Add iterator range variants of isGuaranteedToTransferExecutionToSucce…

…ssor [mostly-nfc]

This factors out utilities for scanning a bounded block of instructions since we have this code repeated in a bunch of places.  The change to InlineFunction isn't strictly NFC as the limit mechanism there didn't handle debug instructions correctly.

llvm/include/llvm/Analysis/ValueTracking.h

@@ -574,6 +574,18 @@ constexpr unsigned MaxAnalysisRecursionDepth = 6;
   /// instruction variant of this function.
   bool isGuaranteedToTransferExecutionToSuccessor(const BasicBlock *BB);
 
+  /// Return true if every instruction in the range (Begin, End) is
+  /// guaranteed to transfer execution to its static successor. \p ScanLimit
+  /// bounds the search to avoid scanning huge blocks.
+  bool isGuaranteedToTransferExecutionToSuccessor(
+     BasicBlock::const_iterator Begin, BasicBlock::const_iterator End,
+     unsigned ScanLimit = 32);
+
+  /// Same as previous, but with range expressed via iterator_range.
+  bool isGuaranteedToTransferExecutionToSuccessor(
+     iterator_range<BasicBlock::const_iterator> Range,
+     unsigned ScanLimit = 32);
+
   /// Return true if this function can prove that the instruction I
   /// is executed for every iteration of the loop L.
   ///

llvm/lib/Analysis/ScalarEvolution.cpp

@@ -6631,39 +6631,20 @@ ScalarEvolution::getDefiningScopeBound(ArrayRef<const SCEV *> Ops) {
   return Bound ? Bound : &*F.getEntryBlock().begin();
 }
 
-
-static bool
-isGuaranteedToTransferExecutionToSuccessor(BasicBlock::const_iterator Begin,
-                                           BasicBlock::const_iterator End) {
-  // Limit number of instructions we look at, to avoid scanning through large
-  // blocks. The current limit is chosen arbitrarily.
-  unsigned ScanLimit = 32;
-  for (const Instruction &I : make_range(Begin, End)) {
-    if (isa<DbgInfoIntrinsic>(I))
-        continue;
-    if (--ScanLimit == 0)
-      return false;
-
-    if (!isGuaranteedToTransferExecutionToSuccessor(&I))
-      return false;
-  }
-  return true;
-}
-
 bool ScalarEvolution::isGuaranteedToTransferExecutionTo(const Instruction *A,
                                                         const Instruction *B) {
   if (A->getParent() == B->getParent() &&
-      ::isGuaranteedToTransferExecutionToSuccessor(A->getIterator(),
-                                                   B->getIterator()))
+      isGuaranteedToTransferExecutionToSuccessor(A->getIterator(),
+                                                 B->getIterator()))
     return true;
 
   auto *BLoop = LI.getLoopFor(B->getParent());
   if (BLoop && BLoop->getHeader() == B->getParent() &&
       BLoop->getLoopPreheader() == A->getParent() &&
-      ::isGuaranteedToTransferExecutionToSuccessor(A->getIterator(),
-                                                   A->getParent()->end()) &&
-      ::isGuaranteedToTransferExecutionToSuccessor(B->getParent()->begin(),
-                                                   B->getIterator()))
+      isGuaranteedToTransferExecutionToSuccessor(A->getIterator(),
+                                                 A->getParent()->end()) &&
+      isGuaranteedToTransferExecutionToSuccessor(B->getParent()->begin(),
+                                                 B->getIterator()))
     return true;
   return false;
 }

llvm/lib/Analysis/ValueTracking.cpp

@@ -542,10 +542,9 @@ bool llvm::isValidAssumeForContext(const Instruction *Inv,
     // We limit the scan distance between the assume and its context instruction
     // to avoid a compile-time explosion. This limit is chosen arbitrarily, so
     // it can be adjusted if needed (could be turned into a cl::opt).
-    unsigned ScanLimit = 15;
-    for (BasicBlock::const_iterator I(CxtI), IE(Inv); I != IE; ++I)
-      if (!isGuaranteedToTransferExecutionToSuccessor(&*I) || --ScanLimit == 0)
-        return false;
+    auto Range = make_range(CxtI->getIterator(), Inv->getIterator());
+    if (!isGuaranteedToTransferExecutionToSuccessor(Range, 15))
+      return false;
 
     return !isEphemeralValueOf(Inv, CxtI);
   }
@@ -5331,6 +5330,27 @@ bool llvm::isGuaranteedToTransferExecutionToSuccessor(const BasicBlock *BB) {
   return true;
 }
 
+bool llvm::isGuaranteedToTransferExecutionToSuccessor(
+   BasicBlock::const_iterator Begin, BasicBlock::const_iterator End,
+   unsigned ScanLimit) {
+  return isGuaranteedToTransferExecutionToSuccessor(make_range(Begin, End),
+                                                    ScanLimit);
+}
+
+bool llvm::isGuaranteedToTransferExecutionToSuccessor(
+   iterator_range<BasicBlock::const_iterator> Range, unsigned ScanLimit) {
+  assert(ScanLimit && "scan limit must be non-zero");
+  for (const Instruction &I : Range) {
+    if (isa<DbgInfoIntrinsic>(I))
+        continue;
+    if (--ScanLimit == 0)
+      return false;
+    if (!isGuaranteedToTransferExecutionToSuccessor(&I))
+      return false;
+  }
+  return true;
+}
+
 bool llvm::isGuaranteedToExecuteForEveryIteration(const Instruction *I,
                                                   const Loop *L) {
   // The loop header is guaranteed to be executed for every iteration.

llvm/lib/Transforms/Utils/InlineFunction.cpp

@@ -1177,14 +1177,8 @@ static bool MayContainThrowingOrExitingCall(Instruction *Begin,
 
   assert(Begin->getParent() == End->getParent() &&
          "Expected to be in same basic block!");
-  unsigned NumInstChecked = 0;
-  // Check that all instructions in the range [Begin, End) are guaranteed to
-  // transfer execution to successor.
-  for (auto &I : make_range(Begin->getIterator(), End->getIterator()))
-    if (NumInstChecked++ > InlinerAttributeWindow ||
-        !isGuaranteedToTransferExecutionToSuccessor(&I))
-      return true;
-  return false;
+  return !llvm::isGuaranteedToTransferExecutionToSuccessor(
+      Begin->getIterator(), End->getIterator(), InlinerAttributeWindow + 1);
 }
 
 static AttrBuilder IdentifyValidAttributes(CallBase &CB) {