[Bug target/70123] [6 Regression] Miscompilation of cfitsio testcase on s390x-linux starting with r222144

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70123

--- Comment #2 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Ah, the spilled value is pseudo 240, which holds &b.  Dunno why instead of
spilling it it couldn't be rematerialized.  Anyway, the value in r6 after the
f9 call is needed, so all that seems to be wrong is the order of the
instructions after the f9 call:

        stg     %r6,192(%r15)   ! The spill of &b
        lgf     %r4,252(%r15)
        larl    %r3,.LC6
        lghi    %r2,1
        lgr     %r6,%r10        ! %r10 holds g value, copy it into argument reg
        lghi    %r11,0
        brasl   %r14,bar@PLT    ! bar shouldn't clobber %r6
        stg     %r8,168(%r15)
        stg     %r9,160(%r15)
        lgr     %r4,%r10
        lghi    %r5,1
        lghi    %r3,3   
        lg      %r2,280(%r15)
        brasl   %r14,f9@PLT     ! nor f9; and f9 takes it as g as its 3rd
! and 5th arg; so in %r4 and %r6, %r4 is call clobbered, %r6 and %r10 are
! call-saved
        lg      %r6,192(%r15)   ! this fills the &b value
        lgr     %r10,%r6        ! but, here we want the g value instead;
! That value is live in both %r6 before the above fill, or in %r10 as well.
! So either removing the lgr %r10,%r6 instruction, or moving it before
! lg %r6,192(%r15) instruction fixes the testcase.