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| <h4 class="subsection">3.17.45 Xtensa Options</h4> |
| |
| <p><a name="index-Xtensa-Options-2087"></a> |
| These options are supported for Xtensa targets: |
| |
| <dl> |
| <dt><code>-mconst16</code><dt><code>-mno-const16</code><dd><a name="index-mconst16-2088"></a><a name="index-mno_002dconst16-2089"></a>Enable or disable use of <code>CONST16</code> instructions for loading |
| constant values. The <code>CONST16</code> instruction is currently not a |
| standard option from Tensilica. When enabled, <code>CONST16</code> |
| instructions are always used in place of the standard <code>L32R</code> |
| instructions. The use of <code>CONST16</code> is enabled by default only if |
| the <code>L32R</code> instruction is not available. |
| |
| <br><dt><code>-mfused-madd</code><dt><code>-mno-fused-madd</code><dd><a name="index-mfused_002dmadd-2090"></a><a name="index-mno_002dfused_002dmadd-2091"></a>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 <em>more</em> 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. |
| |
| <br><dt><code>-mserialize-volatile</code><dt><code>-mno-serialize-volatile</code><dd><a name="index-mserialize_002dvolatile-2092"></a><a name="index-mno_002dserialize_002dvolatile-2093"></a>When this option is enabled, GCC inserts <code>MEMW</code> instructions before |
| <code>volatile</code> memory references to guarantee sequential consistency. |
| The default is <samp><span class="option">-mserialize-volatile</span></samp>. Use |
| <samp><span class="option">-mno-serialize-volatile</span></samp> to omit the <code>MEMW</code> instructions. |
| |
| <br><dt><code>-mtext-section-literals</code><dt><code>-mno-text-section-literals</code><dd><a name="index-mtext_002dsection_002dliterals-2094"></a><a name="index-mno_002dtext_002dsection_002dliterals-2095"></a>Control the treatment of literal pools. The default is |
| <samp><span class="option">-mno-text-section-literals</span></samp>, 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 <samp><span class="option">-mtext-section-literals</span></samp>, 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. |
| |
| <br><dt><code>-mtarget-align</code><dt><code>-mno-target-align</code><dd><a name="index-mtarget_002dalign-2096"></a><a name="index-mno_002dtarget_002dalign-2097"></a>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 will be performed. The |
| default is <samp><span class="option">-mtarget-align</span></samp>. These options do not affect the |
| treatment of auto-aligned instructions like <code>LOOP</code>, which the |
| assembler will always align, either by widening density instructions or |
| by inserting no-op instructions. |
| |
| <br><dt><code>-mlongcalls</code><dt><code>-mno-longcalls</code><dd><a name="index-mlongcalls-2098"></a><a name="index-mno_002dlongcalls-2099"></a>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 <code>CALL</code> |
| instruction into an <code>L32R</code> followed by a <code>CALLX</code> instruction. |
| The default is <samp><span class="option">-mno-longcalls</span></samp>. 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 will still show direct call |
| instructions—look at the disassembled object code to see the actual |
| instructions. Note that the assembler will use an indirect call for |
| every cross-file call, not just those that really will be out of range. |
| </dl> |
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