re PR tree-optimization/59747 (wrong code at -Os and above on x86_64-linux-gnu in 64-bit mode)

	PR tree-optimization/59747
	* ree.c (find_and_remove_re): Properly handle case where a second
	eliminated extension requires widening a copy created for elimination
	of a prior extension.
	(combine_set_extension): Ensure that the number of hard regs needed
	for a destination register does not change when we widen it.

	PR tree-optimization/59747
	* gcc.c-torture/execute/pr59747.c: New test.

From-SVN: r206638

1 files changed, 18 insertions, 3 deletions

diff --git a/gcc/ree.c b/gcc/ree.c
index 63cc8cc..19d821c 100644
--- a/gcc/ree.c
+++ b/gcc/ree.c
@@ -297,6 +297,12 @@ combine_set_extension (ext_cand *cand, rtx curr_insn, rtx *orig_set)
   else
     new_reg = gen_rtx_REG (cand->mode, REGNO (SET_DEST (*orig_set)));
 
+  /* We're going to be widening the result of DEF_INSN, ensure that doing so
+     doesn't change the number of hard registers needed for the result.  */
+  if (HARD_REGNO_NREGS (REGNO (new_reg), cand->mode)
+      != HARD_REGNO_NREGS (REGNO (orig_src), GET_MODE (SET_DEST (*orig_set))))
+	return false;
+
   /* Merge constants by directly moving the constant into the register under
      some conditions.  Recall that RTL constants are sign-extended.  */
   if (GET_CODE (orig_src) == CONST_INT
@@ -1017,11 +1023,20 @@ find_and_remove_re (void)
   for (unsigned int i = 0; i < reinsn_copy_list.length (); i += 2)
     {
       rtx curr_insn = reinsn_copy_list[i];
+      rtx def_insn = reinsn_copy_list[i + 1];
+
+      /* Use the mode of the destination of the defining insn
+	 for the mode of the copy.  This is necessary if the
+	 defining insn was used to eliminate a second extension
+	 that was wider than the first.  */
+      rtx sub_rtx = *get_sub_rtx (def_insn);
       rtx pat = PATTERN (curr_insn);
-      rtx new_reg = gen_rtx_REG (GET_MODE (SET_DEST (pat)),
+      rtx new_dst = gen_rtx_REG (GET_MODE (SET_DEST (sub_rtx)),
 				 REGNO (XEXP (SET_SRC (pat), 0)));
-      rtx set = gen_rtx_SET (VOIDmode, new_reg, SET_DEST (pat));
-      emit_insn_after (set, reinsn_copy_list[i + 1]);
+      rtx new_src = gen_rtx_REG (GET_MODE (SET_DEST (sub_rtx)),
+				 REGNO (SET_DEST (pat)));
+      rtx set = gen_rtx_SET (VOIDmode, new_dst, new_src);
+      emit_insn_after (set, def_insn);
     }
 
   /* Delete all useless extensions here in one sweep.  */