This occured if a stack-promoted object with a devirtualized final release is not actually allocated on the stack.
Now the ReleaseDevirtualizer models the procedure of a final release more accurately.
It inserts a set_deallocating instruction and calles the deallocator (instead of just the deinit).
This changes also includes two peephole optimizations in IRGen and LLVMStackPromotion which get rid of
unused runtime calls in case the stack promoted object is really allocated on the stack.
This fixes rdar://problem/25068118
Assertion failed: (NumUsePointsToFind > 0 && "There must be at least one
releasing instruction for an alloc"), function canPromoteAlloc
Revert "Fix comment for StackPromotion pass in SIL Passes"
Revert "Reapply the StackPromotion commit
0dd045ca04dcc10a33abf57f7e1b08260c4e3de1."
This reverts commit 3f4b1496bd and commit
199cfca13b.
It promotes allocations of native swift objects and array buffers to the stack if it is possible.
The SIL StackPromotion pass is the main part of the optimization. For details see comments there.
Unfortunately we need an additional LLVM pass to handle array buffers, which is not very nice.
I hope that we can get rid of it in future (again: for details see the comments in StackPromotion.cpp)
The optimization gives performance improvements in some benchmarks, mostly related to array literals:
ArrayLiteral: +12%
Combos: +16%
DictionaryLiteral: + 37%
RIPEMD: +10%
StringBuilder: +27%
StringInterpolation: +11%
And last but not least the new benchmark which is dedicated to test stack promotion:
ObjectAllocation: +52%
