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| <a name="Gimplification-pass-1"></a> |
| <h3 class="section">9.3 Gimplification pass</h3> |
| |
| <a name="index-gimplification-1"></a> |
| <a name="index-GIMPLE-1"></a> |
| <p><em>Gimplification</em> is a whimsical term for the process of converting |
| the intermediate representation of a function into the GIMPLE language |
| (see <a href="GIMPLE.html#GIMPLE">GIMPLE</a>). The term stuck, and so words like “gimplification”, |
| “gimplify”, “gimplifier” and the like are sprinkled throughout this |
| section of code. |
| </p> |
| <p>While a front end may certainly choose to generate GIMPLE directly if |
| it chooses, this can be a moderately complex process unless the |
| intermediate language used by the front end is already fairly simple. |
| Usually it is easier to generate GENERIC trees plus extensions |
| and let the language-independent gimplifier do most of the work. |
| </p> |
| <a name="index-gimplify_005ffunction_005ftree"></a> |
| <a name="index-gimplify_005fexpr"></a> |
| <a name="index-lang_005fhooks_002egimplify_005fexpr"></a> |
| <p>The main entry point to this pass is <code>gimplify_function_tree</code> |
| located in <samp>gimplify.c</samp>. From here we process the entire |
| function gimplifying each statement in turn. The main workhorse |
| for this pass is <code>gimplify_expr</code>. Approximately everything |
| passes through here at least once, and it is from here that we |
| invoke the <code>lang_hooks.gimplify_expr</code> callback. |
| </p> |
| <p>The callback should examine the expression in question and return |
| <code>GS_UNHANDLED</code> if the expression is not a language specific |
| construct that requires attention. Otherwise it should alter the |
| expression in some way to such that forward progress is made toward |
| producing valid GIMPLE. If the callback is certain that the |
| transformation is complete and the expression is valid GIMPLE, it |
| should return <code>GS_ALL_DONE</code>. Otherwise it should return |
| <code>GS_OK</code>, which will cause the expression to be processed again. |
| If the callback encounters an error during the transformation (because |
| the front end is relying on the gimplification process to finish |
| semantic checks), it should return <code>GS_ERROR</code>. |
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