From 8539fe26b7927f7a0c6228e488b8e8957e9726c6 Mon Sep 17 00:00:00 2001
From: Nick Lewycky <nicholas@mxc.ca>
Date: Fri, 23 May 2008 04:14:51 +0000
Subject: [PATCH] Implement X + X for vectors.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@51472 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Transforms/Scalar/InstructionCombining.cpp | 18 +++++++++++++-----
 .../InstCombine/2008-05-22-FoldAddIVec.ll      |  6 ++++++
 2 files changed, 19 insertions(+), 5 deletions(-)
 create mode 100644 test/Transforms/InstCombine/2008-05-22-FoldAddIVec.ll

diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp
index a398884e592..1a878681056 100644
--- a/lib/Transforms/Scalar/InstructionCombining.cpp
+++ b/lib/Transforms/Scalar/InstructionCombining.cpp
@@ -2292,14 +2292,22 @@ static Instruction *AssociativeOpt(BinaryOperator &Root, const Functor &F) {
 
 namespace {
 
-// AddRHS - Implements: X + X --> X << 1
+// AddRHS - Implements: X + X --> X << 1 and X + X --> X * 2 for vectors
 struct AddRHS {
   Value *RHS;
   AddRHS(Value *rhs) : RHS(rhs) {}
   bool shouldApply(Value *LHS) const { return LHS == RHS; }
   Instruction *apply(BinaryOperator &Add) const {
-    return BinaryOperator::CreateShl(Add.getOperand(0),
-                                  ConstantInt::get(Add.getType(), 1));
+    if (Add.getType()->getTypeID() == Type::VectorTyID) {
+      const VectorType *VTy = cast<VectorType>(Add.getType());
+      ConstantInt *CI = ConstantInt::get(VTy->getElementType(), 2);
+      std::vector<Constant*> Elts(VTy->getNumElements(), CI);
+      return BinaryOperator::CreateMul(Add.getOperand(0),
+                                       ConstantVector::get(Elts));
+    } else {
+      return BinaryOperator::CreateShl(Add.getOperand(0),
+                                       ConstantInt::get(Add.getType(), 1));
+    }
   }
 };
 
@@ -2627,8 +2635,8 @@ Instruction *InstCombiner::visitAdd(BinaryOperator &I) {
     }
   }
 
-  // X + X --> X << 1
-  if (I.getType()->isInteger() && I.getType() != Type::Int1Ty) {
+  // X + X --> X << 1 and X + X --> X * 2 for vectors
+  if (I.getType()->isIntOrIntVector() && I.getType() != Type::Int1Ty) {
     if (Instruction *Result = AssociativeOpt(I, AddRHS(RHS))) return Result;
 
     if (Instruction *RHSI = dyn_cast<Instruction>(RHS)) {
diff --git a/test/Transforms/InstCombine/2008-05-22-FoldAddIVec.ll b/test/Transforms/InstCombine/2008-05-22-FoldAddIVec.ll
new file mode 100644
index 00000000000..8bdf9bb2b8d
--- /dev/null
+++ b/test/Transforms/InstCombine/2008-05-22-FoldAddIVec.ll
@@ -0,0 +1,6 @@
+; RUN: llvm-as < %s | opt -instcombine | llvm-dis | grep mul
+
+define <3 x i8> @f(<3 x i8> %i) {
+  %A = add <3 x i8> %i, %i
+  ret <3 x i8> %A
+}