path: root/gcc/config/aarch64/aarch64.opt

; Machine description for AArch64 architecture.
; Copyright (C) 2009-2025 Free Software Foundation, Inc.
; Contributed by ARM Ltd.
;
; This file is part of GCC.
;
; GCC is free software; you can redistribute it and/or modify it
; under the terms of the GNU General Public License as published by
; the Free Software Foundation; either version 3, or (at your option)
; any later version.
;
; GCC is distributed in the hope that it will be useful, but
; WITHOUT ANY WARRANTY; without even the implied warranty of
; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
; General Public License for more details.
;
; You should have received a copy of the GNU General Public License
; along with GCC; see the file COPYING3.  If not see
; <http://www.gnu.org/licenses/>.

HeaderInclude
config/aarch64/aarch64-opts.h

HeaderInclude
config/arm/aarch-common.h

TargetVariable
enum aarch64_processor selected_tune = aarch64_none

TargetVariable
enum aarch64_arch selected_arch = aarch64_no_arch

TargetVariable
uint64_t aarch64_asm_isa_flags_0 = 0

TargetVariable
uint64_t aarch64_asm_isa_flags_1 = 0

TargetVariable
uint64_t aarch64_isa_flags_0 = 0

TargetVariable
uint64_t aarch64_isa_flags_1 = 0

TargetVariable
unsigned aarch_enable_bti = 2

TargetVariable
unsigned aarch64_enable_gcs = 2

TargetVariable
enum aarch64_key_type aarch64_ra_sign_key = AARCH64_KEY_A

; The TLS dialect names to use with -mtls-dialect.

Enum
Name(tls_type) Type(enum aarch64_tls_type)
The possible TLS dialects:

EnumValue
Enum(tls_type) String(trad) Value(TLS_TRADITIONAL)

EnumValue
Enum(tls_type) String(desc) Value(TLS_DESCRIPTORS)

; The code model option names for -mcmodel.

Enum
Name(cmodel) Type(enum aarch64_code_model)
The code model option names for -mcmodel:

EnumValue
Enum(cmodel) String(tiny) Value(AARCH64_CMODEL_TINY)

EnumValue
Enum(cmodel) String(small) Value(AARCH64_CMODEL_SMALL)

EnumValue
Enum(cmodel) String(large) Value(AARCH64_CMODEL_LARGE)

mbig-endian
Target RejectNegative Mask(BIG_END)
Assume target CPU is configured as big endian.

mgeneral-regs-only
Target RejectNegative Mask(GENERAL_REGS_ONLY) Save
Generate code which uses only the general registers.

mharden-sls=
Target RejectNegative Joined Var(aarch64_harden_sls_string)
Generate code to mitigate against straight line speculation.

mfix-cortex-a53-835769
Target Var(aarch64_fix_a53_err835769) Init(2) Save
Workaround for ARM Cortex-A53 Erratum number 835769.

mfix-cortex-a53-843419
Target Var(aarch64_fix_a53_err843419) Init(2) Save
Workaround for ARM Cortex-A53 Erratum number 843419.

mlittle-endian
Target RejectNegative InverseMask(BIG_END)
Assume target CPU is configured as little endian.

mcmodel=
Target RejectNegative Joined Enum(cmodel) Var(aarch64_cmodel_var) Init(AARCH64_CMODEL_SMALL) Save
Specify the code model.

Enum
Name(tp_reg) Type(enum aarch64_tp_reg)
The register used to access the thread pointer:

EnumValue
Enum(tp_reg) String(el0) Value(AARCH64_TPIDR_EL0)

EnumValue
Enum(tp_reg) String(tpidr_el0) Value(AARCH64_TPIDR_EL0)

EnumValue
Enum(tp_reg) String(el1) Value(AARCH64_TPIDR_EL1)

EnumValue
Enum(tp_reg) String(tpidr_el1) Value(AARCH64_TPIDR_EL1)

EnumValue
Enum(tp_reg) String(el2) Value(AARCH64_TPIDR_EL2)

EnumValue
Enum(tp_reg) String(tpidr_el2) Value(AARCH64_TPIDR_EL2)

EnumValue
Enum(tp_reg) String(el3) Value(AARCH64_TPIDR_EL3)

EnumValue
Enum(tp_reg) String(tpidr_el3) Value(AARCH64_TPIDR_EL3)

