[PATCH] xtensa: Optimize boolean evaluation when SImode EQ/NE to zero if TARGET_MINMAX

[PATCH] xtensa: Optimize boolean evaluation when SImode EQ/NE to zero if TARGET_MINMAX

[Takayuki 'January June' Suwa]

This patch optimizes the boolean evaluation for equality to 0 in SImode
using the MINU (Minimum Value Unsigned) machine instruction available
when TARGET_MINMAX is configured, for example, (x != 0) to MINU(x, 1)
and (x == 0) to (MINU(x, 1) ^ 1).

    /* example */
    int test0(int x) {
      return x == 0;
    }
    int test1(int x) {
      return x != 0;
    }

    ;; before
    test0:
	mov.n	a10, a2
	movi.n	a9, 1
	movi.n	a2, 0
	moveqz	a2, a9, a10
	ret.n
    test1:
	mov.n	a10, a2
	movi.n	a9, 1
	movi.n	a2, 0
	movnez	a2, a9, a10
	ret.n

    ;; after (prereq. TARGET_MINMAX)
    test0:
	movi.n	a9, 1
	minu	a2, a2, a9
	xor	a2, a2, a9
	ret.n
    test1:
	movi.n	a9, 1
	minu	a2, a2, a9
	ret.n

gcc/ChangeLog:

	* config/xtensa/xtensa.cc (xtensa_expand_scc):
	Add code for particular constants (only 0 and INT_MIN for now)
	for EQ/NE boolean evaluation in SImode.
	* config/xtensa/xtensa.md (*eqne_INT_MIN): Remove because its
	implementation has been integrated into the above.
---
 gcc/config/xtensa/xtensa.cc | 43 +++++++++++++++++++++++++++++++------
 gcc/config/xtensa/xtensa.md | 34 -----------------------------
 2 files changed, 37 insertions(+), 40 deletions(-)

diff --git a/gcc/config/xtensa/xtensa.cc b/gcc/config/xtensa/xtensa.cc
index af71e2179d0..1afaa1cc94e 100644
--- a/gcc/config/xtensa/xtensa.cc
+++ b/gcc/config/xtensa/xtensa.cc
@@ -994,15 +994,46 @@ xtensa_expand_scc (rtx operands[4], machine_mode cmp_mode)
   rtx cmp;
   rtx one_tmp, zero_tmp;
   rtx (*gen_fn) (rtx, rtx, rtx, rtx, rtx);
+  enum rtx_code code = GET_CODE (operands[1]);
 
-  if (!(cmp = gen_conditional_move (GET_CODE (operands[1]), cmp_mode,
-				    operands[2], operands[3])))
+  if (cmp_mode == SImode && CONST_INT_P (operands[3])
+      && (code == EQ || code == NE))
+    switch (INTVAL (operands[3]))
+      {
+      case 0:
+	if (TARGET_MINMAX)
+	  {
+	    one_tmp = force_reg (SImode, const1_rtx);
+	    emit_insn (gen_uminsi3 (dest, operands[2], one_tmp));
+	    if (code == EQ)
+	      emit_insn (gen_xorsi3 (dest, dest, one_tmp));
+	    return 1;
+	  }
+	break;
+      case -2147483648:
+	if (TARGET_ABS)
+	  {
+	    emit_insn (gen_abssi2 (dest, operands[2]));
+	    if (code == EQ)
+	      emit_insn (gen_lshrsi3 (dest, dest, GEN_INT (31)));
+	    else
+	      {
+		emit_insn (gen_ashrsi3 (dest, dest, GEN_INT (31)));
+		emit_insn (gen_addsi3 (dest, dest, const1_rtx));
+	      }
+	    return 1;
+	  }
+	break;
+      default:
+	break;
+      }
+
+  if (! (cmp = gen_conditional_move (code, cmp_mode,
+				     operands[2], operands[3])))
     return 0;
 
-  one_tmp = gen_reg_rtx (SImode);
-  zero_tmp = gen_reg_rtx (SImode);
-  emit_insn (gen_movsi (one_tmp, const_true_rtx));
-  emit_insn (gen_movsi (zero_tmp, const0_rtx));
+  one_tmp = force_reg (SImode, const1_rtx);
+  zero_tmp = force_reg (SImode, const0_rtx);
 
   gen_fn = (cmp_mode == SImode
 	    ? gen_movsicc_internal0
diff --git a/gcc/config/xtensa/xtensa.md b/gcc/config/xtensa/xtensa.md
index 5386e45b51d..d6505e7eb70 100644
--- a/gcc/config/xtensa/xtensa.md
+++ b/gcc/config/xtensa/xtensa.md
@@ -3188,40 +3188,6 @@
 		      (const_int 5)
 		      (const_int 6)))])
 
