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#### 3.18.3 ARC Options

The following options control the architecture variant for which code is being compiled:

`-mbarrel-shifter`

  Generate instructions supported by barrel shifter. This is the default unless `-mcpu=ARC601` or ‘`-mcpu=ARCEM`’ is in effect.

`-mcpu=cpu`

  Set architecture type, register usage, and instruction scheduling parameters for cpu. There are also shortcut alias options available for backward compatibility and convenience. Supported values for cpu are

  ‘`arc600`’

    Compile for ARC600. Aliases: `-mA6`, `-mARC600`.

  ‘`arc601`’

    Compile for ARC601. Alias: `-mARC601`.

  ‘`arc700`’

    Compile for ARC700. Aliases: `-mA7`, `-mARC700`. This is the default when configured with `--with-cpu=arc700`.

  ‘`arcem`’

    Compile for ARC EM.

  ‘`archs`’

    Compile for ARC HS.

  ‘`em`’

    Compile for ARC EM CPU with no hardware extensions.

  ‘`em4`’

    Compile for ARC EM4 CPU.

  ‘`em4_dmips`’

    Compile for ARC EM4 DMIPS CPU.

  ‘`em4_fpus`’

    Compile for ARC EM4 DMIPS CPU with the single-precision floating-point extension.

  ‘`em4_fpuda`’

    Compile for ARC EM4 DMIPS CPU with single-precision floating-point and double assist instructions.

  ‘`hs`’

    Compile for ARC HS CPU with no hardware extensions except the atomic instructions.

  ‘`hs34`’

    Compile for ARC HS34 CPU.

  ‘`hs38`’

    Compile for ARC HS38 CPU.

  ‘`hs38_linux`’

    Compile for ARC HS38 CPU with all hardware extensions on.

  ‘`arc600_norm`’

    Compile for ARC 600 CPU with `norm` instructions enabled.

  ‘`arc600_mul32x16`’

    Compile for ARC 600 CPU with `norm` and 32x16-bit multiply instructions enabled.

  ‘`arc600_mul64`’

    Compile for ARC 600 CPU with `norm` and `mul64`-family instructions enabled.

  ‘`arc601_norm`’

    Compile for ARC 601 CPU with `norm` instructions enabled.

  ‘`arc601_mul32x16`’

    Compile for ARC 601 CPU with `norm` and 32x16-bit multiply instructions enabled.

  ‘`arc601_mul64`’

    Compile for ARC 601 CPU with `norm` and `mul64`-family instructions enabled.

  ‘`nps400`’

    Compile for ARC 700 on NPS400 chip.

`-mdpfp`
`-mdpfp-compact`

  Generate double-precision FPX instructions, tuned for the compact implementation.

`-mdpfp-fast`

  Generate double-precision FPX instructions, tuned for the fast implementation.

`-mno-dpfp-lrsr`

  Disable `lr` and `sr` instructions from using FPX extension aux registers.

`-mea`

  Generate extended arithmetic instructions. Currently only `divaw`, `adds`, `subs`, and `sat16` are supported. This is always enabled for `-mcpu=ARC700`.

`-mno-mpy`

  Do not generate `mpy`-family instructions for ARC700. This option is deprecated.

`-mmul32x16`

  Generate 32x16-bit multiply and multiply-accumulate instructions.

`-mmul64`

  Generate `mul64` and `mulu64` instructions. Only valid for `-mcpu=ARC600`.

`-mnorm`

  Generate `norm` instructions. This is the default if `-mcpu=ARC700` is in effect.

`-mspfp`
`-mspfp-compact`

  Generate single-precision FPX instructions, tuned for the compact implementation.

`-mspfp-fast`

  Generate single-precision FPX instructions, tuned for the fast implementation.

`-msimd`

  Enable generation of ARC SIMD instructions via target-specific builtins. Only valid for `-mcpu=ARC700`.

`-msoft-float`

  This option ignored; it is provided for compatibility purposes only. Software floating-point code is emitted by default, and this default can overridden by FPX options; `-mspfp`, `-mspfp-compact`, or `-mspfp-fast` for single precision, and `-mdpfp`, `-mdpfp-compact`, or `-mdpfp-fast` for double precision.

`-mswap`

  Generate `swap` instructions.

`-matomic`

  This enables use of the locked load/store conditional extension to implement atomic memory built-in functions. Not available for ARC 6xx or ARC EM cores.

`-mdiv-rem`

  Enable `div` and `rem` instructions for ARCv2 cores.

