tree-optimization/103596 - fix missed propagation into switches
may_propagate_copy unnecessarily restricts propagating non-abnormals
into places that currently contain an abnormal SSA name but are
not the PHI argument for an abnormal edge. This causes VN to
not elide a CFG path that it assumes is elided, resulting in
released SSA names in the IL.
The fix is to enhance the may_propagate_copy API to specify the
destination is _not_ a PHI argument. I chose to not update only
the relevant caller in VN and the may_propagate_copy_into_stmt API
at this point because this is a regression and needs backporting.
2021-12-07 Richard Biener <rguenther@suse.de>
PR tree-optimization/103596
* tree-ssa-sccvn.c (eliminate_dom_walker::eliminate_stmt):
Note we are not propagating into a PHI argument to may_propagate_copy.
* tree-ssa-propagate.h (may_propagate_copy): Add
argument specifying whether we propagate into a PHI arg.
* tree-ssa-propagate.c (may_propagate_copy): Likewise.
When not doing so we can replace an abnormal with
something else.
(may_propagate_into_stmt): Update may_propagate_copy calls.
(replace_exp_1): Move propagation checking code to
propagate_value and rename to ...
(replace_exp): ... this and elide previous wrapper.
(propagate_value): Perform checking with adjusted
may_propagate_copy call and dispatch to replace_exp.
* gcc.dg/torture/pr103596.c: New testcase.