[PATCH v2 1/4] LoongArch: Optimize f{max,min}imum{,f}
Xi Ruoyao
xry111@xry111.site
Mon Feb 24 12:49:15 GMT 2025
The code now looks like:
fclass.s $fa2, $fa0
movfr2gr.s $t0, $fa2
slli.w $t0, $t0, 0x0
fclass.s $fa2, $fa1
movfr2gr.s $t1, $fa2
or $t0, $t0, $t1
andi $t0, $t0, 0x3
bnez $t0, 1f
fmin.s $fa0, $fa0, $fa1
ret
1:
fmul.s $fa0, $fa0, $fa1
ret
This looks really bad, with expensive movfr2gr instructions, redundant
sign-extensions and masking (arguably it's a compiler
missed-optimzation), and a branch. Rewrite it with inline assembly:
fcmp.cor.s $fcc0, $fa0, $fa0
fcmp.cor.s $fcc1, $fa1, $fa1
fsel $fa2, $fa0, $fa1, $fcc0
fsel $fa0, $fa1, $fa0, $fcc1
fmax.s $fa0, $fa2, $fa0
ret
Note that we cannot make it more readable with
"double a = __builtin_isnanf (x) ? y : x" because this C statement only
happens to produce what we want with https://gcc.gnu.org/PR66462, if
this bug is fixed in the future the generated code may change.
Signed-off-by: Xi Ruoyao <xry111@xry111.site>
---
.../loongarch/fpu/math-type-macros-double.h | 21 ++++++++++
.../loongarch/fpu/math-type-macros-float.h | 21 ++++++++++
sysdeps/loongarch/fpu/s_fmaximum.c | 40 -------------------
sysdeps/loongarch/fpu/s_fmaximum_template.c | 39 ++++++++++++++++++
sysdeps/loongarch/fpu/s_fmaximumf.c | 40 -------------------
sysdeps/loongarch/fpu/s_fminimum.c | 40 -------------------
sysdeps/loongarch/fpu/s_fminimum_template.c | 39 ++++++++++++++++++
sysdeps/loongarch/fpu/s_fminimumf.c | 40 -------------------
8 files changed, 120 insertions(+), 160 deletions(-)
create mode 100644 sysdeps/loongarch/fpu/math-type-macros-double.h
create mode 100644 sysdeps/loongarch/fpu/math-type-macros-float.h
delete mode 100644 sysdeps/loongarch/fpu/s_fmaximum.c
create mode 100644 sysdeps/loongarch/fpu/s_fmaximum_template.c
delete mode 100644 sysdeps/loongarch/fpu/s_fmaximumf.c
delete mode 100644 sysdeps/loongarch/fpu/s_fminimum.c
create mode 100644 sysdeps/loongarch/fpu/s_fminimum_template.c
delete mode 100644 sysdeps/loongarch/fpu/s_fminimumf.c
diff --git a/sysdeps/loongarch/fpu/math-type-macros-double.h b/sysdeps/loongarch/fpu/math-type-macros-double.h
new file mode 100644
index 0000000000..dd53885144
--- /dev/null
+++ b/sysdeps/loongarch/fpu/math-type-macros-double.h
@@ -0,0 +1,21 @@
+/* Helper macros for double variants of type generic functions of libm,
+ LoongArch version.
+ Copyright (C) 2025 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <https://www.gnu.org/licenses/>. */
+
+#include_next <math-type-macros-double.h>
+#define INSN_FMT "d"
diff --git a/sysdeps/loongarch/fpu/math-type-macros-float.h b/sysdeps/loongarch/fpu/math-type-macros-float.h
new file mode 100644
index 0000000000..ee5f7847c8
--- /dev/null
+++ b/sysdeps/loongarch/fpu/math-type-macros-float.h
@@ -0,0 +1,21 @@
+/* Helper macros for float variants of type generic functions of libm,
+ LoongArch version.
+ Copyright (C) 2025 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <https://www.gnu.org/licenses/>. */
+
+#include_next <math-type-macros-float.h>
+#define INSN_FMT "s"
diff --git a/sysdeps/loongarch/fpu/s_fmaximum.c b/sysdeps/loongarch/fpu/s_fmaximum.c
deleted file mode 100644
index 07fc7214a1..0000000000
--- a/sysdeps/loongarch/fpu/s_fmaximum.c
+++ /dev/null
@@ -1,40 +0,0 @@
-/* fmaximum(). LoongArch version.
- Copyright (C) 2022-2025 Free Software Foundation, Inc.
- This file is part of the GNU C Library.
-
- The GNU C Library is free software; you can redistribute it and/or
- modify it under the terms of the GNU Lesser General Public
- License as published by the Free Software Foundation; either
- version 2.1 of the License, or (at your option) any later version.