`-mcode-density`

  Enable code density instructions for ARC EM. This option is on by default for ARC HS.

`-mll64`

  Enable double load/store operations for ARC HS cores.

`-mtp-regno=regno`

  Specify thread pointer register number.

`-mmpy-option=multo`

  Compile ARCv2 code with a multiplier design option. You can specify the option using either a string or numeric value for multo. ‘`wlh1`’ is the default value. The recognized values are:

  ‘`0`’
  ‘`none`’

    No multiplier available.

  ‘`1`’
  ‘`w`’

    16x16 multiplier, fully pipelined. The following instructions are enabled: `mpyw` and `mpyuw`.

  ‘`2`’
  ‘`wlh1`’

    32x32 multiplier, fully pipelined (1 stage). The following instructions are additionally enabled: `mpy`, `mpyu`, `mpym`, `mpymu`, and `mpy_s`.

  ‘`3`’
  ‘`wlh2`’

    32x32 multiplier, fully pipelined (2 stages). The following instructions are additionally enabled: `mpy`, `mpyu`, `mpym`, `mpymu`, and `mpy_s`.

  ‘`4`’
  ‘`wlh3`’

    Two 16x16 multipliers, blocking, sequential. The following instructions are additionally enabled: `mpy`, `mpyu`, `mpym`, `mpymu`, and `mpy_s`.

  ‘`5`’
  ‘`wlh4`’

    One 16x16 multiplier, blocking, sequential. The following instructions are additionally enabled: `mpy`, `mpyu`, `mpym`, `mpymu`, and `mpy_s`.

  ‘`6`’
  ‘`wlh5`’

    One 32x4 multiplier, blocking, sequential. The following instructions are additionally enabled: `mpy`, `mpyu`, `mpym`, `mpymu`, and `mpy_s`.

  ‘`7`’
  ‘`plus_dmpy`’

    ARC HS SIMD support.

  ‘`8`’
  ‘`plus_macd`’

    ARC HS SIMD support.

  ‘`9`’
  ‘`plus_qmacw`’

    ARC HS SIMD support.

  This option is only available for ARCv2 cores.

`-mfpu=fpu`

  Enables support for specific floating-point hardware extensions for ARCv2 cores. Supported values for fpu are:

  ‘`fpus`’

    Enables support for single-precision floating-point hardware extensions.

  ‘`fpud`’

    Enables support for double-precision floating-point hardware extensions. The single-precision floating-point extension is also enabled. Not available for ARC EM.

  ‘`fpuda`’

    Enables support for double-precision floating-point hardware extensions using double-precision assist instructions. The single-precision floating-point extension is also enabled. This option is only available for ARC EM.

  ‘`fpuda_div`’

    Enables support for double-precision floating-point hardware extensions using double-precision assist instructions. The single-precision floating-point, square-root, and divide extensions are also enabled. This option is only available for ARC EM.

  ‘`fpuda_fma`’

    Enables support for double-precision floating-point hardware extensions using double-precision assist instructions. The single-precision floating-point and fused multiply and add hardware extensions are also enabled. This option is only available for ARC EM.

  ‘`fpuda_all`’

    Enables support for double-precision floating-point hardware extensions using double-precision assist instructions. All single-precision floating-point hardware extensions are also enabled. This option is only available for ARC EM.

  ‘`fpus_div`’

    Enables support for single-precision floating-point, square-root and divide hardware extensions.

  ‘`fpud_div`’

    Enables support for double-precision floating-point, square-root and divide hardware extensions. This option includes option ‘`fpus_div`’. Not available for ARC EM.

  ‘`fpus_fma`’

    Enables support for single-precision floating-point and fused multiply and add hardware extensions.

  ‘`fpud_fma`’

    Enables support for double-precision floating-point and fused multiply and add hardware extensions. This option includes option ‘`fpus_fma`’. Not available for ARC EM.

  ‘`fpus_all`’

    Enables support for all single-precision floating-point hardware extensions.

  ‘`fpud_all`’

    Enables support for all single- and double-precision floating-point hardware extensions. Not available for ARC EM.

The following options are passed through to the assembler, and also define preprocessor macro symbols.

`-mdsp-packa`

  Passed down to the assembler to enable the DSP Pack A extensions. Also sets the preprocessor symbol `__Xdsp_packa`. This option is deprecated.

`-mdvbf`

  Passed down to the assembler to enable the dual Viterbi butterfly extension. Also sets the preprocessor symbol `__Xdvbf`. This option is deprecated.

