Index: llvm/trunk/lib/Target/WebAssembly/WebAssemblyRuntimeLibcallSignatures.cpp
===================================================================
--- llvm/trunk/lib/Target/WebAssembly/WebAssemblyRuntimeLibcallSignatures.cpp
+++ llvm/trunk/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);
 }
Index: llvm/trunk/test/CodeGen/WebAssembly/stack-protector.ll
===================================================================
--- llvm/trunk/test/CodeGen/WebAssembly/stack-protector.ll
+++ llvm/trunk/test/CodeGen/WebAssembly/stack-protector.ll
@@ -0,0 +1,30 @@
+; RUN: llc -verify-machineinstrs -mtriple=wasm32-unknown-unknown < %s | FileCheck -check-prefix=WASM32 %s
+
+; WASM32: i32.load        28
+; WASM32-NEXT: i32.sub
+; WASM32-NEXT: br_if           0
+
+; WASM32: __stack_chk_fail
+
+@"\01LC" = internal constant [11 x i8] c"buf == %s\0A\00"		; <[11 x i8]*> [#uses=1]
+
+define void @test(i8* %a) nounwind ssp {
+entry:
+	%a_addr = alloca i8*		; <i8**> [#uses=2]
+	%buf = alloca [8 x i8]		; <[8 x i8]*> [#uses=2]
+  %"alloca point" = bitcast i32 0 to i32		; <i32> [#uses=0]
+	store i8* %a, i8** %a_addr
+	%buf1 = bitcast [8 x i8]* %buf to i8*		; <i8*> [#uses=1]
+	%0 = load i8*, i8** %a_addr, align 4		; <i8*> [#uses=1]
+	%1 = call i8* @strcpy(i8* %buf1, i8* %0) nounwind		; <i8*> [#uses=0]
+  %buf2 = bitcast [8 x i8]* %buf to i8*		; <i8*> [#uses=1]
+	%2 = call i32 (i8*, ...) @printf(i8* getelementptr ([11 x i8], [11 x i8]* @"\01LC", i32 0, i32 0), i8* %buf2) nounwind		; <i32> [#uses=0]
+	br label %return
+
+return:		; preds = %entry
+	ret void
+}
+
+declare i8* @strcpy(i8*, i8*) nounwind
+
+declare i32 @printf(i8*, ...) nounwind