Automerge: [InstCombine] Extend bitmask mul combine to handle independent operands (#142503)

This extends llvm/llvm-project#136013 to capture
cases where the combineable bitmask muls are nested under multiple
or-disjoints.

This PR is meant for commits starting at
8c403c912046505ffc10378560c2fc48f214af6a

op1 = or-disjoint mul(and (X, C1), D) , reg1
op2 = or-disjoint mul(and (X, C2), D) , reg2
out = or-disjoint op1, op2

->

temp1 = or-disjoint reg1, reg2
out = or-disjoint mul(and (X, (C1 + C2)), D), temp1

Case1: https://alive2.llvm.org/ce/z/dHApyV
Case2: https://alive2.llvm.org/ce/z/Jz-Nag
Case3: https://alive2.llvm.org/ce/z/3xBnEV

Author: jrbyrnes

llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp

@@ -3602,6 +3602,11 @@ struct DecomposedBitMaskMul {
   APInt Mask;
   bool NUW;
   bool NSW;
+
+  bool isCombineableWith(const DecomposedBitMaskMul Other) {
+    return X == Other.X && !Mask.intersects(Other.Mask) &&
+           Factor == Other.Factor;
+  }
 };
 
 static std::optional<DecomposedBitMaskMul> matchBitmaskMul(Value *V) {
@@ -3659,6 +3664,59 @@ static std::optional<DecomposedBitMaskMul> matchBitmaskMul(Value *V) {
   return std::nullopt;
 }
 
+/// (A & N) * C + (A & M) * C -> (A & (N + M)) & C
+/// This also accepts the equivalent select form of (A & N) * C
+/// expressions i.e. !(A & N) ? 0 : N * C)
+static Value *foldBitmaskMul(Value *Op0, Value *Op1,
+                             InstCombiner::BuilderTy &Builder) {
+  auto Decomp1 = matchBitmaskMul(Op1);
+  if (!Decomp1)
+    return nullptr;
+
+  auto Decomp0 = matchBitmaskMul(Op0);
+  if (!Decomp0)
+    return nullptr;
+
+  if (Decomp0->isCombineableWith(*Decomp1)) {
+    Value *NewAnd = Builder.CreateAnd(
+        Decomp0->X,
+        ConstantInt::get(Decomp0->X->getType(), Decomp0->Mask + Decomp1->Mask));
+
+    return Builder.CreateMul(
+        NewAnd, ConstantInt::get(NewAnd->getType(), Decomp1->Factor), "",
+        Decomp0->NUW && Decomp1->NUW, Decomp0->NSW && Decomp1->NSW);
+  }
+
+  return nullptr;
+}
+
+Value *InstCombinerImpl::foldDisjointOr(Value *LHS, Value *RHS) {
+  if (Value *Res = foldBitmaskMul(LHS, RHS, Builder))
+    return Res;
+
+  return nullptr;
+}
+
+Value *InstCombinerImpl::reassociateDisjointOr(Value *LHS, Value *RHS) {
+
+  Value *X, *Y;
+  if (match(RHS, m_OneUse(m_DisjointOr(m_Value(X), m_Value(Y))))) {
+    if (Value *Res = foldDisjointOr(LHS, X))
+      return Builder.CreateOr(Res, Y, "", /*IsDisjoint=*/true);
+    if (Value *Res = foldDisjointOr(LHS, Y))
+      return Builder.CreateOr(Res, X, "", /*IsDisjoint=*/true);
+  }
+
+  if (match(LHS, m_OneUse(m_DisjointOr(m_Value(X), m_Value(Y))))) {
+    if (Value *Res = foldDisjointOr(X, RHS))
+      return Builder.CreateOr(Res, Y, "", /*IsDisjoint=*/true);
+    if (Value *Res = foldDisjointOr(Y, RHS))
+      return Builder.CreateOr(Res, X, "", /*IsDisjoint=*/true);
+  }
+
+  return nullptr;
+}
+
 // FIXME: We use commutative matchers (m_c_*) for some, but not all, matches
 // here. We should standardize that construct where it is needed or choose some
 // other way to ensure that commutated variants of patterns are not missed.
@@ -3741,28 +3799,11 @@ Instruction *InstCombinerImpl::visitOr(BinaryOperator &I) {
                                    /*NSW=*/true, /*NUW=*/true))
       return R;
 
-    // (A & N) * C + (A & M) * C -> (A & (N + M)) & C
-    // This also accepts the equivalent select form of (A & N) * C
-    // expressions i.e. !(A & N) ? 0 : N * C)
-    auto Decomp1 = matchBitmaskMul(I.getOperand(1));
-    if (Decomp1) {
-      auto Decomp0 = matchBitmaskMul(I.getOperand(0));
-      if (Decomp0 && Decomp0->X == Decomp1->X &&
-          (Decomp0->Mask & Decomp1->Mask).isZero() &&
-          Decomp0->Factor == Decomp1->Factor) {
-
-        Value *NewAnd = Builder.CreateAnd(
-            Decomp0->X, ConstantInt::get(Decomp0->X->getType(),
-                                         (Decomp0->Mask + Decomp1->Mask)));
-
-        auto *Combined = BinaryOperator::CreateMul(
-            NewAnd, ConstantInt::get(NewAnd->getType(), Decomp1->Factor));
-
-        Combined->setHasNoUnsignedWrap(Decomp0->NUW && Decomp1->NUW);
-        Combined->setHasNoSignedWrap(Decomp0->NSW && Decomp1->NSW);
-        return Combined;
-      }
-    }
+    if (Value *Res = foldBitmaskMul(I.getOperand(0), I.getOperand(1), Builder))
+      return replaceInstUsesWith(I, Res);
+
+    if (Value *Res = reassociateDisjointOr(I.getOperand(0), I.getOperand(1)))
+      return replaceInstUsesWith(I, Res);
   }
 
   Value *X, *Y;

llvm/lib/Transforms/InstCombine/InstCombineInternal.h

@@ -439,6 +439,10 @@ class LLVM_LIBRARY_VISIBILITY InstCombinerImpl final
   Value *reassociateBooleanAndOr(Value *LHS, Value *X, Value *Y, Instruction &I,
                                  bool IsAnd, bool RHSIsLogical);
 
+  Value *foldDisjointOr(Value *LHS, Value *RHS);
+
+  Value *reassociateDisjointOr(Value *LHS, Value *RHS);
+
   Instruction *
   canonicalizeConditionalNegationViaMathToSelect(BinaryOperator &i);