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LoongArch: Optimize f{max,min}imum{,f}
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>
This commit is contained in:
Xi Ruoyao
caiyinyu
parent
0f044be1da
commit
0195552e15
4 changed files with 48 additions and 88 deletions
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/* fmaximum(). LoongArch version.
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Copyright (C) 2022-2025 Free Software Foundation, Inc.
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/* Helper macros for double variants of type generic functions of libm,
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LoongArch version.
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Copyright (C) 2025 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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@ -16,25 +17,5 @@
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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#define NO_MATH_REDIRECT
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#include <math.h>
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#include <libm-alias-double.h>
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#include <fpu_control.h>
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double
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__fmaximum (double x, double y)
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{
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int x_cond;
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int y_cond;
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asm volatile ("fclass.d \t%0, %1" : "=f" (x_cond) : "f" (x));
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asm volatile ("fclass.d \t%0, %1" : "=f" (y_cond) : "f" (y));
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if (__glibc_unlikely((x_cond | y_cond) & _FCLASS_NAN))
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return x * y;
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else
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{
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asm volatile ("fmax.d \t%0, %1, %2" : "=f" (x) : "f" (x), "f" (y));
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return x;
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}
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}
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libm_alias_double (__fmaximum, fmaximum)
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#include_next <math-type-macros-double.h>
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#define INSN_FMT "d"
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@ -1,5 +1,6 @@
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/* fminimum(). LoongArch version.
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Copyright (C) 2022-2025 Free Software Foundation, Inc.
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/* Helper macros for float variants of type generic functions of libm,
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LoongArch version.
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Copyright (C) 2025 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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@ -16,25 +17,5 @@
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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#define NO_MATH_REDIRECT
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#include <math.h>
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#include <libm-alias-double.h>
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#include <fpu_control.h>
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double
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__fminimum (double x, double y)
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{
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int x_cond;
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int y_cond;
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asm volatile ("fclass.d \t%0, %1" : "=f" (x_cond) : "f" (x));
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asm volatile ("fclass.d \t%0, %1" : "=f" (y_cond) : "f" (y));
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if (__glibc_unlikely((x_cond | y_cond) & _FCLASS_NAN))
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return x * y;
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else
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{
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asm volatile ("fmin.d \t%0, %1, %2" : "=f" (x) : "f" (x), "f" (y));
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return x;
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}
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}
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libm_alias_double (__fminimum, fminimum)
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#include_next <math-type-macros-float.h>
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#define INSN_FMT "s"
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@ -1,5 +1,5 @@
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/* fmaximumf(). LoongArch version.
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Copyright (C) 2022-2025 Free Software Foundation, Inc.
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/* Return maximum of X and Y. LoongArch version.
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Copyright (C) 2025 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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@ -16,25 +16,24 @@
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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#define NO_MATH_REDIRECT
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#ifndef INSN_FMT
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#include_next <s_fmaximum_template.c>
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#else
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#include <math.h>
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#include <libm-alias-float.h>
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#include <fpu_control.h>
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float
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__fmaximumf (float x, float y)
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FLOAT
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M_DECL_FUNC (__fmaximum) (FLOAT x, FLOAT y)
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{
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int x_cond;
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int y_cond;
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asm volatile ("fclass.s \t%0, %1" : "=f" (x_cond) : "f" (x));
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asm volatile ("fclass.s \t%0, %1" : "=f" (y_cond) : "f" (y));
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if (__glibc_unlikely((x_cond | y_cond) & _FCLASS_NAN))
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return x * y;
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else
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{
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asm volatile ("fmax.s \t%0, %1, %2" : "=f" (x) : "f" (x), "f" (y));
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return x;
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}
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FLOAT a, b;
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asm("fcmp.cor." INSN_FMT "\t$fcc0, %2, %2\n\t"
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"fcmp.cor." INSN_FMT "\t$fcc1, %3, %3\n\t"
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"fsel" "\t%0, %2, %3, $fcc0\n\t"
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"fsel" "\t%1, %3, %2, $fcc1\n\t"
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"fmax." INSN_FMT "\t%1, %0, %1"
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: "=&f" (a), "=f" (b) : "f" (x), "f" (y) : "fcc0", "fcc1");
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return b;
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}
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libm_alias_float (__fmaximum, fmaximum)
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declare_mgen_alias (__fmaximum, fmaximum);
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#endif
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@ -1,5 +1,5 @@
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/* fminimumf(). LoongArch version.
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Copyright (C) 2022-2025 Free Software Foundation, Inc.
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/* Return minimum of X and Y. LoongArch version.
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Copyright (C) 2025 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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@ -16,25 +16,24 @@
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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#define NO_MATH_REDIRECT
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#ifndef INSN_FMT
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#include_next <s_fminimum_template.c>
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#else
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#include <math.h>
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#include <libm-alias-float.h>
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#include <fpu_control.h>
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float
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__fminimumf (float x, float y)
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FLOAT
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M_DECL_FUNC (__fminimum) (FLOAT x, FLOAT y)
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{
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int x_cond;
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int y_cond;
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asm volatile ("fclass.s \t%0, %1" : "=f" (x_cond) : "f" (x));
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asm volatile ("fclass.s \t%0, %1" : "=f" (y_cond) : "f" (y));
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if (__glibc_unlikely((x_cond | y_cond) & _FCLASS_NAN))
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return x * y;
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else
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{
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asm volatile ("fmin.s \t%0, %1, %2" : "=f" (x) : "f" (x), "f" (y));
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return x;
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}
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FLOAT a, b;
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asm("fcmp.cor." INSN_FMT "\t$fcc0, %2, %2\n\t"
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"fcmp.cor." INSN_FMT "\t$fcc1, %3, %3\n\t"
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"fsel" "\t%0, %2, %3, $fcc0\n\t"
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"fsel" "\t%1, %3, %2, $fcc1\n\t"
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"fmin." INSN_FMT "\t%1, %0, %1"
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: "=&f" (a), "=f" (b) : "f" (x), "f" (y) : "fcc0", "fcc1");
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return b;
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}
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libm_alias_float (__fminimum, fminimum)
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declare_mgen_alias (__fminimum, fminimum);
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#endif
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