These options are supported for Xtensa targets:
-mconst16
¶-mno-const16
Enable or disable use of CONST16
instructions for loading
constant values. The CONST16
instruction is currently not a
standard option from Tensilica. When enabled, CONST16
instructions are always used in place of the standard L32R
instructions. The use of CONST16
is enabled by default only if
the L32R
instruction is not available.
-mfused-madd
¶-mno-fused-madd
Enable or disable use of fused multiply/add and multiply/subtract instructions in the floating-point option. This has no effect if the floating-point option is not also enabled. Disabling fused multiply/add and multiply/subtract instructions forces the compiler to use separate instructions for the multiply and add/subtract operations. This may be desirable in some cases where strict IEEE 754-compliant results are required: the fused multiply add/subtract instructions do not round the intermediate result, thereby producing results with more bits of precision than specified by the IEEE standard. Disabling fused multiply add/subtract instructions also ensures that the program output is not sensitive to the compiler’s ability to combine multiply and add/subtract operations.
-mserialize-volatile
¶-mno-serialize-volatile
When this option is enabled, GCC inserts MEMW
instructions before
volatile
memory references to guarantee sequential consistency.
The default is -mserialize-volatile. Use
-mno-serialize-volatile to omit the MEMW
instructions.
-mforce-no-pic
¶For targets, like GNU/Linux, where all user-mode Xtensa code must be position-independent code (PIC), this option disables PIC for compiling kernel code.
-mtext-section-literals
¶-mno-text-section-literals
These options control the treatment of literal pools. The default is -mno-text-section-literals, which places literals in a separate section in the output file. This allows the literal pool to be placed in a data RAM/ROM, and it also allows the linker to combine literal pools from separate object files to remove redundant literals and improve code size. With -mtext-section-literals, the literals are interspersed in the text section in order to keep them as close as possible to their references. This may be necessary for large assembly files. Literals for each function are placed right before that function.
-mauto-litpools
¶-mno-auto-litpools
These options control the treatment of literal pools. The default is
-mno-auto-litpools, which places literals in a separate
section in the output file unless -mtext-section-literals is
used. With -mauto-litpools the literals are interspersed in
the text section by the assembler. Compiler does not produce explicit
.literal
directives and loads literals into registers with
MOVI
instructions instead of L32R
to let the assembler
do relaxation and place literals as necessary. This option allows
assembler to create several literal pools per function and assemble
very big functions, which may not be possible with
-mtext-section-literals.
-mtarget-align
¶-mno-target-align
When this option is enabled, GCC instructs the assembler to
automatically align instructions to reduce branch penalties at the
expense of some code density. The assembler attempts to widen density
instructions to align branch targets and the instructions following call
instructions. If there are not enough preceding safe density
instructions to align a target, no widening is performed. The
default is -mtarget-align. These options do not affect the
treatment of auto-aligned instructions like LOOP
, which the
assembler always aligns, either by widening density instructions or
by inserting NOP instructions.
-mlongcalls
¶-mno-longcalls
When this option is enabled, GCC instructs the assembler to translate
direct calls to indirect calls unless it can determine that the target
of a direct call is in the range allowed by the call instruction. This
translation typically occurs for calls to functions in other source
files. Specifically, the assembler translates a direct CALL
instruction into an L32R
followed by a CALLX
instruction.
The default is -mno-longcalls. This option should be used in
programs where the call target can potentially be out of range. This
option is implemented in the assembler, not the compiler, so the
assembly code generated by GCC still shows direct call
instructions—look at the disassembled object code to see the actual
instructions. Note that the assembler uses an indirect call for
every cross-file call, not just those that really are out of range.
-mabi=name
¶Generate code for the specified ABI. Permissible values are: ‘call0’, ‘windowed’. Default ABI is chosen by the Xtensa core configuration.
-mabi=call0
¶When this option is enabled function parameters are passed in registers
a2
through a7
, registers a12
through a15
are
caller-saved, and register a15
may be used as a frame pointer.
When this version of the ABI is enabled the C preprocessor symbol
__XTENSA_CALL0_ABI__
is defined.
-mabi=windowed
¶When this option is enabled function parameters are passed in registers
a10
through a15
, and called function rotates register window
by 8 registers on entry so that its arguments are found in registers
a2
through a7
. Register a7
may be used as a frame
pointer. Register window is rotated 8 registers back upon return.
When this version of the ABI is enabled the C preprocessor symbol
__XTENSA_WINDOWED_ABI__
is defined.
-mextra-l32r-costs=n
¶Specify an extra cost of instruction RAM/ROM access for L32R
instructions, in clock cycles. This affects, when optimizing for speed,
whether loading a constant from literal pool using L32R
or
synthesizing the constant from a small one with a couple of arithmetic
instructions. The default value is 0.
-mstrict-align
¶-mno-strict-align
Avoid or allow generating memory accesses that may not be aligned on a natural object boundary as described in the architecture specification. The default is -mno-strict-align for cores that support both unaligned loads and stores in hardware and -mstrict-align for all other cores.