Using as: MIPS Options

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#### 9.27.1 Assembler options

The MIPS configurations of GNU `as` support these special options:

`-G num`

  Set the “small data” limit to n bytes. The default limit is 8 bytes. See Controlling the use of small data accesses.

`-EB`
`-EL`

  Any MIPS configuration of `as` can select big-endian or little-endian output at run time (unlike the other GNU development tools, which must be configured for one or the other). Use ‘`-EB`’ to select big-endian output, and ‘`-EL`’ for little-endian.

`-KPIC`

  Generate SVR4-style PIC. This option tells the assembler to generate SVR4-style position-independent macro expansions. It also tells the assembler to mark the output file as PIC.

`-mvxworks-pic`

  Generate VxWorks PIC. This option tells the assembler to generate VxWorks-style position-independent macro expansions.

`-mips1`
`-mips2`
`-mips3`
`-mips4`
`-mips5`
`-mips32`
`-mips32r2`
`-mips64`
`-mips64r2`

  Generate code for a particular MIPS Instruction Set Architecture level. ‘`-mips1`’ corresponds to the R2000 and R3000 processors, ‘`-mips2`’ to the R6000 processor, ‘`-mips3`’ to the R4000 processor, and ‘`-mips4`’ to the R8000 and R10000 processors. ‘`-mips5`’, ‘`-mips32`’, ‘`-mips32r2`’, ‘`-mips64`’, and ‘`-mips64r2`’ correspond to generic MIPS V, MIPS32, MIPS32 Release 2, MIPS64, and MIPS64 Release 2 ISA processors, respectively. You can also switch instruction sets during the assembly; see Directives to override the ISA level.

`-mgp32`
`-mfp32`

  Some macros have different expansions for 32-bit and 64-bit registers. The register sizes are normally inferred from the ISA and ABI, but these flags force a certain group of registers to be treated as 32 bits wide at all times. ‘`-mgp32`’ controls the size of general-purpose registers and ‘`-mfp32`’ controls the size of floating-point registers.

  The `.set gp=32` and `.set fp=32` directives allow the size of registers to be changed for parts of an object. The default value is restored by `.set gp=default` and `.set fp=default`.

  On some MIPS variants there is a 32-bit mode flag; when this flag is set, 64-bit instructions generate a trap. Also, some 32-bit OSes only save the 32-bit registers on a context switch, so it is essential never to use the 64-bit registers.

`-mgp64`
`-mfp64`

  Assume that 64-bit registers are available. This is provided in the interests of symmetry with ‘`-mgp32`’ and ‘`-mfp32`’.

  The `.set gp=64` and `.set fp=64` directives allow the size of registers to be changed for parts of an object. The default value is restored by `.set gp=default` and `.set fp=default`.

`-mips16`
`-no-mips16`

  Generate code for the MIPS 16 processor. This is equivalent to putting `.set mips16` at the start of the assembly file. ‘`-no-mips16`’ turns off this option.

`-mmicromips`
`-mno-micromips`

  Generate code for the microMIPS processor. This is equivalent to putting `.set micromips` at the start of the assembly file. ‘`-mno-micromips`’ turns off this option. This is equivalent to putting `.set nomicromips` at the start of the assembly file.

`-msmartmips`
`-mno-smartmips`

  Enables the SmartMIPS extensions to the MIPS32 instruction set, which provides a number of new instructions which target smartcard and cryptographic applications. This is equivalent to putting `.set smartmips` at the start of the assembly file. ‘`-mno-smartmips`’ turns off this option.

`-mips3d`
`-no-mips3d`

  Generate code for the MIPS-3D Application Specific Extension. This tells the assembler to accept MIPS-3D instructions. ‘`-no-mips3d`’ turns off this option.

`-mdmx`
`-no-mdmx`

  Generate code for the MDMX Application Specific Extension. This tells the assembler to accept MDMX instructions. ‘`-no-mdmx`’ turns off this option.

`-mdsp`
`-mno-dsp`

  Generate code for the DSP Release 1 Application Specific Extension. This tells the assembler to accept DSP Release 1 instructions. ‘`-mno-dsp`’ turns off this option.

`-mdspr2`
`-mno-dspr2`

  Generate code for the DSP Release 2 Application Specific Extension. This option implies -mdsp. This tells the assembler to accept DSP Release 2 instructions. ‘`-mno-dspr2`’ turns off this option.

