(emit_reload_insns): Add another way to delete an output reload.

From-SVN: r7209

diff --git a/gcc/reload1.c b/gcc/reload1.c
index 7a44245468c62604d57c7428ed7a2d02bb1a0036..c5877e3174a72b3bb62dcc496fcb5e044dcab26d 100644 (file)
--- a/gcc/reload1.c
+++ b/gcc/reload1.c
@@ -5614,6 +5614,21 @@ emit_reload_insns (insn)
          else if (GET_CODE (oldequiv) == SUBREG)
            oldequiv_reg = SUBREG_REG (oldequiv);
 
+         /* If we are reloading from a register that was recently stored in
+            with an output-reload, see if we can prove there was
+            actually no need to store the old value in it.  */
+
+         if (optimize && GET_CODE (oldequiv) == REG
+             && REGNO (oldequiv) < FIRST_PSEUDO_REGISTER
+             && spill_reg_order[REGNO (oldequiv)] >= 0
+             && spill_reg_store[reload_spill_index[REGNO (oldequiv)]] != 0
+             && dead_or_set_p (insn, reload_in[j])
+             /* This is unsafe if operand occurs more than once in current
+            insn.  Perhaps some occurrences weren't reloaded.  */
+             && count_occurrences (PATTERN (insn), reload_in[j]) == 1)
+           delete_output_reload
+             (insn, j, spill_reg_store[spill_reg_order[REGNO (oldequiv)]]);
+
          /* Encapsulate both RELOADREG and OLDEQUIV into that mode,
             then load RELOADREG from OLDEQUIV.  Note that we cannot use
             gen_lowpart_common since it can do the wrong thing when