1 files changed, 81 insertions, 0 deletions
diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyUtilities.cpp b/llvm/lib/Target/WebAssembly/WebAssemblyUtilities.cpp
new file mode 100644
index 000000000000..a237da8154ab
--- /dev/null
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyUtilities.cpp
@@ -0,0 +1,81 @@
+//===-- WebAssemblyUtilities.cpp - WebAssembly Utility Functions ----------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// This file implements several utility functions for WebAssembly.
+///
+//===----------------------------------------------------------------------===//
+
+#include "WebAssemblyUtilities.h"
+#include "WebAssemblyMachineFunctionInfo.h"
+#include "llvm/CodeGen/MachineInstr.h"
+#include "llvm/CodeGen/MachineLoopInfo.h"
+using namespace llvm;
+
+const char *const WebAssembly::ClangCallTerminateFn = "__clang_call_terminate";
+const char *const WebAssembly::CxaBeginCatchFn = "__cxa_begin_catch";
+const char *const WebAssembly::CxaRethrowFn = "__cxa_rethrow";
+const char *const WebAssembly::StdTerminateFn = "_ZSt9terminatev";
+const char *const WebAssembly::PersonalityWrapperFn =
+    "_Unwind_Wasm_CallPersonality";
+
+/// Test whether MI is a child of some other node in an expression tree.
+bool WebAssembly::isChild(const MachineInstr &MI,
+                          const WebAssemblyFunctionInfo &MFI) {
+  if (MI.getNumOperands() == 0)
+    return false;
+  const MachineOperand &MO = MI.getOperand(0);
+  if (!MO.isReg() || MO.isImplicit() || !MO.isDef())
+    return false;
+  Register Reg = MO.getReg();
+  return Register::isVirtualRegister(Reg) && MFI.isVRegStackified(Reg);
+}
+
+bool WebAssembly::mayThrow(const MachineInstr &MI) {
+  switch (MI.getOpcode()) {
+  case WebAssembly::THROW:
+  case WebAssembly::THROW_S:
+  case WebAssembly::RETHROW:
+  case WebAssembly::RETHROW_S:
+    return true;
+  }
+  if (isCallIndirect(MI.getOpcode()))
+    return true;
+  if (!MI.isCall())
+    return false;
+
+  const MachineOperand &MO = MI.getOperand(getCalleeOpNo(MI.getOpcode()));
+  assert(MO.isGlobal() || MO.isSymbol());
+
+  if (MO.isSymbol()) {
+    // Some intrinsics are lowered to calls to external symbols, which are then
+    // lowered to calls to library functions. Most of libcalls don't throw, but
+    // we only list some of them here now.
+    // TODO Consider adding 'nounwind' info in TargetLowering::CallLoweringInfo
+    // instead for more accurate info.
+    const char *Name = MO.getSymbolName();
+    if (strcmp(Name, "memcpy") == 0 || strcmp(Name, "memmove") == 0 ||
+        strcmp(Name, "memset") == 0)
+      return false;
+    return true;
+  }
+
+  const auto *F = dyn_cast<Function>(MO.getGlobal());
+  if (!F)
+    return true;
+  if (F->doesNotThrow())
+    return false;
+  // These functions never throw
+  if (F->getName() == CxaBeginCatchFn || F->getName() == PersonalityWrapperFn ||
+      F->getName() == ClangCallTerminateFn || F->getName() == StdTerminateFn)
+    return false;
+
+  // TODO Can we exclude call instructions that are marked as 'nounwind' in the
+  // original LLVm IR? (Even when the callee may throw)
+  return true;
+}