m68040' Generate output for a 68040. This is the default when the compiler is configured for 68040-based systems. This option inhibits the use of 68881/68882 instructions that have to be emulated by software on the 68040. Use this option if your 68040 does not have code to emulate those instructions. `-m68060' Generate output for a 68060. This is the default when the compiler is configured for 68060-based systems. This option inhibits the use of 68020 and 68881/68882 instructions that have to be emulated by software on the 68060. Use this option if your 68060 does not have code to emulate those instructions. `-mcpu32' Generate output for a CPU32. This is the default when the compiler is configured for CPU32-based systems. Use this option for microcontrollers with a CPU32 or CPU32+ core, including the 68330, 68331, 68332, 68333, 68334, 68336, 68340, 68341, 68349 and 68360. `-m5200' Generate output for a 520X "coldfire" family cpu. This is the default when the compiler is configured for 520X-based systems. Use this option for microcontroller with a 5200 core, including the MCF5202, MCF5203, MCF5204 and MCF5202. `-m68020-40' Generate output for a 68040, without using any of the new instructions. This results in code which can run relatively efficiently on either a 68020/68881 or a 68030 or a 68040. The generated code does use the 68881 instructions that are emulated on the 68040. `-m68020-60' Generate output for a 68060, without using any of the new instructions. This results in code which can run relatively efficiently on either a 68020/68881 or a 68030 or a 68040. The generated code does use the 68881 instructions that are emulated on the 68060. `-mfpa' Generate output containing Sun FPA instructions for floating point. `-msoft-float' Generate output containing library calls for floating point. *Warning:* the requisite libraries are not available for all m68k targets. Normally the facilities of the machine's usual C compiler are used, but this can't be done directly in cross-compilation. You must make your own arrangements to provide suitable library functions for cross-compilation. The embedded targets `m68k-*-aout' and `m68k-*-coff' do provide software floating point support. `-mshort' Consider type `int' to be 16 bits wide, like `short int'. `-mnobitfield' Do not use the bit-field instructions. The `-m68000', `-mcpu32' and `-m5200' options imply `-mnobitfield'. `-mbitfield' Do use the bit-field instructions. The `-m68020' option implies `-mbitfield'. This is the default if you use a configuration designed for a 68020. `-mrtd' Use a different function-calling convention, in which functions that take a fixed number of arguments return with the `rtd' instruction, which pops their arguments while returning. This saves one instruction in the caller since there is no need to pop the arguments there. This calling convention is incompatible with the one normally used on Unix, so you cannot use it if you need to call libraries compiled with the Unix compiler. Also, you must provide function prototypes for all functions that take variable numbers of arguments (including `printf'); otherwise incorrect code will be generated for calls to those functions. In addition, seriously incorrect code will result if you call a function with too many arguments. (Normally, extra arguments are harmlessly ignored.) The `rtd' instruction is supported by the 68010, 68020, 68030, 68040, 68060 and CPU32 processors, but not by the 68000 or 5200. `-malign-int' `-mno-align-int' Control whether GCC aligns `int', `long', `long long', `float', `double', and `long double' variables on a 32-bit boundary (`-malign-int') or a 16-bit boundary (`-mno-align-int'). Aligning variables on 32-bit boundaries produces code that runs somewhat faster on processors with 32-bit busses at the expense of more memory. *Warning:* if you use the `-malign-int' switch, GCC will align structures containing the above types differently than most published application binary interface specifications for the m68k. File: gcc.info, Node: VAX Options, Next: SPARC Options, Prev: M680x0 Options, Up: Submodel Options VAX Options ----------- These `-m' options are defined for the Vax: `-munix' Do not output certain jump instructions (`aobleq' and so on) that the Unix assembler for the Vax cannot handle across long ranges. `-mgnu' Do output those jump instructions, on the assumption that you will assemble with the GNU assembler. `-mg' Output code for g-format floating point numbers instead of d-format. File: gcc.info, Node: SPARC Options, Next: Convex Options, Prev: VAX Options, Up: Submodel Options SPARC Options ------------- These `-m' switches are supported on the SPARC: `-mno-app-regs' `-mapp-regs' Specify `-mapp-regs' to generate output using the global registers 2 through 4, which the SPARC SVR4 ABI reserves for applications. This is the default. To be fully SVR4 ABI compliant at the cost of some performance loss, specify `-mno-app-regs'. You should compile libraries and system software with this option. `-mfpu' `-mhard-float' Generate output containing floating point instructions. This is the default. `-mno-fpu' `-msoft-float' Generate output