Re: [PATCH] xtensa: Optimize integer constant addition that is between -32896 and 32639

[Max Filippov via Gcc-patches]

On Sun, Jun 26, 2022 at 7:53 AM Takayuki 'January June' Suwa
 wrote:
>
> Such constants are often subject to the constant synthesis:
>
> int test(int a) {
>   return a - 31999;
> }
>
> test:
> movia3, 1
> addmi   a3, a3, -0x7d00
> add a2, a2, a3
> ret
>
> This patch optimizes such case as follows:
>
> test:
> addia2, a2, 1
> addmi   a2, a2, -0x7d00
> ret
>
> gcc/ChangeLog:
>
> * config/xtensa/xtensa.md:
> Suppress unnecessary emitting nop insn in the split patterns for
> integer/FP constant synthesis, and add new peephole2 pattern that
> folds such synthesized additions.
> ---
>  gcc/config/xtensa/xtensa.md | 35 +++
>  1 file changed, 35 insertions(+)

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

-- 
Thanks.
-- Max

[PATCH] xtensa: Optimize integer constant addition that is between -32896 and 32639

[Takayuki 'January June' Suwa via Gcc-patches]

Such constants are often subject to the constant synthesis:

int test(int a) {
  return a - 31999;
}

test:
movia3, 1
addmi   a3, a3, -0x7d00
add a2, a2, a3
ret

This patch optimizes such case as follows:

test:
addia2, a2, 1
addmi   a2, a2, -0x7d00
ret

gcc/ChangeLog:

* config/xtensa/xtensa.md:
Suppress unnecessary emitting nop insn in the split patterns for
integer/FP constant synthesis, and add new peephole2 pattern that
folds such synthesized additions.
---
 gcc/config/xtensa/xtensa.md | 35 +++
 1 file changed, 35 insertions(+)

diff --git a/gcc/config/xtensa/xtensa.md b/gcc/config/xtensa/xtensa.md
index f31ec33b362..9d998589631 100644
--- a/gcc/config/xtensa/xtensa.md
+++ b/gcc/config/xtensa/xtensa.md
@@ -1033,6 +1033,7 @@
 FAIL;
   if (! xtensa_constantsynth (operands[0], INTVAL (x)))
 emit_move_insn (operands[0], x);
+  DONE;
 })
 
 ;; 16-bit Integer moves
@@ -1272,6 +1273,7 @@
   x = gen_rtx_REG (SImode, REGNO (operands[0]));
   if (! xtensa_constantsynth (x, l[i]))
 emit_move_insn (x, GEN_INT (l[i]));
+  DONE;
 })
 
 ;; 64-bit floating point moves
@@ -2808,3 +2810,36 @@
 && REGNO (x) == regno + REG_NREGS (operands[0]) / 2))
 FAIL;
 })
+
+(define_peephole2
+  [(set (match_operand:SI 0 "register_operand")
+   (match_operand:SI 1 "const_int_operand"))
+   (set (match_dup 0)
+   (plus:SI (match_dup 0)
+(match_operand:SI 2 "const_int_operand")))
+   (set (match_operand:SI 3 "register_operand")
+   (plus:SI (match_operand:SI 4 "register_operand")
+(match_dup 0)))]
+  "IN_RANGE (INTVAL (operands[1]) + INTVAL (operands[2]),
+(-128 - 32768), (127 + 32512))
+   && REGNO (operands[0]) != REGNO (operands[3])
+   && REGNO (operands[0]) != REGNO (operands[4])
+   && peep2_reg_dead_p (3, operands[0])"
+  [(set (match_dup 3)
+   (plus:SI (match_dup 4)
+(match_dup 1)))
+   (set (match_dup 3)
+   (plus:SI (match_dup 3)
+(match_dup 2)))]
+{
+  HOST_WIDE_INT value = INTVAL (operands[1]) + INTVAL (operands[2]);
+  int imm0, imm1;
+  value += 128;
+  if (value > 32512)
+imm1 = 32512;
+  else
+imm1 = value & ~255;
+  imm0 = value - imm1 - 128;
+  operands[1] = GEN_INT (imm0);
+  operands[2] = GEN_INT (imm1);
+})
-- 
2.20.1