[WebAssembly] Exception handling: Switch to the new proposal
Summary:
This switches the EH implementation to the new proposal:
https://github.com/WebAssembly/exception-handling/blob/master/proposals/Exceptions.md
(The previous proposal was
https://github.com/WebAssembly/exception-handling/blob/master/proposals/old/Exceptions.md)
- Instruction changes
- Now we have one single `catch` instruction that returns a except_ref
value
- `throw` now can take variable number of operations
- `rethrow` does not have 'depth' argument anymore
- `br_on_exn` queries an except_ref to see if it matches the tag and
branches to the given label if true.
- `extract_exception` is a pseudo instruction that simulates popping
values from wasm stack. This is to make `br_on_exn`, a very special
instruction, work: `br_on_exn` puts values onto the stack only if it
is taken, and the # of values can vay depending on the tag.
- Now there's only one `catch` per `try`, this patch removes all special
handling for terminate pad with a call to `__clang_call_terminate`.
Before it was the only case there are two catch clauses (a normal
`catch` and `catch_all` per `try`).
- Make `rethrow` act as a terminator like `throw`. This splits BB after
`rethrow` in WasmEHPrepare, and deletes an unnecessary `unreachable`
after `rethrow` in LateEHPrepare.
- Now we stop at all catchpads (because we add wasm `catch` instruction
that catches all exceptions), this creates new
`findWasmUnwindDestinations` function in SelectionDAGBuilder.
- Now we use `br_on_exn` instrution to figure out if an except_ref
matches the current tag or not, LateEHPrepare generates this sequence
for catch pads:
```
catch
block i32
br_on_exn $__cpp_exception
end_block
extract_exception
```
- Branch analysis for `br_on_exn` in WebAssemblyInstrInfo
- Other various misc. changes to switch to the new proposal.
Reviewers: dschuff
Subscribers: sbc100, jgravelle-google, sunfish, llvm-commits
Differential Revision: https://reviews.llvm.org/D57134
llvm-svn: 352598
diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyUtilities.cpp b/llvm/lib/Target/WebAssembly/WebAssemblyUtilities.cpp
index f1cb579..4edd546 100644
--- a/llvm/lib/Target/WebAssembly/WebAssemblyUtilities.cpp
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyUtilities.cpp
@@ -242,50 +242,10 @@
}
}
-bool WebAssembly::isThrow(const MachineInstr &MI) {
- switch (MI.getOpcode()) {
- case WebAssembly::THROW_I32:
- case WebAssembly::THROW_I32_S:
- case WebAssembly::THROW_I64:
- case WebAssembly::THROW_I64_S:
- return true;
- default:
- return false;
- }
-}
-
-bool WebAssembly::isRethrow(const MachineInstr &MI) {
- switch (MI.getOpcode()) {
- case WebAssembly::RETHROW:
- case WebAssembly::RETHROW_S:
- case WebAssembly::RETHROW_TO_CALLER:
- case WebAssembly::RETHROW_TO_CALLER_S:
- return true;
- default:
- return false;
- }
-}
-
-bool WebAssembly::isCatch(const MachineInstr &MI) {
- switch (MI.getOpcode()) {
- case WebAssembly::CATCH_I32:
- case WebAssembly::CATCH_I32_S:
- case WebAssembly::CATCH_I64:
- case WebAssembly::CATCH_I64_S:
- case WebAssembly::CATCH_ALL:
- case WebAssembly::CATCH_ALL_S:
- return true;
- default:
- return false;
- }
-}
-
bool WebAssembly::mayThrow(const MachineInstr &MI) {
switch (MI.getOpcode()) {
- case WebAssembly::THROW_I32:
- case WebAssembly::THROW_I32_S:
- case WebAssembly::THROW_I64:
- case WebAssembly::THROW_I64_S:
+ case WebAssembly::THROW:
+ case WebAssembly::THROW_S:
case WebAssembly::RETHROW:
case WebAssembly::RETHROW_S:
return true;
@@ -308,41 +268,3 @@
return false;
return true;
}
-
-bool WebAssembly::isCatchTerminatePad(const MachineBasicBlock &MBB) {
- if (!MBB.isEHPad())
- return false;
- bool SeenCatch = false;
- for (auto &MI : MBB) {
- if (MI.getOpcode() == WebAssembly::CATCH_I32 ||
- MI.getOpcode() == WebAssembly::CATCH_I64 ||
- MI.getOpcode() == WebAssembly::CATCH_I32_S ||
- MI.getOpcode() == WebAssembly::CATCH_I64_S)
- SeenCatch = true;
- if (SeenCatch && MI.isCall()) {
- const MachineOperand &CalleeOp = MI.getOperand(getCalleeOpNo(MI));
- if (CalleeOp.isGlobal() &&
- CalleeOp.getGlobal()->getName() == ClangCallTerminateFn)
- return true;
- }
- }
- return false;
-}
-
-bool WebAssembly::isCatchAllTerminatePad(const MachineBasicBlock &MBB) {
- if (!MBB.isEHPad())
- return false;
- bool SeenCatchAll = false;
- for (auto &MI : MBB) {
- if (MI.getOpcode() == WebAssembly::CATCH_ALL ||
- MI.getOpcode() == WebAssembly::CATCH_ALL_S)
- SeenCatchAll = true;
- if (SeenCatchAll && MI.isCall()) {
- const MachineOperand &CalleeOp = MI.getOperand(getCalleeOpNo(MI));
- if (CalleeOp.isGlobal() &&
- CalleeOp.getGlobal()->getName() == StdTerminateFn)
- return true;
- }
- }
- return false;
-}