[llvm] [llvm-objdump] Add triple support to `mcpu=help` (PR #165661)

[Ruoyu Qiu via llvm-commits]

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@@ -3533,6 +3533,35 @@ commaSeparatedValues(const llvm::opt::InputArgList &InputArgs, int ID) {
   return Values;
 }
 
+static void mcpuHelp() {
+  std::string Error;
+  Triple DummyTriple;
+
+  if (!TripleName.empty())
+    DummyTriple.setTriple(TripleName);
+  else {
+    // If the target triple is derived from the files, we display help message
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cabbaken wrote:

Apologies for overlooking the `--triple=x86_64` flag in `llvm-objdump -d --mcpu=help ./arm.o --triple=x86_64`. You are correct that the output of `--mcpu=help` depends on the triple. With that in mind, my change is consistent with the original behavior.

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