https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90810
Bug ID: 90810
Summary: Different intrinsics behavior on G++ 7.4 and G++ 8.3
Product: gcc
Version: 8.3.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: ra22341 at ya dot ru
Target Milestone: ---
Created attachment 46470
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=46470&action=edit
Preprocessed files from two G++ compilers of a same code
Hello! Sorry for formatting (it's my first report) and my English (i'm not a
native speaker). Please let me know if i can provide more information.
Following code with simple intrinsics stuff works differently on G++ 7.4
(correct output) and G++ 8.3 (incorrect output)
b.cpp:
#include <iostream>
#include <xmmintrin.h>
void foo(const float num, const float denom)
{
// typedef __v4sf Vec4;
typedef __m128 Vec4;
const Vec4 num4 = {
num,
num,
num,
num,
};
const Vec4 denom4 = {
denom,
denom,
denom,
denom,
};
float res_arr[] = {0, 0, 0, 0};
Vec4 *res = (Vec4*)res_arr;
*res = num4 / denom4;
std::cout << res_arr[0] << std::endl;
std::cout << res_arr[1] << std::endl;
std::cout << res_arr[2] << std::endl;
std::cout << res_arr[3] << std::endl;
}
b.h:
#ifndef B_H
#define B_H
void foo(const float num, const float denom);
#endif
a.cpp:
#include "b.h"
int main (void)
{
const float denominator = 1.0f;
const float numerator = 12.0f;
foo(numerator, denominator);
return 0;
}
Commands to reproduce
$ g++-7 -c -Wall -Wextra -O0 -save-temps b.cpp -o b.o && g++-7 -Wall -Wextra
-O0 -save-temps a.cpp b.o -o a.out && ./a.out
Output:
12
12
12
12
$ g++-8 -c -Wall -Wextra -O0 -save-temps b.cpp -o b.o && g++-8 -Wall -Wextra
-O0 -save-temps a.cpp b.o -o a.out && ./a.out
Output:
inf
inf
inf
inf
Putting everything in one file makes everything works well
G++-7 version
$ g++-7 -v
Using built-in specs.
COLLECT_GCC=g++-7
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/7/lto-wrapper
OFFLOAD_TARGET_NAMES=nvptx-none
OFFLOAD_TARGET_DEFAULT=1
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Ubuntu
7.4.0-1ubuntu1~18.10' --with-bugurl=file:///usr/share/doc/gcc-7/README.Bugs
--enable-languages=c,ada,c++,go,brig,d,fortran,objc,obj-c++ --prefix=/usr
--with-gcc-major-version-only --program-suffix=-7
--program-prefix=x86_64-linux-gnu- --enable-shared --enable-linker-build-id
--libexecdir=/usr/lib --without-included-gettext --enable-threads=posix
--libdir=/usr/lib --enable-nls --with-sysroot=/ --enable-clocale=gnu
--enable-libstdcxx-debug --enable-libstdcxx-time=yes
--with-default-libstdcxx-abi=new --enable-gnu-unique-object
--disable-vtable-verify --enable-libmpx --enable-plugin --enable-default-pie
--with-system-zlib --with-target-system-zlib --enable-objc-gc=auto
--enable-multiarch --disable-werror --with-arch-32=i686 --with-abi=m64
--with-multilib-list=m32,m64,mx32 --enable-multilib --with-tune=generic
--enable-offload-targets=nvptx-none --without-cuda-driver
--enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu
--target=x86_64-linux-gnu
Thread model: posix
gcc version 7.4.0 (Ubuntu 7.4.0-1ubuntu1~18.10)
G++-8 version
$ g++-8 -v
Using built-in specs.
COLLECT_GCC=g++-8
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/8/lto-wrapper
OFFLOAD_TARGET_NAMES=nvptx-none
OFFLOAD_TARGET_DEFAULT=1
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Ubuntu
8.3.0-6ubuntu1~18.10' --with-bugurl=file:///usr/share/doc/gcc-8/README.Bugs
--enable-languages=c,ada,c++,go,brig,d,fortran,objc,obj-c++ --prefix=/usr
--with-gcc-major-version-only --program-suffix=-8
--program-prefix=x86_64-linux-gnu- --enable-shared --enable-linker-build-id
--libexecdir=/usr/lib --without-included-gettext --enable-threads=posix
--libdir=/usr/lib --enable-nls --enable-bootstrap --enable-clocale=gnu
--enable-libstdcxx-debug --enable-libstdcxx-time=yes
--with-default-libstdcxx-abi=new --enable-gnu-unique-object
--disable-vtable-verify --enable-libmpx --enable-plugin --enable-default-pie
--with-system-zlib --with-target-system-zlib --enable-objc-gc=auto
--enable-multiarch --disable-werror --with-arch-32=i686 --with-abi=m64
--with-multilib-list=m32,m64,mx32 --enable-multilib --with-tune=generic
--enable-offload-targets=nvptx-none --without-cuda-driver
--enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu
--target=x86_64-linux-gnu
Thread model: posix
gcc version 8.3.0 (Ubuntu 8.3.0-6ubuntu1~18.10)
