[Bug rtl-optimization/64317] [5 Regression] Ineffective allocation of PIC base register

[law at redhat dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64317

--- Comment #18 from Jeffrey A. Law <law at redhat dot com> ---
Sigh...

reload_cse_regs doesn't help us because of the CODE_LABEL at the start of block
C in the mini-cfg referenced in c#17.  In essence it's using the same extended
block definition as LRA.

postreload-gcse doesn't help us because it computes local properties, but never
propagates them through the CFG.  So a memory load that occurs in block A and
is transparent through B is not seen as available at the end of B.  Thus the
load is only considered partially redundant at the start of C.

SIGH.