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