EnumValue
Enum(tp_reg) String(tpidrro_el0) Value(AARCH64_TPIDRRO_EL0)

mtp=
Target RejectNegative Joined Enum(tp_reg) Var(aarch64_tpidr_reg) Init(AARCH64_TPIDR_EL0) Save
Specify the thread pointer register.

mstrict-align
Target Mask(STRICT_ALIGN) Save
Don't assume that unaligned accesses are handled by the system.

momit-leaf-frame-pointer
Target Var(flag_omit_leaf_frame_pointer) Init(2) Save
Omit the frame pointer in leaf functions.

mtls-dialect=
Target RejectNegative Joined Enum(tls_type) Var(aarch64_tls_dialect) Init(TLS_DESCRIPTORS) Save
Specify TLS dialect.

mtls-size=
Target RejectNegative Joined Var(aarch64_tls_size) Enum(aarch64_tls_size)
Specifies bit size of immediate TLS offsets.  Valid values are 12, 24, 32, 48.

Enum
Name(aarch64_tls_size) Type(int)

EnumValue
Enum(aarch64_tls_size) String(12) Value(12)

EnumValue
Enum(aarch64_tls_size) String(24) Value(24)

EnumValue
Enum(aarch64_tls_size) String(32) Value(32)

EnumValue
Enum(aarch64_tls_size) String(48) Value(48)

march=
Target RejectNegative Negative(march=) ToLower Joined Var(aarch64_arch_string)
Use features of architecture ARCH.

mcpu=
Target RejectNegative Negative(mcpu=) ToLower Joined Var(aarch64_cpu_string)
Use features of and optimize for CPU.

mtune=
Target RejectNegative Negative(mtune=) ToLower Joined Var(aarch64_tune_string)
Optimize for CPU.

mabi=
Target RejectNegative Joined Enum(aarch64_abi) Var(aarch64_abi) Init(AARCH64_ABI_DEFAULT)
Generate code that conforms to the specified ABI.

moverride=
Target RejectNegative ToLower Joined Var(aarch64_override_tune_string) Save
-moverride=<string>	Power users only! Override CPU optimization parameters.

Enum
Name(aarch64_abi) Type(int)
Known AArch64 ABIs (for use with the -mabi= option):

EnumValue
Enum(aarch64_abi) String(ilp32) Value(AARCH64_ABI_ILP32)

EnumValue
Enum(aarch64_abi) String(lp64) Value(AARCH64_ABI_LP64)

mpc-relative-literal-loads
Target Save Var(pcrelative_literal_loads) Init(2) Save
PC relative literal loads.

mbranch-protection=
Target RejectNegative Joined Var(aarch64_branch_protection_string) Save
Use branch-protection features.

msign-return-address=
Target WarnRemoved RejectNegative Joined Enum(aarch_ra_sign_scope_t) Var(aarch_ra_sign_scope) Init(AARCH_FUNCTION_NONE) Save
Select return address signing scope.

Enum
Name(aarch_ra_sign_scope_t) Type(enum aarch_function_type)
Supported AArch64 return address signing scope (for use with -msign-return-address= option):

EnumValue
Enum(aarch_ra_sign_scope_t) String(none) Value(AARCH_FUNCTION_NONE)

EnumValue
Enum(aarch_ra_sign_scope_t) String(non-leaf) Value(AARCH_FUNCTION_NON_LEAF)

EnumValue
Enum(aarch_ra_sign_scope_t) String(all) Value(AARCH_FUNCTION_ALL)

mlow-precision-recip-sqrt
Target Var(flag_mrecip_low_precision_sqrt) Optimization
Enable the reciprocal square root approximation.  Enabling this reduces
precision of reciprocal square root results to about 16 bits for
single precision and to 32 bits for double precision.

mlow-precision-sqrt
Target Var(flag_mlow_precision_sqrt) Optimization
Enable the square root approximation.  Enabling this reduces
precision of square root results to about 16 bits for
single precision and to 32 bits for double precision.
If enabled, it implies -mlow-precision-recip-sqrt.

mlow-precision-div
Target Var(flag_mlow_precision_div) Optimization
Enable the division approximation.  Enabling this reduces
precision of division results to about 16 bits for
single precision and to 32 bits for double precision.

