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| <a name="AArch64-Options"></a> |
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| <a name="AArch64-Options-1"></a> |
| <h4 class="subsection">3.17.1 AArch64 Options</h4> |
| <a name="index-AArch64-Options"></a> |
| |
| <p>These options are defined for AArch64 implementations: |
| </p> |
| <dl compact="compact"> |
| <dt><code>-mabi=<var>name</var></code></dt> |
| <dd><a name="index-mabi"></a> |
| <p>Generate code for the specified data model. Permissible values |
| are ‘<samp>ilp32</samp>’ for SysV-like data model where int, long int and pointer |
| are 32-bit, and ‘<samp>lp64</samp>’ for SysV-like data model where int is 32-bit, |
| but long int and pointer are 64-bit. |
| </p> |
| <p>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. |
| </p> |
| </dd> |
| <dt><code>-mbig-endian</code></dt> |
| <dd><a name="index-mbig_002dendian"></a> |
| <p>Generate big-endian code. This is the default when GCC is configured for an |
| ‘<samp>aarch64_be-*-*</samp>’ target. |
| </p> |
| </dd> |
| <dt><code>-mgeneral-regs-only</code></dt> |
| <dd><a name="index-mgeneral_002dregs_002donly"></a> |
| <p>Generate code which uses only the general registers. |
| </p> |
| </dd> |
| <dt><code>-mlittle-endian</code></dt> |
| <dd><a name="index-mlittle_002dendian"></a> |
| <p>Generate little-endian code. This is the default when GCC is configured for an |
| ‘<samp>aarch64-*-*</samp>’ but not an ‘<samp>aarch64_be-*-*</samp>’ target. |
| </p> |
| </dd> |
| <dt><code>-mcmodel=tiny</code></dt> |
| <dd><a name="index-mcmodel_003dtiny"></a> |
| <p>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 ‘<samp>small</samp>’. |
| </p> |
| </dd> |
| <dt><code>-mcmodel=small</code></dt> |
| <dd><a name="index-mcmodel_003dsmall"></a> |
| <p>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. |
| </p> |
| </dd> |
| <dt><code>-mcmodel=large</code></dt> |
| <dd><a name="index-mcmodel_003dlarge"></a> |
| <p>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. |
| </p> |
| </dd> |
| <dt><code>-mstrict-align</code></dt> |
| <dd><a name="index-mstrict_002dalign"></a> |
| <p>Do not assume that unaligned memory references will be handled by the system. |
| </p> |
| </dd> |
| <dt><code>-momit-leaf-frame-pointer</code></dt> |
| <dt><code>-mno-omit-leaf-frame-pointer</code></dt> |
| <dd><a name="index-momit_002dleaf_002dframe_002dpointer"></a> |
| <a name="index-mno_002domit_002dleaf_002dframe_002dpointer"></a> |
| <p>Omit or keep the frame pointer in leaf functions. The former behaviour is the |
| default. |
| </p> |
| </dd> |
| <dt><code>-mtls-dialect=desc</code></dt> |
| <dd><a name="index-mtls_002ddialect_003ddesc"></a> |
| <p>Use TLS descriptors as the thread-local storage mechanism for dynamic accesses |
| of TLS variables. This is the default. |
| </p> |
| </dd> |
| <dt><code>-mtls-dialect=traditional</code></dt> |
| <dd><a name="index-mtls_002ddialect_003dtraditional"></a> |
| <p>Use traditional TLS as the thread-local storage mechanism for dynamic accesses |
| of TLS variables. |
| </p> |
| </dd> |
| <dt><code>-mfix-cortex-a53-835769</code></dt> |
| <dt><code>-mno-fix-cortex-a53-835769</code></dt> |
| <dd><a name="index-_002dmfix_002dcortex_002da53_002d835769"></a> |
| <a name="index-_002dmno_002dfix_002dcortex_002da53_002d835769"></a> |
| <p>Enable or disable the workaround for the ARM Cortex-A53 erratum number 835769. |
| This will involve inserting a NOP instruction between memory instructions and |
| 64-bit integer multiply-accumulate instructions. |
| </p> |
| </dd> |
| <dt><code>-mfix-cortex-a53-843419</code></dt> |
| <dt><code>-mno-fix-cortex-a53-843419</code></dt> |
| <dd><a name="index-mfix_002dcortex_002da53_002d843419"></a> |
| <a name="index-mno_002dfix_002dcortex_002da53_002d843419"></a> |
| <p>Enable or disable the workaround for the ARM Cortex-A53 erratum number 843419. |
| This erratum workaround is made at link time and this will only pass the |
| corresponding flag to the linker. |
| </p> |
| </dd> |
| <dt><code>-march=<var>name</var></code></dt> |
| <dd><a name="index-march"></a> |
