How to do bitcast for double to <2 x double>

How can I write code to generate IR for:
%2 = bitcast double* %1 to <2 x double>.
%3 = load <2 x double>
%2, align 16
Basically, it is similar to x86 _mm_load_pd1 intrinsics.


Create a type that is a "vector (array) of 2 double", and then a
pointer to that. Now use bitcast your on double pointer to that
pointer type you've created, and then create a load...

If you need more help, it would help if you post the code you are working on...

What I want to do is to change the pInst from : 2%= load double* %1, align 8 to 2% = load < 2 x double>* %1, align 16, where <2 x double> should be two double identical double values that is same as the one in the previous instruction

Instruction* ScalarToVectorLoad(Instruction* pInst) {
Value *loadValue = pInst->getOperand(0);
Instruction newLoad; //this one should be 2% = load < 2 x double> %1

BitCastInst *scalarToVector = new BitCastInst(loadValue, VectorType::get(Type::getDoubleTy(currF->getContext()), 2), “vectorizedLoad”, pInst);
newLoad = new LoadInst(); //to be implemented…
return newLoad;

So, you need to bitcast `pinst` to a pointer to Vector of double,
since it (I hope for your sake) is a pointer to integer. What you are
trying to do is bitcast a pointer into a vector, which probably will
lead to an assert or "bad code that doesn't work".

Thanks Mats. Yes, it currently leads to “Illegal BitCast”. Can I change the pInst directly to generate the code I want?

Without knowing how you generated the original instruction, don't
know, but it should be possible to just have say `alloca` or `gep` for
vector of 2 doubles and o `load` on that.

I have a few bitcasts in my Pascal compiler, and they are all based
one kind of pointer being cast to another pointer type - although
bitcast can be used for other purposes too, I believe that is the
"common use". In every case, the input and output must be the same