[2/2] xtensa: constantsynth: Add new 2-insns synthesis pattern
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Commit Message
This patch adds a new 2-instructions constant synthesis pattern:
- A non-negative square value that root can fit into a signed 12-bit:
=> "MOVI(.N) Ax, simm12" + "MULL Ax, Ax, Ax"
Due to the execution cost of the integer multiply instruction (MULL), this
synthesis works only when the 32-bit Integer Multiply Option is configured
and optimize for size is specified.
gcc/ChangeLog:
* config/xtensa/xtensa.cc (xtensa_constantsynth_2insn):
Add new pattern for the abovementioned case.
---
gcc/config/xtensa/xtensa.cc | 12 ++++++++++--
1 file changed, 10 insertions(+), 2 deletions(-)
Comments
On Sun, Jun 18, 2023 at 12:10 AM Takayuki 'January June' Suwa
<jjsuwa_sys3175@yahoo.co.jp> wrote:
>
> This patch adds a new 2-instructions constant synthesis pattern:
>
> - A non-negative square value that root can fit into a signed 12-bit:
> => "MOVI(.N) Ax, simm12" + "MULL Ax, Ax, Ax"
>
> Due to the execution cost of the integer multiply instruction (MULL), this
> synthesis works only when the 32-bit Integer Multiply Option is configured
> and optimize for size is specified.
>
> gcc/ChangeLog:
>
> * config/xtensa/xtensa.cc (xtensa_constantsynth_2insn):
> Add new pattern for the abovementioned case.
> ---
> gcc/config/xtensa/xtensa.cc | 12 ++++++++++--
> 1 file changed, 10 insertions(+), 2 deletions(-)
Regtested for target=xtensa-linux-uclibc, no new regressions.
Committed to master.
@@ -58,6 +58,7 @@ along with GCC; see the file COPYING3. If not see
#include "insn-attr.h"
#include "tree-pass.h"
#include "print-rtl.h"
+#include <math.h>
/* This file should be included last. */
#include "target-def.h"
@@ -1067,7 +1068,7 @@ xtensa_constantsynth_2insn (rtx dst, HOST_WIDE_INT srcval,
{
HOST_WIDE_INT imm = INT_MAX;
rtx x = NULL_RTX;
- int shift;
+ int shift, sqr;
gcc_assert (REG_P (dst));
@@ -1078,7 +1079,6 @@ xtensa_constantsynth_2insn (rtx dst, HOST_WIDE_INT srcval,
x = gen_lshrsi3 (dst, dst, GEN_INT (32 - shift));
}
-
shift = ctz_hwi (srcval);
if ((!x || (TARGET_DENSITY && ! IN_RANGE (imm, -32, 95)))
&& xtensa_simm12b (srcval >> shift))
@@ -1105,6 +1105,14 @@ xtensa_constantsynth_2insn (rtx dst, HOST_WIDE_INT srcval,
x = gen_addsi3 (dst, dst, GEN_INT (imm1));
}
+ sqr = (int) floorf (sqrtf (srcval));
+ if (TARGET_MUL32 && optimize_size
+ && !x && IN_RANGE (srcval, 0, (2047 * 2047)) && sqr * sqr == srcval)
+ {
+ imm = sqr;
+ x = gen_mulsi3 (dst, dst, dst);
+ }
+
if (!x)
return 0;