containing library calls for floating point. *Warning:* the requisite libraries are not available for all SPARC targets. Normally the facilities of the machine's usual C compiler are used, but this cannot be done directly in cross-compilation. You must make your own arrangements to provide suitable library functions for cross-compilation. The embedded targets `sparc-*-aout' and `sparclite-*-*' do provide software floating point support. `-msoft-float' changes the calling convention in the output file; therefore, it is only useful if you compile *all* of a program with this option. In particular, you need to compile `libgcc.a', the library that comes with GCC, with `-msoft-float' in order for this to work. `-mhard-quad-float' Generate output containing quad-word (long double) floating point instructions. `-msoft-quad-float' Generate output containing library calls for quad-word (long double) floating point instructions. The functions called are those specified in the SPARC ABI. This is the default. As of this writing, there are no sparc implementations that have hardware support for the quad-word floating point instructions. They all invoke a trap handler for one of these instructions, and then the trap handler emulates the effect of the instruction. Because of the trap handler overhead, this is much slower than calling the ABI library routines. Thus the `-msoft-quad-float' option is the default. `-mno-epilogue' `-mepilogue' With `-mepilogue' (the default), the compiler always emits code for function exit at the end of each function. Any function exit in the middle of the function (such as a return statement in C) will generate a jump to the exit code at the end of the function. With `-mno-epilogue', the compiler tries to emit exit code inline at every function exit. `-mno-flat' `-mflat' With `-mflat', the compiler does not generate save/restore instructions and will use a "flat" or single register window calling convention. This model uses %i7 as the frame pointer and is compatible with the normal register window model. Code from either may be intermixed. The local registers and the input registers (0-5) are still treated as "call saved" registers and will be saved on the stack as necessary. With `-mno-flat' (the default), the compiler emits save/restore instructions (except for leaf functions) and is the normal mode of operation. `-mno-unaligned-doubles' `-munaligned-doubles' Assume that doubles have 8 byte alignment. This is the default. With `-munaligned-doubles', GCC assumes that doubles have 8 byte alignment only if they are contained in another type, or if they have an absolute address. Otherwise, it assumes they have 4 byte alignment. Specifying this option avoids some rare compatibility problems with code generated by other compilers. It is not the default because it results in a performance loss, especially for floating point code. `-mv8' `-msparclite' These two options select variations on the SPARC architecture. By default (unless specifically configured for the Fujitsu SPARClite), GCC generates code for the v7 variant of the SPARC architecture. `-mv8' will give you SPARC v8 code. The only difference from v7 code is that the compiler emits the integer multiply and integer divide instructions which exist in SPARC v8 but not in SPARC v7. `-msparclite' will give you SPARClite code. This adds the integer multiply, integer divide step and scan (`ffs') instructions which exist in SPARClite but not in SPARC v7. These options are deprecated and will be deleted in a future GCC release. They have been replaced with `-mcpu=xxx'. `-mcypress' `-msupersparc' These two options select the processor for which the code is optimised. With `-mcypress' (the default), the compiler optimizes code for the Cypress CY7C602 chip, as used in the SparcStation/SparcServer 3xx series. This is also appropriate for the older SparcStation 1, 2, IPX etc. With `-msupersparc' the compiler optimizes code for the SuperSparc cpu, as used in the SparcStation 10, 1000 and 2000 series. This flag also enables use of the full SPARC v8 instruction set. These options are deprecated and will be deleted in a future GCC release. They have been replaced with `-mcpu=xxx'. `-mcpu=CPU_TYPE' Set the instruction set, register set, and instruction scheduling parameters for machine type CPU_TYPE. Supported values for CPU_TYPE are `v7', `cypress', `v8', `supersparc', `sparclite', `hypersparc', `sparclite86x', `f930', `f934', `sparclet', `tsc701', `v9', and `ultrasparc'. Default instruction scheduling parameters are used for values that select an architecture and not an implementation. These are `v7', `v8', `sparclite', `sparclet', `v9'. Here is a list of each supported architecture and their supported implementations. v7: cypress v8: supersparc, hypersparc sparclite: f930, f934, sparclite86x sparclet: tsc701 v9: ultrasparc `-mtune=CPU_TYPE' Set the instruction scheduling parameters for machine type CPU_TYPE, but do not set the instruction set or register set that the option `-mcpu='CPU_TYPE would. The same values for `-mcpu='CPU_TYPE are used for `-mtune=' CPU_TYPE, though the only useful values are those that select a particular