[Bug rtl-optimization/52573] [4.6/4.7/4.8 regression] regrename creates overlapping register allocations for output operands

[aoliva at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52573



--- Comment #6 from Alexandre Oliva <aoliva at gcc dot gnu.org> 2012-12-07 
11:16:55 UTC ---

I don't get the invalid insn in the trunk, in spite of still having both REG

%d2 notes on it before rnreg.



My attempts to avoid the REG_DEAD note were unfruitful (reg-stack wasn't happy

with my moving the REG_UNUSED note emission out of the CLOBBER conditional on

CALLs, nor with my attempt to mark clobbers as do_not_gen in non-calls,but I

didn't try to find out why yet), but this one, that makes behavior consistent

for calls and non-calls, seems to at least complete the stage1 libgcc build. 

However, rather than removing the bogus REG_DEAD note, it drops the REG_UNUSED

one.



--- a/gcc/df-problems.c

+++ b/gcc/df-problems.c

@@ -3277,11 +3277,12 @@ df_note_bb_compute (unsigned int bb_index,

         {

           df_ref def = *def_rec;

           unsigned int dregno = DF_REF_REGNO (def);

-          df_create_unused_note (insn,

-                     def, live, artificial_uses, &debug);

-

           if (!DF_REF_FLAGS_IS_SET (def, DF_REF_MUST_CLOBBER |

DF_REF_MAY_CLOBBER))

-        bitmap_set_bit (do_not_gen, dregno);

+        {

+          df_create_unused_note (insn,

+                     def, live, artificial_uses, &debug);

+          bitmap_set_bit (do_not_gen, dregno);

+        }



           if (!DF_REF_FLAGS_IS_SET (def, DF_REF_PARTIAL | DF_REF_CONDITIONAL))

         bitmap_clear_bit (live, dregno);