Options for ARCompact¶

Target Options¶

Here is a list of target specific options for ARCompact with information about availability for ARC 700 and ARC 600 targets:

Feature	GCC option	ARC 700	ARC 600
Select a set of predefined values for target options	`-mcpu=...`	Available	Available
Enable shift instructions	`-mbarrel-shifter`	Available	Available
Enable bitscan instructions	`-mnorm`	Available	Available
Enable swap instruction	`-mswap`	Available	Available
Enable swap byte ordering instruction	`-mswape`	Available	Available
Use 16 register file	`-mrf16`¹	Available	Available
Enable atomic instructions	`-matomic`	Available	N/A
Generate Single Precision FPX (compact) instructions	`-mspfp`	Available	N/A
Generate Single Precision FPX (compact) instructions	`-mspfp-compact`	Available	N/A
Generate Single Precision FPX (fast) instructions	`-mspfp-fast`	Available	N/A
Generate Double Precision FPX (compact) instructions	`-mdpfp`	Available	N/A
Generate Double Precision FPX (compact) instructions	`-mdpfp-compact`	Available	N/A
Generate Double Precision FPX (fast) instructions	`-mdpfp-fast`	Available	N/A
Enable generation of SIMD instructions via target-specific builtins	`-msimd`	Available	N/A
Enable Argonaut double precision floating point extensions	`-margonaut`	Available	Available
Generate extended arithmetic instructions	`-mea`	Available	N/A
Generate `mul64` and `mulu64` instructions	`-mmul64`	N/A	Available
Generate 32x16 multiply and mac instructions	`-mmul32x16`	N/A	Available
Enable unaligned word and halfword accesses to packed data	`-munaligned-access`	Available	Available
Enable XY memory extension for the assembler (DSP version 3)	`-mxy`	Available	Available
Enable uncached access for volatile memories	`-mvolatile-di`	Available	Available

You can find a short description for all target options using --target-help option:

$ arc-snps-elf-gcc --target-help
The following options are target specific:
...
  -mbitops                    Enable use of NPS400 bit operations.
  -mbranch-index              Enable use of BI/BIH instructions when available.
  -mcase-vector-pcrel         Use pc-relative switch case tables - this enables case table shortening.
  -mcmem                      Enable use of NPS400 xld/xst extension.
  -mcode-density              Enable code density instructions for ARCv2.
  -mcode-density-frame        Enable ENTER_S and LEAVE_S opcodes for ARCv2.
  -mcompact-casesi            Enable compact casesi pattern.  Uses of this option are diagnosed.
  -mcpu=CPU                   Compile code for ARC variant CPU.
...

You can find out what target options are enabled or disabled with a particular set of options using -Q flag:

$ arc-snps-elf-gcc -mcpu=arc700 --target-help -Q
The following options are target specific:
...
  -mbitops                              [disabled]
  -mbranch-index                        [disabled]
  -mcase-vector-pcrel                   [disabled]
  -mcmem                                [disabled]
  -mcode-density                        [disabled]
  -mcode-density-frame                  [disabled]
  -mcompact-casesi                      [disabled]
  -mcpu=CPU                             arc700
...

Default Options for Base Targets¶

A particular ARCompact target is selected by -mcpu= option. Each -mcpu= value selects a corresponding prebuilt library and a set of options:

-mcpu= values for ARC 700: arc700.
-mcpu= values for ARC 600: arc600, arc600_norm, arc600_mul64, arc600_mul32x16, arc601, arc601_norm, arc601_mul64, arc601_mul32x16.

Here is a table of default values for targets options for base ARC 700 (-mcpu=arc700) and ARC 600 (-mcpu=arc601) configurations:

GCC option	`-mcpu=arc700`	`-mcpu=arc601`
`-mbarrel-shifter`	On	Off
`-mnorm`	On	Off
`-mswap`	On	Off
`-mswape`	Off	Off
`-mrf16`	Off	Off
`-matomic`	Off	N/A
`-mspfp`	Off	N/A
`-mspfp-compact`	Off	N/A
`-mspfp-fast`	Off	N/A
`-mdpfp`	Off	N/A
`-mdpfp-compact`	Off	N/A
`-mdpfp-fast`	Off	N/A
`-msimd`	Off	N/A
`-mmargonaut`	Off	Off
`-mea`	Off	N/A
`-mmul64`	N/A	Off
`-mmul32x16`	N/A	Off
`-munaligned-access`	Off	Off
`-mxy`	Off	Off
`-mvolatile-di`	On	On

Selecting Targets¶

A particular ARCompact target is selected by -mcpu= option. Each -mcpu= value selects a corresponding prebuilt library and a set of options in addition to default values set by -mcpu=arc700 (for ARC 700) or -mcpu=arc601 (for ARC 600):

`-mcpu=`	`-mnorm`	`-mswap`	`-mbarrel-shifter`	Multiplier
`arc700`	On	On	On	Full support
`arc600`			On
`arc600_norm`	On		On
`arc600_mul64`	On		On	`-mmul64`
`arc600_mul32x16`	On		On	`-mmul32x16`
`arc601`
`arc601_norm`	On
`arc601_mul64`	On			`-mmul64`
`arc601_mul32x16`	On			`-mmul32x16`

Compatibility with Other Tools¶

Refer to Compatibility with Other Tools for ARCv2 for compatibility information for options common to ARCompact and ARCv2. For other ARCompact specific options see below.

Multiplication Options for ARC 700:

GCC	CCAC/MDB	nSIM
`-mea`	`-Xea`	`nsim_isa_sat=1`

Multiplication Options for ARC 600:

GCC	CCAC/MDB	nSIM
`-mmul32x16`	`-Xmul32x16`	`nsim_isa_mul32x16=1`
`-mmul64`	`-Xmult32d`	`nsim_isa_mult32d=1`
N/A	`-Xea`	`nsim_isa_sat=1`

Note that -mrf16 may be used only with -mcpu=em_mini option. ↩