cpu implementation: `cypress', `supersparc', `hypersparc', `f930', `f934', `sparclite86x', `tsc701', `ultrasparc'. `-malign-loops=NUM' Align loops to a 2 raised to a NUM byte boundary. If `-malign-loops' is not specified, the default is 2. `-malign-jumps=NUM' Align instructions that are only jumped to to a 2 raised to a NUM byte boundary. If `-malign-jumps' is not specified, the default is 2. `-malign-functions=NUM' Align the start of functions to a 2 raised to NUM byte boundary. If `-malign-functions' is not specified, the default is 2 if compiling for 32 bit sparc, and 5 if compiling for 64 bit sparc. These `-m' switches are supported in addition to the above on the SPARCLET processor. `-mlittle-endian' Generate code for a processor running in little-endian mode. `-mlive-g0' Treat register `%g0' as a normal register. GCC will continue to clobber it as necessary but will not assume it always reads as 0. `-mbroken-saverestore' Generate code that does not use non-trivial forms of the `save' and `restore' instructions. Early versions of the SPARCLET processor do not correctly handle `save' and `restore' instructions used with arguments. They correctly handle them used without arguments. A `save' instruction used without arguments increments the current window pointer but does not allocate a new stack frame. It is assumed that the window overflow trap handler will properly handle this case as will interrupt handlers. These `-m' switches are supported in addition to the above on SPARC V9 processors in 64 bit environments. `-mlittle-endian' Generate code for a processor running in little-endian mode. `-m32' `-m64' Generate code for a 32 bit or 64 bit environment. The 32 bit environment sets int, long and pointer to 32 bits. The 64 bit environment sets int to 32 bits and long and pointer to 64 bits. `-mcmodel=medlow' Generate code for the Medium/Low code model: the program must be linked in the low 32 bits of the address space. Pointers are 64 bits. Programs can be statically or dynamically linked. `-mcmodel=medmid' Generate code for the Medium/Middle code model: the program must be linked in the low 44 bits of the address space, the text segment must be less than 2G bytes, and data segment must be within 2G of the text segment. Pointers are 64 bits. `-mcmodel=medany' Generate code for the Medium/Anywhere code model: the program may be linked anywhere in the address space, the text segment must be less than 2G bytes, and data segment must be within 2G of the text segment. Pointers are 64 bits. `-mcmodel=embmedany' Generate code for the Medium/Anywhere code model for embedded systems: assume a 32 bit text and a 32 bit data segment, both starting anywhere (determined at link time). Register %g4 points to the base of the data segment. Pointers still 64 bits. Programs are statically linked, PIC is not supported. `-mstack-bias' `-mno-stack-bias' With `-mstack-bias', GCC assumes that the stack pointer, and frame pointer if present, are offset by -2047 which must be added back when making stack frame references. Otherwise, assume no such offset is present. File: gcc.info, Node: Convex Options, Next: AMD29K Options, Prev: SPARC Options, Up: Submodel Options Convex Options -------------- These `-m' options are defined for Convex: `-mc1' Generate output for C1. The code will run on any Convex machine. The preprocessor symbol `__convex__c1__' is defined. `-mc2' Generate output for C2. Uses instructions not available on C1. Scheduling and other optimizations are chosen for max performance on C2. The preprocessor symbol `__convex_c2__' is defined. `-mc32' Generate output for C32xx. Uses instructions not available on C1. Scheduling and other optimizations are chosen for max performance on C32. The preprocessor symbol `__convex_c32__' is defined. `-mc34' Generate output for C34xx. Uses instructions not available on C1. Scheduling and other optimizations are chosen for max performance on C34. The preprocessor symbol `__convex_c34__' is defined. `-mc38' Generate output for C38xx. Uses instructions not available on C1. Scheduling and other optimizations are chosen for max performance on C38. The preprocessor symbol `__convex_c38__' is defined. `-margcount' Generate code which puts an argument count in the word preceding each argument list. This is compatible with regular CC, and a few programs may need the argument count word. GDB and other source-level debuggers do not need it; this info is in the symbol table. `-mnoargcount' Omit the argument count word. This is the default. `-mvolatile-cache' Allow volatile references to be cached. This is the default. `-mvolatile-nocache' Volatile references bypass the data cache, going all the way to memory. This is only needed for multi-processor code that does not use standard synchronization instructions. Making non-volatile references to volatile locations will not necessarily work. `-mlong32' Type long is 32 bits, the same as type int. This is the default. `-mlong64' Type long is 64 bits, the same as type long long. This option is useless, because no library support exists for it. File: gcc.info, Node: AMD29K Options, Next: ARM Options, Prev: Convex Options, Up: