Commit
This commit does not belong to any branch on this repository, and may belong to a fork outside of the repository.
[WebAssembly] Treat 'rethrow' as terminator in custom isel (llvm#95967)
`rethrow` instruction is a terminator, but when when its DAG is built in `SelectionDAGBuilder` in a custom routine, it was NOT treated as such. ```ll rethrow: ; preds = %catch.start invoke void @llvm.wasm.rethrow() #1 [ "funclet"(token %1) ] to label %unreachable unwind label %ehcleanup ehcleanup: ; preds = %rethrow, %catch.dispatch %tmp = phi i32 [ 10, %catch.dispatch ], [ 20, %rethrow ] ... ``` In this bitcode, because of the `phi`, a `CONST_I32` will be created in the `rethrow` BB. Without this patch, the DAG for the `rethrow` BB looks like this: ``` t0: ch,glue = EntryToken t3: ch = CopyToReg t0, Register:i32 %9, Constant:i32<20> t5: ch = llvm.wasm.rethrow t0, TargetConstant:i32<12161> t6: ch = TokenFactor t3, t5 t8: ch = br t6, BasicBlock:ch<unreachable 0x562532e43c50> ``` Note that `CopyToReg` and `llvm.wasm.rethrow` don't have dependence so either can come first in the selected code, which can result in the code like ```mir bb.3.rethrow: RETHROW 0, implicit-def dead $arguments %9:i32 = CONST_I32 20, implicit-def dead $arguments BR %bb.6, implicit-def dead $arguments ``` After this patch, `llvm.wasm.rethrow` is treated as a terminator, and the DAG will look like ``` t0: ch,glue = EntryToken t3: ch = CopyToReg t0, Register:i32 %9, Constant:i32<20> t5: ch = llvm.wasm.rethrow t3, TargetConstant:i32<12161> t7: ch = br t5, BasicBlock:ch<unreachable 0x5555e3d32c70> ``` Note that now `rethrow` takes a token from `CopyToReg`, so `rethrow` has to come after `CopyToReg`. And the resulting code will be ```mir bb.3.rethrow: %9:i32 = CONST_I32 20, implicit-def dead $arguments RETHROW 0, implicit-def dead $arguments BR %bb.6, implicit-def dead $arguments ``` I'm not very familiar with the internals of `getRoot` vs. `getControlRoot`, but other terminator instructions seem to use the latter, and using it for `rethrow` too worked.
- Loading branch information