On 7/23/22 03:26, Roger Sayle wrote:
This patch is a one line correction/clarification to GCC's current
RTL documentation that explains a USE of a MEM is permissible.
PR rtl-optimization/99930 is an interesting example on x86_64 where
the backend generates better code when a USE is a (const) MEM than
when it is a REG. In fact the backend relies on CSE to propagate the
MEM (a constant pool reference) into the USE, to enable combine to
merge/simplify instructions.
This change has been tested with a make bootstrap, but as it might
provoke a discussion, I've decided to not consider it "obvious".
Ok for mainline (to document the actual current behavior)?
2022-07-23 Roger Sayle <ro...@nextmovesoftware.com>
gcc/ChangeLog
* doc/rtl.texi (use): Document that the operand may be a MEM.
Given this is documenting existing behavior and it's not hard to
envision the MEM being useful in this context. OK.
jeff
