diff options
Diffstat (limited to 'llvm/lib/Target/WebAssembly/WebAssemblyLateEHPrepare.cpp')
| -rw-r--r-- | llvm/lib/Target/WebAssembly/WebAssemblyLateEHPrepare.cpp | 34 |
1 files changed, 31 insertions, 3 deletions
diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyLateEHPrepare.cpp b/llvm/lib/Target/WebAssembly/WebAssemblyLateEHPrepare.cpp index 94037b9ab189..b8f3bcb57f6b 100644 --- a/llvm/lib/Target/WebAssembly/WebAssemblyLateEHPrepare.cpp +++ b/llvm/lib/Target/WebAssembly/WebAssemblyLateEHPrepare.cpp @@ -245,11 +245,39 @@ bool WebAssemblyLateEHPrepare::replaceFuncletReturns(MachineFunction &MF) { Changed = true; break; } + case WebAssembly::RETHROW: + // These RETHROWs here were lowered from llvm.wasm.rethrow() intrinsics, + // generated in Clang for when an exception is not caught by the given + // type (e.g. catch (int)). + // + // RETHROW's BB argument is the EH pad where the exception to rethrow has + // been caught. (Until this point, RETHROW has just a '0' as a placeholder + // argument.) For these llvm.wasm.rethrow()s, we can safely assume the + // exception comes from the nearest dominating EH pad, because catch.start + // EH pad is structured like this: + // + // catch.start: + // catchpad ... + // %matches = compare ehselector with typeid + // br i1 %matches, label %catch, label %rethrow + // + // rethrow: + // ;; rethrows the exception caught in 'catch.start' + // call @llvm.wasm.rethrow() + TI->removeOperand(0); + TI->addOperand(MachineOperand::CreateMBB(getMatchingEHPad(TI))); + Changed = true; + break; case WebAssembly::CLEANUPRET: { - // Replace a cleanupret with a rethrow. For C++ support, currently - // rethrow's immediate argument is always 0 (= the latest exception). + // CLEANUPRETs have the EH pad BB the exception to rethrow has been caught + // as an argument. Use it and change the instruction opcode to 'RETHROW' + // to make rethrowing instructions consistent. + // + // This is because we cannot safely assume that it is always the nearest + // dominating EH pad, in case there are code transformations such as + // inlining. BuildMI(MBB, TI, TI->getDebugLoc(), TII.get(WebAssembly::RETHROW)) - .addImm(0); + .addMBB(TI->getOperand(0).getMBB()); TI->eraseFromParent(); Changed = true; break; |