Submodel Options AMD29K Options -------------- These `-m' options are defined for the AMD Am29000: `-mdw' Generate code that assumes the `DW' bit is set, i.e., that byte and halfword operations are directly supported by the hardware. This is the default. `-mndw' Generate code that assumes the `DW' bit is not set. `-mbw' Generate code that assumes the system supports byte and halfword write operations. This is the default. `-mnbw' Generate code that assumes the systems does not support byte and halfword write operations. `-mnbw' implies `-mndw'. `-msmall' Use a small memory model that assumes that all function addresses are either within a single 256 KB segment or at an absolute address of less than 256k. This allows the `call' instruction to be used instead of a `const', `consth', `calli' sequence. `-mnormal' Use the normal memory model: Generate `call' instructions only when calling functions in the same file and `calli' instructions otherwise. This works if each file occupies less than 256 KB but allows the entire executable to be larger than 256 KB. This is the default. `-mlarge' Always use `calli' instructions. Specify this option if you expect a single file to compile into more than 256 KB of code. `-m29050' Generate code for the Am29050. `-m29000' Generate code for the Am29000. This is the default. `-mkernel-registers' Generate references to registers `gr64-gr95' instead of to registers `gr96-gr127'. This option can be used when compiling kernel code that wants a set of global registers disjoint from that used by user-mode code. Note that when this option is used, register names in `-f' flags must use the normal, user-mode, names. `-muser-registers' Use the normal set of global registers, `gr96-gr127'. This is the default. `-mstack-check' `-mno-stack-check' Insert (or do not insert) a call to `__msp_check' after each stack adjustment. This is often used for kernel code. `-mstorem-bug' `-mno-storem-bug' `-mstorem-bug' handles 29k processors which cannot handle the separation of a mtsrim insn and a storem instruction (most 29000 chips to date, but not the 29050). `-mno-reuse-arg-regs' `-mreuse-arg-regs' `-mno-reuse-arg-regs' tells the compiler to only use incoming argument registers for copying out arguments. This helps detect calling a function with fewer arguments than it was declared with. `-mno-impure-text' `-mimpure-text' `-mimpure-text', used in addition to `-shared', tells the compiler to not pass `-assert pure-text' to the linker when linking a shared object. `-msoft-float' Generate output containing library calls for floating point. *Warning:* the requisite libraries are not part of GCC. Normally the facilities of the machine's usual C compiler are used, but this can't be done directly in cross-compilation. You must make your own arrangements to provide suitable library functions for cross-compilation. `-mno-multm' Do not generate multm or multmu instructions. This is useful for some embedded systems which do not have trap handlers for these instructions. File: gcc.info, Node: ARM Options, Next: Thumb Options, Prev: AMD29K Options, Up: Submodel Options ARM Options ----------- These `-m' options are defined for Advanced RISC Machines (ARM) architectures: `-mapcs-frame' Generate a stack frame that is compliant with the ARM Procedure Call Standard for all functions, even if this is not strictly necessary for correct execution of the code. Specifying `-fomit-frame-pointer' with this option will cause the stack frames not to be generated for leaf functions. The default is `-mno-apcs-frame'. `-mapcs' This is a synonym for `-mapcs-frame'. `-mapcs-26' Generate code for a processor running with a 26-bit program counter, and conforming to the function calling standards for the APCS 26-bit option. This option replaces the `-m2' and `-m3' options of previous releases of the compiler. `-mapcs-32' Generate code for a processor running with a 32-bit program counter, and conforming to the function calling standards for the APCS 32-bit option. This option replaces the `-m6' option of previous releases of the compiler. `-mapcs-stack-check' Generate code to check the amount of stack space available upon entry to every function (that actually uses some stack space). If there is insufficient space available then either the function `__rt_stkovf_split_small' or `__rt_stkovf_split_big' will be called, depending upon the amount of stack space required. The run time system is required to provide these functions. The default is `-mno-apcs-stack-check', since this produces smaller code. `-mapcs-float' Pass floating point arguments using the float point registers. This is one of the variants of the APCS. This option is reccommended if the target hardware has a floating point unit or if a lot of floating point arithmetic is going to be performed by the code. The default is `-mno-apcs-float', since integer only code is slightly increased in size if `-mapcs-float' is used. `-mapcs-reentrant' Generate reentrant, position independent code. This is the equivalent to specifying the `-fpic' option. The default is `-mno-apcs-reentrant'. `-mthumb-interwork' Generate code which supports calling between