[PATCH 4/5] xtensa: Eliminate unwanted reg-reg moves during DFmode input reloads

[PATCH 4/5] xtensa: Eliminate unwanted reg-reg moves during DFmode input reloads

[Takayuki 'January June' Suwa]

When spilled DFmode registers are reloaded in, once loaded into a pair of
SImode regs and then copied from that regs.  Such unwanted reg-reg moves
seems not to be eliminated at the "cprop_hardreg" stage, despite no problem
in output reloads.

Luckily it is easy to resolve such inefficiencies, with the use of peephole2
pattern.

gcc/ChangeLog:

	* config/xtensa/predicates.md (reload_operand):
	New predicate.
	* config/xtensa/xtensa.md: New peephole2 pattern.
---
 gcc/config/xtensa/predicates.md | 13 +++++++++++++
 gcc/config/xtensa/xtensa.md     | 31 +++++++++++++++++++++++++++++++
 2 files changed, 44 insertions(+)

diff --git a/gcc/config/xtensa/predicates.md b/gcc/config/xtensa/predicates.md
index d63a6cf034c..edd13ae41b9 100644
--- a/gcc/config/xtensa/predicates.md
+++ b/gcc/config/xtensa/predicates.md
@@ -165,6 +165,19 @@
   (and (match_code "const_int")
        (match_test "xtensa_mem_offset (INTVAL (op), SFmode)")))
 
+(define_predicate "reload_operand"
+  (match_code "mem")
+{
+  const_rtx addr = XEXP (op, 0);
+  if (REG_P (addr))
+    return REGNO (addr) == A1_REG;
+  if (GET_CODE (addr) == PLUS)
+    return REG_P (XEXP (addr, 0))
+	   && REGNO (XEXP (addr, 0)) == A1_REG
+	   && CONST_INT_P (XEXP (addr, 1));
+  return false;
+})
+
 (define_predicate "branch_operator"
   (match_code "eq,ne,lt,ge"))
 
diff --git a/gcc/config/xtensa/xtensa.md b/gcc/config/xtensa/xtensa.md
index 9588a829136..e6f5594762f 100644
--- a/gcc/config/xtensa/xtensa.md
+++ b/gcc/config/xtensa/xtensa.md
@@ -2724,3 +2724,34 @@
 	(if_then_else (match_test "TARGET_DENSITY")
 		      (const_int 5)
 		      (const_int 6)))])
+
+(define_peephole2
+  [(set (match_operand:SI 0 "register_operand")
+	(match_operand:SI 6 "reload_operand"))
+   (set (match_operand:SI 1 "register_operand")
+	(match_operand:SI 7 "reload_operand"))
+   (set (match_operand:SF 2 "register_operand")
+	(match_operand:SF 4 "register_operand"))
+   (set (match_operand:SF 3 "register_operand")
+	(match_operand:SF 5 "register_operand"))]
+  "REGNO (operands[0]) == REGNO (operands[4])
+   && REGNO (operands[1]) == REGNO (operands[5])
+   && peep2_reg_dead_p (4, operands[0])
+   && peep2_reg_dead_p (4, operands[1])"
+  [(set (match_dup 2)
+	(match_dup 6))
+   (set (match_dup 3)
+	(match_dup 7))]
+{
+  uint32_t check = 0;
+  int i;
+  for (i = 0; i <= 3; ++i)
+    {
+      uint32_t mask = (uint32_t)1 << REGNO (operands[i]);
+      if (check & mask)
+	FAIL;
+      check |= mask;
+    }
+  operands[6] = gen_rtx_MEM (SFmode, XEXP (operands[6], 0));
+  operands[7] = gen_rtx_MEM (SFmode, XEXP (operands[7], 0));
+})
-- 
2.20.1

Re: [PATCH 4/5] xtensa: Eliminate unwanted reg-reg moves during DFmode input reloads

[Max Filippov]

On Mon, Jun 13, 2022 at 8:54 PM Takayuki 'January June' Suwa
<jjsuwa_sys3175@yahoo.co.jp> wrote:
>
> When spilled DFmode registers are reloaded in, once loaded into a pair of
> SImode regs and then copied from that regs.  Such unwanted reg-reg moves
> seems not to be eliminated at the "cprop_hardreg" stage, despite no problem
> in output reloads.
>
> Luckily it is easy to resolve such inefficiencies, with the use of peephole2
> pattern.
>
> gcc/ChangeLog:
>
>         * config/xtensa/predicates.md (reload_operand):
>         New predicate.
>         * config/xtensa/xtensa.md: New peephole2 pattern.
> ---
>  gcc/config/xtensa/predicates.md | 13 +++++++++++++
>  gcc/config/xtensa/xtensa.md     | 31 +++++++++++++++++++++++++++++++
>  2 files changed, 44 insertions(+)

Regtested for target=xtensa-linux-uclibc, no new regressions.
Committed to master.

-- 
Thanks.
-- Max