[PATCH] D142849: [ValueTracking] Add helper for handling `computeKnownBits` for and/xor/or; NFC

[Nikita Popov via Phabricator via llvm-commits]

nikic added inline comments.


================
Comment at: llvm/lib/Analysis/ValueTracking.cpp:1071
+
+  // We don't want to put this before the Known.One.isZero check.
+  switch (I->getOpcode()) {
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I don't understand this comment.


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Comment at: llvm/lib/Analysis/ValueTracking.cpp:1087
+
+  // and(x, -x)/xor(x, x-1) are common idioms that will  clearing all but
+  // lowest set bit. If we have a single known bit in x, we can clear all bits
----------------
clearing -> clear?


================
Comment at: llvm/lib/Analysis/ValueTracking.cpp:1100
+                                m_c_Add(m_Deferred(X), m_AllOnes()))))) {
+    if (IsAnd) {
+      // -(-x) == x so using whichever (LHS/RHS) gets us a better result.
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It doesn't look like the and/xor cases here really share any code -- makes more sense to handle them in separate ifs ... or better, move them into the respective switch cases above?


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D142849/new/

https://reviews.llvm.org/D142849