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authorBjörn Gustavsson <[email protected]>2017-06-07 14:27:15 +0200
committerBjörn Gustavsson <[email protected]>2017-06-07 16:32:35 +0200
commit09112806c15a81be86730503af36e304ac11d1ed (patch)
tree8f66b637b02762737f4e91bd7077428c736fed0e /.dir-locals.el
parent1ee59088c52ff18e3917d7f453a5947d0fe1cadd (diff)
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Fix unsafe bit syntax matching optimization
As part of sys_core_fold, variables involved in bit syntax matching would be annotated when it would be safe for a later pass to do the delayed sub-binary creation optimization. An implicit assumption regarding the annotation was that the code must not be further optimized. That assumption was broken in 05130e48555891, which introduced a fixpoint iteration (applying the optimizations until there were no more changes). That means that a variable could be annotated as safe for reusing the match context in one iteration, but a later iteration could rewrite the code in a way that would make the optimization unsafe. One way to fix this would be to clear all reuse_for_context annotations before each iteration. But that would be wasteful. Instead I chose to fix the problem by moving out the annotation code to a separate pass (sys_core_bsm) that is run later after all major optimizations of Core Erlang has been done.
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