`-mlock`

  Passed down to the assembler to enable the locked load/store conditional extension. Also sets the preprocessor symbol `__Xlock`.

`-mmac-d16`

  Passed down to the assembler. Also sets the preprocessor symbol `__Xxmac_d16`. This option is deprecated.

`-mmac-24`

  Passed down to the assembler. Also sets the preprocessor symbol `__Xxmac_24`. This option is deprecated.

`-mrtsc`

  Passed down to the assembler to enable the 64-bit time-stamp counter extension instruction. Also sets the preprocessor symbol `__Xrtsc`. This option is deprecated.

`-mswape`

  Passed down to the assembler to enable the swap byte ordering extension instruction. Also sets the preprocessor symbol `__Xswape`.

`-mtelephony`

  Passed down to the assembler to enable dual- and single-operand instructions for telephony. Also sets the preprocessor symbol `__Xtelephony`. This option is deprecated.

`-mxy`

  Passed down to the assembler to enable the XY memory extension. Also sets the preprocessor symbol `__Xxy`.

The following options control how the assembly code is annotated:

`-misize`

  Annotate assembler instructions with estimated addresses.

`-mannotate-align`

  Explain what alignment considerations lead to the decision to make an instruction short or long.

The following options are passed through to the linker:

`-marclinux`

  Passed through to the linker, to specify use of the `arclinux` emulation. This option is enabled by default in tool chains built for `arc-linux-uclibc` and `arceb-linux-uclibc` targets when profiling is not requested.

`-marclinux_prof`

  Passed through to the linker, to specify use of the `arclinux_prof` emulation. This option is enabled by default in tool chains built for `arc-linux-uclibc` and `arceb-linux-uclibc` targets when profiling is requested.

The following options control the semantics of generated code:

`-mlong-calls`

  Generate calls as register indirect calls, thus providing access to the full 32-bit address range.

`-mmedium-calls`

  Don’t use less than 25-bit addressing range for calls, which is the offset available for an unconditional branch-and-link instruction. Conditional execution of function calls is suppressed, to allow use of the 25-bit range, rather than the 21-bit range with conditional branch-and-link. This is the default for tool chains built for `arc-linux-uclibc` and `arceb-linux-uclibc` targets.

`-mno-sdata`

  Do not generate sdata references. This is the default for tool chains built for `arc-linux-uclibc` and `arceb-linux-uclibc` targets.

`-mvolatile-cache`

  Use ordinarily cached memory accesses for volatile references. This is the default.

`-mno-volatile-cache`

  Enable cache bypass for volatile references.

The following options fine tune code generation:

`-malign-call`

  Do alignment optimizations for call instructions.

`-mauto-modify-reg`

  Enable the use of pre/post modify with register displacement.

`-mbbit-peephole`

  Enable bbit peephole2.

`-mno-brcc`

  This option disables a target-specific pass in `arc_reorg` to generate compare-and-branch (`brcc`) instructions. It has no effect on generation of these instructions driven by the combiner pass.

`-mcase-vector-pcrel`

  Use PC-relative switch case tables to enable case table shortening. This is the default for `-Os`.

`-mcompact-casesi`

  Enable compact `casesi` pattern. This is the default for `-Os`, and only available for ARCv1 cores.

`-mno-cond-exec`

  Disable the ARCompact-specific pass to generate conditional execution instructions.

  Due to delay slot scheduling and interactions between operand numbers, literal sizes, instruction lengths, and the support for conditional execution, the target-independent pass to generate conditional execution is often lacking, so the ARC port has kept a special pass around that tries to find more conditional execution generation opportunities after register allocation, branch shortening, and delay slot scheduling have been done. This pass generally, but not always, improves performance and code size, at the cost of extra compilation time, which is why there is an option to switch it off. If you have a problem with call instructions exceeding their allowable offset range because they are conditionalized, you should consider using `-mmedium-calls` instead.

`-mearly-cbranchsi`

  Enable pre-reload use of the `cbranchsi` pattern.

`-mexpand-adddi`

  Expand `adddi3` and `subdi3` at RTL generation time into `add.f`, `adc` etc.

`-mindexed-loads`

  Enable the use of indexed loads. This can be problematic because some optimizers then assume that indexed stores exist, which is not the case.

  Enable Local Register Allocation. This is still experimental for ARC, so by default the compiler uses standard reload (i.e. `-mno-lra`).

