Struct-path aware TBAA: change the format of TBAAStructType node.

We switch the order of offset and field type to make TBAAStructType node
(name, parent node, offset) similar to scalar TBAA node (name, parent node).
TypeIsImmutable is added to TBAAStructTag node.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@180654 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 30 insertions, 13 deletions

diff --git a/lib/Analysis/TypeBasedAliasAnalysis.cpp b/lib/Analysis/TypeBasedAliasAnalysis.cpp
index 442145f596..bbf3c3a2a5 100644
--- a/lib/Analysis/TypeBasedAliasAnalysis.cpp
+++ b/lib/Analysis/TypeBasedAliasAnalysis.cpp
@@ -134,6 +134,17 @@ namespace {
     uint64_t getOffset() const {
       return cast<ConstantInt>(Node->getOperand(2))->getZExtValue();
     }
+    /// TypeIsImmutable - Test if this TBAAStructTagNode represents a type for
+    /// objects which are not modified (by any means) in the context where this
+    /// AliasAnalysis is relevant.
+    bool TypeIsImmutable() const {
+      if (Node->getNumOperands() < 4)
+        return false;
+      ConstantInt *CI = dyn_cast<ConstantInt>(Node->getOperand(3));
+      if (!CI)
+        return false;
+      return CI->getValue()[0];
+    }
   };
 
   /// This is a simple wrapper around an MDNode which provides a
@@ -153,14 +164,24 @@ namespace {
     /// Get this TBAAStructTypeNode's field in the type DAG with
     /// given offset. Update the offset to be relative to the field type.
     TBAAStructTypeNode getParent(uint64_t &Offset) const {
+      // Parent can be omitted for the root node.
       if (Node->getNumOperands() < 2)
         return TBAAStructTypeNode();
 
+      // Special handling for a scalar type node. 
+      if (Node->getNumOperands() <= 3) {
+        MDNode *P = dyn_cast_or_null<MDNode>(Node->getOperand(1));
+        if (!P)
+          return TBAAStructTypeNode();
+        return TBAAStructTypeNode(P);
+      }
+
       // Assume the offsets are in order. We return the previous field if
       // the current offset is bigger than the given offset.
       unsigned TheIdx = 0;
       for (unsigned Idx = 1; Idx < Node->getNumOperands(); Idx += 2) {
-        uint64_t Cur = cast<ConstantInt>(Node->getOperand(Idx))->getZExtValue();
+        uint64_t Cur = cast<ConstantInt>(Node->getOperand(Idx + 1))->
+                         getZExtValue();
         if (Cur > Offset) {
           assert(Idx >= 3 &&
                  "TBAAStructTypeNode::getParent should have an offset match!");
@@ -171,10 +192,10 @@ namespace {
       // Move along the last field.
       if (TheIdx == 0)
         TheIdx = Node->getNumOperands() - 2;
-      uint64_t Cur = cast<ConstantInt>(Node->getOperand(TheIdx))->
+      uint64_t Cur = cast<ConstantInt>(Node->getOperand(TheIdx + 1))->
                        getZExtValue();
       Offset -= Cur;
-      MDNode *P = dyn_cast_or_null<MDNode>(Node->getOperand(TheIdx + 1));
+      MDNode *P = dyn_cast_or_null<MDNode>(Node->getOperand(TheIdx));
       if (!P)
         return TBAAStructTypeNode();
       return TBAAStructTypeNode(P);
@@ -376,7 +397,8 @@ bool TypeBasedAliasAnalysis::pointsToConstantMemory(const Location &Loc,
 
   // If this is an "immutable" type, we can assume the pointer is pointing
   // to constant memory.
-  if (!EnableStructPathTBAA && TBAANode(M).TypeIsImmutable())
+  if ((!EnableStructPathTBAA && TBAANode(M).TypeIsImmutable()) ||
+      (EnableStructPathTBAA && TBAAStructTagNode(M).TypeIsImmutable()))
     return true;
 
   return AliasAnalysis::pointsToConstantMemory(Loc, OrLocal);
@@ -392,7 +414,8 @@ TypeBasedAliasAnalysis::getModRefBehavior(ImmutableCallSite CS) {
   // If this is an "immutable" type, we can assume the call doesn't write
   // to memory.
   if (const MDNode *M = CS.getInstruction()->getMetadata(LLVMContext::MD_tbaa))
-    if (!EnableStructPathTBAA && TBAANode(M).TypeIsImmutable())
+    if ((!EnableStructPathTBAA && TBAANode(M).TypeIsImmutable()) ||
+        (EnableStructPathTBAA && TBAAStructTagNode(M).TypeIsImmutable()))
       Min = OnlyReadsMemory;
 
   return ModRefBehavior(AliasAnalysis::getModRefBehavior(CS) & Min);
@@ -454,20 +477,14 @@ MDNode *MDNode::getMostGenericTBAA(MDNode *A, MDNode *B) {
   MDNode *T = A;
   while (T) {
     PathA.push_back(T);
-    if (EnableStructPathTBAA)
-      T = T->getNumOperands() >= 3 ? cast_or_null<MDNode>(T->getOperand(2)) : 0;
-    else
-      T = T->getNumOperands() >= 2 ? cast_or_null<MDNode>(T->getOperand(1)) : 0;
+    T = T->getNumOperands() >= 2 ? cast_or_null<MDNode>(T->getOperand(1)) : 0;
   }
 
   SmallVector<MDNode *, 4> PathB;
   T = B;
   while (T) {
     PathB.push_back(T);
-    if (EnableStructPathTBAA)
-      T = T->getNumOperands() >= 3 ? cast_or_null<MDNode>(T->getOperand(2)) : 0;
-    else
-      T = T->getNumOperands() >= 2 ? cast_or_null<MDNode>(T->getOperand(1)) : 0;
+    T = T->getNumOperands() >= 2 ? cast_or_null<MDNode>(T->getOperand(1)) : 0;
   }
 
   int IA = PathA.size() - 1;