keep_alive(potential_endless_loop_block);
get_store(); /* force construction of memory Phi */
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Warning
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This article is work in progress. It is incomplete and can contain errors. Help in finishing the article is appreciated. |
Many languages allow allocating data on the stack. Stack data is valid until the function finishes. Each firm-graph has an associated type called frame-type. This is a struct-type which contains entities for data on the stack.
Entities can be added to the frame-type. However calculation of the final entity offsets is left to libfirm. Hence you should not layout this type or set its size.
TODO
Endless loops are a tricky case, since they don’t reach the end-block (or return node) so noone is using the data produced by them. However the memory changes and control flow changes still need to be present (it’s an endless loop and you can actually experience the things that happened before the loop). So the correct thing when creating loops or label blocks that could potentially form a loop is using keep_alive on querying the state at least once:
keep_alive(potential_endless_loop_block);
get_store(); /* force construction of memory Phi */