[Bug target/48990] MIPS wrong code error with -O1

[pkoning at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48990

--- Comment #6 from Paul Koning <pkoning at gcc dot gnu.org> 2011-05-13 20:29:50 UTC ---
Created attachment 24243
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=24243
debug dump from the pass before machdep

After some debugging, I see that the problem is that register 4 (A0) is marked
dead in the prologue, and then afterwards is still used.  This causes the delay
slot fill logic to believe it can put li $4,32 into the delay slot -- because
it appears not to be needed.

So the question now is why that register is marked dead and still used.