https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100264
Bug ID: 100264
Summary: REE does not work on PARALLEL expressions with a
single register SET child
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: rtl-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: christophm30 at gmail dot com
Target Milestone: ---
REE iterates over all SET expressions and tries to eliminate redundant
zero-extensions. In case of a PARALLEL expression, there is a check in place to
ensure that "only one child of a PARALLEL expression is a SET".
Let's imagine a PARALLEL expression with two register SETs.
An example would be store-conditional, which sets a memory location (store
target) as well as a register (return success value).
The current implementation is not able to optimize a zero-extension of the
return value of store-conditional.
This can be solved, by moving the check for register targets (i.e. REG_P ())
into the function get_sub_rtx () and change the restriction of REE to "only one
child of a PARALLEL expression is a SET register".
