Add a ConstantDataVector::getSplatValue() method, for parity with

ConstantVector.  Fix some outright bugs in the implementation of
ConstantArray and Constant struct, which would cause us to not make
one big UndefValue when asking for an array/struct with all undef
elements.  Enhance Constant::isAllOnesValue to work with
ConstantDataVector.

llvm-svn: 149021

2 files changed, 91 insertions, 39 deletions

diff --git a/llvm/include/llvm/Constants.h b/llvm/include/llvm/Constants.h
index a685ccc31c6..1180b955f27 100644
--- a/llvm/include/llvm/Constants.h
+++ b/llvm/include/llvm/Constants.h
@@ -766,6 +766,10 @@ public:
   /// i32/i64/float/double) and must be a ConstantFP or ConstantInt.
   static Constant *getSplat(unsigned NumElts, Constant *Elt);
 
+  /// getSplatValue - If this is a splat constant, meaning that all of the
+  /// elements have the same value, return that value. Otherwise return NULL.
+  Constant *getSplatValue() const;
+  
   /// getType - Specialize the getType() method to always return a VectorType,
   /// which reduces the amount of casting needed in parts of the compiler.
   ///
diff --git a/llvm/lib/VMCore/Constants.cpp b/llvm/lib/VMCore/Constants.cpp
index c1d6da5465c..f5239e15697 100644
--- a/llvm/lib/VMCore/Constants.cpp
+++ b/llvm/lib/VMCore/Constants.cpp
@@ -78,6 +78,11 @@ bool Constant::isAllOnesValue() const {
     if (Constant *Splat = CV->getSplatValue())
       return Splat->isAllOnesValue();
 
+  // Check for constant vectors which are splats of -1 values.
+  if (const ConstantDataVector *CV = dyn_cast<ConstantDataVector>(this))
+    if (Constant *Splat = CV->getSplatValue())
+      return Splat->isAllOnesValue();
+
   return false;
 }
 
@@ -711,17 +716,27 @@ Constant *ConstantArray::get(ArrayType *Ty, ArrayRef<Constant*> V) {
   }
   LLVMContextImpl *pImpl = Ty->getContext().pImpl;
   // If this is an all-zero array, return a ConstantAggregateZero object
+  bool isAllZero = true;
+  bool isUndef = false;
   if (!V.empty()) {
     Constant *C = V[0];
-    if (!C->isNullValue())
-      return pImpl->ArrayConstants.getOrCreate(Ty, V);
-    
-    for (unsigned i = 1, e = V.size(); i != e; ++i)
-      if (V[i] != C)
-        return pImpl->ArrayConstants.getOrCreate(Ty, V);
+    isAllZero = C->isNullValue();
+    isUndef = isa<UndefValue>(C);
+
+    if (isAllZero || isUndef)
+      for (unsigned i = 1, e = V.size(); i != e; ++i)
+        if (V[i] != C) {
+          isAllZero = false;
+          isUndef = false;
+          break;
+        }
   }
-  
-  return ConstantAggregateZero::get(Ty);
+
+  if (isAllZero)
+    return ConstantAggregateZero::get(Ty);
+  if (isUndef)
+    return UndefValue::get(Ty);
+  return pImpl->ArrayConstants.getOrCreate(Ty, V);
 }
 
 /// ConstantArray::get(const string&) - Return an array that is initialized to
@@ -780,14 +795,31 @@ ConstantStruct::ConstantStruct(StructType *T, ArrayRef<Constant *> V)
 
 // ConstantStruct accessors.
 Constant *ConstantStruct::get(StructType *ST, ArrayRef<Constant*> V) {
-  // Create a ConstantAggregateZero value if all elements are zeros.
-  for (unsigned i = 0, e = V.size(); i != e; ++i)
-    if (!V[i]->isNullValue())
-      return ST->getContext().pImpl->StructConstants.getOrCreate(ST, V);
-
   assert((ST->isOpaque() || ST->getNumElements() == V.size()) &&
          "Incorrect # elements specified to ConstantStruct::get");
-  return ConstantAggregateZero::get(ST);
+
+  // Create a ConstantAggregateZero value if all elements are zeros.
+  bool isZero = true;
+  bool isUndef = false;
+  
+  if (!V.empty()) {
+    isUndef = isa<UndefValue>(V[0]);
+    isZero = V[0]->isNullValue();
+    if (isUndef || isZero) {
+      for (unsigned i = 0, e = V.size(); i != e; ++i) {
+        if (!V[i]->isNullValue())
+          isZero = false;
+        if (!isa<UndefValue>(V[i]))
+          isUndef = false;
+      }
+    }
+  }  
+  if (isZero)
+    return ConstantAggregateZero::get(ST);
+  if (isUndef)
+    return UndefValue::get(ST);
+    
+  return ST->getContext().pImpl->StructConstants.getOrCreate(ST, V);
 }
 
