JIT: Add missing lvTracked check in optLocalHasNonLoopUses
#109505
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`optLocalHasNonLoopUses` checks if a local might be used after a loop by making use of its liveness information, but it does not check `lvTracked` before doing so. This is generally not a problem as there are other checks that the local is in SSA, and normally SSA implies lvTracked, but that's not the case for locals put into SSA by CSE. Since it is possible to have CSE defs in a loop with uses outside the loop, this check is necessary for correctness. It is expected to regress a bunch of IV opts cases, but in the future we can get those back by computing the necessary liveness when we insert into SSA.
ghost
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Tagging subscribers to this area: @JulieLeeMSFT, @jakobbotsch |
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I added this check in #106637 and identified it as the cause of regressions like #106637 (comment). |
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cc @dotnet/jit-contrib PTAL @AndyAyersMS I plan to add the necessary liveness computations as part of #106637, or maybe as a follow-up. |
AndyAyersMS
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Nov 4, 2024
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/ba-g MacOS 12 brownout and infra timeouts |
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optLocalHasNonLoopUseschecks if a local might be used after a loop by making use of its liveness information, but it does not checklvTrackedbefore doing so. This is generally not a problem as there are other checks that the local is in SSA, and normally SSA implieslvTracked, but that's not the case for locals put into SSA by CSE.Since it is possible to have CSE defs in a loop with uses outside the loop, this check is necessary for correctness. It is expected to regress a bunch of IV opts cases, but in the future we can get those back by computing the necessary liveness when we insert into SSA.