[PATCH][4.9]Backport "Fix register corruption bug in ree"

[Renlin Li]

Hi all,

This is a backport patch for branch 4.9. You can find the original patch 
here: https://gcc.gnu.org/ml/gcc-patches/2014-09/msg00356.html
And it has been commit on the trunk as r215205.
This fixes a few libstdc++-v3 test suite failures.
x86_64 bootstraps Okay, aarch64_be-none-elf libstdc++-v3 tested Okay.

Okay to commit on branch 4.9?

Regards,
Renlin Li

2015-02-06  Renlin Li  <renlin...@arm.com>

    Backport from mainline
    2014-09-12  Wilco Dijkstra  <wilco.dijks...@arm.com>

    * gcc/ree.c (combine_reaching_defs): Ensure inserted copy don't change
    the number of hard registers.
diff --git a/gcc/ree.c b/gcc/ree.c
index 67fc9c3..e9ff904 100644
--- a/gcc/ree.c
+++ b/gcc/ree.c
@@ -793,6 +793,14 @@ combine_reaching_defs (ext_cand *cand, const_rtx set_pat, ext_state *state)
       if (state->modified[INSN_UID (cand->insn)].kind != EXT_MODIFIED_NONE)
 	return false;
 
+      enum machine_mode dst_mode = GET_MODE (SET_DEST (PATTERN (cand->insn)));
+      rtx src_reg = get_extended_src_reg (SET_SRC (PATTERN (cand->insn)));
+
+      /* Ensure the number of hard registers of the copy match.  */
+      if (HARD_REGNO_NREGS (REGNO (src_reg), dst_mode)
+	  != HARD_REGNO_NREGS (REGNO (src_reg), GET_MODE (src_reg)))
+	return false;
+
       /* There's only one reaching def.  */
       rtx def_insn = state->defs_list[0];
 
@@ -842,7 +850,7 @@ combine_reaching_defs (ext_cand *cand, const_rtx set_pat, ext_state *state)
       start_sequence ();
       rtx pat = PATTERN (cand->insn);
       rtx new_dst = gen_rtx_REG (GET_MODE (SET_DEST (pat)),
-                                 REGNO (XEXP (SET_SRC (pat), 0)));
+				 REGNO (get_extended_src_reg (SET_SRC (pat))));
       rtx new_src = gen_rtx_REG (GET_MODE (SET_DEST (pat)),
                                  REGNO (SET_DEST (pat)));
       emit_move_insn (new_dst, new_src);