 Constant *ConstantStruct::get(StructType *T, ...) {
@@ -2329,6 +2361,20 @@ bool ConstantDataSequential::isCString() const {
   return Str.drop_back().find(0) == StringRef::npos;
 }
 
+/// getSplatValue - If this is a splat constant, meaning that all of the
+/// elements have the same value, return that value. Otherwise return NULL.
+Constant *ConstantDataVector::getSplatValue() const {
+  const char *Base = getRawDataValues().data();
+  
+  // Compare elements 1+ to the 0'th element.
+  unsigned EltSize = getElementByteSize();
+  for (unsigned i = 1, e = getNumElements(); i != e; ++i)
+    if (memcmp(Base, Base+i*EltSize, EltSize))
+      return 0;
+  
+  // If they're all the same, return the 0th one as a representative.
+  return getElementAsConstant(0);
+}
 
 //===----------------------------------------------------------------------===//
 //                replaceUsesOfWithOnConstant implementations
@@ -2360,33 +2406,25 @@ void ConstantArray::replaceUsesOfWithOnConstant(Value *From, Value *To,
 
   // Fill values with the modified operands of the constant array.  Also, 
   // compute whether this turns into an all-zeros array.
-  bool isAllZeros = false;
   unsigned NumUpdated = 0;
-  if (!ToC->isNullValue()) {
-    for (Use *O = OperandList, *E = OperandList+getNumOperands(); O != E; ++O) {
-      Constant *Val = cast<Constant>(O->get());
-      if (Val == From) {
-        Val = ToC;
-        ++NumUpdated;
-      }
-      Values.push_back(Val);
-    }
-  } else {
-    isAllZeros = true;
-    for (Use *O = OperandList, *E = OperandList+getNumOperands();O != E; ++O) {
-      Constant *Val = cast<Constant>(O->get());
-      if (Val == From) {
-        Val = ToC;
-        ++NumUpdated;
-      }
-      Values.push_back(Val);
-      if (isAllZeros) isAllZeros = Val->isNullValue();
+  
+  // Keep track of whether all the values in the array are "ToC".
+  bool AllSame = true;
+  for (Use *O = OperandList, *E = OperandList+getNumOperands(); O != E; ++O) {
+    Constant *Val = cast<Constant>(O->get());
+    if (Val == From) {
+      Val = ToC;
+      ++NumUpdated;
     }
+    Values.push_back(Val);
+    AllSame = Val == ToC;
   }
   
   Constant *Replacement = 0;
-  if (isAllZeros) {
+  if (AllSame && ToC->isNullValue()) {
     Replacement = ConstantAggregateZero::get(getType());
+  } else if (AllSame && isa<UndefValue>(ToC)) {
+    Replacement = UndefValue::get(getType());
   } else {
     // Check to see if we have this array type already.
     bool Exists;
@@ -2446,16 +2484,24 @@ void ConstantStruct::replaceUsesOfWithOnConstant(Value *From, Value *To,
   // Fill values with the modified operands of the constant struct.  Also, 
   // compute whether this turns into an all-zeros struct.
   bool isAllZeros = false;
-  if (!ToC->isNullValue()) {
-    for (Use *O = OperandList, *E = OperandList + getNumOperands(); O != E; ++O)
-      Values.push_back(cast<Constant>(O->get()));
-  } else {
+  bool isAllUndef = false;
+  if (ToC->isNullValue()) {
     isAllZeros = true;
     for (Use *O = OperandList, *E = OperandList+getNumOperands(); O != E; ++O) {
       Constant *Val = cast<Constant>(O->get());
       Values.push_back(Val);
       if (isAllZeros) isAllZeros = Val->isNullValue();
     }
+  } else if (isa<UndefValue>(ToC)) {
+    isAllUndef = true;
+    for (Use *O = OperandList, *E = OperandList+getNumOperands(); O != E; ++O) {
+      Constant *Val = cast<Constant>(O->get());
+      Values.push_back(Val);
+      if (isAllUndef) isAllUndef = isa<UndefValue>(Val);
+    }
+  } else {
+    for (Use *O = OperandList, *E = OperandList + getNumOperands(); O != E; ++O)
+      Values.push_back(cast<Constant>(O->get()));
   }
   Values[OperandToUpdate] = ToC;
   
@@ -2464,6 +2510,8 @@ void ConstantStruct::replaceUsesOfWithOnConstant(Value *From, Value *To,
   Constant *Replacement = 0;
   if (isAllZeros) {
     Replacement = ConstantAggregateZero::get(getType());
+  } else if (isAllUndef) {
+    Replacement = UndefValue::get(getType());
   } else {
     // Check to see if we have this struct type already.
     bool Exists;