[PATCH] D133695: [InstCombine] Optimize multiplication where both operands are negated

[Sanjay Patel via Phabricator via llvm-commits]

spatel added inline comments.


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Comment at: llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp:1834
+    // Optimize multiplication where both operators are negated
+    // ~A * ~ B = A * B
+    Value *Op0 = II->getArgOperand(0);
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I read "~" as "bitwise not". I expect this comment to be something like this:
 // -[A] * -[B] --> [A] * [B]


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Comment at: llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp:1838-1839
+    if (match(Op0, m_FNeg(m_Value())) && match(Op1, m_FNeg(m_Value()))) {
+      Value *Op0NotNeg = cast<Instruction>(Op0)->getOperand(0);
+      Value *Op1NotNeg = cast<Instruction>(Op1)->getOperand(0);
+      replaceOperand(*II, 0, Op0NotNeg);
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The casting is unnecessary, and the code doesn't match the code comment. Capture the source values as "A" and "B" inside the match() statement (the same way it is done in the existing variants of this transform).


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D133695/new/

https://reviews.llvm.org/D133695