| <p>Specify the name of the target architecture, optionally suffixed by one or |
| more feature modifiers. This option has the form |
| <samp>-march=<var>arch</var><span class="roman">{</span>+<span class="roman">[</span>no<span class="roman">]</span><var>feature</var><span class="roman">}*</span></samp>, where the |
| only permissible value for <var>arch</var> is ‘<samp>armv8-a</samp>’. The permissible |
| values for <var>feature</var> are documented in the sub-section below. |
| </p> |
| <p>Where conflicting feature modifiers are specified, the right-most feature is |
| used. |
| </p> |
| <p>GCC uses this name to determine what kind of instructions it can emit when |
| generating assembly code. |
| </p> |
| <p>Where <samp>-march</samp> is specified without either of <samp>-mtune</samp> |
| or <samp>-mcpu</samp> also being specified, the code will be tuned to perform |
| well across a range of target processors implementing the target |
| architecture. |
| </p> |
| </dd> |
| <dt><code>-mtune=<var>name</var></code></dt> |
| <dd><a name="index-mtune"></a> |
| <p>Specify the name of the target processor for which GCC should tune the |
| performance of the code. Permissible values for this option are: |
| ‘<samp>generic</samp>’, ‘<samp>cortex-a53</samp>’, ‘<samp>cortex-a57</samp>’, |
| ‘<samp>cortex-a72</samp>’, ‘<samp>thunderx</samp>’, ‘<samp>xgene1</samp>’. |
| </p> |
| <p>Additionally, this option can specify that GCC should tune the performance |
| of the code for a big.LITTLE system. Permissible values for this |
| option are: ‘<samp>cortex-a57.cortex-a53</samp>’, ‘<samp>cortex-a72.cortex-a53</samp>’. |
| </p> |
| <p>Where none of <samp>-mtune=</samp>, <samp>-mcpu=</samp> or <samp>-march=</samp> |
| are specified, the code will be tuned to perform well across a range |
| of target processors. |
| </p> |
| <p>This option cannot be suffixed by feature modifiers. |
| </p> |
| </dd> |
| <dt><code>-mcpu=<var>name</var></code></dt> |
| <dd><a name="index-mcpu"></a> |
| <p>Specify the name of the target processor, optionally suffixed by one or more |
| feature modifiers. This option has the form |
| <samp>-mcpu=<var>cpu</var><span class="roman">{</span>+<span class="roman">[</span>no<span class="roman">]</span><var>feature</var><span class="roman">}*</span></samp>, where the |
| permissible values for <var>cpu</var> are the same as those available for |
| <samp>-mtune</samp>. |
| </p> |
| <p>The permissible values for <var>feature</var> are documented in the sub-section |
| below. |
| </p> |
| <p>Where conflicting feature modifiers are specified, the right-most feature is |
| used. |
| </p> |
| <p>GCC uses this name to determine what kind of instructions it can emit when |
| generating assembly code (as if by <samp>-march</samp>) and to determine |
| the target processor for which to tune for performance (as if |
| by <samp>-mtune</samp>). Where this option is used in conjunction |
| with <samp>-march</samp> or <samp>-mtune</samp>, those options take precedence |
| over the appropriate part of this option. |
| </p></dd> |
| </dl> |
| |
| <a name="g_t_002dmarch-and-_002dmcpu-feature-modifiers"></a> |
| <h4 class="subsubsection">3.17.1.1 <samp>-march</samp> and <samp>-mcpu</samp> feature modifiers</h4> |
| <a name="index-_002dmarch-feature-modifiers"></a> |
| <a name="index-_002dmcpu-feature-modifiers"></a> |
| <p>Feature modifiers used with <samp>-march</samp> and <samp>-mcpu</samp> can be one |
| the following: |
| </p> |
| <dl compact="compact"> |
| <dt>‘<samp>crc</samp>’</dt> |
| <dd><p>Enable CRC extension. |
| </p></dd> |
| <dt>‘<samp>crypto</samp>’</dt> |
| <dd><p>Enable Crypto extension. This implies Advanced SIMD is enabled. |
| </p></dd> |
| <dt>‘<samp>fp</samp>’</dt> |
| <dd><p>Enable floating-point instructions. |
| </p></dd> |
| <dt>‘<samp>simd</samp>’</dt> |
| <dd><p>Enable Advanced SIMD instructions. This implies floating-point instructions |
| are enabled. This is the default for all current possible values for options |
| <samp>-march</samp> and <samp>-mcpu=</samp>. |
| </p></dd> |
| </dl> |
| |
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