`-mlra-priority-none`

  Don’t indicate any priority for target registers.

`-mlra-priority-compact`

  Indicate target register priority for r0..r3 / r12..r15.

`-mlra-priority-noncompact`

  Reduce target register priority for r0..r3 / r12..r15.

`-mno-millicode`

  When optimizing for size (using `-Os`), prologues and epilogues that have to save or restore a large number of registers are often shortened by using call to a special function in libgcc; this is referred to as a millicode call. As these calls can pose performance issues, and/or cause linking issues when linking in a nonstandard way, this option is provided to turn off millicode call generation.

`-mmixed-code`

  Tweak register allocation to help 16-bit instruction generation. This generally has the effect of decreasing the average instruction size while increasing the instruction count.

`-mq-class`

  Enable ‘`q`’ instruction alternatives. This is the default for `-Os`.

`-mRcq`

  Enable ‘`Rcq`’ constraint handling. Most short code generation depends on this. This is the default.

`-mRcw`

  Enable ‘`Rcw`’ constraint handling. Most ccfsm condexec mostly depends on this. This is the default.

`-msize-level=level`

  Fine-tune size optimization with regards to instruction lengths and alignment. The recognized values for level are:

  ‘`0`’

    No size optimization. This level is deprecated and treated like ‘`1`’.

  ‘`1`’

    Short instructions are used opportunistically.

  ‘`2`’

    In addition, alignment of loops and of code after barriers are dropped.

  ‘`3`’

    In addition, optional data alignment is dropped, and the option `Os` is enabled.

  This defaults to ‘`3`’ when `-Os` is in effect. Otherwise, the behavior when this is not set is equivalent to level ‘`1`’.

`-mtune=cpu`

  Set instruction scheduling parameters for cpu, overriding any implied by `-mcpu=`.

  Supported values for cpu are

  ‘`ARC600`’

    Tune for ARC600 CPU.

  ‘`ARC601`’

    Tune for ARC601 CPU.

  ‘`ARC700`’

    Tune for ARC700 CPU with standard multiplier block.

  ‘`ARC700-xmac`’

    Tune for ARC700 CPU with XMAC block.

  ‘`ARC725D`’

    Tune for ARC725D CPU.

  ‘`ARC750D`’

    Tune for ARC750D CPU.

`-mmultcost=num`

  Cost to assume for a multiply instruction, with ‘`4`’ being equal to a normal instruction.

`-munalign-prob-threshold=probability`

  Set probability threshold for unaligning branches. When tuning for ‘`ARC700`’ and optimizing for speed, branches without filled delay slot are preferably emitted unaligned and long, unless profiling indicates that the probability for the branch to be taken is below probability. See Cross-profiling. The default is (REG_BR_PROB_BASE/2), i.e. 5000.

The following options are maintained for backward compatibility, but are now deprecated and will be removed in a future release:

`-margonaut`

  Obsolete FPX.

`-mbig-endian`
`-EB`

  Compile code for big-endian targets. Use of these options is now deprecated. Big-endian code is supported by configuring GCC to build `arceb-elf32` and `arceb-linux-uclibc` targets, for which big endian is the default.

`-mlittle-endian`
`-EL`

  Compile code for little-endian targets. Use of these options is now deprecated. Little-endian code is supported by configuring GCC to build `arc-elf32` and `arc-linux-uclibc` targets, for which little endian is the default.

`-mbarrel_shifter`

  Replaced by `-mbarrel-shifter`.

`-mdpfp_compact`

  Replaced by `-mdpfp-compact`.

`-mdpfp_fast`

  Replaced by `-mdpfp-fast`.

`-mdsp_packa`

  Replaced by `-mdsp-packa`.

`-mEA`

  Replaced by `-mea`.

`-mmac_24`

  Replaced by `-mmac-24`.

`-mmac_d16`

  Replaced by `-mmac-d16`.

`-mspfp_compact`

  Replaced by `-mspfp-compact`.

`-mspfp_fast`

  Replaced by `-mspfp-fast`.

`-mtune=cpu`

  Values ‘`arc600`’, ‘`arc601`’, ‘`arc700`’ and ‘`arc700-xmac`’ for cpu are replaced by ‘`ARC600`’, ‘`ARC601`’, ‘`ARC700`’ and ‘`ARC700-xmac`’ respectively.

`-multcost=num`

  Replaced by `-mmultcost`.

Next: ARM Options, Previous: Adapteva Epiphany Options, Up: Submodel Options [Contents][Index]