https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106195
Bug ID: 106195
Summary: RFE: Split -msse into -msse and -fenable-intrinsics
Product: gcc
Version: 12.1.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: jengelh at inai dot de
Target Milestone: ---
Some libraries may use cpuid to runtime-test for SSE availability, yet their
authors may, intentionally or not, cause a profound lack of #ifdef __SSE__
guards around sections that do use _mm_* functions. The problem is not tied to
SSE specifically; any CPU extension may be affected. Consider this source code:
#include <string>
#include <cpuid.h>
#include <xmmintrin.h>
struct ADLConfig {
int cc=6,eid=0,bank=14,vol=0,pcm=0,pan=1,ban2k=false;
std::string cbank;
};
ADLConfig adlConfig; // generates MOVAPS under -O2 -msse
int main()
{
long x=0,a=0,b=0,c=0,d=0;
__cpuid(x,a,b,c,d);
if (x) {
__m128 a,b;
_mm_add_ss(a,b);
} else {
// <non-SIMD variant>
}
}
Without -msse, compilation of the snippet fails.
With -msse, the program builds but then won't run on SSE-less CPUs, because SSE
is emitted in a place where it's undesired - basically the only places where it
*is* desired is the _mm calls. There should be a better option than to find and
edit all _mm callsites and add #ifdef __SSE__.
If only I could tell the compiler "-mno-sse -fenable-sse-intrinsics" or so..
