[llvm] r279113 - Add a version of Intrinsic::getName which is more efficient when there are no overloads.

[Philip Reames via llvm-commits]

On 08/18/2016 11:30 AM, Pete Cooper via llvm-commits wrote:
> Author: pete
> Date: Thu Aug 18 13:30:54 2016
> New Revision: 279113
>
> URL: http://llvm.org/viewvc/llvm-project?rev=279113&view=rev
> Log:
> Add a version of Intrinsic::getName which is more efficient when there are no overloads.
>
> When running 'opt -O2 verify-uselistorder-nodbg.lto.bc', there are 33m allocations.  8.2m
> come from std::string allocations in Intrinsic::getName().  Turns out this method only
> returns a std::string because it needs to handle overloads, but that is not the common case.
>
> This adds an overload of getName which just returns a StringRef when there are no overloads
> and so saves on the allocations.
>
> Modified:
>      llvm/trunk/include/llvm/IR/Intrinsics.h
>      llvm/trunk/lib/IR/Function.cpp
>
> Modified: llvm/trunk/include/llvm/IR/Intrinsics.h
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/IR/Intrinsics.h?rev=279113&r1=279112&r2=279113&view=diff
> ==============================================================================
> --- llvm/trunk/include/llvm/IR/Intrinsics.h (original)
> +++ llvm/trunk/include/llvm/IR/Intrinsics.h Thu Aug 18 13:30:54 2016
> @@ -45,7 +45,10 @@ namespace Intrinsic {
>     };
>   
>     /// Return the LLVM name for an intrinsic, such as "llvm.ppc.altivec.lvx".
> -  std::string getName(ID id, ArrayRef<Type*> Tys = None);
> +  StringRef getName(ID id);
> +
> +  /// Return the LLVM name for an intrinsic, such as "llvm.ppc.altivec.lvx".
> +  std::string getName(ID id, ArrayRef<Type*> Tys);
Can you add clarifying comments to explain when each should be used?
>   
>     /// Return the function type for an intrinsic.
>     FunctionType *getType(LLVMContext &Context, ID id,
>
> Modified: llvm/trunk/lib/IR/Function.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/IR/Function.cpp?rev=279113&r1=279112&r2=279113&view=diff
> ==============================================================================
> --- llvm/trunk/lib/IR/Function.cpp (original)
> +++ llvm/trunk/lib/IR/Function.cpp Thu Aug 18 13:30:54 2016
> @@ -551,6 +551,11 @@ static std::string getMangledTypeStr(Typ
>     return Result;
>   }
>   
> +StringRef Intrinsic::getName(ID id) {
> +  assert(id < num_intrinsics && "Invalid intrinsic ID!");
> +  return IntrinsicNameTable[id];
Can we add an assert that this intrinsic is not overloaded?
> +}
> +
>   std::string Intrinsic::getName(ID id, ArrayRef<Type*> Tys) {
>     assert(id < num_intrinsics && "Invalid intrinsic ID!");
>     std::string Result(IntrinsicNameTable[id]);
>
>
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