-
- The GNU C Library is distributed in the hope that it will be useful,
- but WITHOUT ANY WARRANTY; without even the implied warranty of
- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
- Lesser General Public License for more details.
-
- You should have received a copy of the GNU Lesser General Public
- License along with the GNU C Library; if not, see
- <https://www.gnu.org/licenses/>. */
-
-#define NO_MATH_REDIRECT
-#include <math.h>
-#include <libm-alias-double.h>
-#include <fpu_control.h>
-
-double
-__fmaximum (double x, double y)
-{
- int x_cond;
- int y_cond;
- asm volatile ("fclass.d \t%0, %1" : "=f" (x_cond) : "f" (x));
- asm volatile ("fclass.d \t%0, %1" : "=f" (y_cond) : "f" (y));
-
- if (__glibc_unlikely((x_cond | y_cond) & _FCLASS_NAN))
- return x * y;
- else
- {
- asm volatile ("fmax.d \t%0, %1, %2" : "=f" (x) : "f" (x), "f" (y));
- return x;
- }
-}
-libm_alias_double (__fmaximum, fmaximum)
diff --git a/sysdeps/loongarch/fpu/s_fmaximum_template.c b/sysdeps/loongarch/fpu/s_fmaximum_template.c
new file mode 100644
index 0000000000..701850ea73
--- /dev/null
+++ b/sysdeps/loongarch/fpu/s_fmaximum_template.c
@@ -0,0 +1,39 @@
+/* Return maximum of X and Y. LoongArch version.
+ Copyright (C) 2025 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <https://www.gnu.org/licenses/>. */
+
+#ifndef INSN_FMT
+#include_next <s_fmaximum_template.c>
+#else
+
+#include <math.h>
+
+FLOAT
+M_DECL_FUNC (__fmaximum) (FLOAT x, FLOAT y)
+{
+ FLOAT a, b;
+ asm("fcmp.cor." INSN_FMT "\t$fcc0, %2, %2\n\t"
+ "fcmp.cor." INSN_FMT "\t$fcc1, %3, %3\n\t"
+ "fsel" "\t%0, %2, %3, $fcc0\n\t"
+ "fsel" "\t%1, %3, %2, $fcc1\n\t"
+ "fmax." INSN_FMT "\t%1, %0, %1"
+ : "=&f" (a), "=f" (b) : "f" (x), "f" (y) : "fcc0", "fcc1");
+ return b;
+}
+declare_mgen_alias (__fmaximum, fmaximum);
+
+#endif
diff --git a/sysdeps/loongarch/fpu/s_fmaximumf.c b/sysdeps/loongarch/fpu/s_fmaximumf.c
deleted file mode 100644
index a518ccf348..0000000000
--- a/sysdeps/loongarch/fpu/s_fmaximumf.c
+++ /dev/null
@@ -1,40 +0,0 @@
-/* fmaximumf(). LoongArch version.
- Copyright (C) 2022-2025 Free Software Foundation, Inc.
- This file is part of the GNU C Library.
-
- The GNU C Library is free software; you can redistribute it and/or
- modify it under the terms of the GNU Lesser General Public
- License as published by the Free Software Foundation; either
- version 2.1 of the License, or (at your option) any later version.
-
- The GNU C Library is distributed in the hope that it will be useful,
- but WITHOUT ANY WARRANTY; without even the implied warranty of
- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
- Lesser General Public License for more details.
-
- You should have received a copy of the GNU Lesser General Public
- License along with the GNU C Library; if not, see
- <https://www.gnu.org/licenses/>. */
-
-#define NO_MATH_REDIRECT
-#include <math.h>
-#include <libm-alias-float.h>
-#include <fpu_control.h>
-
-float
-__fmaximumf (float x, float y)
-{
- int x_cond;
- int y_cond;
- asm volatile ("fclass.s \t%0, %1" : "=f" (x_cond) : "f" (x));
- asm volatile ("fclass.s \t%0, %1" : "=f" (y_cond) : "f" (y));
-
- if (__glibc_unlikely((x_cond | y_cond) & _FCLASS_NAN))
- return x * y;
- else
- {
- asm volatile ("fmax.s \t%0, %1, %2" : "=f" (x) : "f" (x), "f" (y));
- return x;
- }
-}
-libm_alias_float (__fmaximum, fmaximum)
diff --git a/sysdeps/loongarch/fpu/s_fminimum.c b/sysdeps/loongarch/fpu/s_fminimum.c
deleted file mode 100644
index a63c357957..0000000000
--- a/sysdeps/loongarch/fpu/s_fminimum.c
+++ /dev/null
@@ -1,40 +0,0 @@
-/* fminimum(). LoongArch version.
