[PATCH] D93838: [SCCP] Add Function Specialization pass

[Chuanqi Xu via Phabricator via llvm-commits]

ChuanqiXu added a comment.

In D93838#2769900 <https://reviews.llvm.org/D93838#2769900>, @davidxl wrote:

> For the motivating case from MCF, there is actually code in InlineCost Analysis to handle it.  See InlineCostCallAnalyzer::onLoweredCall(..).  If it is not already handled there, it is a bug to be fixed there.

It is hard to believe that inline could handle the case in MCF. The case in MCF is there is a function `spec_qsort` with signature `(void*, size_t, size_t, int*(const void*, const void*))`. And there is two calls to `spec_qsort`:

  spec_qsort(perm + 1, basket_sizes[thread], sizeof(BASKET*),
              (int (*)(const void *, const void *))cost_compare);
  // and
  spec_qsort(arcs_pointer_sorted[thread], new_arcs_array[thread], sizeof(arc_p),
                  (int (*)(const void *, const void *))arc_compare);

And the benefit comes from function specialization specialize spec_qsort with cost_compare and arc_compare. And finally, cost_compare and arc_compare are inlined in the specialized function. In my minds, without function specialization, compiler couldn't determine the value for the function pointer at compile time. So the inlining couldn't happen.


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https://reviews.llvm.org/D93838