Optimizer: re-implement the RedundantLoadElimination pass in Swift #67395
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…tore [assign]` So far we unconditionally treated `store [assign]` to have side effects because it destructs the old value. But we can do better by checking if the address in question actually can escape to a destructor.
…struction for a `yield` access base A begin_apply can yield multiple addresses. We need to store the result of the apply in order to distinguish between two AccessBases with different results from the same begin_apply.
…e equivalent This is possible now because projection path now models index-addressing correctly.
…n` when getting the root of a reference
To make it available in other optimizations as well. Also, a few problems: * Use destructre instructions when in OSSA * Don't split the store if it's nominal type has unreferenceable stoarge * rename it to `trySplit` because it's not guaranteed to work Also, add the counterpart for load instructions: `LoadInst.trySplit()`
The new implementation has several benefits compared to the old C++ implementation: * It is significantly simpler. It optimizes each load separately instead of all at once with bit-field based dataflow. * It's using alias analysis more accurately which enables more loads to be optimized * It avoids inserting additional copies in OSSA The algorithm is a data flow analysis which starts at the original load and searches for preceding stores or loads by following the control flow in backward direction. The preceding stores and loads provide the "available values" with which the original load can be replaced.
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The new implementation has several benefits compared to the old C++ implementation:
The algorithm is a data flow analysis which starts at the original load and searches for preceding stores or loads by following the control flow in backward direction.
The preceding stores and loads provide the "available values" with which the original load can be replaced.
This is the counterpart to the new implementation of dead-store elimination (#67122)