http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57202
Bug #: 57202
Summary: Please make the intrinsics headers like immintrin.h be
usable without compiler flags
Classification: Unclassified
Product: gcc
Version: 4.8.1
Status: UNCONFIRMED
Severity: enhancement
Priority: P3
Component: other
AssignedTo: unassig...@gcc.gnu.org
ReportedBy: thi...@kde.org
Please make all headers for intrinsics be includable without special compiler
flags.
In other words, I want the following to work:
$ gcc -fsyntax-only -include smmintrin.h -xc /dev/null
In file included from <command-line>:0:0:
/usr/lib/gcc/x86_64-redhat-linux/4.7.2/include/smmintrin.h:31:3: error: #error
"SSE4.1 instruction set not enabled"
Note it works with ICC:
$ icc -fsyntax-only -include smmintrin.h -xc /dev/null && echo works
works
Not only that, please make all the intrinsics functions be defined and ready to
be used.
This is necessary so that the following source file could compile even if
-msse4.1 is not passed on the command-line (adapted from
http://gcc.gnu.org/gcc-4.8/changes.html):
#include <smmintrin.h>
__attribute__ ((target ("default")))
int foo(void)
{
return 1;
}
__attribute__ ((target ("sse4.2")))
int foo(void)
{
__m128i v;
_mm_blendv_epi8(v, v, v);
return 2;
}
There are several reasons for that, number one among them that it makes the GCC
4.8 feature above actually useful for non-trivial code. Also, passing extra
options on the command-line are simply not an option for C++ code (where the
feature above is useful) if that code is moderately complex and uses inline
functions, and those options cannot be used if LTO is to be used (bug 54231).
