[PATCH] D112108: [InstCombine] Fold `(a & ~b) & ~c` to `a & ~(b | c)`

[Sanjay Patel via Phabricator via llvm-commits]

spatel added inline comments.


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Comment at: llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp:2018-2020
+    if (match(Op0, m_c_And(m_Value(A), m_Not(m_Value(B)))))
+      if (match(Op1, m_Not(m_Value(C))))
+        if (Op0->hasOneUse())
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You can fold the one-use check into the 1st match with m_OneUse(). Could also use && for the match clauses instead of nested ifs to make the structure more like the code above here.


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Comment at: llvm/test/Transforms/InstCombine/and-xor-or.ll:556
 
 define i32 @not_and_and_not_commute1(i32 %a0, i32 %b, i32 %c) {
 ; CHECK-LABEL: @not_and_and_not_commute1(
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In this test, we do not want to thwart complexity-based canonicalization - we want `%a` to remain as op1, so you don't need the extra `sdiv`.


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Comment at: llvm/test/Transforms/InstCombine/and-xor-or.ll:574
 
 define i32 @not_and_and_not_commute2(i32 %a0, i32 %b, i32 %c) {
 ; CHECK-LABEL: @not_and_and_not_commute2(
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This one is going to be commuted no matter what we do. It's fine to include this for completeness, but let's have it show another variation - add an extra use for `%not2` with something like:
  call void @use(i32 %not2)

Similarly, we should have a negative test for the transform when `%and1` has another use.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D112108/new/

https://reviews.llvm.org/D112108