[PATCH] llvm.noalias - GetUnderlyingObjects to optionally collect noalias calls

[hfinkel at anl.gov]

Hi chandlerc, reames,

This is part of the series started by D9375, and lets GetUnderlyingObjects, optionally, collect the llvm.noalias calls that it has looked through. This will be used by the AA implementation for llvm.noalias, to avoid double-walking (which could be expensive) and copy-and-paste.

http://reviews.llvm.org/D9398

Files:
  include/llvm/Analysis/ValueTracking.h
  lib/Analysis/ValueTracking.cpp

Index: include/llvm/Analysis/ValueTracking.h
===================================================================
--- include/llvm/Analysis/ValueTracking.h
+++ include/llvm/Analysis/ValueTracking.h
@@ -170,11 +170,13 @@
   /// specified value does.  If the MaxLookup value is non-zero, it limits the
   /// number of instructions to be stripped off.
   Value *GetUnderlyingObject(Value *V, const DataLayout &DL,
-                             unsigned MaxLookup = 6);
-  static inline const Value *GetUnderlyingObject(const Value *V,
-                                                 const DataLayout &DL,
-                                                 unsigned MaxLookup = 6) {
-    return GetUnderlyingObject(const_cast<Value *>(V), DL, MaxLookup);
+                             unsigned MaxLookup = 6,
+                             SmallVectorImpl<Instruction *> *NoAlias = nullptr);
+  static inline
+  const Value *GetUnderlyingObject(const Value *V,
+                 const DataLayout &DL, unsigned MaxLookup = 6,
+                 SmallVectorImpl<Instruction *> *NoAlias = nullptr) {
+    return GetUnderlyingObject(const_cast<Value *>(V), DL, MaxLookup, NoAlias);
   }
 
   /// \brief This method is similar to GetUnderlyingObject except that it can
@@ -207,7 +209,8 @@
   /// it shouldn't look through the phi above.
   void GetUnderlyingObjects(Value *V, SmallVectorImpl<Value *> &Objects,
                             const DataLayout &DL, LoopInfo *LI = nullptr,
-                            unsigned MaxLookup = 6);
+                            unsigned MaxLookup = 6,
+                            SmallVectorImpl<Instruction *> *NoAlias = nullptr);
 
   /// onlyUsedByLifetimeMarkers - Return true if the only users of this pointer
   /// are lifetime markers.
Index: lib/Analysis/ValueTracking.cpp
===================================================================
--- lib/Analysis/ValueTracking.cpp
+++ lib/Analysis/ValueTracking.cpp
@@ -2769,7 +2769,8 @@
 }
 
 Value *llvm::GetUnderlyingObject(Value *V, const DataLayout &DL,
-                                 unsigned MaxLookup) {
+                                 unsigned MaxLookup,
+                                 SmallVectorImpl<Instruction *> *NoAlias) {
   if (!V->getType()->isPointerTy())
     return V;
   for (unsigned Count = 0; MaxLookup == 0 || Count < MaxLookup; ++Count) {
@@ -2785,6 +2786,9 @@
     } else {
       if (IntrinsicInst *I = dyn_cast<IntrinsicInst>(V))
         if (I->getIntrinsicID() == Intrinsic::noalias) {
+          if (NoAlias)
+            NoAlias->push_back(I);
+
           V = I->getOperand(0);
           continue;
         }
@@ -2806,13 +2810,14 @@
 
 void llvm::GetUnderlyingObjects(Value *V, SmallVectorImpl<Value *> &Objects,
                                 const DataLayout &DL, LoopInfo *LI,
-                                unsigned MaxLookup) {
+                                unsigned MaxLookup,
+                                SmallVectorImpl<Instruction *> *NoAlias) {
   SmallPtrSet<Value *, 4> Visited;
   SmallVector<Value *, 4> Worklist;
   Worklist.push_back(V);
   do {
     Value *P = Worklist.pop_back_val();
-    P = GetUnderlyingObject(P, DL, MaxLookup);
+    P = GetUnderlyingObject(P, DL, MaxLookup, NoAlias);
 
     if (!Visited.insert(P).second)
       continue;

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