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0195552e15
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>
40 lines
1.3 KiB
C
40 lines
1.3 KiB
C
/* 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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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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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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#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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FLOAT
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M_DECL_FUNC (__fmaximum) (FLOAT x, FLOAT y)
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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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declare_mgen_alias (__fmaximum, fmaximum);
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#endif
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