https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109973
--- Comment #4 from Benji Smith <benjsith at gmail dot com> --- Just as follow-up, I also tested the same code with _mm_and_si128/_mm_testc_si128 on SSE4.1, and the same issue repros (via `gcc -O1 -msse4.1`): #include <immintrin.h> int do_stuff(__m128i Y0, __m128i Y1, __m128i X2) { __m128i And01 = _mm_and_si128(Y0, Y1); int TestResult = _mm_testc_si128(And01, And01); return TestResult; }