2 files changed, 63 insertions, 0 deletions

diff --git a/llvm/include/llvm/Analysis/MustExecute.h b/llvm/include/llvm/Analysis/MustExecute.h
index f136ff750de..62d9b056e88 100644
--- a/llvm/include/llvm/Analysis/MustExecute.h
+++ b/llvm/include/llvm/Analysis/MustExecute.h
@@ -19,6 +19,7 @@
 
 #include "llvm/ADT/DenseMap.h"
 #include "llvm/Analysis/EHPersonalities.h"
+#include "llvm/Analysis/InstructionPrecedenceTracking.h"
 #include "llvm/Analysis/LoopInfo.h"
 #include "llvm/IR/BasicBlock.h"
 #include "llvm/IR/Dominators.h"
@@ -122,6 +123,37 @@ public:
   virtual ~SimpleLoopSafetyInfo() {};
 };
 
+/// This implementation of LoopSafetyInfo use ImplicitControlFlowTracking to
+/// give precise answers on "may throw" queries. This implementation uses cache
+/// that should be invalidated by calling the method dropCachedInfo whenever we
+/// modify a basic block's contents by adding or removing instructions.
+class ICFLoopSafetyInfo: public LoopSafetyInfo {
+  bool MayThrow = false;       // The current loop contains an instruction which
+                               // may throw.
+  // Contains information about implicit control flow in this loop's blocks.
+  mutable ImplicitControlFlowTracking ICF;
+
+public:
+  virtual bool blockMayThrow(const BasicBlock *BB) const;
+
+  virtual bool anyBlockMayThrow() const;
+
+  virtual void computeLoopSafetyInfo(const Loop *CurLoop);
+
+  virtual bool isGuaranteedToExecute(const Instruction &Inst,
+                                     const DominatorTree *DT,
+                                     const Loop *CurLoop) const;
+
+  /// Drops cached information regarding the implicit control flow in block
+  /// \p BB. It should be called for every block in which we add or remove any
+  /// instructions  to a block before we make queries to it.
+  void dropCachedInfo(const BasicBlock *BB);
+
+  ICFLoopSafetyInfo(DominatorTree *DT) : LoopSafetyInfo(), ICF(DT) {};
+
+  virtual ~ICFLoopSafetyInfo() {};
+};
+
 }
 
 #endif
diff --git a/llvm/lib/Analysis/MustExecute.cpp b/llvm/lib/Analysis/MustExecute.cpp
index 4e42f336dc7..64ee2a7e5b0 100644
--- a/llvm/lib/Analysis/MustExecute.cpp
+++ b/llvm/lib/Analysis/MustExecute.cpp
@@ -61,6 +61,31 @@ void SimpleLoopSafetyInfo::computeLoopSafetyInfo(const Loop *CurLoop) {
   computeBlockColors(CurLoop);
 }
 
+bool ICFLoopSafetyInfo::blockMayThrow(const BasicBlock *BB) const {
+  return ICF.hasICF(BB);
+}
+
+bool ICFLoopSafetyInfo::anyBlockMayThrow() const {
+  return MayThrow;
+}
+
+void ICFLoopSafetyInfo::computeLoopSafetyInfo(const Loop *CurLoop) {
+  assert(CurLoop != nullptr && "CurLoop can't be null");
+  ICF.clear();
+  MayThrow = false;
+  // Figure out the fact that at least one block may throw.
+  for (auto &BB : CurLoop->blocks())
+    if (ICF.hasICF(&*BB)) {
+      MayThrow = true;
+      break;
+    }
+  computeBlockColors(CurLoop);
+}
+
+void ICFLoopSafetyInfo::dropCachedInfo(const BasicBlock *BB) {
+  ICF.invalidateBlock(BB);
+}
+
 void LoopSafetyInfo::computeBlockColors(const Loop *CurLoop) {
   // Compute funclet colors if we might sink/hoist in a function with a funclet
   // personality routine.
@@ -215,6 +240,12 @@ bool SimpleLoopSafetyInfo::isGuaranteedToExecute(const Instruction &Inst,
   return allLoopPathsLeadToBlock(CurLoop, Inst.getParent(), DT);
 }
 
+bool ICFLoopSafetyInfo::isGuaranteedToExecute(const Instruction &Inst,
+                                              const DominatorTree *DT,
+                                              const Loop *CurLoop) const {
+  return !ICF.isDominatedByICFIFromSameBlock(&Inst) &&
+         allLoopPathsLeadToBlock(CurLoop, Inst.getParent(), DT);
+}
 
 namespace {
   struct MustExecutePrinter : public FunctionPass {