[PATCH] combine: Fix various shortcomings in make_more_copies (PR87701, PR87780)

[Segher Boessenkool]

This rewrites most of make_more_copies, in the process fixing a few PRs
and some other bugs, and working around a few target problems.  Certain
notes turn out to actually change the meaning of the RTL, so we cannot
drop them; and i386 takes subregs of hard regs.

Committing.


Segher


2018-10-29  Segher Boessenkool  <seg...@kernel.crashing.org>

        PR rtl-optimization/87701
        PR rtl-optimization/87780
        * combine.c (make_more_copies): Rewrite.

---
 gcc/combine.c | 15 +++++----------
 1 file changed, 5 insertions(+), 10 deletions(-)

diff --git a/gcc/combine.c b/gcc/combine.c
index bd593bdc..dfb0b44 100644
--- a/gcc/combine.c
+++ b/gcc/combine.c
@@ -14990,25 +14990,20 @@ make_more_copies (void)
          rtx set = single_set (insn);
          if (!set)
            continue;
-         rtx src = SET_SRC (set);
          rtx dest = SET_DEST (set);
          if (dest == pc_rtx)
            continue;
-         if (GET_CODE (src) == SUBREG)
-           src = SUBREG_REG (src);
+         rtx src = SET_SRC (set);
          if (!(REG_P (src) && HARD_REGISTER_P (src)))
            continue;
          if (TEST_HARD_REG_BIT (fixed_reg_set, REGNO (src)))
            continue;
 
          rtx new_reg = gen_reg_rtx (GET_MODE (dest));
-         rtx_insn *insn1 = gen_move_insn (new_reg, src);
-         rtx_insn *insn2 = gen_move_insn (dest, new_reg);
-         emit_insn_after (insn1, insn);
-         emit_insn_after (insn2, insn1);
-         delete_insn (insn);
-
-         insn = insn2;
+         rtx_insn *new_insn = gen_move_insn (new_reg, src);
+         SET_SRC (set) = new_reg;
+         emit_insn_before (new_insn, insn);
+         df_insn_rescan (insn);
        }
     }
 }
-- 
1.8.3.1