From bd0a28d1e41171a5361292e52c745bc8e48d3dde Mon Sep 17 00:00:00 2001
From: Colin Finck
Date: Fri, 1 Mar 2019 17:49:03 +0100
Subject: [PATCH] Fix the MSVC version of ldexp filling up the FPU stack and
bailing out with #IND after a few calls. Additionally, add it back to
libcntpr.
MSVC was previously given a "result" variable to copy the fscale result from st(0). This led to another "fld" FPU stack push at the very end without popping the source value from the FPU stack.
Moreover, this copy isn't even needed: A simple "fstp st(1)" at the end pops an element from the FPU stack while effectively storing the result in st(0), the register used for returning a double value.
This problem didn't affect GCC, as it is only given the "fscale" instruction and does all necessary stack operations itself.
However, looking into the CRT sources, I found many other i386 implementations with inline assembly suffering from the same problem.
Fortunately, they have been replaced by pure assembly implementations a while ago, so it's time to finally remove them.
ldexp would have also been a candidate for a pure assembly implementation, but the required check for NaN and setting errno (verified on Win2003) already outweighs the benefits.
And we cannot just do a NaN check with FUCOMI as this is an i686/pentiumpro instruction while we're still targeting i586/pentium.
I'm also using this opportunity to clean up the ldexp.c header and only put in the remaining contributors as returned by "git blame".
Thanks to NightWolve1975 for reporting the problem! (https://twitter.com/nightwolve1975/status/1099042477531643912)

sdk/lib/crt/libcntpr.cmake  3 +
sdk/lib/crt/math/i386/atan2.c  27 
sdk/lib/crt/math/i386/exp.c  64 
sdk/lib/crt/math/i386/fmod.c  49 
sdk/lib/crt/math/i386/fmodf.c  28 
sdk/lib/crt/math/i386/ldexp.c  45 ++++++++++
6 files changed, 19 insertions(+), 197 deletions()
delete mode 100644 sdk/lib/crt/math/i386/atan2.c
delete mode 100644 sdk/lib/crt/math/i386/exp.c
delete mode 100644 sdk/lib/crt/math/i386/fmod.c
delete mode 100644 sdk/lib/crt/math/i386/fmodf.c
diff git a/sdk/lib/crt/libcntpr.cmake b/sdk/lib/crt/libcntpr.cmake
index 8014bd370ec..aa3b1d4fa67 100644
 a/sdk/lib/crt/libcntpr.cmake
+++ b/sdk/lib/crt/libcntpr.cmake
@@ 105,7 +105,8 @@ if(ARCH STREQUAL "i386")
math/i386/cilog.c
math/i386/cipow.c
math/i386/cisin.c
 math/i386/cisqrt.c)
+ math/i386/cisqrt.c
+ math/i386/ldexp.c)
if(NOT MSVC)
list(APPEND LIBCNTPR_SOURCE except/i386/chkstk_ms.s)
endif()
diff git a/sdk/lib/crt/math/i386/atan2.c b/sdk/lib/crt/math/i386/atan2.c
deleted file mode 100644
index 7b7ebac8a22..00000000000
 a/sdk/lib/crt/math/i386/atan2.c
+++ /dev/null
@@ 1,27 +0,0 @@

#include

double atan2 (double __y, double __x);

/*
 * @implemented
 */
double atan2 (double __y, double __x)
{
 register double __val;
#ifdef __GNUC__
 __asm __volatile__
 ("fpatan\n\t"
 "fld %%st(0)"
 : "=t" (__val) : "0" (__x), "u" (__y));
#else
 __asm
 {
 fld __y
 fld __x
 fpatan
 fstp __val
 }
#endif /*__GNUC__*/
 return __val;
}
diff git a/sdk/lib/crt/math/i386/exp.c b/sdk/lib/crt/math/i386/exp.c
deleted file mode 100644
index 727a1cb5419..00000000000
 a/sdk/lib/crt/math/i386/exp.c
+++ /dev/null
@@ 1,64 +0,0 @@
/* Math functions for i387.
 Copyright (C) 1995, 1996, 1997 Free Software Foundation, Inc.
 This file is part of the GNU C Library.
 Contributed by John C. Bowman , 1995.

