[llvm] [GlobalOpt] Add TTI interface useFastCCForInternalCall for FASTCC (PR #164768)

[Nikita Popov via llvm-commits]

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@@ -319,6 +319,10 @@ class X86TTIImpl final : public BasicTTIImplBase<X86TTIImpl> {
   unsigned getStoreMinimumVF(unsigned VF, Type *ScalarMemTy,
                              Type *ScalarValTy) const override;
 
+  bool useFastCCForInternalCall(Function &F) const override {
+    return !ST->is64Bit() || ST->hasEGPR();
+  }
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nikic wrote:

Hm, I don't really follow.

If we have no-EGPR -> EGPR, then the EGPR function may expect arguments to be passed in EGPR registers, while the no-EGPR function will push them to the stack.

If we have EGPR -> no-EGPR, then the EGPR function may pass arguments in EGPR registers, while the no-EGPR function will expect them to be on the stack.

Am I missing something here?

https://github.com/llvm/llvm-project/pull/164768