- Copyright (C) 2022-2025 Free Software Foundation, Inc.
- This file is part of the GNU C Library.
-
- The GNU C Library is free software; you can redistribute it and/or
- modify it under the terms of the GNU Lesser General Public
- License as published by the Free Software Foundation; either
- version 2.1 of the License, or (at your option) any later version.
-
- The GNU C Library is distributed in the hope that it will be useful,
- but WITHOUT ANY WARRANTY; without even the implied warranty of
- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
- Lesser General Public License for more details.
-
- You should have received a copy of the GNU Lesser General Public
- License along with the GNU C Library; if not, see
- <https://www.gnu.org/licenses/>. */
-
-#define NO_MATH_REDIRECT
-#include <math.h>
-#include <libm-alias-double.h>
-#include <fpu_control.h>
-
-double
-__fminimum (double x, double y)
-{
- int x_cond;
- int y_cond;
- asm volatile ("fclass.d \t%0, %1" : "=f" (x_cond) : "f" (x));
- asm volatile ("fclass.d \t%0, %1" : "=f" (y_cond) : "f" (y));
-
- if (__glibc_unlikely((x_cond | y_cond) & _FCLASS_NAN))
- return x * y;
- else
- {
- asm volatile ("fmin.d \t%0, %1, %2" : "=f" (x) : "f" (x), "f" (y));
- return x;
- }
-}
-libm_alias_double (__fminimum, fminimum)
diff --git a/sysdeps/loongarch/fpu/s_fminimum_template.c b/sysdeps/loongarch/fpu/s_fminimum_template.c
new file mode 100644
index 0000000000..80db72ee3c
--- /dev/null
+++ b/sysdeps/loongarch/fpu/s_fminimum_template.c
@@ -0,0 +1,39 @@
+/* Return minimum of X and Y. LoongArch version.
+ Copyright (C) 2025 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <https://www.gnu.org/licenses/>. */
+
+#ifndef INSN_FMT
+#include_next <s_fminimum_template.c>
+#else
+
+#include <math.h>
+
+FLOAT
+M_DECL_FUNC (__fminimum) (FLOAT x, FLOAT y)
+{
+ FLOAT a, b;
+ asm("fcmp.cor." INSN_FMT "\t$fcc0, %2, %2\n\t"
+ "fcmp.cor." INSN_FMT "\t$fcc1, %3, %3\n\t"
+ "fsel" "\t%0, %2, %3, $fcc0\n\t"
+ "fsel" "\t%1, %3, %2, $fcc1\n\t"
+ "fmin." INSN_FMT "\t%1, %0, %1"
+ : "=&f" (a), "=f" (b) : "f" (x), "f" (y) : "fcc0", "fcc1");
+ return b;
+}
+declare_mgen_alias (__fminimum, fminimum);
+
+#endif
diff --git a/sysdeps/loongarch/fpu/s_fminimumf.c b/sysdeps/loongarch/fpu/s_fminimumf.c
deleted file mode 100644
index 973a9f75d1..0000000000
--- a/sysdeps/loongarch/fpu/s_fminimumf.c
+++ /dev/null
@@ -1,40 +0,0 @@
-/* fminimumf(). LoongArch version.
- Copyright (C) 2022-2025 Free Software Foundation, Inc.
- This file is part of the GNU C Library.
-
- The GNU C Library is free software; you can redistribute it and/or
- modify it under the terms of the GNU Lesser General Public
- License as published by the Free Software Foundation; either
- version 2.1 of the License, or (at your option) any later version.
-
- The GNU C Library is distributed in the hope that it will be useful,
- but WITHOUT ANY WARRANTY; without even the implied warranty of
- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
- Lesser General Public License for more details.
-
- You should have received a copy of the GNU Lesser General Public
- License along with the GNU C Library; if not, see
- <https://www.gnu.org/licenses/>. */
-
-#define NO_MATH_REDIRECT
-#include <math.h>
-#include <libm-alias-float.h>
-#include <fpu_control.h>
-
-float
-__fminimumf (float x, float y)
-{
- int x_cond;
- int y_cond;
- asm volatile ("fclass.s \t%0, %1" : "=f" (x_cond) : "f" (x));
- asm volatile ("fclass.s \t%0, %1" : "=f" (y_cond) : "f" (y));
-
- if (__glibc_unlikely((x_cond | y_cond) & _FCLASS_NAN))
- return x * y;
- else
- {
- asm volatile ("fmin.s \t%0, %1, %2" : "=f" (x) : "f" (x), "f" (y));
- return x;
- }
-}
-libm_alias_float (__fminimum, fminimum)
--
2.48.1
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