[hjl@gnu-cfl-2 tmp]$ cat x.c #include <stdlib.h> [hjl@gnu-cfl-2 tmp]$ gcc -S -mno-sse x.c [hjl@gnu-cfl-2 tmp]$ gcc -S -mno-sse x.c -O In file included from /usr/include/stdlib.h:1014, from x.c:1: /usr/include/bits/stdlib-float.h: In function ‘atof’: /usr/include/bits/stdlib-float.h:26:1: error: SSE register return with SSE disabled 26 | { | ^ [hjl@gnu-cfl-2 tmp]$
Does -mno-sse actually make sense with x86-64 as SSE is a required part of the ABI? I think this is a GCC bug.
GCC bug: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99652
Fixed for GCC 11.