[llvm] [InstCombine] Fold commuted add of udiv/urem by two (#206272) (PR #207462)

[Igor Shevlyakov via llvm-commits]

================
@@ -1192,34 +1192,41 @@ Value *InstCombinerImpl::SimplifyAddWithRemainder(BinaryOperator &I) {
     }
   }
 
-  // Match I = (X / C0) * C1 + (X % C0) * C2
-  Value *Div, *Rem;
-  APInt C1, C2;
-  if (!LHS->hasOneUse() || !MatchMul(LHS, Div, C1))
-    Div = LHS, C1 = APInt(I.getType()->getScalarSizeInBits(), 1);
-  if (!RHS->hasOneUse() || !MatchMul(RHS, Rem, C2))
-    Rem = RHS, C2 = APInt(I.getType()->getScalarSizeInBits(), 1);
-  if (match(Div, m_IRem(m_Value(), m_Value()))) {
-    std::swap(Div, Rem);
-    std::swap(C1, C2);
-  }
-  Value *DivOpV;
-  APInt DivOpC;
-  if (MatchRem(Rem, X, C0, IsSigned) &&
-      MatchDiv(Div, DivOpV, DivOpC, IsSigned) && X == DivOpV && C0 == DivOpC &&
-      // Avoid unprofitable replacement of and with mul.
-      !(C1.isOne() && !IsSigned && DivOpC.isPowerOf2() && DivOpC != 2)) {
-    APInt NewC = C1 - C2 * C0;
-    if (!NewC.isZero() && !Rem->hasOneUse())
-      return nullptr;
-    if (!isGuaranteedNotToBeUndef(X, &AC, &I, &DT))
-      return nullptr;
-    Value *MulXC2 = Builder.CreateMul(X, ConstantInt::get(X->getType(), C2));
-    if (NewC.isZero())
-      return MulXC2;
-    return Builder.CreateAdd(
-        Builder.CreateMul(Div, ConstantInt::get(X->getType(), NewC)), MulXC2);
-  }
+  // Match I = (X / C0) * C1 + (X % C0) * C2. The division and remainder may
+  // appear in either operand order, and the remainder may be spelled
----------------
ishevlyakov wrote:

I trimmed comment back to the original form

https://github.com/llvm/llvm-project/pull/207462