QIR runtime heap alloc and heap free functions should be removed

[swernli]

The QIR runtime currently includes functions for allocating and freeing memory from the heap:

qsharp-runtime/src/Qir/Runtime/lib/QIR/bridge-rt.ll

Line 124 in 380003f

define dllexport i8* @__quantum__rt__heap_alloc(i64 %size) {

qsharp-runtime/src/Qir/Runtime/lib/QIR/bridge-rt.ll

Line 129 in 380003f

define dllexport void @__quantum__rt__heap_free(i8* %mem) {

These two methods are neither part of the QIR specification, nor are they used anywhere in the runtime implementation or in QIR generation, making them dead code. If we expect them to be needed in the future then we should update the QIR spec to describe their intended use, otherwise we should remove them and the underlying support to avoid the cost of maintaining them.

@bettinaheim @alan-geller @kuzminrobin FYI.

[Patil2099]

I would love to work on it. @swernli.

[swernli]

Thanks @Patil2099! Always happy to see involvement from the community! Just as a heads up, we may end up deciding to keep the functions, depending on feedback from the rest of the team on whether removal is the right way to go. I'll follow up on the PR with feedback there, and if the issue is triaged and accepted we can use your PR to resolve it.

[swernli]

Sounds like we have consensus that this is a good removal to make. Removing needs triage label.