[llvm] [llvm] Consistently respect `naked` fn attribute in `TargetFrameLowering::hasFP()` (PR #106014)

[Alexander Richardson via llvm-commits]

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@@ -286,7 +286,11 @@ class TargetFrameLowering {
   /// hasFP - Return true if the specified function should have a dedicated
   /// frame pointer register. For most targets this is true only if the function
   /// has variable sized allocas or if frame pointer elimination is disabled.
-  virtual bool hasFP(const MachineFunction &MF) const = 0;
+  /// For all targets, this is false if the function has the naked attribute
+  /// since there is no prologue to set up the frame pointer.
+  bool hasFP(const MachineFunction &MF) const {
+    return !MF.getFunction().hasFnAttribute(Attribute::Naked) && hasFPImpl(MF);
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arichardson wrote:

If my reading of the GCC attribute documentation is correct, naked functions should behave in the same way as if you had just declared a function in assembly plus the appropriate directives to emit `.cfi_{end,start}proc`, `.size` etc. but no code being generated - so the function can only have a frame pointer if the inline assembly sets one up?

Always calling the base implementation would work and allow targets to override it, but if that is ever needed we could make it a virtual function?


https://github.com/llvm/llvm-project/pull/106014