rs6000: Give an argument to every REG_CFA_REGISTER (PR85645)

The one for the prologue mflr did not have any value set, which means
use the SET that is in the insn pattern.  This works fine, except when
some late pass decides to replace the SET_SRC -- this changes the
meaning of the REG_CFA_REGISTER!  Such passes should not do these
things, but let's be more explicit here, for extra robustness.  It
could be argued that this defaulting is a design misfeature (it does
not save much space either, etc.)

	PR rtl-optimization/85645
	* config/rs6000/rs6000.c (rs6000_emit_prologue_components): Put a SET
	in the REG_CFA_REGISTER note for LR, don't leave it empty.

From-SVN: r260077

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 1c81e4f555299362100abc1cd70c7224a8111b4b..0acd815b35c8457929282fbd60dbbf0ae0861e0f 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
+       * config/rs6000/rs6000.c (rs6000_emit_prologue_components): Put a SET
+       in the REG_CFA_REGISTER note for LR, don't leave it empty.
+
 2018-05-09  Segher Boessenkool  <segher@kernel.crashing.org>
 
        PR rtl-optimization/85645

diff --git a/gcc/config/rs6000/rs6000.c b/gcc/config/rs6000/rs6000.c
index 6fb79f29a6255b37c2f49b37702e85444aa6d875..19913da9584ad8f508d99677f75ad312fb4bf6c1 100644 (file)
--- a/gcc/config/rs6000/rs6000.c
+++ b/gcc/config/rs6000/rs6000.c
@@ -26151,10 +26151,11 @@ rs6000_emit_prologue_components (sbitmap components)
   /* Prologue for LR.  */
   if (bitmap_bit_p (components, 0))
     {
+      rtx lr = gen_rtx_REG (reg_mode, LR_REGNO);
       rtx reg = gen_rtx_REG (reg_mode, 0);
-      rtx_insn *insn = emit_move_insn (reg, gen_rtx_REG (reg_mode, LR_REGNO));
+      rtx_insn *insn = emit_move_insn (reg, lr);
       RTX_FRAME_RELATED_P (insn) = 1;
-      add_reg_note (insn, REG_CFA_REGISTER, NULL);
+      add_reg_note (insn, REG_CFA_REGISTER, gen_rtx_SET (reg, lr));
 
       int offset = info->lr_save_offset;
       if (info->push_p)
@@ -26162,7 +26163,6 @@ rs6000_emit_prologue_components (sbitmap components)
 
       insn = emit_insn (gen_frame_store (reg, ptr_reg, offset));
       RTX_FRAME_RELATED_P (insn) = 1;
-      rtx lr = gen_rtx_REG (reg_mode, LR_REGNO);
       rtx mem = copy_rtx (SET_DEST (single_set (insn)));
       add_reg_note (insn, REG_CFA_OFFSET, gen_rtx_SET (mem, lr));
     }