Two optimization improvements to fix dead-object-elimination with OSSA #78163
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…ead arrays This is part of fixing regressions when enabling OSSA modules: rdar://140229560
Canonicalize a `fix_lifetime` from an address to a `load` + `fix_lifetime`: ``` %1 = alloc_stack $T ... fix_lifetime %1 ``` -> ``` %1 = alloc_stack $T ... %2 = load %1 fix_lifetime %2 ``` This transformation is done for `alloc_stack` and `store_borrow` (which always has an `alloc_stack` operand). The benefit of this transformation is that it enables other optimizations, like mem2reg. This peephole optimization was already done in SILCombine, but it didn't handle store_borrow. A good opportunity to make an instruction simplification out of it. This is part of fixing regressions when enabling OSSA modules: rdar://140229560
eeckstein
requested review from
nate-chandler,
meg-gupta and
atrick
and removed request for
nate-chandler
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DeadObjectElimination: handle
begin_borrow/end_borrowwhen deleting dead arraysadd simplification for fix_lifetime: canonicalize a
fix_lifetimefrom an address to aload+fix_lifetime:->
This peephole optimization was already done in SILCombine, but it didn't handle store_borrow - a good opportunity to make an instruction simplification out of it.
This is part of fixing regressions when enabling OSSA modules:
rdar://140229560