[llvm] [InstCombine] Combine and->cmp->sel->or-disjoint into and->mul (PR #135274)

[Jeffrey Byrnes via llvm-commits]

================
@@ -3643,6 +3643,48 @@ Instruction *InstCombinerImpl::visitOr(BinaryOperator &I) {
             foldAddLikeCommutative(I.getOperand(1), I.getOperand(0),
                                    /*NSW=*/true, /*NUW=*/true))
       return R;
+
+    Value *Cond0 = nullptr, *Cond1 = nullptr;
+    ConstantInt *Op0True = nullptr, *Op0False = nullptr;
+    ConstantInt *Op1True = nullptr, *Op1False = nullptr;
+
+    //  (!(A & N) ? 0 : N * C) + (!(A & M) ? 0 : M * C) -> A & (N + M) * C
+    if (match(I.getOperand(0), m_Select(m_Value(Cond0), m_ConstantInt(Op0True),
+                                        m_ConstantInt(Op0False))) &&
+        match(I.getOperand(1), m_Select(m_Value(Cond1), m_ConstantInt(Op1True),
+                                        m_ConstantInt(Op1False))) &&
+        Op0True->isZero() && Op1True->isZero() &&
----------------
jrbyrnes wrote:

Thanks, I also missed the check that the result of the and masking must equal the and mask or 0 -- no partial matching. To do this, I've made sure the and masks have only 1 active bit. There are a couple other conditions which I've tried to denote in the generalized test.

https://github.com/llvm/llvm-project/pull/135274