Lines Matching refs:VFP

6 * Use only NEON instructions, or VFP instructions that don't rely on support
18 It is possible to use NEON instructions (and in some cases, VFP instructions) in
19 code that runs in kernel mode. However, for performance reasons, the NEON/VFP
23 may call schedule()], as NEON or VFP instructions will be executed in a
29 The NEON/VFP register file is managed using lazy preserve (on UP systems) and
32 contending for the NEON/VFP unit (or, in the SMP case, when a task migrates to
33 another core). Lazy restore is implemented by disabling the NEON/VFP unit after
34 every context switch, resulting in a trap when subsequently a NEON/VFP
38 Any use of the NEON/VFP unit in kernel mode should not interfere with this, so
39 it is required to do an 'eager' preserve of the NEON/VFP register file, and
40 enable the NEON/VFP unit explicitly so no exceptions are generated on first
42 should be called before any kernel mode NEON or VFP instructions are issued.
43 Likewise, the NEON/VFP unit should be disabled again after use to make sure user
51 preserve/restore mechanism for the kernel mode NEON/VFP register contents. This
53 they are guaranteed not to touch the NEON/VFP registers. For this reason, the
55 * NEON/VFP code is not allowed in interrupt context;
56 * NEON/VFP code is not allowed to sleep;
57 * NEON/VFP code is executed with preemption disabled.
65 VFP and support code
67 Earlier versions of VFP (prior to version 3) rely on software support for things
68 like IEEE-754 compliant underflow handling etc. When the VFP unit needs such
70 exception. The kernel responds by inspecting the VFP control registers and the
73 Such software assistance is currently not implemented for VFP instructions
81 kernel_neon_end(), i.e., that it is only allowed to issue NEON/VFP instructions
84 kernel is currently compiled at -O2, future changes may result in NEON/VFP
87 Therefore, the recommended and only supported way of using NEON/VFP in the
96 both NEON and VFP instructions will only ever appear in designated compilation