If built with -ffast-math, clang replaces the call to pow(2, x) with
exp2(x) directly, making the implementation of exp2() an infinite
recursion. This can be either avoided by building these object files
with -fno-builtin, -fno-builtin-pow, or by implementing the function
in assembly.
For aarch64, the same already happens even without -ffast-math,
and due to that, the aarch64 exp2 function wrapper already is
implemented in assembly.
While building with -ffast-math can break certain math routines and
thus can be considered a self-inflicted issue, it's safest to avoid
constructs that potentially can be optimized into an infinite self
recursion.
Signed-off-by: Martin Storsjö <mar...@martin.st>
---
mingw-w64-crt/Makefile.am | 3 +-
mingw-w64-crt/math/arm/exp2.S | 19 ++++++++++
mingw-w64-crt/math/arm/exp2.c | 64 ----------------------------------
mingw-w64-crt/math/arm/exp2f.S | 16 +++++++++
4 files changed, 37 insertions(+), 65 deletions(-)
create mode 100644 mingw-w64-crt/math/arm/exp2.S
delete mode 100644 mingw-w64-crt/math/arm/exp2.c
create mode 100644 mingw-w64-crt/math/arm/exp2f.S
diff --git a/mingw-w64-crt/Makefile.am b/mingw-w64-crt/Makefile.am
index 7b1b7433d..3feaa447b 100644
--- a/mingw-w64-crt/Makefile.am
+++ b/mingw-w64-crt/Makefile.am
@@ -276,7 +276,8 @@ src_msvcrtarm32=\
if !ENABLE_SOFTMATH
src_msvcrtarm32+=\
- math/arm/exp2.c \
+ math/arm/exp2.S \
+ math/arm/exp2f.S \
math/arm/nearbyint.S \
math/arm/nearbyintf.S \
math/arm/nearbyintl.S \
diff --git a/mingw-w64-crt/math/arm/exp2.S b/mingw-w64-crt/math/arm/exp2.S
new file mode 100644
index 000000000..6918ce19d
--- /dev/null
+++ b/mingw-w64-crt/math/arm/exp2.S
@@ -0,0 +1,19 @@
+/**
+ * This file has no copyright assigned and is placed in the Public Domain.
+ * This file is part of the mingw-w64 runtime package.
+ * No warranty is given; refer to the file DISCLAIMER.PD within this package.
+ */
+#include <_mingw_mac.h>
+
+ .file "exp2.S"
+ .text
+ .align 2
+ .globl __MINGW_USYMBOL(exp2)
+ .globl __MINGW_USYMBOL(exp2l)
+ .def __MINGW_USYMBOL(exp2); .scl 2; .type 32; .endef
+ .def __MINGW_USYMBOL(exp2l); .scl 2; .type 32; .endef
+__MINGW_USYMBOL(exp2):
+__MINGW_USYMBOL(exp2l):
+ vmov.f64 d1, d0
+ vmov.f64 d0, #2.0
+ b pow
diff --git a/mingw-w64-crt/math/arm/exp2.c b/mingw-w64-crt/math/arm/exp2.c
deleted file mode 100644
index 77e914d98..000000000
--- a/mingw-w64-crt/math/arm/exp2.c
+++ /dev/null
@@ -1,64 +0,0 @@
-/*
- This Software is provided under the Zope Public License (ZPL) Version 2.1.
-
- Copyright (c) 2014 by the mingw-w64 project
-
- See the AUTHORS file for the list of contributors to the mingw-w64 project.
-
- This license has been certified as open source. It has also been designated
- as GPL compatible by the Free Software Foundation (FSF).
-
- Redistribution and use in source and binary forms, with or without
- modification, are permitted provided that the following conditions are met:
-
- 1. Redistributions in source code must retain the accompanying copyright
- notice, this list of conditions, and the following disclaimer.
- 2. Redistributions in binary form must reproduce the accompanying
- copyright notice, this list of conditions, and the following disclaimer
- in the documentation and/or other materials provided with the
- distribution.
- 3. Names of the copyright holders must not be used to endorse or promote
- products derived from this software without prior written permission
- from the copyright holders.
- 4. The right to distribute this software or to use it for any purpose does
- not give you the right to use Servicemarks (sm) or Trademarks (tm) of
- the copyright holders. Use of them is covered by separate agreement
- with the copyright holders.
- 5. If any files are modified, you must cause the modified files to carry
- prominent notices stating that you changed the files and the date of
- any change.
-
- Disclaimer
-
- THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS ``AS IS'' AND ANY EXPRESSED
- OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
- OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
- EVENT SHALL THE COPYRIGHT HOLDERS BE LIABLE FOR ANY DIRECT, INDIRECT,
- INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
- LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA,
- OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
- LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
- NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
- EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
-*/
-
-#include <math.h>
-
-double exp2(double x)
-{
- return pow(2, x);
-}
-
-float exp2f(float x)
-{
- return powf(2, x);
-}
-
-long double exp2l(long double x)
-{
-#if defined(__arm__) || defined(_ARM_)
- return exp2(x);
-#else
-#error Not supported on your platform yet
-#endif
-}
diff --git a/mingw-w64-crt/math/arm/exp2f.S b/mingw-w64-crt/math/arm/exp2f.S
new file mode 100644
index 000000000..452cd9a95
--- /dev/null
+++ b/mingw-w64-crt/math/arm/exp2f.S
@@ -0,0 +1,16 @@
+/**
+ * This file has no copyright assigned and is placed in the Public Domain.
+ * This file is part of the mingw-w64 runtime package.
+ * No warranty is given; refer to the file DISCLAIMER.PD within this package.
+ */
+#include <_mingw_mac.h>
+
+ .file "exp2f.S"
+ .text
+ .align 2
+ .globl __MINGW_USYMBOL(exp2f)
+ .def __MINGW_USYMBOL(exp2f); .scl 2; .type 32; .endef
+__MINGW_USYMBOL(exp2f):
+ vmov s1, s0
+ vmov.f32 s0, #2.0
+ b powf
--
2.17.1
_______________________________________________
Mingw-w64-public mailing list
Mingw-w64-public@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/mingw-w64-public