`-mmt`
`-mno-mt`

  Generate code for the MT Application Specific Extension. This tells the assembler to accept MT instructions. ‘`-mno-mt`’ turns off this option.

`-mmcu`
`-mno-mcu`

  Generate code for the MCU Application Specific Extension. This tells the assembler to accept MCU instructions. ‘`-mno-mcu`’ turns off this option.

`-mvirt`
`-mno-virt`

  Generate code for the Virtualization Application Specific Extension. This tells the assembler to accept Virtualization instructions. ‘`-mno-virt`’ turns off this option.

`-minsn32`
`-mno-insn32`

  Only use 32-bit instruction encodings when generating code for the microMIPS processor. This option inhibits the use of any 16-bit instructions. This is equivalent to putting `.set insn32` at the start of the assembly file. ‘`-mno-insn32`’ turns off this option. This is equivalent to putting `.set noinsn32` at the start of the assembly file. By default ‘`-mno-insn32`’ is selected, allowing all instructions to be used.

`-mfix7000`
`-mno-fix7000`

  Cause nops to be inserted if the read of the destination register of an mfhi or mflo instruction occurs in the following two instructions.

`-mfix-loongson2f-jump`
`-mno-fix-loongson2f-jump`

  Eliminate instruction fetch from outside 256M region to work around the Loongson2F ‘`jump`’ instructions. Without it, under extreme cases, the kernel may crash. The issue has been solved in latest processor batches, but this fix has no side effect to them.

`-mfix-loongson2f-nop`
`-mno-fix-loongson2f-nop`

  Replace nops by `or at,at,zero` to work around the Loongson2F ‘`nop`’ errata. Without it, under extreme cases, the CPU might deadlock. The issue has been solved in later Loongson2F batches, but this fix has no side effect to them.

`-mfix-vr4120`
`-mno-fix-vr4120`

  Insert nops to work around certain VR4120 errata. This option is intended to be used on GCC-generated code: it is not designed to catch all problems in hand-written assembler code.

`-mfix-vr4130`
`-mno-fix-vr4130`

  Insert nops to work around the VR4130 ‘`mflo`’/‘`mfhi`’ errata.

`-mfix-24k`
`-mno-fix-24k`

  Insert nops to work around the 24K ‘`eret`’/‘`deret`’ errata.

`-mfix-cn63xxp1`
`-mno-fix-cn63xxp1`

  Replace `pref` hints 0 - 4 and 6 - 24 with hint 28 to work around certain CN63XXP1 errata.

`-m4010`
`-no-m4010`

  Generate code for the LSI R4010 chip. This tells the assembler to accept the R4010-specific instructions (‘`addciu`’, ‘`ffc`’, etc.), and to not schedule ‘`nop`’ instructions around accesses to the ‘`HI`’ and ‘`LO`’ registers. ‘`-no-m4010`’ turns off this option.

`-m4650`
`-no-m4650`

  Generate code for the MIPS R4650 chip. This tells the assembler to accept the ‘`mad`’ and ‘`madu`’ instruction, and to not schedule ‘`nop`’ instructions around accesses to the ‘`HI`’ and ‘`LO`’ registers. ‘`-no-m4650`’ turns off this option.

`-m3900`
`-no-m3900`
`-m4100`
`-no-m4100`

  For each option ‘`-mnnnn`’, generate code for the MIPS Rnnnn chip. This tells the assembler to accept instructions specific to that chip, and to schedule for that chip’s hazards.

`-march=cpu`

  Generate code for a particular MIPS CPU. It is exactly equivalent to ‘`-mcpu`’, except that there are more value of cpu understood. Valid cpu value are:

  > 2000, 3000, 3900, 4000, 4010, 4100, 4111, vr4120, vr4130, vr4181, 4300, 4400, 4600, 4650, 5000, rm5200, rm5230, rm5231, rm5261, rm5721, vr5400, vr5500, 6000, rm7000, 8000, rm9000, 10000, 12000, 14000, 16000, 4kc, 4km, 4kp, 4ksc, 4kec, 4kem, 4kep, 4ksd, m4k, m4kp, m14k, m14kc, m14ke, m14kec, 24kc, 24kf2_1, 24kf, 24kf1_1, 24kec, 24kef2_1, 24kef, 24kef1_1, 34kc, 34kf2_1, 34kf, 34kf1_1, 34kn, 74kc, 74kf2_1, 74kf, 74kf1_1, 74kf3_2, 1004kc, 1004kf2_1, 1004kf, 1004kf1_1, 5kc, 5kf, 20kc, 25kf, sb1, sb1a, loongson2e, loongson2f, loongson3a, octeon, octeon+, octeon2, xlr, xlp

  For compatibility reasons, ‘`nx`’ and ‘`bfx`’ are accepted as synonyms for ‘`nf1_1`’. These values are deprecated.

