[CaptureTracking] Allow passing LI to PointerMayBeCapturedBefore (NFC).

isPotentiallyReachable can use LoopInfo to return earlier. This patch
allows passing an optional LI to PointerMayBeCapturedBefore. Used in
D109844.

Reviewed By: nikic, asbirlea

Differential Revision: https://reviews.llvm.org/D109978

(cherry-picked from 7f6a482)

Author: fhahn

llvm/include/llvm/Analysis/CaptureTracking.h

@@ -22,6 +22,7 @@ namespace llvm {
   class DataLayout;
   class Instruction;
   class DominatorTree;
+  class LoopInfo;
 
   /// getDefaultMaxUsesToExploreForCaptureTracking - Return default value of
   /// the maximal number of uses to explore before giving up. It is used by
@@ -55,10 +56,12 @@ namespace llvm {
   /// MaxUsesToExplore specifies how many uses the analysis should explore for
   /// one value before giving up due too "too many uses". If MaxUsesToExplore
   /// is zero, a default value is assumed.
-  bool PointerMayBeCapturedBefore(
-      const Value *V, bool ReturnCaptures, bool StoreCaptures,
-      const Instruction *I, const DominatorTree *DT, bool IncludeI = false,
-      unsigned MaxUsesToExplore = 0);
+  bool PointerMayBeCapturedBefore(const Value *V, bool ReturnCaptures,
+                                  bool StoreCaptures, const Instruction *I,
+                                  const DominatorTree *DT,
+                                  bool IncludeI = false,
+                                  unsigned MaxUsesToExplore = 0,
+                                  const LoopInfo *LI = nullptr);
 
   /// This callback is used in conjunction with PointerMayBeCaptured. In
   /// addition to the interface here, you'll need to provide your own getters

llvm/lib/Analysis/CaptureTracking.cpp

@@ -98,10 +98,10 @@ namespace {
   /// as the given instruction and the use.
   struct CapturesBefore : public CaptureTracker {
 
-    CapturesBefore(bool ReturnCaptures, const Instruction *I, const DominatorTree *DT,
-                   bool IncludeI)
-      : BeforeHere(I), DT(DT),
-        ReturnCaptures(ReturnCaptures), IncludeI(IncludeI), Captured(false) {}
+    CapturesBefore(bool ReturnCaptures, const Instruction *I,
+                   const DominatorTree *DT, bool IncludeI, const LoopInfo *LI)
+        : BeforeHere(I), DT(DT), ReturnCaptures(ReturnCaptures),
+          IncludeI(IncludeI), Captured(false), LI(LI) {}
 
     void tooManyUses() override { Captured = true; }
 
@@ -115,7 +115,7 @@ namespace {
         return true;
 
       // Check whether there is a path from I to BeforeHere.
-      return !isPotentiallyReachable(I, BeforeHere, nullptr, DT);
+      return !isPotentiallyReachable(I, BeforeHere, nullptr, DT, LI);
     }
 
     bool captured(const Use *U) override {
@@ -140,6 +140,8 @@ namespace {
     bool IncludeI;
 
     bool Captured;
+
+    const LoopInfo *LI;
   };
 }
 
@@ -183,7 +185,8 @@ bool llvm::PointerMayBeCaptured(const Value *V,
 bool llvm::PointerMayBeCapturedBefore(const Value *V, bool ReturnCaptures,
                                       bool StoreCaptures, const Instruction *I,
                                       const DominatorTree *DT, bool IncludeI,
-                                      unsigned MaxUsesToExplore) {
+                                      unsigned MaxUsesToExplore,
+                                      const LoopInfo *LI) {
   assert(!isa<GlobalValue>(V) &&
          "It doesn't make sense to ask whether a global is captured.");
 
@@ -194,7 +197,7 @@ bool llvm::PointerMayBeCapturedBefore(const Value *V, bool ReturnCaptures,
   // TODO: See comment in PointerMayBeCaptured regarding what could be done
   // with StoreCaptures.
 
-  CapturesBefore CB(ReturnCaptures, I, DT, IncludeI);
+  CapturesBefore CB(ReturnCaptures, I, DT, IncludeI, LI);
   PointerMayBeCaptured(V, &CB, MaxUsesToExplore);
   if (CB.Captured)
     ++NumCapturedBefore;