Support sub-register code-gen for XADD is like supporting any other Load
and Store patterns.
No new instruction is introduced.
lock *(u32 *)(r1 + 0) += w2
has exactly the same underlying insn as:
lock *(u32 *)(r1 + 0) += r2
BPF_W width modifier has guaranteed they behave the same at runtime. This
patch merely teaches BPF back-end that BPF_W width modifier could work
GPR32 register class and that's all needed for sub-register code-gen
support for XADD.
test/CodeGen/BPF/xadd.ll updated to include sub-register code-gen tests.
A new testcase test/CodeGen/BPF/xadd_legal.ll is added to make sure the
legal case could pass on all code-gen modes. It could also test dead Def
check on GPR32. If there is no proper handling like what has been done
inside BPFMIChecking.cpp:hasLivingDefs, then this testcase will fail.
Acked-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Jiong Wang <jiong.wang@netronome.com>
llvm-svn: 355126
Currently, BPF has XADD (locked add) insn support and the
asm looks like:
lock *(u32 *)(r1 + 0) += r2
lock *(u64 *)(r1 + 0) += r2
The instruction itself does not have a return value.
At the source code level, users often use
__sync_fetch_and_add()
which eventually translates to XADD. The return value of
__sync_fetch_and_add() is supposed to be the old value
in the xadd memory location. Since BPF::XADD insn does not
support such a return value, this patch added a PreEmit
phase to check such a usage. If such an illegal usage
pattern is detected, a fatal error will be reported like
line 4: Invalid usage of the XADD return value
if compiled with -g, or
Invalid usage of the XADD return value
if compiled without -g.
Signed-off-by: Yonghong Song <yhs@fb.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
llvm-svn: 342692
Jiong Wang