From 380a3255203ce0bac81dbb7f3526e517f32d61cf Mon Sep 17 00:00:00 2001
From: Chris Lattner <sabre@nondot.org>
Date: Tue, 24 Jan 2012 14:31:22 +0000
Subject: [PATCH] basic instcombine support for CDS.

llvm-svn: 148806
---
 .../InstCombineSimplifyDemanded.cpp           | 35 +++++++++++++------
 .../InstCombine/InstCombineVectorOps.cpp      | 11 ++++--
 2 files changed, 32 insertions(+), 14 deletions(-)

diff --git a/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp b/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
index 91a48a84739..ed9442511d2 100644
--- a/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
+++ b/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
@@ -855,23 +855,36 @@ Value *InstCombiner::SimplifyDemandedVectorElts(Value *V, APInt DemandedElts,
     return NewCP != CV ? NewCP : 0;
   }
   
-  if (isa<ConstantAggregateZero>(V)) {
-    // Simplify the CAZ to a ConstantVector where the non-demanded elements are
-    // set to undef.
+  if (ConstantDataVector *CDV = dyn_cast<ConstantDataVector>(V)) {
+    // Check if this is identity. If so, return 0 since we are not simplifying
+    // anything.
+    if (DemandedElts.isAllOnesValue())
+      return 0;
+
+    // Simplify to a ConstantVector where the non-demanded elements are undef.
+    Constant *Undef = UndefValue::get(CDV->getElementType());
     
+    SmallVector<Constant*, 16> Elts;
+    for (unsigned i = 0; i != VWidth; ++i)
+      Elts.push_back(DemandedElts[i] ? CDV->getElementAsConstant(i) : Undef);
+    UndefElts = DemandedElts ^ EltMask;
+    return ConstantVector::get(Elts);
+
+  }
+  
+  if (ConstantAggregateZero *CAZ = dyn_cast<ConstantAggregateZero>(V)) {
     // Check if this is identity. If so, return 0 since we are not simplifying
     // anything.
     if (DemandedElts.isAllOnesValue())
       return 0;
     
-    Type *EltTy = cast<VectorType>(V->getType())->getElementType();
-    Constant *Zero = Constant::getNullValue(EltTy);
-    Constant *Undef = UndefValue::get(EltTy);
-    std::vector<Constant*> Elts;
-    for (unsigned i = 0; i != VWidth; ++i) {
-      Constant *Elt = DemandedElts[i] ? Zero : Undef;
-      Elts.push_back(Elt);
-    }
+    // Simplify the CAZ to a ConstantVector where the non-demanded elements are
+    // set to undef.
+    Constant *Zero = CAZ->getSequentialElement();
+    Constant *Undef = UndefValue::get(Zero->getType());
+    SmallVector<Constant*, 16> Elts;
+    for (unsigned i = 0; i != VWidth; ++i)
+      Elts.push_back(DemandedElts[i] ? Zero : Undef);
     UndefElts = DemandedElts ^ EltMask;
     return ConstantVector::get(Elts);
   }
diff --git a/lib/Transforms/InstCombine/InstCombineVectorOps.cpp b/lib/Transforms/InstCombine/InstCombineVectorOps.cpp
index 0995d467223..0f8ffb9aebc 100644
--- a/lib/Transforms/InstCombine/InstCombineVectorOps.cpp
+++ b/lib/Transforms/InstCombine/InstCombineVectorOps.cpp
@@ -16,7 +16,8 @@
 using namespace llvm;
 
 /// CheapToScalarize - Return true if the value is cheaper to scalarize than it
-/// is to leave as a vector operation.
+/// is to leave as a vector operation.  isConstant indicates whether we're
+/// extracting one known element.  If false we're extracting a variable index.
 static bool CheapToScalarize(Value *V, bool isConstant) {
   if (isa<ConstantAggregateZero>(V))
     return true;
@@ -335,10 +336,14 @@ static Value *CollectShuffleElements(Value *V, std::vector<Constant*> &Mask,
   if (isa<UndefValue>(V)) {
     Mask.assign(NumElts, UndefValue::get(Type::getInt32Ty(V->getContext())));
     return V;
-  } else if (isa<ConstantAggregateZero>(V)) {
+  }
+  
+  if (isa<ConstantAggregateZero>(V)) {
     Mask.assign(NumElts, ConstantInt::get(Type::getInt32Ty(V->getContext()),0));
     return V;
-  } else if (InsertElementInst *IEI = dyn_cast<InsertElementInst>(V)) {
+  }
+  
+  if (InsertElementInst *IEI = dyn_cast<InsertElementInst>(V)) {
     // If this is an insert of an extract from some other vector, include it.
     Value *VecOp    = IEI->getOperand(0);
     Value *ScalarOp = IEI->getOperand(1);