[SIL Optimization] Improve dead-code in OSLogOptimization pass, fix a bug and add helper functions to the new InstructionDeleter utility #29447
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evaluable calls. The fix makes the check more conservative and assumes that calls with generic arguments are not dead, as generic functions with arbitrary side-effects can be invoked through them. Also, add a few helper functions to the InstructionDeleter utility that will enable deleting an instruction along with its users.
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using the new InstructionDeleter utility. The elimination logic exploits the fact that constant_evaluable function calls have been evaluated and folded, in order to remove such calls that may possibly take @inout parameters.
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This PR consists of two commits. The first one fixes a bug in the identification of dead constant evaluable calls in the new InstructionDeleter utility. The fix makes the check more conservative and assumes that calls with generic arguments are not dead, as generic functions with arbitrary side-effects can be invoked through them.
The second commit improves the OSLogOptimization pass so that it can remove alloc_stacks that are dead as a result of the optimization. This change is specific to the pass and exploits the constant-evaluableness of the calls evaluated in that pass. At this point, this cannot be generalized outside of this pass, as it relies on the fact that the constant_evaluable calls "have been" evaluated successfully, which means that they did not have any side-effects (in that calling context) and were only using constants supported by the constant evaluator (all of which have value semantics).