1 files changed, 96 insertions, 0 deletions
diff --git a/llvm/lib/CodeGen/AsmPrinter/WasmException.cpp b/llvm/lib/CodeGen/AsmPrinter/WasmException.cpp
new file mode 100644
index 000000000000..444b0ed17b6d
--- /dev/null
+++ b/llvm/lib/CodeGen/AsmPrinter/WasmException.cpp
@@ -0,0 +1,96 @@
+//===-- CodeGen/AsmPrinter/WasmException.cpp - Wasm Exception Impl --------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This file contains support for writing WebAssembly exception info into asm
+// files.
+//
+//===----------------------------------------------------------------------===//
+
+#include "WasmException.h"
+#include "llvm/IR/Mangler.h"
+#include "llvm/MC/MCContext.h"
+#include "llvm/MC/MCStreamer.h"
+using namespace llvm;
+
+void WasmException::endModule() {
+  // This is the symbol used in 'throw' and 'br_on_exn' instruction to denote
+  // this is a C++ exception. This symbol has to be emitted somewhere once in
+  // the module.  Check if the symbol has already been created, i.e., we have at
+  // least one 'throw' or 'br_on_exn' instruction in the module, and emit the
+  // symbol only if so.
+  SmallString<60> NameStr;
+  Mangler::getNameWithPrefix(NameStr, "__cpp_exception", Asm->getDataLayout());
+  if (Asm->OutContext.lookupSymbol(NameStr)) {
+    MCSymbol *ExceptionSym = Asm->GetExternalSymbolSymbol("__cpp_exception");
+    Asm->OutStreamer->EmitLabel(ExceptionSym);
+  }
+}
+
+void WasmException::markFunctionEnd() {
+  // Get rid of any dead landing pads.
+  if (!Asm->MF->getLandingPads().empty()) {
+    auto *NonConstMF = const_cast<MachineFunction *>(Asm->MF);
+    // Wasm does not set BeginLabel and EndLabel information for landing pads,
+    // so we should set the second argument false.
+    NonConstMF->tidyLandingPads(nullptr, /* TidyIfNoBeginLabels */ false);
+  }
+}
+
+void WasmException::endFunction(const MachineFunction *MF) {
+  bool ShouldEmitExceptionTable = false;
+  for (const LandingPadInfo &Info : MF->getLandingPads()) {
+    if (MF->hasWasmLandingPadIndex(Info.LandingPadBlock)) {
+      ShouldEmitExceptionTable = true;
+      break;
+    }
+  }
+  if (!ShouldEmitExceptionTable)
+    return;
+  MCSymbol *LSDALabel = emitExceptionTable();
+  assert(LSDALabel && ".GCC_exception_table has not been emitted!");
+
+  // Wasm requires every data section symbol to have a .size set. So we emit an
+  // end marker and set the size as the difference between the start end the end
+  // marker.
+  MCSymbol *LSDAEndLabel = Asm->createTempSymbol("GCC_except_table_end");
+  Asm->OutStreamer->EmitLabel(LSDAEndLabel);
+  MCContext &OutContext = Asm->OutStreamer->getContext();
+  const MCExpr *SizeExp = MCBinaryExpr::createSub(
+      MCSymbolRefExpr::create(LSDAEndLabel, OutContext),
+      MCSymbolRefExpr::create(LSDALabel, OutContext), OutContext);
+  Asm->OutStreamer->emitELFSize(LSDALabel, SizeExp);
+}
+
+// Compute the call-site table for wasm EH. Even though we use the same function
+// name to share the common routines, a call site entry in the table corresponds
+// to not a call site for possibly-throwing functions but a landing pad. In wasm
+// EH the VM is responsible for stack unwinding. After an exception occurs and
+// the stack is unwound, the control flow is transferred to wasm 'catch'
+// instruction by the VM, after which the personality function is called from
+// the compiler-generated code. Refer to WasmEHPrepare pass for more
+// information.
+void WasmException::computeCallSiteTable(
+    SmallVectorImpl<CallSiteEntry> &CallSites,
+    const SmallVectorImpl<const LandingPadInfo *> &LandingPads,
+    const SmallVectorImpl<unsigned> &FirstActions) {
+  MachineFunction &MF = *Asm->MF;
+  for (unsigned I = 0, N = LandingPads.size(); I < N; ++I) {
+    const LandingPadInfo *Info = LandingPads[I];
+    MachineBasicBlock *LPad = Info->LandingPadBlock;
+    // We don't emit LSDA for single catch (...).
+    if (!MF.hasWasmLandingPadIndex(LPad))
+      continue;
+    // Wasm EH must maintain the EH pads in the order assigned to them by the
+    // WasmEHPrepare pass.
+    unsigned LPadIndex = MF.getWasmLandingPadIndex(LPad);
+    CallSiteEntry Site = {nullptr, nullptr, Info, FirstActions[I]};
+    if (CallSites.size() < LPadIndex + 1)
+      CallSites.resize(LPadIndex + 1);
+    CallSites[LPadIndex] = Site;
+  }
+}