[llvm] [llvm-objdump] Support --mcpu=help/--mattr=help without -d (PR #165661)

[James Henderson via llvm-commits]

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@@ -3533,6 +3533,33 @@ commaSeparatedValues(const llvm::opt::InputArgList &InputArgs, int ID) {
   return Values;
 }
 
+static void mcpuHelp() {
+  std::string Error;
+  Triple TheTriple;
+
+  if (!TripleName.empty()) {
+    TheTriple.setTriple(TripleName);
+  } else {
+    // We can guarantee that InputFilenames won't be empty.
+    Expected<OwningBinary<Binary>> OBinary = createBinary(InputFilenames[0]);
+    // OwningBinary<Binary> OBinary =
+    if (!OBinary)
+      reportError(InputFilenames[0],
+                  "A target triple was not specified and could "
+                  " not be inferred from the input file.");
+
+    Binary *Bin = OBinary->getBinary();
+    if (ObjectFile *Obj = dyn_cast<ObjectFile>(Bin))
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jh7370 wrote:

Under what contexts can the `dyn_cast` fail? In other words, when could `Obj` be `nullptr`? If it never can, it should be `cast`, not `dyn_cast`, I believe.

https://github.com/llvm/llvm-project/pull/165661