GCC 4 brings many changes to the standard compiler suite, the biggest of which is around support for optimizations with the introduction of the tree Static Single Assignment (SSA) form.

GCC 4为标准的编译器套件带来了很多变化，最大的变化是为了支持优化而引入的树的Static Single Assignment (ssa)形式。

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This release included a large number of changes-two in particular being the introduction of a new optimization framework (Tree SSA) and support for autovectorization.

这个发行版包含很多变化—其中两个特别的变化是引入了新的优化框架(Tree ssa)和支持自动向量化(autovectorization)。

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Another interesting change for GCC 4 is the addition of a loop vectorizer (based on the Tree SSA framework).

GCC 4 的另一个有趣的变化是增加了一个循环向量器（基于 Tree SSA 框架）。

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