[WebAssembly] Define the signature for __stack_chk_fail

[sunfish]

Summary

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.

[sbc100]

I think I may have seen a crash recently related to this.

Can we add a test?

Also, IIRC the crash the is reported doesn't include the symbol name, which would be useful in the future perhaps?

[sunfish]

I made the error message include the name of the function, and added a test.

[sbc100]

llvm/trunk/lib/Target/WebAssembly/WebAssemblyRuntimeLibcallSignatures.cpp

846

Wouldn't it be nicer to do something like: llvm_unreachable("unexpected runtime library name: " + Name);

[sunfish]

llvm/trunk/lib/Target/WebAssembly/WebAssemblyRuntimeLibcallSignatures.cpp

846

It's a little more involved in that because all the types are char* and the argument is char*, but it's doable. Done, in r359509.

llvm/trunk/lib/Target/WebAssembly/WebAssemblyRuntimeLibcallSignatures.cpp

RuntimeLibcallSignatureTable() : Table(RTLIB::UNKNOWN_LIBCALL, unsupported) {
     Table[RTLIB::O_F64] = unsupported;
     Table[RTLIB::O_F128] = unsupported;
 
     // Memory
     Table[RTLIB::MEMCPY] = iPTR_func_iPTR_iPTR_iPTR;
     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;
     Table[RTLIB::MEMCPY_ELEMENT_UNORDERED_ATOMIC_2] = unsupported;
     Table[RTLIB::MEMCPY_ELEMENT_UNORDERED_ATOMIC_4] = unsupported;
     Table[RTLIB::MEMCPY_ELEMENT_UNORDERED_ATOMIC_8] = unsupported;
     Table[RTLIB::MEMCPY_ELEMENT_UNORDERED_ATOMIC_16] = unsupported;
     Table[RTLIB::MEMMOVE_ELEMENT_UNORDERED_ATOMIC_1] = unsupported;

 // TODO: If the RTLIB::Libcall-taking flavor of GetSignature remains unsed
 // other than here, just roll its logic into this version.
 void llvm::getLibcallSignature(const WebAssemblySubtarget &Subtarget,
                                const char *Name,
                                SmallVectorImpl<wasm::ValType> &Rets,
                                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);
 }

llvm/trunk/test/CodeGen/WebAssembly/stack-protector.ll

+; 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