On Tue, Jun 23, 2020 at 06:51:20AM -0400, Bryan Steele wrote: > On Mon, Jun 22, 2020 at 11:10:10PM -0700, [email protected] wrote: > > Are SSE instructions allowed in the AMD64 kernel? Is #ifdef __SSE__ > > a sufficient guard? > > > > I have a rasops32 putchar with SSE that is 2x faster. > > No, in general you cannot using FP instructions in the kernel, also the > kernel is often compiled with -msoft-float on platforms that support it.
Exceptions are being made for amdgpu drm, where some of the files are compiled with sse enabled, though the code is guarded with fpu_kernel_enter(). DC_FP_START() and DC_FP_END() to be precise, which are macros pointing to the kernel functions.