Enum
Name(early_ra_scope) Type(enum aarch64_early_ra_scope)

EnumValue
Enum(early_ra_scope) String(all) Value(AARCH64_EARLY_RA_ALL)

EnumValue
Enum(early_ra_scope) String(strided) Value(AARCH64_EARLY_RA_STRIDED)

EnumValue
Enum(early_ra_scope) String(none) Value(AARCH64_EARLY_RA_NONE)

mearly-ra=
Target RejectNegative Joined Enum(early_ra_scope) Var(aarch64_early_ra) Init(AARCH64_EARLY_RA_NONE) Optimization
Specify when to enable an early register allocation pass.  The possibilities
are: all functions, functions that have access to strided multi-register
instructions, and no functions.

Enum
Name(sve_vector_bits) Type(enum aarch64_sve_vector_bits_enum)
The possible SVE vector lengths:

EnumValue
Enum(sve_vector_bits) String(scalable) Value(SVE_SCALABLE)

EnumValue
Enum(sve_vector_bits) String(128) Value(SVE_128)

EnumValue
Enum(sve_vector_bits) String(256) Value(SVE_256)

EnumValue
Enum(sve_vector_bits) String(512) Value(SVE_512)

EnumValue
Enum(sve_vector_bits) String(1024) Value(SVE_1024)

EnumValue
Enum(sve_vector_bits) String(2048) Value(SVE_2048)

msve-vector-bits=
Target RejectNegative Joined Enum(sve_vector_bits) Var(aarch64_sve_vector_bits) Init(SVE_SCALABLE)
-msve-vector-bits=<number>	Set the number of bits in an SVE vector register.

mverbose-cost-dump
Target Undocumented Var(flag_aarch64_verbose_cost)
Enables verbose cost model dumping in the debug dump files.

mtrack-speculation
Target Var(aarch64_track_speculation)
Generate code to track when the CPU might be speculating incorrectly.

mearly-ldp-fusion
Target Var(flag_aarch64_early_ldp_fusion) Optimization Init(1)
Enable the copy of the AArch64 load/store pair fusion pass that runs before
register allocation.

mlate-ldp-fusion
Target Var(flag_aarch64_late_ldp_fusion) Optimization Init(1)
Enable the copy of the AArch64 load/store pair fusion pass that runs after
register allocation.

mstack-protector-guard=
Target RejectNegative Joined Enum(stack_protector_guard) Var(aarch64_stack_protector_guard) Init(SSP_GLOBAL)
Use given stack-protector guard.

Enum
Name(stack_protector_guard) Type(enum stack_protector_guard)
Valid arguments to -mstack-protector-guard=:

EnumValue
Enum(stack_protector_guard) String(sysreg) Value(SSP_SYSREG)

EnumValue
Enum(stack_protector_guard) String(global) Value(SSP_GLOBAL)

mstack-protector-guard-reg=
Target Joined RejectNegative String Var(aarch64_stack_protector_guard_reg_str)
Use the system register specified on the command line as the stack protector
guard register. This option is for use with fstack-protector-strong and
not for use in user-land code.

mstack-protector-guard-offset=
Target Joined RejectNegative String Var(aarch64_stack_protector_guard_offset_str)
Use an immediate to offset from the stack protector guard register, sp_el0.
This option is for use with fstack-protector-strong and not for use in
user-land code.

TargetVariable
long aarch64_stack_protector_guard_offset = 0

moutline-atomics
Target Var(aarch64_flag_outline_atomics) Init(2) Save
Generate local calls to out-of-line atomic operations.

-param=aarch64-vect-compare-costs=
Target Joined UInteger Var(aarch64_vect_compare_costs) Init(1) IntegerRange(0, 1) Param
When vectorizing, consider using multiple different approaches and use
the cost model to choose the cheapest one.

-param=aarch64-float-recp-precision=
Target Joined UInteger Var(aarch64_float_recp_precision) Init(1) IntegerRange(1, 5) Param
The number of Newton iterations for calculating the reciprocal for float type.  The precision of division is proportional to this param when division approximation is enabled.  The default value is 1.

-param=aarch64-double-recp-precision=
Target Joined UInteger Var(aarch64_double_recp_precision) Init(2) IntegerRange(1, 5) Param
The number of Newton iterations for calculating the reciprocal for double type.  The precision of division is proportional to this param when division approximation is enabled.  The default value is 2.