-
-(define_insn_and_split "*eqne_INT_MIN"
-  [(set (match_operand:SI 0 "register_operand" "=a")
-	(match_operator:SI 2 "boolean_operator"
-		[(match_operand:SI 1 "register_operand" "r")
-		 (const_int -2147483648)]))]
-  "TARGET_ABS"
-  "#"
-  "&& 1"
-  [(set (match_dup 0)
-	(abs:SI (match_dup 1)))
-   (set (match_dup 0)
-	(match_op_dup:SI 2
-		[(match_dup 0)
-		 (const_int 31)]))
-   (match_dup 3)]
-{
-  enum rtx_code code = GET_CODE (operands[2]);
-  operands[2] = gen_rtx_fmt_ee ((code == EQ) ? LSHIFTRT : ASHIFTRT,
-				SImode, XEXP (operands[2], 0),
-				XEXP (operands[2], 1));
-  operands[3] = (code != EQ) ? gen_addsi3 (operands[0],
-					   operands[0], const1_rtx)
-			     : const0_rtx;
-}
-  [(set_attr "type"	"move")
-   (set_attr "mode"	"SI")
-   (set (attr "length")
-	(if_then_else (match_test "GET_CODE (operands[2]) == EQ")
-		      (const_int 3)
-		      (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"))
-- 
2.30.2

Re: [PATCH] xtensa: Optimize boolean evaluation when SImode EQ/NE to zero if TARGET_MINMAX

[Max Filippov]

Hi Suwa-san,

On Tue, Sep 5, 2023 at 2:29 AM Takayuki 'January June' Suwa
<jjsuwa_sys3175@yahoo.co.jp> wrote:
>
> This patch optimizes the boolean evaluation for equality to 0 in SImode
> using the MINU (Minimum Value Unsigned) machine instruction available
> when TARGET_MINMAX is configured, for example, (x != 0) to MINU(x, 1)
> and (x == 0) to (MINU(x, 1) ^ 1).
>
>     /* example */
>     int test0(int x) {
>       return x == 0;
>     }
>     int test1(int x) {
>       return x != 0;
>     }
>
>     ;; before
>     test0:
>         mov.n   a10, a2
>         movi.n  a9, 1
>         movi.n  a2, 0
>         moveqz  a2, a9, a10
>         ret.n
>     test1:
>         mov.n   a10, a2
>         movi.n  a9, 1
>         movi.n  a2, 0
>         movnez  a2, a9, a10
>         ret.n
>
>     ;; after (prereq. TARGET_MINMAX)
>     test0:
>         movi.n  a9, 1
>         minu    a2, a2, a9
>         xor     a2, a2, a9
>         ret.n

ISTM that test0 could be done with movnez in the same three instructions:

  movi a9, 1
  movnez a2, a9, a2
  xor a2, a2, a9

>     test1:
>         movi.n  a9, 1
>         minu    a2, a2, a9
>         ret.n

ISTM that test1 could be done with movnez in the same two instructions:

  movi a9, 1
  movnez a2, a9, a2

-- 
Thanks.
-- Max

Re: [PATCH] xtensa: Optimize boolean evaluation when SImode EQ/NE to zero if TARGET_MINMAX

[Takayuki 'January June' Suwa]

On 2023/09/06 8:01, Max Filippov wrote:
> Hi Suwa-san,
Hi!

> 
> On Tue, Sep 5, 2023 at 2:29 AM Takayuki 'January June' Suwa
> <jjsuwa_sys3175@yahoo.co.jp> wrote:
>>
>> This patch optimizes the boolean evaluation for equality to 0 in SImode
>> using the MINU (Minimum Value Unsigned) machine instruction available
>> when TARGET_MINMAX is configured, for example, (x != 0) to MINU(x, 1)
>> and (x == 0) to (MINU(x, 1) ^ 1).
>>
>>     /* example */
>>     int test0(int x) {
>>       return x == 0;
>>     }
>>     int test1(int x) {
>>       return x != 0;
>>     }
>>
>>     ;; before
>>     test0:
>>         mov.n   a10, a2
>>         movi.n  a9, 1
>>         movi.n  a2, 0
>>         moveqz  a2, a9, a10
>>         ret.n
>>     test1:
>>         mov.n   a10, a2
>>         movi.n  a9, 1
>>         movi.n  a2, 0
>>         movnez  a2, a9, a10
>>         ret.n
>>
>>     ;; after (prereq. TARGET_MINMAX)
>>     test0:
>>         movi.n  a9, 1
>>         minu    a2, a2, a9
>>         xor     a2, a2, a9
>>         ret.n
> 
> ISTM that test0 could be done with movnez in the same three instructions:
> 
>   movi a9, 1
>   movnez a2, a9, a2
>   xor a2, a2, a9

