From d6f487863dc951d467b545b86b9ea62980569b5a Mon Sep 17 00:00:00 2001 From: Heejin Ahn Date: Wed, 30 Jan 2019 03:21:57 +0000 Subject: [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 --- .../Target/WebAssembly/WebAssemblyISelLowering.cpp | 76 ++++++++++------------ 1 file changed, 35 insertions(+), 41 deletions(-) (limited to 'llvm/lib/Target/WebAssembly/WebAssemblyISelLowering.cpp') diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyISelLowering.cpp b/llvm/lib/Target/WebAssembly/WebAssemblyISelLowering.cpp index 7cb7f2750ff..52d9d282159 100644 --- a/llvm/lib/Target/WebAssembly/WebAssemblyISelLowering.cpp +++ b/llvm/lib/Target/WebAssembly/WebAssemblyISelLowering.cpp @@ -884,13 +884,13 @@ SDValue WebAssemblyTargetLowering::LowerOperation(SDValue Op, return LowerFRAMEADDR(Op, DAG); case ISD::CopyToReg: return LowerCopyToReg(Op, DAG); - case ISD::INTRINSIC_WO_CHAIN: - return LowerINTRINSIC_WO_CHAIN(Op, DAG); case ISD::EXTRACT_VECTOR_ELT: case ISD::INSERT_VECTOR_ELT: return LowerAccessVectorElement(Op, DAG); case ISD::INTRINSIC_VOID: - return LowerINTRINSIC_VOID(Op, DAG); + case ISD::INTRINSIC_WO_CHAIN: + case ISD::INTRINSIC_W_CHAIN: + return LowerIntrinsic(Op, DAG); case ISD::SIGN_EXTEND_INREG: return LowerSIGN_EXTEND_INREG(Op, DAG); case ISD::BUILD_VECTOR: @@ -1035,17 +1035,28 @@ SDValue WebAssemblyTargetLowering::LowerVASTART(SDValue Op, MachinePointerInfo(SV), 0); } -SDValue -WebAssemblyTargetLowering::LowerINTRINSIC_WO_CHAIN(SDValue Op, - SelectionDAG &DAG) const { - unsigned IntNo = cast(Op.getOperand(0))->getZExtValue(); +SDValue WebAssemblyTargetLowering::LowerIntrinsic(SDValue Op, + SelectionDAG &DAG) const { + MachineFunction &MF = DAG.getMachineFunction(); + unsigned IntNo; + switch (Op.getOpcode()) { + case ISD::INTRINSIC_VOID: + case ISD::INTRINSIC_W_CHAIN: + IntNo = cast(Op.getOperand(1))->getZExtValue(); + break; + case ISD::INTRINSIC_WO_CHAIN: + IntNo = cast(Op.getOperand(0))->getZExtValue(); + break; + default: + llvm_unreachable("Invalid intrinsic"); + } SDLoc DL(Op); + switch (IntNo) { default: return {}; // Don't custom lower most intrinsics. case Intrinsic::wasm_lsda: { - MachineFunction &MF = DAG.getMachineFunction(); EVT VT = Op.getValueType(); const TargetLowering &TLI = DAG.getTargetLoweringInfo(); MVT PtrVT = TLI.getPointerTy(DAG.getDataLayout()); @@ -1055,43 +1066,26 @@ WebAssemblyTargetLowering::LowerINTRINSIC_WO_CHAIN(SDValue Op, return DAG.getNode(WebAssemblyISD::Wrapper, DL, VT, DAG.getMCSymbol(S, PtrVT)); } - } -} - -SDValue -WebAssemblyTargetLowering::LowerINTRINSIC_VOID(SDValue Op, - SelectionDAG &DAG) const { - MachineFunction &MF = DAG.getMachineFunction(); - unsigned IntNo = cast(Op.getOperand(1))->getZExtValue(); - SDLoc DL(Op); - - switch (IntNo) { - default: - return {}; // Don't custom lower most intrinsics. case Intrinsic::wasm_throw: { + // We only support C++ exceptions for now int Tag = cast(Op.getOperand(2).getNode())->getZExtValue(); - switch (Tag) { - case CPP_EXCEPTION: { - const TargetLowering &TLI = DAG.getTargetLoweringInfo(); - MVT PtrVT = TLI.getPointerTy(DAG.getDataLayout()); - const char *SymName = MF.createExternalSymbolName("__cpp_exception"); - SDValue SymNode = - DAG.getNode(WebAssemblyISD::Wrapper, DL, PtrVT, - DAG.getTargetExternalSymbol( - SymName, PtrVT, WebAssemblyII::MO_SYMBOL_EVENT)); - return DAG.getNode(WebAssemblyISD::THROW, DL, - MVT::Other, // outchain type - { - Op.getOperand(0), // inchain - SymNode, // exception symbol - Op.getOperand(3) // thrown value - }); - } - default: + if (Tag != CPP_EXCEPTION) llvm_unreachable("Invalid tag!"); - } - break; + const TargetLowering &TLI = DAG.getTargetLoweringInfo(); + MVT PtrVT = TLI.getPointerTy(DAG.getDataLayout()); + const char *SymName = MF.createExternalSymbolName("__cpp_exception"); + SDValue SymNode = + DAG.getNode(WebAssemblyISD::Wrapper, DL, PtrVT, + DAG.getTargetExternalSymbol( + SymName, PtrVT, WebAssemblyII::MO_SYMBOL_EVENT)); + return DAG.getNode(WebAssemblyISD::THROW, DL, + MVT::Other, // outchain type + { + Op.getOperand(0), // inchain + SymNode, // exception symbol + Op.getOperand(3) // thrown value + }); } } } -- cgit v1.2.3