Re: frv flow crash on direct returns

[Aldy Hernandez <aldyh at redhat dot com>]

Richard approved this off-list.  I'm going to install it.

Thanks guys.

 > When tree-ssa was merged, frv-elf stopped building.  cmovh.c for
 > libgcc was what failed to build.  Here's a minimized testcase:

 > void f(int a, int b, int c) {
 >   if (a < b || a > b + 1)
 >     while (c)
 >       --c;
 > }

 > This crashed when flow for sched2 realized LR, that wasn't live
 > before, had become live because a direct return (that uses LR) was
 > inserted in postreload.

 > Richard Sandiford had already written a patch for what I believe to be
 > an earlier occurrence of this problem, back when he introduced
 > conditional returns.  Here's the patch.  I'm tempted to install it as
 > obvious, but...  Ok?

 > Index: gcc/ChangeLog
 > from  Alexandre Oliva  <aoliva@redhat.com>

 > 	2003-11-19  Richard Sandiford <rsandifo@redhat.com>
 > 	* config/frv/frv.h (EPILOGUE_USES): New.  Use LR.

 > Index: gcc/config/frv/frv.h
 > ===================================================================
 > RCS file: /cvs/uberbaum/gcc/config/frv/frv.h,v
 > retrieving revision 1.47
 > diff -u -p -r1.47 frv.h
 > --- gcc/config/frv/frv.h 21 May 2004 01:03:17 -0000 1.47
 > +++ gcc/config/frv/frv.h 28 May 2004 06:52:49 -0000
 > @@ -959,6 +959,8 @@ extern int target_flags;
 >  #define EH_RETURN_STACKADJ_RTX	gen_rtx_REG (SImode, STACKADJ_REGNO)
 >  #define EH_RETURN_HANDLER_RTX   RETURN_ADDR_RTX (0, frame_pointer_rtx)
 
 > +#define EPILOGUE_USES(REGNO) ((REGNO) == LR_REGNO)
 > +
 >  /* An initializer that says which registers are used for fixed purposes all
 >     throughout the compiled code and are therefore not available for general
 >     allocation.  These would include the stack pointer, the frame pointer

 > -- 
 > Alexandre Oliva             http://www.ic.unicamp.br/~oliva/
 > Red Hat Compiler Engineer   aoliva@{redhat.com, gcc.gnu.org}
 > Free Software Evangelist  oliva@{lsd.ic.unicamp.br, gnu.org}