[WebAssembly] Define the signature for __stack_chk_fail

The WebAssembly backend needs to know the signatures of all runtime
libcall functions. This adds the signature for __stack_chk_fail which was
previously missing.

Also, make the error message for a missing libcall include the name of
the function.

Differential Revision: https://reviews.llvm.org/D59521

Reviewed By: sbc100

llvm-svn: 359505
diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyRuntimeLibcallSignatures.cpp b/llvm/lib/Target/WebAssembly/WebAssemblyRuntimeLibcallSignatures.cpp
index fbdf9c5..215c63c 100644
--- a/llvm/lib/Target/WebAssembly/WebAssemblyRuntimeLibcallSignatures.cpp
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyRuntimeLibcallSignatures.cpp
@@ -309,6 +309,9 @@
     Table[RTLIB::MEMSET] = iPTR_func_iPTR_i32_iPTR;
     Table[RTLIB::MEMMOVE] = iPTR_func_iPTR_iPTR_iPTR;
 
+    // __stack_chk_fail
+    Table[RTLIB::STACKPROTECTOR_CHECK_FAIL] = func;
+
     // Element-wise Atomic memory
     // TODO: Fix these when we implement atomic support
     Table[RTLIB::MEMCPY_ELEMENT_UNORDERED_ATOMIC_1] = unsupported;
@@ -837,6 +840,11 @@
                                SmallVectorImpl<wasm::ValType> &Params) {
   auto &Map = LibcallNameMap->Map;
   auto Val = Map.find(Name);
-  assert(Val != Map.end() && "unexpected runtime library name");
+#ifndef NDEBUG
+  if (Val == Map.end()) {
+    errs() << "runtime library name: " << Name << "\n";
+    llvm_unreachable("unexpected runtime library name");
+  }
+#endif
   return getLibcallSignature(Subtarget, Val->second, Rets, Params);
 }