[PATCH] D59473: [ValueTracking] Avoid redundant known bits calculation in computeOverflowForSignedAdd()
Roman Lebedev via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Sun Mar 17 14:21:22 PDT 2019
lebedev.ri added inline comments.
================
Comment at: llvm/lib/Analysis/ValueTracking.cpp:4192-4194
+ KnownBits AddKnown(LHSKnown.getBitWidth());
+ computeKnownBitsFromAssume(
+ Add, AddKnown, /*Depth=*/0, Query(DL, AC, CxtI, DT, true));
----------------
What about this comment in `computeKnownBits()`:
```
// computeKnownBitsFromAssume strictly refines Known.
// Therefore, we run them after computeKnownBitsFromOperator.
```
By looking at `computeKnownBitsFromAssume()`, it doesn't look like that will affect the correctness of output,
the bits that weren't inferred from assumption will simply remain unknown, correct?
Repository:
rL LLVM
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D59473/new/
https://reviews.llvm.org/D59473
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