[llvm] Refactor try demangle for vfabi to use only the vector abi mangled names (PR #67430)

[via llvm-commits]

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@@ -27,15 +27,22 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size) {
   // present. We need to make sure we can even invoke
   // `getOrInsertFunction` because such method asserts on strings with
   // zeroes.
-  if (!MangledName.empty() && MangledName.find_first_of(0) == StringRef::npos)
-    M->getOrInsertFunction(
-        MangledName,
-        FunctionType::get(Type::getVoidTy(M->getContext()), false));
-  const auto Info = VFABI::tryDemangleForVFABI(MangledName, *M);
+  if (!MangledName.empty() && MangledName.find_first_of(0) == StringRef::npos) {
+    FunctionType *FTy =
+        FunctionType::get(Type::getVoidTy(M->getContext()), false);
+    FunctionCallee F = M->getOrInsertFunction(MangledName, FTy);
+    // Fake the arguments to the CallInst.
+    SmallVector<Value *> Args;
+    for (Type *ParamTy : FTy->params()) {
+      Args.push_back(Constant::getNullValue(ParamTy));
+    }
+    std::unique_ptr<CallInst> CI(CallInst::Create(F, Args));
+    const auto Info = VFABI::tryDemangleForVFABI(MangledName, *(CI.get()));
 
-  // Do not optimize away the return value. Inspired by
-  // https://github.com/google/benchmark/blob/main/include/benchmark/benchmark.h#L307-L345
-  asm volatile("" : : "r,m"(Info) : "memory");
+    // Do not optimize away the return value. Inspired by
+    // https://github.com/google/benchmark/blob/main/include/benchmark/benchmark.h#L307-L345
+    asm volatile("" : : "r,m"(Info) : "memory");
 
-  return 0;
+    return 0;
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JolantaJensen wrote:

Here, I'm only returning a value if the if condition is true but it does not make a sense to me to try to call `VFABI::tryDemangleForVFABI` if we do not have a CI. Grateful for suggestions how to rewrite this part. 

https://github.com/llvm/llvm-project/pull/67430