How to call the llvm.prefetch intrinsic ?

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1

Hello,

Can anyone please guide me how can I replace a load instruction with a prefetch. I was looking at the intrinsic creation methods of the IRBuilder, but I can only find functions corresponding to memset, memcpy and memmove intrinsics, not for prefetching.

Also, I target x86-64 architectures. Is it sufficient to insert a call to the intrinsic in the LLVM IR to have the corresponding prefetch instruction generated for this target?

Thank you for your help,
Alexandra

2

Alexandra,

I'm not sure what you mean by "replace", but I have code that does this to insert prefetches:

      Type *I8Ptr = Type::getInt8PtrTy((*I)->getContext(), PtrAddrSpace);
      Value *PrefPtrValue = ...

      IRBuilder<> Builder(MemI);
      Module *M = (*I)->getParent()->getParent();
      Type *I32 = Type::getInt32Ty((*I)->getContext());
      Value *PrefetchFunc = Intrinsic::getDeclaration(M, Intrinsic::prefetch);
      Builder.CreateCall4(PrefetchFunc, PrefPtrValue,
        ConstantInt::get(I32, MemI->mayReadFromMemory() ? 0 : 1),
        ConstantInt::get(I32, 3), ConstantInt::get(I32, 1));

-Hal

3

Thank you, this is what I was looking for.

Alexandra