regcprop: Avoid REG_CFA_REGISTER notes (PR85645)

Changing a SET that has a REG_CFA_REGISTER note is wrong if we are
changing the SET_DEST, or if the REG_CFA_REGISTER has nil as its
argument, and maybe some other cases.  It's never really useful to
propagate into such an instruction, so let's just bail whenever we
see such a note.

	PR rtl-optimization/85645
	*  regcprop.c (copyprop_hardreg_forward_1): Don't propagate into an
	insn that has a REG_CFA_REGISTER note.

From-SVN: r260074

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 83d01edb0408da1469880c157b5562c3c76a0c25..580f41b2e088fc9fbfc7a0fa3cdbbbfd92d1c94e 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,9 @@
+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.
+
 2018-05-09  Richard Sandiford  <richard.sandiford@linaro.org>
 
        * cfgexpand.c (expand_clobber): New function.

diff --git a/gcc/regcprop.c b/gcc/regcprop.c
index a664f76a8b0fe7667a63895ee79ad663b7624e9c..18132425ab2929eb346a2985dd8304c7227dec45 100644 (file)
--- a/gcc/regcprop.c
+++ b/gcc/regcprop.c
@@ -848,6 +848,12 @@ copyprop_hardreg_forward_1 (basic_block bb, struct value_data *vd)
                  && reg_overlap_mentioned_p (XEXP (link, 0), SET_SRC (set)))
                set = NULL;
            }
+
+         /* We need to keep CFI info correct, and the same on all paths,
+            so we cannot normally replace the registers REG_CFA_REGISTER
+            refers to.  Bail.  */
+         if (REG_NOTE_KIND (link) == REG_CFA_REGISTER)
+           goto did_replacement;
        }
 
       /* Special-case plain move instructions, since we may well