[llvm] [ARM] Emit a warning when the hard-float ABI is enabled but can't be used. (PR #111334)

[Chris Copeland via llvm-commits]

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@@ -791,7 +791,9 @@ ARMTargetLowering::ARMTargetLowering(const TargetMachine &TM,
       setAllExpand(MVT::f32);
     if (!Subtarget->hasFP64())
       setAllExpand(MVT::f64);
-  }
+  } else if (TM.Options.FloatABIType == FloatABI::Hard)
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chrisnc wrote:

The first version of the PR did put the check in that spot, but it leads to several required test changes because many tests invoke llc or lto with hardfp and no fp support, but then don't actually use fp, whereas the current patch does not result in those tests failing. Moving the check there means that those tests will need to be changed to invoke the LLVM tools with correct options. What is the reviewers' preference? @ostannard @smithp35

https://github.com/llvm/llvm-project/pull/111334