From e8d6f34445856fcdf9224095441a04457b626f83 Mon Sep 17 00:00:00 2001
From: Sanjay Patel <spatel@rotateright.com>
Date: Tue, 15 May 2018 21:23:58 +0000
Subject: [PATCH] [InstCombine] clean up code for binop-shuffle transforms;
 NFCI

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@332399 91177308-0d34-0410-b5e6-96231b3b80d8
---
 .../InstCombine/InstructionCombining.cpp           | 73 ++++++++++------------
 1 file changed, 34 insertions(+), 39 deletions(-)

diff --git a/lib/Transforms/InstCombine/InstructionCombining.cpp b/lib/Transforms/InstCombine/InstructionCombining.cpp
index c913988d164..7f97b78986a 100644
--- a/lib/Transforms/InstCombine/InstructionCombining.cpp
+++ b/lib/Transforms/InstCombine/InstructionCombining.cpp
@@ -1351,17 +1351,6 @@ Value *InstCombiner::Descale(Value *Val, APInt Scale, bool &NoSignedWrap) {
   } while (true);
 }
 
-/// Creates node of binary operation with the same attributes as the
-/// specified one but with other operands.
-static Value *CreateBinOpAsGiven(BinaryOperator &Inst, Value *LHS, Value *RHS,
-                                 InstCombiner::BuilderTy &B) {
-  Value *BO = B.CreateBinOp(Inst.getOpcode(), LHS, RHS);
-  // If LHS and RHS are constant, BO won't be a binary operator.
-  if (BinaryOperator *NewBO = dyn_cast<BinaryOperator>(BO))
-    NewBO->copyIRFlags(&Inst);
-  return BO;
-}
-
 /// Makes transformation of binary operation specific for vector types.
 /// \param Inst Binary operator to transform.
 /// \return Pointer to node that must replace the original binary operator, or
@@ -1380,6 +1369,13 @@ Value *InstCombiner::SimplifyVectorOp(BinaryOperator &Inst) {
   assert(cast<VectorType>(LHS->getType())->getNumElements() == VWidth);
   assert(cast<VectorType>(RHS->getType())->getNumElements() == VWidth);
 
+  auto createBinOpShuffle = [&](Value *X, Value *Y, Constant *M) {
+    Value *XY = Builder.CreateBinOp(Inst.getOpcode(), X, Y);
+    if (auto *BO = dyn_cast<BinaryOperator>(XY))
+      BO->copyIRFlags(&Inst);
+    return Builder.CreateShuffleVector(XY, UndefValue::get(XY->getType()), M);
+  };
+
   // If both arguments of the binary operation are shuffles that use the same
   // mask and shuffle within a single vector, move the shuffle after the binop.
   Value *V1, *V2;
@@ -1389,47 +1385,46 @@ Value *InstCombiner::SimplifyVectorOp(BinaryOperator &Inst) {
       V1->getType() == V2->getType() &&
       (LHS->hasOneUse() || RHS->hasOneUse() || LHS == RHS)) {
     // Op(shuffle(V1, Mask), shuffle(V2, Mask)) -> shuffle(Op(V1, V2), Mask)
-    Value *B = CreateBinOpAsGiven(Inst, V1, V2, Builder);
-    return Builder.CreateShuffleVector(B, UndefValue::get(V1->getType()), Mask);
+    return createBinOpShuffle(V1, V2, Mask);
   }
 
-  // If one argument is a shuffle within one vector, the other is a constant,
-  // try moving the shuffle after the binary operation.
-  ShuffleVectorInst *Shuffle = nullptr;
-  Constant *C1 = nullptr;
-  if (isa<ShuffleVectorInst>(LHS)) Shuffle = cast<ShuffleVectorInst>(LHS);
-  if (isa<ShuffleVectorInst>(RHS)) Shuffle = cast<ShuffleVectorInst>(RHS);
-  if (isa<Constant>(LHS)) C1 = cast<Constant>(LHS);
-  if (isa<Constant>(RHS)) C1 = cast<Constant>(RHS);
-  if (Shuffle && C1 &&
-      (isa<ConstantVector>(C1) || isa<ConstantDataVector>(C1)) &&
-      isa<UndefValue>(Shuffle->getOperand(1)) &&
-      Shuffle->getType() == Shuffle->getOperand(0)->getType()) {
-    SmallVector<int, 16> ShMask = Shuffle->getShuffleMask();
-    // Find constant C2 that has property:
-    //   shuffle(C2, ShMask) = C1
-    // If such constant does not exist (example: ShMask=<0,0> and C1=<1,2>)
+  // If one argument is a shuffle within one vector and the other is a constant,
+  // try moving the shuffle after the binary operation. This canonicalization
+  // intends to move shuffles closer to other shuffles and binops closer to
+  // other binops, so they can be folded. It may also enable demanded elements
+  // transforms.
+  Constant *C;
+  if (match(&Inst, m_c_BinOp(
+          m_ShuffleVector(m_Value(V1), m_Undef(), m_Constant(Mask)),
+          m_Constant(C))) &&
+      V1->getType() == Inst.getType()) {
+    // Find constant NewC that has property:
+    //   shuffle(NewC, ShMask) = C
+    // If such constant does not exist (example: ShMask=<0,0> and C=<1,2>)
     // reorder is not possible.
-    SmallVector<Constant*, 16> C2M(VWidth,
-                               UndefValue::get(C1->getType()->getScalarType()));
+    SmallVector<int, 16> ShMask;
+    ShuffleVectorInst::getShuffleMask(Mask, ShMask);
+    SmallVector<Constant *, 16>
+        NewVecC(VWidth, UndefValue::get(C->getType()->getScalarType()));
     bool MayChange = true;
     for (unsigned I = 0; I < VWidth; ++I) {
       if (ShMask[I] >= 0) {
         assert(ShMask[I] < (int)VWidth);
-        if (!isa<UndefValue>(C2M[ShMask[I]])) {
+        Constant *CElt = C->getAggregateElement(I);
+        if (!CElt || !isa<UndefValue>(NewVecC[ShMask[I]])) {
           MayChange = false;
           break;
         }
-        C2M[ShMask[I]] = C1->getAggregateElement(I);
+        NewVecC[ShMask[I]] = CElt;
       }
     }
     if (MayChange) {
-      Constant *C2 = ConstantVector::get(C2M);
-      Value *NewLHS = isa<Constant>(LHS) ? C2 : Shuffle->getOperand(0);
-      Value *NewRHS = isa<Constant>(LHS) ? Shuffle->getOperand(0) : C2;
-      Value *NewBO = CreateBinOpAsGiven(Inst, NewLHS, NewRHS, Builder);
-      return Builder.CreateShuffleVector(NewBO,
-          UndefValue::get(Inst.getType()), Shuffle->getMask());
+      // Op(shuffle(V1, Mask), C) -> shuffle(Op(V1, NewC), Mask)
+      // Op(C, shuffle(V1, Mask)) -> shuffle(Op(NewC, V1), Mask)
+      Constant *NewC = ConstantVector::get(NewVecC);
+      Value *NewLHS = isa<Constant>(LHS) ? NewC : V1;
+      Value *NewRHS = isa<Constant>(LHS) ? V1 : NewC;
+      return createBinOpShuffle(NewLHS, NewRHS, Mask);
     }
   }
 
-- 
2.11.0