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

[Chris Copeland via llvm-commits]

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@@ -311,11 +311,15 @@ ARMBaseTargetMachine::getSubtargetImpl(const Function &F) const {
     // function that reside in TargetOptions.
     resetTargetOptions(F);
     I = std::make_unique<ARMSubtarget>(TargetTriple, CPU, FS, *this, isLittle,
-                                        F.hasMinSize());
+                                       F.hasMinSize());
 
     if (!I->isThumb() && !I->hasARMOps())
       F.getContext().emitError("Function '" + F.getName() + "' uses ARM "
           "instructions, but the target does not support ARM mode execution.");
+
+    if (I->isTargetHardFloat() && !I->hasFPRegs())
+      F.getContext().emitError("The hard-float ABI is enabled, but the target "
+                               "lacks floating-point registers.");
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chrisnc wrote:

I think you are right. I initially avoided that because one of the values is `Default` which is meant to defer to the triple, but in the constructor of `ARMBaseTargetMachine` it sets the internal `Options.FloatABIType` to one or the other based on the passed in option and the triple, so it should be correct to just use that. I was testing with things like `--target=arm-none-eabi -mcpu=cortex-m0 -mfloat-abi=hard` and seeing the error trigger, so something else in the frontend may be generating a different triple that makes this "work".

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