..
  Copyright 1988-2022 Free Software Foundation, Inc.
  This is part of the GCC manual.
  For copying conditions, see the copyright.rst file.

.. program:: Xtensa

.. index:: Xtensa Options

.. _xtensa-options:

Xtensa Options
^^^^^^^^^^^^^^

These options are supported for Xtensa targets:

.. option:: -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.

.. option:: -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.

.. option:: -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 :option:`-mserialize-volatile`.  Use
  :option:`-mno-serialize-volatile` to omit the ``MEMW`` instructions.

.. option:: -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.

.. option:: -mtext-section-literals, -mno-text-section-literals

  These options control the treatment of literal pools.  The default is
  :option:`-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 :option:`-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.

.. option:: -mauto-litpools, -mno-auto-litpools

  These options control the treatment of literal pools.  The default is
  :option:`-mno-auto-litpools`, which places literals in a separate
  section in the output file unless :option:`-mtext-section-literals` is
  used.  With :option:`-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
  :option:`-mtext-section-literals`.

.. option:: -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 :option:`-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.

.. option:: -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 :option:`-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.

.. option:: -mabi={name}

  Generate code for the specified ABI.  Permissible values are: :samp:`call0`,
  :samp:`windowed`.  Default ABI is chosen by the Xtensa core configuration.

.. option:: -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.

.. option:: -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.

.. option:: -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.