the ARM and THUMB instruction sets. Without this option the two instruction sets cannot be reliably used inside one program. The default is `-mno-thumb-interwork', since slightly larger code is generated when `-mthumb-interwork' is specified. `-mno-sched-prolog' Prevent the reordering of instructions in the function prolog, or the merging of those instruction with the instructions in the function's body. This means that all functions will start with a recognisable set of instructions (or in fact one of a chioce from a small set of different function prologues), and this information can be used to locate the start if functions inside an executable piece of code. The default is `-msched-prolog'. `-mhard-float' Generate output containing floating point instructions. This is the default. `-msoft-float' Generate output containing library calls for floating point. *Warning:* the requisite libraries are not available for all ARM targets. Normally the facilities of the machine's usual C compiler are used, but this cannot be done directly in cross-compilation. You must make your own arrangements to provide suitable library functions for cross-compilation. `-msoft-float' changes the calling convention in the output file; therefore, it is only useful if you compile *all* of a program with this option. In particular, you need to compile `libgcc.a', the library that comes with GCC, with `-msoft-float' in order for this to work. `-mlittle-endian' Generate code for a processor running in little-endian mode. This is the default for all standard configurations. `-mbig-endian' Generate code for a processor running in big-endian mode; the default is to compile code for a little-endian processor. `-mwords-little-endian' This option only applies when generating code for big-endian processors. Generate code for a little-endian word order but a big-endian byte order. That is, a byte order of the form `32107654'. Note: this option should only be used if you require compatibility with code for big-endian ARM processors generated by versions of the compiler prior to 2.8. `-mshort-load-bytes' Do not try to load half-words (eg `short's) by loading a word from an unaligned address. For some targets the MMU is configured to trap unaligned loads; use this option to generate code that is safe in these environments. `-mno-short-load-bytes' Use unaligned word loads to load half-words (eg `short's). This option produces more efficient code, but the MMU is sometimes configured to trap these instructions. `-mshort-load-words' This is a synonym for the `-mno-short-load-bytes'. `-mno-short-load-words' This is a synonym for the `-mshort-load-bytes'. `-mbsd' This option only applies to RISC iX. Emulate the native BSD-mode compiler. This is the default if `-ansi' is not specified. `-mxopen' This option only applies to RISC iX. Emulate the native X/Open-mode compiler. `-mno-symrename' This option only applies to RISC iX. Do not run the assembler post-processor, `symrename', after code has been assembled. Normally it is necessary to modify some of the standard symbols in preparation for linking with the RISC iX C library; this option suppresses this pass. The post-processor is never run when the compiler is built for cross-compilation. `-mcpu=<name>' `-mtune=<name>' This specifies the name of the target ARM processor. GCC uses this name to determine what kind of instructions it can use when generating assembly code. Permissable names are: arm2, arm250, arm3, arm6, arm60, arm600, arm610, arm620, arm7, arm7m, arm7d, arm7dm, arm7di, arm7dmi, arm70, arm700, arm700i, arm710, arm710c, arm7100, arm7500, arm7500fe, arm7tdmi, arm8, strongarm, strongarm110, strongarm1100, arm8, arm810, arm9, arm9tdmi. `-mtune=' is a synonym for `-mcpue=' to support older versions of GCC. `-march=<name>' This specifies the name of the target ARM architecture. GCC uses this name to determine what kind of instructions it can use when generating assembly code. This option can be used in conjunction with or instead of the `-mcpu=' option. Permissable names are: armv2, armv2a, armv3, armv3m, armv4, armv4t `-mfpe=<number>' `-mfp=<number>' This specifes the version of the floating point emulation available on the target. Permissable values are 2 and 3. `-mfp=' is a synonym for `-mfpe=' to support older versions of GCC. `-mstructure-size-boundary=<n>' The size of all structures and unions will be rounded up to a multiple of the number of bits set by this option. Permissable values are 8 and 32. The default value varies for different toolchains. For the COFF targeted toolchain the default value is 8. Specifying the larger number can produced faster, more efficient code, but can also increase the size of the program. The two values are potentially incompatible. Code compiled with one value cannot necessarily expect to work with code or libraries compiled with the other value, if they exchange information using structures or unions. Programmers are encouraged to use the 32 value as future versions of the toolchain may default to this value. `-mabort-on-noreturn' Generate a call to the function abort at the end of a noreturn function. It will be executed if the