[BPF] Fix dst/val mismatch in class ATOMIC_NOFETCH #107288
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eddyz87 reviewed Sep 4, 2024
All ATOMIC_NOFETCH insns have "$dst = $val" constraints. So let us enforce "$dst = $val" having the same register type in ATOMIC_NOFETCH as well. Currently, things work since ATOMIC_NOFETCH does not have source code pattern matching. I am experimenting to introduce memory ordering to BPFInstrInfo.td file and pattern matching will be needed. Eventually, for atomic_fetch_*() insns locked insns could be generated if memory ordering is memory_order_relaxed. [1] https://lore.kernel.org/bpf/7b941f53-2a05-48ec-9032-8f106face3a3@linux.dev/
yonghong-song force-pushed the fix-atomic-nofetch branch from 3093e82 to 5db101f Compare eddyz87 approved these changes Sep 4, 2024
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All ATOMIC_NOFETCH insns have "$dst = $val" constraints. So let us enforce "$dst = $val" having the same register type in ATOMIC_NOFETCH as well.
Currently, things work since ATOMIC_NOFETCH does not have source code pattern matching. I am experimenting to introduce memory ordering to BPFInstrInfo.td file and pattern matching will be needed. Eventually, for atomic_fetch_*() insns locked insns could be generated if memory ordering is memory_order_relaxed.
[1] https://lore.kernel.org/bpf/7b941f53-2a05-48ec-9032-8f106face3a3@linux.dev/