[Attributor] Loads in readonly functions are replaced with wrong value #53726
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/cherry-pick d1387a2 |
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/branch llvmbot/llvm-project/issue53726 |
llvmbot
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Feb 11, 2022
The oversight caused us to ignore call sites that are effectively dead when we computed reachability (or more precise the call edges of a function). The problem is that loads in the readonly callee might depend on stores prior to the callee. If we do not track the call edge we mistakenly assumed the store before the call cannot reach the load. The problem is nicely visible in: `llvm/test/Transforms/Attributor/ArgumentPromotion/basictest.ll` Caused by D118673. Fixes llvm#53726 (cherry picked from commit d1387a2)
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/pull-request llvmbot#41 |
jdoerfert
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Feb 17, 2022
The oversight caused us to ignore call sites that are effectively dead when we computed reachability (or more precise the call edges of a function). The problem is that loads in the readonly callee might depend on stores prior to the callee. If we do not track the call edge we mistakenly assumed the store before the call cannot reach the load. The problem is nicely visible in: `llvm/test/Transforms/Attributor/ArgumentPromotion/basictest.ll` Caused by D118673. Fixes llvm#53726
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/branch jdoerfert/llvm-project/issue53726 |
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/pull-request llvmbot#73 |
tstellar
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Feb 21, 2022
The oversight caused us to ignore call sites that are effectively dead when we computed reachability (or more precise the call edges of a function). The problem is that loads in the readonly callee might depend on stores prior to the callee. If we do not track the call edge we mistakenly assumed the store before the call cannot reach the load. The problem is nicely visible in: `llvm/test/Transforms/Attributor/ArgumentPromotion/basictest.ll` Caused by D118673. Fixes llvm#53726
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Merged: 13fdc7a |
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Readonly function calls are assumed dead if the return value is assumed dead. This is OK but we cannot ignore them when we determine reachability as part of the identification of memory content, e.g., what value is loaded from some ptr. If we ignore the call, the load is not reachable from a store prior to the call, which then leads us to believe the load will result in a different value, often undef.
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