[CodeGen] std::less<llvm::rdf::RegisterRef> and std::equal_to<llvm::rdf::RegisterRef> full specializations don't satisfy the standard requirements

The following full specializations don't satisfy [namespace.std]/5.2.

A program may explicitly instantiate a class template defined in the standard library only if the declaration

(5.1) depends on the name of at least one program-defined type, and

(5.2) the instantiation meets the standard library requirements for the original template.

llvm-project/llvm/include/llvm/CodeGen/RDFRegisters.h

Lines 337 to 347 in c1f8dbb

     template <> struct equal_to<llvm::rdf::RegisterRef> {  
   constexpr equal_to(const llvm::rdf::PhysicalRegisterInfo &pri) : PRI(&pri) {}  
    
   bool operator()(llvm::rdf::RegisterRef A, llvm::rdf::RegisterRef B) const {  
   return PRI->equal_to(A, B);  
   }  
    
   private:  
   // Make it a pointer just in case. See comment in `less` below.  
   const llvm::rdf::PhysicalRegisterInfo *PRI;  
   };  
 

llvm-project/llvm/include/llvm/CodeGen/RDFRegisters.h

Lines 356 to 367 in c1f8dbb

     template <> struct less<llvm::rdf::RegisterRef> {  
   constexpr less(const llvm::rdf::PhysicalRegisterInfo &pri) : PRI(&pri) {}  
    
   bool operator()(llvm::rdf::RegisterRef A, llvm::rdf::RegisterRef B) const {  
   return PRI->less(A, B);  
   }  
    
   private:  
   // Make it a pointer because apparently some versions of MSVC use std::swap  
   // on the std::less specialization.  
   const llvm::rdf::PhysicalRegisterInfo *PRI;  
   };  
 

These full specializations violate the requirements by being non-default-constructible, and arguably, being non-empty/stateful.

Perhaps it's better to specify non-std comparators rather than simply use std::set<RegisterRef> or std::map<RegisterRef, T>.

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[CodeGen] `std::less<llvm::rdf::RegisterRef>` and `std::equal_to<llvm::rdf::RegisterRef>` full specializations don't satisfy the standard requirements #160684

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	template <> struct equal_to<llvm::rdf::RegisterRef> {
	constexpr equal_to(const llvm::rdf::PhysicalRegisterInfo &pri) : PRI(&pri) {}

	bool operator()(llvm::rdf::RegisterRef A, llvm::rdf::RegisterRef B) const {
	return PRI->equal_to(A, B);
	}

	private:
	// Make it a pointer just in case. See comment in `less` below.
	const llvm::rdf::PhysicalRegisterInfo *PRI;
	};

	template <> struct less<llvm::rdf::RegisterRef> {
	constexpr less(const llvm::rdf::PhysicalRegisterInfo &pri) : PRI(&pri) {}

	bool operator()(llvm::rdf::RegisterRef A, llvm::rdf::RegisterRef B) const {
	return PRI->less(A, B);
	}

	private:
	// Make it a pointer because apparently some versions of MSVC use std::swap
	// on the std::less specialization.
	const llvm::rdf::PhysicalRegisterInfo *PRI;
	};

[CodeGen] std::less<llvm::rdf::RegisterRef> and std::equal_to<llvm::rdf::RegisterRef> full specializations don't satisfy the standard requirements #160684

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[CodeGen] `std::less<llvm::rdf::RegisterRef>` and `std::equal_to<llvm::rdf::RegisterRef>` full specializations don't satisfy the standard requirements #160684