[PATCH] D133362: [InstCombine] Fold x + (x | -x) to x & (x - 1)

[Simon Pilgrim via Phabricator via llvm-commits]

RKSimon added a comment.

Sorry for the short/blunt comments - running out of time today!



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Comment at: llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp:1429
+  // (add A (or A (sub 0, A))) --> (and (add A, -1) A)
+  if (match(&I, m_c_BinOp(m_Or(m_Sub(m_ZeroInt(), m_Value(A)), m_Value(A)), m_Value(A)))) {
+    Value *AddInst = Builder.CreateAdd(A, Constant::getAllOnesValue(A->getType()));
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Use m_Neg()? Also, you need to use m_Deferred() for those later m_Value()


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Comment at: llvm/test/Transforms/InstCombine/add_or_sub.ll:26
+  ret i8 %add
+}
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vector cases? multiuse cases? negative cases?


Repository:
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https://reviews.llvm.org/D133362