[clang] [llvm] [ARM] Adding diagnostics for mcmodel=tiny when used in invalid targets (PR #125643)

[Fangrui Song via llvm-commits]

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@@ -1755,6 +1755,18 @@ Compilation *Driver::BuildCompilation(ArrayRef<const char *> ArgList) {
         << TC.getTriple().str();
   }
 
+  // Throw diagnosis if mcmodel=tiny option is passed for targets other than ARM
+  // or AArch64.
+  if (Arg *A = UArgs->getLastArg(options::OPT_mcmodel_EQ)) {
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MaskRay wrote:

Move to clang/lib/Driver/ToolChains/CommonArgs.cpp `addMCModel`. You might delete add an early return to that function and run `check-clang-driver` to find relevant tests. Then follow that style and add one for Arm.

https://github.com/llvm/llvm-project/pull/125643