[SH][committed]

[Oleg Endo <oleg dot endo at t-online dot de>]

Hi,

The attached SH patch converts sequences such as:
	movt	r2
	movt	r13
into:
	movt	r2
	mov	r2,r13

This shortens the live range of the T bit register and is better for
parallel execution.  It doesn't happen often, but it's easy to avoid it.

Unfortunately I had to do this manually because cprop_hardreg gets in
the way here.  If done as a peephole2, cprop_hardreg then
unconditionally just converts it back, because it thinks that all reg
copies are equal in some way.

Tested on sh-elf with
make -k check RUNTESTFLAGS="--target_board=sh-sim
\{-m2/-ml,-m2/-mb,-m2a/-mb,-m4/-ml,-m4/-mb,-m4a/-ml,-m4a/-mb}"

Committed as r228386.

Cheers,
Oleg

gcc/ChangeLog:
	* config/sh/sh.md: Add new unnamed split pattern to handle
	movt-movt sequences.

Index: gcc/config/sh/sh.md
===================================================================
--- gcc/config/sh/sh.md	(revision 228331)
+++ gcc/config/sh/sh.md	(working copy)
@@ -14860,6 +14860,46 @@
 			  gen_rtx_REG (SImode, (REGNO (operands[1])))));
 })
 
+;; This is not a peephole, but it's here because it's actually supposed
+;; to be one.  It tries to convert a sequence such as
+;;	movt	r2	->	movt	r2
+;;	movt	r13		mov	r2,r13
+;; This gives the schduler a bit more freedom to hoist a following
+;; comparison insn.  Moreover, it the reg-reg mov insn is MT group which has
+;; better chances for parallel execution.
+;; We can do this with a peephole2 pattern, but then the cprop_hardreg
+;; pass will revert the change.  See also PR 64331.
+;; Thus do it manually in one of the split passes after register allocation.
+;; Sometimes the cprop_hardreg pass might also eliminate the reg-reg copy.
+(define_split
+  [(set (match_operand:SI 0 "arith_reg_dest")
+	(match_operand:SI 1 "t_reg_operand"))]
+  "TARGET_SH1 && reload_completed"
+  [(set (match_dup 0) (match_dup 1))]
+{
+  rtx t_reg = get_t_reg_rtx ();
+
+  for (rtx_insn* i = prev_nonnote_insn_bb (curr_insn); i != NULL;
+       i = prev_nonnote_insn_bb (i))
+    {
+      if (!INSN_P (i) || DEBUG_INSN_P (i))
+	continue;
+
+      if (modified_in_p (t_reg, i) || BARRIER_P (i))
+	FAIL;
+
+      if (sh_is_movt_insn (i))
+	{
+	  rtx r = sh_movt_set_dest (i);
+	  if (!modified_between_p (r, i, curr_insn))
+	    {
+	      operands[1] = r;
+	      break;
+	   }
+	}
+    }
+})
+
 (define_peephole
   [(set (match_operand:SI 0 "register_operand" "=r")
 	(plus:SI (match_dup 0) (match_operand:SI 1 "register_operand" "r")))