regrename: Don't rename the dest of a REG_CFA_REGISTER (PR85645)

We should never change the destination of a REG_CFA_REGISTER, just
like for insns with a REG_CFA_RESTORE, because we need to have the
same control flow information on all branches that join.  It is very
doubtful that renaming the scratch registers used for prologue/epilogue
will help anything either.

	PR rtl-optimization/85645
	* regrename.c (build_def_use): Also kill the chains that include the
	destination of a REG_CFA_REGISTER note.

From-SVN: r260075

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 580f41b..72e6768 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,6 +1,12 @@
 2018-05-09  Segher Boessenkool  <segher@kernel.crashing.org>
 
        PR rtl-optimization/85645
+       * regrename.c (build_def_use): Also kill the chains that include the
+       destination of a REG_CFA_REGISTER note.
+
+2018-05-09  Segher Boessenkool  <segher@kernel.crashing.org>
+
+       PR rtl-optimization/85645
        *  regcprop.c (copyprop_hardreg_forward_1): Don't propagate into an
        insn that has a REG_CFA_REGISTER note.
 

diff --git a/gcc/regrename.c b/gcc/regrename.c
index 4575481..8424093 100644 (file)
--- a/gcc/regrename.c
+++ b/gcc/regrename.c
@@ -1661,7 +1661,8 @@ build_def_use (basic_block bb)
             (6) For any non-earlyclobber write we find in an operand, make
                 a new chain or mark the hard register as live.
             (7) For any REG_UNUSED, close any chains we just opened.
-            (8) For any REG_CFA_RESTORE, kill any chain containing it.
+            (8) For any REG_CFA_RESTORE or REG_CFA_REGISTER, kill any chain
+                containing its dest.
 
             We cannot deal with situations where we track a reg in one mode
             and see a reference in another mode; these will cause the chain
@@ -1882,10 +1883,20 @@ build_def_use (basic_block bb)
              }
 
          /* Step 8: Kill the chains involving register restores.  Those
-            should restore _that_ register.  */
+            should restore _that_ register.  Similar for REG_CFA_REGISTER.  */
          for (note = REG_NOTES (insn); note; note = XEXP (note, 1))
-           if (REG_NOTE_KIND (note) == REG_CFA_RESTORE)
-             scan_rtx (insn, &XEXP (note, 0), NO_REGS, mark_all_read, OP_IN);
+           if (REG_NOTE_KIND (note) == REG_CFA_RESTORE
+               || REG_NOTE_KIND (note) == REG_CFA_REGISTER)
+             {
+               rtx *x = &XEXP (note, 0);
+               if (!*x)
+                 x = &PATTERN (insn);
+               if (GET_CODE (*x) == PARALLEL)
+                 x = &XVECEXP (*x, 0, 0);
+               if (GET_CODE (*x) == SET)
+                 x = &SET_DEST (*x);
+               scan_rtx (insn, x, NO_REGS, mark_all_read, OP_IN);
+             }
        }
       else if (DEBUG_BIND_INSN_P (insn)
               && !VAR_LOC_UNKNOWN_P (INSN_VAR_LOCATION_LOC (insn)))