-mabi=name- Generate code for the specified data model. Permissible values
are ‘ilp32’ for SysV-like data model where int, long int and pointer
are 32-bit, and ‘lp64’ for SysV-like data model where int is 32-bit,
but long int and pointer are 64-bit.
The default depends on the specific target configuration. Note that
the LP64 and ILP32 ABIs are not link-compatible; you must compile your
entire program with the same ABI, and link with a compatible set of libraries.
-mbig-endian- Generate big-endian code. This is the default when GCC is configured for an
‘aarch64_be-*-*’ target.
-mgeneral-regs-only- Generate code which uses only the general registers.
-mlittle-endian- Generate little-endian code. This is the default when GCC is configured for an
‘aarch64-*-*’ but not an ‘aarch64_be-*-*’ target.
-mcmodel=tiny- Generate code for the tiny code model. The program and its statically defined
symbols must be within 1GB of each other. Pointers are 64 bits. Programs can
be statically or dynamically linked. This model is not fully implemented and
mostly treated as ‘small’.
-mcmodel=small- Generate code for the small code model. The program and its statically defined
symbols must be within 4GB of each other. Pointers are 64 bits. Programs can
be statically or dynamically linked. This is the default code model.
-mcmodel=large- Generate code for the large code model. This makes no assumptions about
addresses and sizes of sections. Pointers are 64 bits. Programs can be
statically linked only.
-mstrict-align- Do not assume that unaligned memory references will be handled by the system.
-momit-leaf-frame-pointer-mno-omit-leaf-frame-pointer- Omit or keep the frame pointer in leaf functions. The former behaviour is the
default.
-mtls-dialect=desc- Use TLS descriptors as the thread-local storage mechanism for dynamic accesses
of TLS variables. This is the default.
-mtls-dialect=traditional- Use traditional TLS as the thread-local storage mechanism for dynamic accesses
of TLS variables.
-march=name- Specify the name of the target architecture, optionally suffixed by one or
more feature modifiers. This option has the form
-march=arch{+[no]feature}*, where the
only permissible value for arch is ‘armv8-a’. The permissible
values for feature are documented in the sub-section below.
Where conflicting feature modifiers are specified, the right-most feature is
used.
GCC uses this name to determine what kind of instructions it can emit when
generating assembly code.
Where -march is specified without either of -mtune
or -mcpu also being specified, the code will be tuned to perform
well across a range of target processors implementing the target
architecture.
-mtune=name- Specify the name of the target processor for which GCC should tune the
performance of the code. Permissible values for this option are:
‘generic’, ‘cortex-a53’, ‘cortex-a57’.
Additionally, this option can specify that GCC should tune the performance
of the code for a big.LITTLE system. The only permissible value is
‘cortex-a57.cortex-a53’.
Where none of -mtune=, -mcpu= or -march=
are specified, the code will be tuned to perform well across a range
of target processors.
This option cannot be suffixed by feature modifiers.
-mcpu=name- Specify the name of the target processor, optionally suffixed by one or more
feature modifiers. This option has the form
-mcpu=cpu{+[no]feature}*, where the
permissible values for cpu are the same as those available for
-mtune.
The permissible values for feature are documented in the sub-section
below.
Where conflicting feature modifiers are specified, the right-most feature is
used.
GCC uses this name to determine what kind of instructions it can emit when
generating assembly code (as if by -march) and to determine
the target processor for which to tune for performance (as if
by -mtune). Where this option is used in conjunction
with -march or -mtune, those options take precedence
over the appropriate part of this option.