Hi I have following questions about web (pseudo register renaming) pass:
1. It is well known that register renaming is a big help to register allocation, but in gcc's backend, the web pass is far before RA, there are about 20 passes between them. Does it mean register renaming can also heavily benefit other optimizations? And the passes between them usually don't generate more register renaming chances? 2. It looks current web pass can't handle AUTOINC expressions, a reg operand is used as both use and def reference in an AUTOINC expression, so this def side should not be renamed. Pass web doesn't explicitly check this case, may rename the reg operand of AUTOINC expression. Is this expected because it is before auto_inc_dec pass? 3. Are AUTOINC expressions only generated by auto_inc_dec pass? All passes before auto_inc_dec including expand should not generate AUTOINC expressions, otherwise it will break web. Could anybody help to answer these questions? thanks a lot Guozhi Wei