 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, write to the Free
 Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
 Boston, MA 021101301, USA.
*/

#include

double exp (double __x);

double exp (double __x)
{
#ifdef __GNUC__
 register double __value, __exponent;
 __asm __volatile__
 ("fldl2e # e^x = 2^(x * log2(e))\n\t"
 "fmul %%st(1) # x * log2(e)\n\t"
 "fst %%st(1)\n\t"
 "frndint # int(x * log2(e))\n\t"
 "fxch\n\t"
 "fsub %%st(1) # fract(x * log2(e))\n\t"
 "f2xm1 # 2^(fract(x * log2(e)))  1\n\t"
 : "=t" (__value), "=u" (__exponent) : "0" (__x));
 __value += 1.0;
 __asm __volatile__
 ("fscale"
 : "=t" (__value) : "0" (__value), "u" (__exponent));

 return __value;
#else
 register double __val;
 __asm
 {
 fld1 // store 1.0 for later use
 fld __x
 fldl2e // e^x = 2^(x * log2(e))
 fmul st,st(1) // x * log2(e)
 fld st(0)
 frndint // int(x * log2(e))
 fsub st,st(1) // fract(x * log2(e))
 fxch
 f2xm1 // 2^(fract(x * log2(e)))  1
 fadd st,st(3) // + 1.0
 fscale
 fstp __val
 }
 return __val;
#endif /*__GNUC__*/
}
diff git a/sdk/lib/crt/math/i386/fmod.c b/sdk/lib/crt/math/i386/fmod.c
deleted file mode 100644
index fe74aa5e4d1..00000000000
 a/sdk/lib/crt/math/i386/fmod.c
+++ /dev/null
@@ 1,49 +0,0 @@
/* Math functions for i387.
 Copyright (C) 1995, 1996, 1997 Free Software Foundation, Inc.
 This file is part of the GNU C Library.
 Contributed by John C. Bowman , 1995.

 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, write to the Free
 Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
 Boston, MA 021101301, USA.
*/

#include

double fmod (double __x, double __y);

double fmod (double __x, double __y)
{
 register double __val;
#ifdef __GNUC__
 __asm __volatile__
 ("1: fprem\n\t"
 "fstsw %%ax\n\t"
 "sahf\n\t"
 "jp 1b"
 : "=t" (__val) : "0" (__x), "u" (__y) : "ax", "cc");
#else
 __asm
 {
 fld __y
 fld __x
L1: fprem1
 fstsw ax
 sahf
 jp L1
 fstp __val
 }
#endif /*__GNUC__*/
 return __val;
}
diff git a/sdk/lib/crt/math/i386/fmodf.c b/sdk/lib/crt/math/i386/fmodf.c
deleted file mode 100644
index 761f56c043e..00000000000
 a/sdk/lib/crt/math/i386/fmodf.c
+++ /dev/null
@@ 1,28 +0,0 @@
/**
 * This file has no copyright assigned and is placed in the Public Domain.
 * This file is part of the w64 mingwruntime package.
 * No warranty is given; refer to the file DISCLAIMER.PD within this package.
 */
/*
 * Written by J.T. Conklin .
 * Public domain.
 *
 * Adapted for float type by Danny Smith
 * .
 */

#include

float
fmodf (float x, float y)
{
 float res = 0.0F;

 asm ("1:\tfprem\n\t"
 "fstsw %%ax\n\t"
 "sahf\n\t"
 "jp 1b\n\t"
 "fstp %%st(1)"
 : "=t" (res) : "0" (x), "u" (y) : "ax", "st(1)");
 return res;
}
diff git a/sdk/lib/crt/math/i386/ldexp.c b/sdk/lib/crt/math/i386/ldexp.c
index 48cbc751d6c..73d3e927724 100644
 a/sdk/lib/crt/math/i386/ldexp.c
+++ b/sdk/lib/crt/math/i386/ldexp.c
@@ 1,33 +1,18 @@
/* Math functions for i387.
 Copyright (C) 1995, 1996, 1997 Free Software Foundation, Inc.
 This file is part of the GNU C Library.
 Contributed by John C. Bowman , 1995.

 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, write to the Free
 Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
 Boston, MA 021101301, USA.
*/
+/*
+ * PROJECT: ReactOS CRT
+ * LICENSE: LGPL2.1orlater (https://spdx.org/licenses/LGPL2.1orlater)
+ * PURPOSE: Implements the ldexp CRT function for IA32 with Windowscompatible error codes.
+ * COPYRIGHT: Copyright 2010 Timo Kreuzer (timo.kreuzer@reactos.org)
+ * Copyright 2011 Pierre Schweitzer (pierre@reactos.org)
+ * Copyright 2019 Colin Finck (colin@reactos.org)
+ */
#include
#include
#include
double ldexp (double value, int exp)
{
+#ifdef __GNUC__
register double result;
#ifndef __GNUC__
 register double __dy = (double)exp;
#endif
/* Check for value correctness
@@ 43,15 +28,19 @@ double ldexp (double value, int exp)
: "=t" (result)
: "0" (value), "u" ((double)exp)
: "1");
+ return result;
#else /* !__GNUC__ */
__asm
{
 fld __dy
+ fild exp
fld value
fscale
 fstp result
+ fstp st(1)
}
+
+ /* "fstp st(1)" has copied st(0) to st(1), then popped the FPU stack,
+ * so that the value is again in st(0) now. Effectively, we have reduced
+ * the FPU stack by one element while preserving st(0).
+ * st(0) is also the register used for returning a double value. */
#endif /* !__GNUC__ */
 return result;
}


2.17.1