[PATCH] D57134: [WebAssembly] Exception handling: Switch to the new proposal

[Heejin Ahn via Phabricator via llvm-commits]

aheejin created this revision.
aheejin added a reviewer: dschuff.
Herald added subscribers: llvm-commits, sunfish, jgravelle-google, sbc100.

This switches the EH implementation to the new proposal:
https://github.com/WebAssembly/exception-handling/blob/master/proposals/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. Also this deletes all EHPadUnwindMap related routines from WasmEHFuncInfo, because we don't need to consider the case an exception is not caught by a catchpad now.

- 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 except_ref
  br_on_exn $__cpp_exception
  end_block
  extract_exception



- Other various misc. changes to switch to the new proposal.


Repository:
  rL LLVM

https://reviews.llvm.org/D57134

Files:
  include/llvm/CodeGen/WasmEHFuncInfo.h
  include/llvm/IR/IntrinsicsWebAssembly.td
  lib/CodeGen/AsmPrinter/WasmException.cpp
  lib/CodeGen/SelectionDAG/FunctionLoweringInfo.cpp
  lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
  lib/CodeGen/WasmEHPrepare.cpp
  lib/Target/WebAssembly/InstPrinter/WebAssemblyInstPrinter.cpp
  lib/Target/WebAssembly/WebAssemblyAsmPrinter.cpp
  lib/Target/WebAssembly/WebAssemblyCFGStackify.cpp
  lib/Target/WebAssembly/WebAssemblyEHRestoreStackPointer.cpp
  lib/Target/WebAssembly/WebAssemblyExceptionInfo.cpp
  lib/Target/WebAssembly/WebAssemblyISelLowering.cpp
  lib/Target/WebAssembly/WebAssemblyISelLowering.h
  lib/Target/WebAssembly/WebAssemblyInstrControl.td
  lib/Target/WebAssembly/WebAssemblyInstrInfo.cpp
  lib/Target/WebAssembly/WebAssemblyInstrInfo.td
  lib/Target/WebAssembly/WebAssemblyLateEHPrepare.cpp
  lib/Target/WebAssembly/WebAssemblyMCInstLower.cpp
  lib/Target/WebAssembly/WebAssemblyRegStackify.cpp
  lib/Target/WebAssembly/WebAssemblyTargetMachine.cpp
  lib/Target/WebAssembly/WebAssemblyUtilities.cpp
  lib/Target/WebAssembly/WebAssemblyUtilities.h
  test/CodeGen/WebAssembly/annotations.mir
  test/CodeGen/WebAssembly/cfg-stackify-eh.ll
  test/CodeGen/WebAssembly/cfg-stackify-eh.mir
  test/CodeGen/WebAssembly/exception.ll
  test/CodeGen/WebAssembly/wasmehprepare.ll
  test/MC/WebAssembly/annotations.s
  test/MC/WebAssembly/basic-assembly.s
  unittests/Target/WebAssembly/WebAssemblyExceptionInfoTest.cpp

-------------- next part --------------
A non-text attachment was scrubbed...
Name: D57134.183226.patch
Type: text/x-patch
Size: 112792 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20190124/c7c14b04/attachment.bin>