-param=aarch64-autovec-preference=
Target Joined Var(aarch64_autovec_preference) Enum(aarch64_autovec_preference) Init(AARCH64_AUTOVEC_DEFAULT) Param
--param=aarch64-autovec-preference=[default|asimd-only|sve-only|prefer-asimd|prefer-sve]
Force an ISA selection strategy for auto-vectorization.

Enum
Name(aarch64_autovec_preference) Type(enum aarch64_autovec_preference_enum) UnknownError(unknown autovec preference %qs)

EnumValue
Enum(aarch64_autovec_preference) String(default) Value(AARCH64_AUTOVEC_DEFAULT)

EnumValue
Enum(aarch64_autovec_preference) String(asimd-only) Value(AARCH64_AUTOVEC_ASIMD_ONLY)

EnumValue
Enum(aarch64_autovec_preference) String(sve-only) Value(AARCH64_AUTOVEC_SVE_ONLY)

EnumValue
Enum(aarch64_autovec_preference) String(prefer-asimd) Value(AARCH64_AUTOVEC_PREFER_ASIMD)

EnumValue
Enum(aarch64_autovec_preference) String(prefer-sve) Value(AARCH64_AUTOVEC_PREFER_SVE)

-param=aarch64-loop-vect-issue-rate-niters=
Target Joined UInteger Var(aarch64_loop_vect_issue_rate_niters) Init(6) IntegerRange(0, 65536) Param

-param=aarch64-mops-memcpy-size-threshold=
Target Joined UInteger Var(aarch64_mops_memcpy_size_threshold) Init(256) Param
Constant memcpy size in bytes above which to start using MOPS sequence.

-param=aarch64-mops-memmove-size-threshold=
Target Joined UInteger Var(aarch64_mops_memmove_size_threshold) Init(256) Param
Constant memmove size in bytes above which to start using MOPS sequence.

-param=aarch64-mops-memset-size-threshold=
Target Joined UInteger Var(aarch64_mops_memset_size_threshold) Init(256) Param
Constant memset size in bytes from which to start using MOPS sequence.

-param=aarch64-vect-unroll-limit=
Target Joined UInteger Var(aarch64_vect_unroll_limit) Init(4) Param
Limit how much the autovectorizer may unroll a loop.

-param=aarch64-ldp-policy=
Target Joined Var(aarch64_ldp_policy_param) Enum(aarch64_ldp_stp_policy) Init(AARCH64_LDP_STP_POLICY_DEFAULT) Param
--param=aarch64-ldp-policy=[default|always|never|aligned] Fine-grained policy for load pairs.

-param=aarch64-stp-policy=
Target Joined Var(aarch64_stp_policy_param) Enum(aarch64_ldp_stp_policy) Init(AARCH64_LDP_STP_POLICY_DEFAULT) Param
--param=aarch64-stp-policy=[default|always|never|aligned] Fine-grained policy for store pairs.

Enum
Name(aarch64_ldp_stp_policy) Type(enum aarch64_ldp_stp_policy) UnknownError(unknown LDP/STP policy %qs)

EnumValue
Enum(aarch64_ldp_stp_policy) String(default) Value(AARCH64_LDP_STP_POLICY_DEFAULT)

EnumValue
Enum(aarch64_ldp_stp_policy) String(always) Value(AARCH64_LDP_STP_POLICY_ALWAYS)

EnumValue
Enum(aarch64_ldp_stp_policy) String(never) Value(AARCH64_LDP_STP_POLICY_NEVER)

EnumValue
Enum(aarch64_ldp_stp_policy) String(aligned) Value(AARCH64_LDP_STP_POLICY_ALIGNED)

-param=aarch64-ldp-alias-check-limit=
Target Joined UInteger Var(aarch64_ldp_alias_check_limit) Init(8) IntegerRange(0, 65536) Param
Limit on number of alias checks performed when attempting to form an ldp/stp.

-param=aarch64-ldp-writeback=
Target Joined UInteger Var(aarch64_ldp_writeback) Init(2) IntegerRange(0,2) Param
Param to control which writeback opportunities we try to handle in the
load/store pair fusion pass.  A value of zero disables writeback
handling.  One means we try to form pairs involving one or more existing
individual writeback accesses where possible.  A value of two means we
also try to opportunistically form writeback opportunities by folding in
trailing destructive updates of the base register used by a pair.

Wexperimental-fmv-target
Target Var(warn_experimental_fmv) Warning Init(1)
Warn about usage of experimental Function Multi Versioning.