[PATCH 3/6] regrename: Don't rename restores

Segher Boessenkool segher@kernel.crashing.org
Mon Oct 3 13:50:00 GMT 2016


A restore is supposed to restore some certain register.  Restoring it
into some other register will not work.  Don't.


2016-06-07  Segher Boessenkool  <segher@kernel.crashing.org>

	* regrename.c (build_def_use): Invalidate chains that have a
	REG_CFA_RESTORE on some instruction.

---
 gcc/regrename.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/gcc/regrename.c b/gcc/regrename.c
index 3509e8b..e0d2dd1 100644
--- a/gcc/regrename.c
+++ b/gcc/regrename.c
@@ -1655,6 +1655,7 @@ 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.
 
 	     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
@@ -1867,6 +1868,12 @@ build_def_use (basic_block bb)
 		scan_rtx (insn, &XEXP (note, 0), NO_REGS, terminate_dead,
 			  OP_IN);
 	      }
+
+	  /* Step 8: Kill the chains involving register restores.  Those
+	     should restore _that_ 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);
 	}
       else if (DEBUG_INSN_P (insn)
 	       && !VAR_LOC_UNKNOWN_P (INSN_VAR_LOCATION_LOC (insn)))
-- 
1.9.3



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