Understanding GCC's Target Specific Options

Overview

In addition to the common options, GCC also supports a set of -m<value> target specific options. Each of them configures a particular feature or an extension. For example, -mno-code-density option disables generating code density instructions.

-mcpu=<core> selects a particular ISA and CPU family and enables/disables a set of other -m options. Each -mcpu value leads to linking with a prebuilt library which corresponds to this particular -mcpu=<value> and is built using this -mcpu=<value>.

For example, option combination -mcpu=em4 -mno-code-density will generate code that doesn't use code density instructions, however it will be linked with standard library that has been built with just -mcpu=em4, which uses code density instructions - therefore a final application still may use code density instructions.

Values of -mcpu for ARC HS5x and ARC HS6x Families

-mcpu=	-msimd	-m128	-mll64
hs5x	Y	N/A
hs58	Y	N/A	Y
hs6x	Y		N/A
hs68	Y	Y	N/A

Values of -mcpu for ARC HS Family

-mcpu=	-mdiv-rem	-matomic	-mll64	-mmpy-option=	-mfpu=
hs		Y
hs34		Y		mpy
archs	Y	Y	Y	mpy
hs38	Y	Y	Y	plus_qmacw
hs4x	Y	Y	Y	plus_qmacw
hs4xd	Y	Y	Y	plus_qmacw
hs38_linux	Y	Y	Y	plus_qmacw	fpud_all

Values of -mcpu for ARC EM Family

-mcpu	-mcode-density	-mnorm	-mswap	-mbarrel-shifter	-mdiv-rem	-mmpy-option=	-mfpu=	-mrf16
em
em_mini								Y
em4	Y							Y
arcem	Y			Y		wlh1		Y
em4_dmips	Y	Y	Y	Y	Y	wlh1		Y
em4_fpus	Y	Y	Y	Y	Y	wlh1	fpus	Y
em4_fpuda	Y	Y	Y	Y	Y	wlh1	fpuda	Y

Values of -mcpu for ARC 600 and 700 Families

-mcpu=	-mnorm	-mswap	-mbarrel-shifter	Multiplier
arc700	Y	Y	Y	-mmpy
arc600			Y
arc600_norm	Y		Y
arc600_mul64	Y		Y	-mmul64
arc600_mul32x16	Y		Y	-mmul32x16
arc601
arc601_norm	Y
arc601_mul64	Y			-mmul64
arc601_mul32x16	Y			-mmul32x16