Paul Berry <stereotype...@gmail.com> writes: > If an ir_loop has a non-null "counter" field, the variable referred to > by this field is implicitly read and written by the loop. We need to > account for this in ir_variable_refcount, otherwise there is a danger > we will try to dead-code-eliminate the loop counter variable. > > Note: at the moment the dead code elimination bug doesn't occur due to > a bug in ir_hierarchical_visitor: it doesn't visit the "counter" > field, so dead code elimination doesn't treat it as a candidate for > elimination. But the patch to follow will fix that bug, so we need to > fix ir_variable_refcount first in order to avoid breaking dead code > elimination.
This series is: Reviewed-by: Eric Anholt <e...@anholt.net> I wish loop_control.cpp would make loop->control informational, and not muck with the existing control flow in the loop. That way we could just ignore loop->control in the backend, and it would only get used by loop unrolling. I'm pretty sure I've seen loops where both loop controls (loop->control and the original variable) end up getting used, and it's something that's going to be hard for the backend to fix back up.
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