[PATCH] D145299: [InstCombine] Generate better code for std::bit_ceil

[Nikita Popov via Phabricator via llvm-commits]

nikic requested changes to this revision.
nikic added a comment.
This revision now requires changes to proceed.

Implementation looks fine, but this needs more test coverage.



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Comment at: llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp:3197
+  auto MatchForward = [&](Value *CommonAncestor) {
+    const APInt *C = nullptr;
+    if (match(CtlzOp, m_Add(m_Specific(CommonAncestor), m_APInt(C)))) {
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Check `CommonAncestor == CtlzOp` here and then drop the first `if` below? So it's one MatchForward plus one MatchForward after peeking through add?


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Comment at: llvm/test/Transforms/InstCombine/bit_ceil.ll:153
   ret i32 %sel
 }
 
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Some missing tests:
 * Commuted select operands.
 * Select constant not 1.
 * Select condition does not imply the needed range.
 * Multi-use test.
 * Vector test.
 * Wrong constant in sub.


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D145299/new/

https://reviews.llvm.org/D145299