function tries to return. File: gcc.info, Node: Thumb Options, Next: MN10200 Options, Prev: ARM Options, Up: Submodel Options Thumb Options ------------- `-mthumb-interwork' Generate code which supports calling between the THUMB and ARM instruction sets. Without this option the two instruction sets cannot be reliably used inside one program. The default is `-mno-thumb-interwork', since slightly smaller code is generated with this option. `-mtpcs-frame' Generate a stack frame that is compliant with the Thumb Procedure Call Standard for all non-leaf functions. (A leaf function is one that does not call any other functions). The default is `-mno-apcs-frame'. `-mtpcs-leaf-frame' Generate a stack frame that is compliant with the Thumb Procedure Call Standard for all leaf functions. (A leaf function is one that does not call any other functions). The default is `-mno-apcs-leaf-frame'. `-mlittle-endian' Generate code for a processor running in little-endian mode. This is the default for all standard configurations. `-mbig-endian' Generate code for a processor running in big-endian mode. `-mstructure-size-boundary=<n>' The size of all structures and unions will be rounded up to a multiple of the number of bits set by this option. Permissable values are 8 and 32. The default value varies for different toolchains. For the COFF targeted toolchain the default value is 8. Specifying the larger number can produced faster, more efficient code, but can also increase the size of the program. The two values are potentially incompatible. Code compiled with one value cannot necessarily expect to work with code or libraries compiled with the other value, if they exchange information using structures or unions. Programmers are encouraged to use the 32 value as future versions of the toolchain may default to this value. File: gcc.info, Node: MN10200 Options, Next: MN10300 Options, Prev: Thumb Options, Up: Submodel Options MN10200 Options --------------- These `-m' options are defined for Matsushita MN10200 architectures: `-mrelax' Indicate to the linker that it should perform a relaxation optimization pass to shorten branches, calls and absolute memory addresses. This option only has an effect when used on the command line for the final link step. This option makes symbolic debugging impossible. File: gcc.info, Node: MN10300 Options, Next: M32R/D Options, Prev: MN10200 Options, Up: Submodel Options MN10300 Options --------------- These `-m' options are defined for Matsushita MN10300 architectures: `-mmult-bug' Generate code to avoid bugs in the multiply instructions for the MN10300 processors. This is the default. `-mno-mult-bug' Do not generate code to avoid bugs in the multiply instructions for the MN10300 processors. `-mrelax' Indicate to the linker that it should perform a relaxation optimization pass to shorten branches, calls and absolute memory addresses. This option only has an effect when used on the command line for the final link step. This option makes symbolic debugging impossible. File: gcc.info, Node: M32R/D Options, Next: M88K Options, Prev: MN10300 Options, Up: Submodel Options M32R/D Options -------------- These `-m' options are defined for Mitsubishi M32R/D architectures: `-mcode-model=small' Assume all objects live in the lower 16MB of memory (so that their addresses can be loaded with the `ld24' instruction), and assume all subroutines are reachable with the `bl' instruction. This is the default. The addressability of a particular object can be set with the `model' attribute. `-mcode-model=medium' Assume objects may be anywhere in the 32 bit address space (the compiler will generate `seth/add3' instructions to load their addresses), and assume all subroutines are reachable with the `bl' instruction. `-mcode-model=large' Assume objects may be anywhere in the 32 bit address space (the compiler will generate `seth/add3' instructions to load their addresses), and assume subroutines may not be reachable with the `bl' instruction (the compiler will generate the much slower `seth/add3/jl' instruction sequence). `-msdata=none' Disable use of the small data area. Variables will be put into one of `.data', `bss', or `.rodata' (unless the `section' attribute has been specified). This is the default. The small data area consists of sections `.sdata' and `.sbss'. Objects may be explicitly put in the small data area with the `section' attribute using one of these sections. `-msdata=sdata' Put small global and static data in the small data area, but do not generate special code to reference them. `-msdata=use' Put small global and static data in the small data area, and generate special instructions to reference them. `-G NUM' Put global and static objects less than or equal to NUM bytes into the small data or bss sections instead of the normal data or bss sections. The default value of NUM is 8. The `-msdata' option must be set to one of `sdata' or `use' for this option to have any effect. All modules should be compiled with the same `-G NUM' value. Compiling with different values of NUM may or may not work; if it doesn't the linker will give an error message - incorrect code will not be generated.