[PATCH] D124503: [InstCombine] sub(add(X,Y),umin(Y,Z)) --> add(X,usub.sat(Y,Z))

[Sanjay Patel via Phabricator via llvm-commits]

spatel added inline comments.


================
Comment at: llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp:2042
+          if (match(Op1, m_UMin(m_Specific(Y), m_Value(Z))) ||
+              match(Op1, m_UMin(m_Value(Z), m_Specific(Y)))) {
+            Value *USub =
----------------
RKSimon wrote:
> Do we have a m_c_UMin that we can use instead?
We do have that matcher, but this would be easier if we match the umin first and then find the common operand in the add?

      // sub(add(X,Y),umin(Y,Z)) --> add(X,usub.sat(Y,Z))
      // sub(add(X,Z),umin(Y,Z)) --> add(X,usub.sat(Y,Z))
      Value *X, *Y, *Z;
      if (match(Op1, m_OneUse(m_UMin(m_Value(Y), m_Value(Z)))) &&
          (match(Op0, m_OneUse(m_c_Add(m_Specific(Y), m_Value(X)))) ||
           match(Op0, m_OneUse(m_c_Add(m_Specific(Z), m_Value(X)))))) {
        Value *USub =
            Builder.CreateIntrinsic(Intrinsic::usub_sat, I.getType(), {Y, Z});
        return BinaryOperator::CreateAdd(X, USub);
      }



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https://reviews.llvm.org/D124503