[PATCH] D9398: llvm.noalias - GetUnderlyingObjects to optionally collect noalias calls

[Hal Finkel via llvm-commits]

hfinkel updated this revision to Diff 63331.
hfinkel added a comment.
Herald added a subscriber: mcrosier.

Rebased.

I've thought about how to generalize this (it seems kind of silly to have GetUnderlyingObject(s) have a special parameter for this), but because I don't think that imposing the overhead of a virtual function call for each visited instruction is reasonable, I think the way to generalize it is to template it on some kind of customization functor. I've done that here, in the name of keeping this change  small, and because I don't yet have a second use case. I'm happy to do the generalization either sequenced before this change or afterward (assuming, of course, we don't decide on a completely different way to satisfy this use case).


http://reviews.llvm.org/D9398

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

Index: lib/Analysis/ValueTracking.cpp
===================================================================
--- lib/Analysis/ValueTracking.cpp
+++ lib/Analysis/ValueTracking.cpp
@@ -2967,7 +2967,8 @@
 }
 
 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) {
@@ -2981,6 +2982,12 @@
         return V;
       V = GA->getAliasee();
     } else {
+      if (IntrinsicInst *I = dyn_cast<IntrinsicInst>(V))
+        if (I->getIntrinsicID() == Intrinsic::noalias) {
+          if (NoAlias)
+            NoAlias->push_back(I);
+        }
+
       // See if InstructionSimplify knows any relevant tricks.
       if (Instruction *I = dyn_cast<Instruction>(V))
         // TODO: Acquire a DominatorTree and AssumptionCache and use them.
@@ -2998,13 +3005,14 @@
 
 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;
Index: include/llvm/Analysis/ValueTracking.h
===================================================================
--- include/llvm/Analysis/ValueTracking.h
+++ include/llvm/Analysis/ValueTracking.h
@@ -221,11 +221,13 @@
   /// 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
@@ -258,7 +260,8 @@
   /// 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);
 
   /// Return true if the only users of this pointer are lifetime markers.
   bool onlyUsedByLifetimeMarkers(const Value *V);


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