[NFC][CaptureTracking] Move static function isNonEscapingLocalObject to llvm namespace

Function isNonEscapingLocalObject is a static one within BasicAliasAnalysis.cpp.
It wraps around PointerMayBeCaptured of CaptureTracking, checking whether a pointer
is to a function-local object, which never escapes from the function.

Although at the moment, isNonEscapingLocalObject is used only by BasicAliasAnalysis,
its functionality can be used by other pass(es), one of which I will put up for review
very soon. Instead of copying the contents of this static function, I move it to llvm
scope, and place it amongst other functions with similar functionality in CaptureTracking.

The rationale for the location are:
- Pointer escape and pointer being captured are actually two sides of the same coin
- isNonEscapingLocalObject is wrapping around another function in CaptureTracking

Reviewed By: jdoerfert (Johannes Doerfert)

Differential Revision: https://reviews.llvm.org/D89465

Author: anhtuyenibm

llvm/include/llvm/Analysis/CaptureTracking.h

@@ -13,6 +13,8 @@
 #ifndef LLVM_ANALYSIS_CAPTURETRACKING_H
 #define LLVM_ANALYSIS_CAPTURETRACKING_H
 
+#include "llvm/ADT/DenseMap.h"
+
 namespace llvm {
 
   class Value;
@@ -94,6 +96,12 @@ namespace llvm {
   /// is zero, a default value is assumed.
   void PointerMayBeCaptured(const Value *V, CaptureTracker *Tracker,
                             unsigned MaxUsesToExplore = 0);
+
+  /// Returns true if the pointer is to a function-local object that never
+  /// escapes from the function.
+  bool isNonEscapingLocalObject(
+      const Value *V,
+      SmallDenseMap<const Value *, bool, 8> *IsCapturedCache = nullptr);
 } // end namespace llvm
 
 #endif

llvm/lib/Analysis/BasicAliasAnalysis.cpp

@@ -115,50 +115,6 @@ bool BasicAAResult::invalidate(Function &Fn, const PreservedAnalyses &PA,
 // Useful predicates
 //===----------------------------------------------------------------------===//
 
-/// Returns true if the pointer is to a function-local object that never
-/// escapes from the function.
-static bool isNonEscapingLocalObject(
-    const Value *V,
-    SmallDenseMap<const Value *, bool, 8> *IsCapturedCache = nullptr) {
-  SmallDenseMap<const Value *, bool, 8>::iterator CacheIt;
-  if (IsCapturedCache) {
-    bool Inserted;
-    std::tie(CacheIt, Inserted) = IsCapturedCache->insert({V, false});
-    if (!Inserted)
-      // Found cached result, return it!
-      return CacheIt->second;
-  }
-
-  // If this is a local allocation, check to see if it escapes.
-  if (isa<AllocaInst>(V) || isNoAliasCall(V)) {
-    // Set StoreCaptures to True so that we can assume in our callers that the
-    // pointer is not the result of a load instruction. Currently
-    // PointerMayBeCaptured doesn't have any special analysis for the
-    // StoreCaptures=false case; if it did, our callers could be refined to be
-    // more precise.
-    auto Ret = !PointerMayBeCaptured(V, false, /*StoreCaptures=*/true);
-    if (IsCapturedCache)
-      CacheIt->second = Ret;
-    return Ret;
-  }
-
-  // If this is an argument that corresponds to a byval or noalias argument,
-  // then it has not escaped before entering the function.  Check if it escapes
-  // inside the function.
-  if (const Argument *A = dyn_cast<Argument>(V))
-    if (A->hasByValAttr() || A->hasNoAliasAttr()) {
-      // Note even if the argument is marked nocapture, we still need to check
-      // for copies made inside the function. The nocapture attribute only
-      // specifies that there are no copies made that outlive the function.
-      auto Ret = !PointerMayBeCaptured(V, false, /*StoreCaptures=*/true);
-      if (IsCapturedCache)
-        CacheIt->second = Ret;
-      return Ret;
-    }
-
-  return false;
-}
-
 /// Returns true if the pointer is one which would have been considered an
 /// escape by isNonEscapingLocalObject.
 static bool isEscapeSource(const Value *V) {

llvm/lib/Analysis/CaptureTracking.cpp

@@ -395,3 +395,44 @@ void llvm::PointerMayBeCaptured(const Value *V, CaptureTracker *Tracker,
 
   // All uses examined.
 }
+
+bool llvm::isNonEscapingLocalObject(
+    const Value *V, SmallDenseMap<const Value *, bool, 8> *IsCapturedCache) {
+  SmallDenseMap<const Value *, bool, 8>::iterator CacheIt;
+  if (IsCapturedCache) {
+    bool Inserted;
+    std::tie(CacheIt, Inserted) = IsCapturedCache->insert({V, false});
+    if (!Inserted)
+      // Found cached result, return it!
+      return CacheIt->second;
+  }
+
+  // If this is a local allocation, check to see if it escapes.
+  if (isa<AllocaInst>(V) || isNoAliasCall(V)) {
+    // Set StoreCaptures to True so that we can assume in our callers that the
+    // pointer is not the result of a load instruction. Currently
+    // PointerMayBeCaptured doesn't have any special analysis for the
+    // StoreCaptures=false case; if it did, our callers could be refined to be
+    // more precise.
+    auto Ret = !PointerMayBeCaptured(V, false, /*StoreCaptures=*/true);
+    if (IsCapturedCache)
+      CacheIt->second = Ret;
+    return Ret;
+  }
+
+  // If this is an argument that corresponds to a byval or noalias argument,
+  // then it has not escaped before entering the function.  Check if it escapes
+  // inside the function.
+  if (const Argument *A = dyn_cast<Argument>(V))
+    if (A->hasByValAttr() || A->hasNoAliasAttr()) {
+      // Note even if the argument is marked nocapture, we still need to check
+      // for copies made inside the function. The nocapture attribute only
+      // specifies that there are no copies made that outlive the function.
+      auto Ret = !PointerMayBeCaptured(V, false, /*StoreCaptures=*/true);
+      if (IsCapturedCache)
+        CacheIt->second = Ret;
+      return Ret;
+    }
+
+  return false;
+}