From fafd6a4d28940626c2b23938baa1babd336d0cd4 Mon Sep 17 00:00:00 2001
From: Arnold Schwaighofer <aschwaighofer@apple.com>
Date: Tue, 12 Feb 2013 02:40:37 +0000
Subject: [PATCH] Cost model: Add check for reverse shuffles to CostModel
 analysis

Check for reverse shuffles in the CostModel analysis pass and query
TargetTransform info accordingly. This allows us we can write test cases for
reverse shuffles.

radar://13171406

llvm-svn: 174932
---
 lib/Analysis/CostModel.cpp | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/lib/Analysis/CostModel.cpp b/lib/Analysis/CostModel.cpp
index 8435e397077..44684a9685b 100644
--- a/lib/Analysis/CostModel.cpp
+++ b/lib/Analysis/CostModel.cpp
@@ -80,6 +80,13 @@ CostModelAnalysis::runOnFunction(Function &F) {
  return false;
 }
 
+static bool isReverseVectorMask(SmallVector<int, 16> &Mask) {
+  for (unsigned i = 0, MaskSize = Mask.size(); i < MaskSize; ++i)
+    if (Mask[i] > 0 && Mask[i] != (int)(MaskSize - 1 - i))
+      return false;
+  return true;
+}
+
 unsigned CostModelAnalysis::getInstructionCost(const Instruction *I) const {
   if (!TTI)
     return -1;
@@ -171,6 +178,17 @@ unsigned CostModelAnalysis::getInstructionCost(const Instruction *I) const {
       return TTI->getVectorInstrCost(I->getOpcode(),
                                      IE->getType(), Idx);
     }
+  case Instruction::ShuffleVector: {
+    const ShuffleVectorInst *Shuffle = cast<ShuffleVectorInst>(I);
+    Type *VecTypOp0 = Shuffle->getOperand(0)->getType();
+    unsigned NumVecElems = VecTypOp0->getVectorNumElements();
+    SmallVector<int, 16> Mask = Shuffle->getShuffleMask();
+
+    if (NumVecElems == Mask.size() && isReverseVectorMask(Mask))
+      return TTI->getShuffleCost(TargetTransformInfo::SK_Reverse, VecTypOp0, 0,
+                                 0);
+    return -1;
+  }
   default:
     // We don't have any information on this instruction.
     return -1;