[clang] [flang]Add vscale argument parsing (PR #67676)

[David Truby via cfe-commits]

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@@ -170,6 +169,38 @@ void Flang::addPicOptions(const ArgList &Args, ArgStringList &CmdArgs) const {
   }
 }
 
+void Flang::AddAArch64TargetArgs(const ArgList &Args,
+                                 ArgStringList &CmdArgs) const {
+  // Handle -msve_vector_bits=<bits>
+  if (Arg *A = Args.getLastArg(options::OPT_msve_vector_bits_EQ)) {
+    StringRef Val = A->getValue();
+    const Driver &D = getToolChain().getDriver();
+    if (Val.equals("128") || Val.equals("256") || Val.equals("512") ||
+        Val.equals("1024") || Val.equals("2048") || Val.equals("128+") ||
+        Val.equals("256+") || Val.equals("512+") || Val.equals("1024+") ||
+        Val.equals("2048+")) {
+      unsigned Bits = 0;
+      if (Val.endswith("+"))
+        Val = Val.substr(0, Val.size() - 1);
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DavidTruby wrote:

very nit: `Val.drop_back()`

https://github.com/llvm/llvm-project/pull/67676