Unfortunately, the MOV[EQ/NE]Z machine instruction can only be used to implement the functionality if the input and output physical registers are the same (a2 in the example).
In fact, when modified to use MOV[EQ/NE]Z, GCC register allocator often prepends a register move instruction to satisfy the above constraint (and thus often does not save instruction count).

I'm currently trying to see if I can somehow follow up after the physical register is determined (around split2 or peephole2).

> 
>>     test1:
>>         movi.n  a9, 1
>>         minu    a2, a2, a9
>>         ret.n
> 
> ISTM that test1 could be done with movnez in the same two instructions:
> 
>   movi a9, 1
>   movnez a2, a9, a2
> 

Re: [PATCH] xtensa: Optimize boolean evaluation when SImode EQ/NE to zero if TARGET_MINMAX

[Max Filippov]

On Tue, Sep 5, 2023 at 9:24 PM Takayuki 'January June' Suwa
<jjsuwa_sys3175@yahoo.co.jp> wrote:
> On 2023/09/06 8:01, Max Filippov wrote:
> > On Tue, Sep 5, 2023 at 2:29 AM Takayuki 'January June' Suwa
> > <jjsuwa_sys3175@yahoo.co.jp> wrote:
> >>     ;; after (prereq. TARGET_MINMAX)
> >>     test0:
> >>         movi.n  a9, 1
> >>         minu    a2, a2, a9
> >>         xor     a2, a2, a9
> >>         ret.n
> >
> > ISTM that test0 could be done with movnez in the same three instructions:
> >
> >   movi a9, 1
> >   movnez a2, a9, a2
> >   xor a2, a2, a9
>
> Unfortunately, the MOV[EQ/NE]Z machine instruction can only be used
> to implement the functionality if the input and output physical registers
> are the same (a2 in the example).

Oh yeah, you're right, I missed that.

-- 
Thanks.
-- Max

Re: [PATCH] xtensa: Optimize boolean evaluation when SImode EQ/NE to zero if TARGET_MINMAX

[Max Filippov]

On Tue, Sep 5, 2023 at 2:29 AM Takayuki 'January June' Suwa
<jjsuwa_sys3175@yahoo.co.jp> wrote:
>
> This patch optimizes the boolean evaluation for equality to 0 in SImode
> using the MINU (Minimum Value Unsigned) machine instruction available
> when TARGET_MINMAX is configured, for example, (x != 0) to MINU(x, 1)
> and (x == 0) to (MINU(x, 1) ^ 1).
>
>     /* example */
>     int test0(int x) {
>       return x == 0;
>     }
>     int test1(int x) {
>       return x != 0;
>     }
>
>     ;; before
>     test0:
>         mov.n   a10, a2
>         movi.n  a9, 1
>         movi.n  a2, 0
>         moveqz  a2, a9, a10
>         ret.n
>     test1:
>         mov.n   a10, a2
>         movi.n  a9, 1
>         movi.n  a2, 0
>         movnez  a2, a9, a10
>         ret.n
>
>     ;; after (prereq. TARGET_MINMAX)
>     test0:
>         movi.n  a9, 1
>         minu    a2, a2, a9
>         xor     a2, a2, a9
>         ret.n
>     test1:
>         movi.n  a9, 1
>         minu    a2, a2, a9
>         ret.n
>
> gcc/ChangeLog:
>
>         * config/xtensa/xtensa.cc (xtensa_expand_scc):
>         Add code for particular constants (only 0 and INT_MIN for now)
>         for EQ/NE boolean evaluation in SImode.
>         * config/xtensa/xtensa.md (*eqne_INT_MIN): Remove because its
>         implementation has been integrated into the above.
> ---
>  gcc/config/xtensa/xtensa.cc | 43 +++++++++++++++++++++++++++++++------
>  gcc/config/xtensa/xtensa.md | 34 -----------------------------
>  2 files changed, 37 insertions(+), 40 deletions(-)

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

-- 
Thanks.
-- Max