`-mtune=cpu`

  Schedule and tune for a particular MIPS CPU. Valid cpu values are identical to ‘`-march=cpu`’.

`-mabi=abi`

  Record which ABI the source code uses. The recognized arguments are: ‘`32`’, ‘`n32`’, ‘`o64`’, ‘`64`’ and ‘`eabi`’.

`-msym32`
`-mno-sym32`

  Equivalent to adding `.set sym32` or `.set nosym32` to the beginning of the assembler input. See MIPS Symbol Sizes.

`-nocpp`

  This option is ignored. It is accepted for command-line compatibility with other assemblers, which use it to turn off C style preprocessing. With GNU `as`, there is no need for ‘`-nocpp`’, because the GNU assembler itself never runs the C preprocessor.

`-msoft-float`
`-mhard-float`

  Disable or enable floating-point instructions. Note that by default floating-point instructions are always allowed even with CPU targets that don’t have support for these instructions.

`-msingle-float`
`-mdouble-float`

  Disable or enable double-precision floating-point operations. Note that by default double-precision floating-point operations are always allowed even with CPU targets that don’t have support for these operations.

`--construct-floats`
`--no-construct-floats`

  The `--no-construct-floats` option disables the construction of double width floating point constants by loading the two halves of the value into the two single width floating point registers that make up the double width register. This feature is useful if the processor support the FR bit in its status register, and this bit is known (by the programmer) to be set. This bit prevents the aliasing of the double width register by the single width registers.

  By default `--construct-floats` is selected, allowing construction of these floating point constants.

`--relax-branch`
`--no-relax-branch`

  The ‘`--relax-branch`’ option enables the relaxation of out-of-range branches. Any branches whose target cannot be reached directly are converted to a small instruction sequence including an inverse-condition branch to the physically next instruction, and a jump to the original target is inserted between the two instructions. In PIC code the jump will involve further instructions for address calculation.

  The `BC1ANY2F`, `BC1ANY2T`, `BC1ANY4F`, `BC1ANY4T`, `BPOSGE32` and `BPOSGE64` instructions are excluded from relaxation, because they have no complementing counterparts. They could be relaxed with the use of a longer sequence involving another branch, however this has not been implemented and if their target turns out of reach, they produce an error even if branch relaxation is enabled.

  Also no MIPS16 branches are ever relaxed.

  By default ‘`--no-relax-branch`’ is selected, causing any out-of-range branches to produce an error.

`-mnan=encoding`

  This option indicates whether the source code uses the IEEE 2008 NaN encoding (`-mnan=2008`) or the original MIPS encoding (`-mnan=legacy`). It is equivalent to adding a `.nan` directive to the beginning of the source file. See MIPS NaN Encodings.

  `-mnan=legacy` is the default if no `-mnan` option or `.nan` directive is used.

`--trap`
`--no-break`

  `as` automatically macro expands certain division and multiplication instructions to check for overflow and division by zero. This option causes `as` to generate code to take a trap exception rather than a break exception when an error is detected. The trap instructions are only supported at Instruction Set Architecture level 2 and higher.

`--break`
`--no-trap`

  Generate code to take a break exception rather than a trap exception when an error is detected. This is the default.

`-mpdr`
`-mno-pdr`

  Control generation of `.pdr` sections. Off by default on IRIX, on elsewhere.

`-mshared`
`-mno-shared`

  When generating code using the Unix calling conventions (selected by ‘`-KPIC`’ or ‘`-mcall_shared`’), gas will normally generate code which can go into a shared library. The ‘`-mno-shared`’ option tells gas to generate code which uses the calling convention, but can not go into a shared library. The resulting code is slightly more efficient. This option only affects the handling of the ‘`.cpload`’ and ‘`.cpsetup`’ pseudo-ops.

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