4 files changed, 39 insertions, 5 deletions
diff --git a/llvm/lib/IR/Constants.cpp b/llvm/lib/IR/Constants.cpp
index bc55d5b..a38b912 100644
--- a/llvm/lib/IR/Constants.cpp
+++ b/llvm/lib/IR/Constants.cpp
@@ -2556,6 +2556,32 @@ Constant *ConstantExpr::getBinOpIdentity(unsigned Opcode, Type *Ty,
   }
 }
 
+Constant *ConstantExpr::getIntrinsicIdentity(Intrinsic::ID ID, Type *Ty) {
+  switch (ID) {
+  case Intrinsic::umax:
+    return Constant::getNullValue(Ty);
+  case Intrinsic::umin:
+    return Constant::getAllOnesValue(Ty);
+  case Intrinsic::smax:
+    return Constant::getIntegerValue(
+        Ty, APInt::getSignedMinValue(Ty->getIntegerBitWidth()));
+  case Intrinsic::smin:
+    return Constant::getIntegerValue(
+        Ty, APInt::getSignedMaxValue(Ty->getIntegerBitWidth()));
+  default:
+    return nullptr;
+  }
+}
+
+Constant *ConstantExpr::getIdentity(Instruction *I, Type *Ty,
+                                    bool AllowRHSConstant, bool NSZ) {
+  if (I->isBinaryOp())
+    return getBinOpIdentity(I->getOpcode(), Ty, AllowRHSConstant, NSZ);
+  if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I))
+    return getIntrinsicIdentity(II->getIntrinsicID(), Ty);
+  return nullptr;
+}
+
 Constant *ConstantExpr::getBinOpAbsorber(unsigned Opcode, Type *Ty) {
   switch (Opcode) {
   default:
diff --git a/llvm/lib/IR/Instruction.cpp b/llvm/lib/IR/Instruction.cpp
index 4b53498..a6e43de 100644
--- a/llvm/lib/IR/Instruction.cpp
+++ b/llvm/lib/IR/Instruction.cpp
@@ -1091,6 +1091,8 @@ const DebugLoc &Instruction::getStableDebugLoc() const {
 }
 
 bool Instruction::isAssociative() const {
+  if (auto *II = dyn_cast<IntrinsicInst>(this))
+    return II->isAssociative();
   unsigned Opcode = getOpcode();
   if (isAssociative(Opcode))
     return true;
diff --git a/llvm/lib/Transforms/Scalar/Reassociate.cpp b/llvm/lib/Transforms/Scalar/Reassociate.cpp
index 0d55c72..d3f6d24 100644
--- a/llvm/lib/Transforms/Scalar/Reassociate.cpp
+++ b/llvm/lib/Transforms/Scalar/Reassociate.cpp
@@ -2554,7 +2554,7 @@ ReassociatePass::BuildPairMap(ReversePostOrderTraversal<Function *> &RPOT) {
   // Make a "pairmap" of how often each operand pair occurs.
   for (BasicBlock *BI : RPOT) {
     for (Instruction &I : *BI) {
-      if (!I.isAssociative())
+      if (!I.isAssociative() || !I.isBinaryOp())
         continue;
 
       // Ignore nodes that aren't at the root of trees.
diff --git a/llvm/lib/Transforms/Scalar/TailRecursionElimination.cpp b/llvm/lib/Transforms/Scalar/TailRecursionElimination.cpp
index 7b850f0..c6e8505 100644
--- a/llvm/lib/Transforms/Scalar/TailRecursionElimination.cpp
+++ b/llvm/lib/Transforms/Scalar/TailRecursionElimination.cpp
@@ -369,8 +369,14 @@ static bool canTransformAccumulatorRecursion(Instruction *I, CallInst *CI) {
   if (!I->isAssociative() || !I->isCommutative())
     return false;
 
-  assert(I->getNumOperands() == 2 &&
-         "Associative/commutative operations should have 2 args!");
+  assert(I->getNumOperands() >= 2 &&
+         "Associative/commutative operations should have at least 2 args!");
+
+  if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) {
+    // Accumulators must have an identity.
+    if (!ConstantExpr::getIntrinsicIdentity(II->getIntrinsicID(), I->getType()))
+      return false;
+  }
 
   // Exactly one operand should be the result of the call instruction.
   if ((I->getOperand(0) == CI && I->getOperand(1) == CI) ||
@@ -569,8 +575,8 @@ void TailRecursionEliminator::insertAccumulator(Instruction *AccRecInstr) {
   for (pred_iterator PI = PB; PI != PE; ++PI) {
     BasicBlock *P = *PI;
     if (P == &F.getEntryBlock()) {
-      Constant *Identity = ConstantExpr::getBinOpIdentity(
-          AccRecInstr->getOpcode(), AccRecInstr->getType());
+      Constant *Identity =
+          ConstantExpr::getIdentity(AccRecInstr, AccRecInstr->getType());
       AccPN->addIncoming(Identity, P);
     } else {
       AccPN->addIncoming(AccPN, P);