vendor/llvm/llvm-trunk-r338150

1 files changed, 64 insertions, 0 deletions

diff --git a/include/llvm/Analysis/MustExecute.h b/include/llvm/Analysis/MustExecute.h
new file mode 100644
index 000000000000..8daf156567cd
--- /dev/null
+++ b/include/llvm/Analysis/MustExecute.h
@@ -0,0 +1,64 @@
+//===- MustExecute.h - Is an instruction known to execute--------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+/// \file
+/// Contains a collection of routines for determining if a given instruction is
+/// guaranteed to execute if a given point in control flow is reached.  The most
+/// common example is an instruction within a loop being provably executed if we
+/// branch to the header of it's containing loop.  
+///
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_ANALYSIS_MUSTEXECUTE_H
+#define LLVM_ANALYSIS_MUSTEXECUTE_H
+
+#include "llvm/ADT/DenseMap.h"
+#include "llvm/Analysis/EHPersonalities.h"
+#include "llvm/Analysis/LoopInfo.h"
+#include "llvm/IR/BasicBlock.h"
+#include "llvm/IR/Dominators.h"
+#include "llvm/IR/Instruction.h"
+
+namespace llvm {
+
+class Instruction;
+class DominatorTree;
+class Loop;
+
+/// Captures loop safety information.
+/// It keep information for loop & its header may throw exception or otherwise
+/// exit abnormaly on any iteration of the loop which might actually execute
+/// at runtime.  The primary way to consume this infromation is via
+/// isGuaranteedToExecute below, but some callers bailout or fallback to
+/// alternate reasoning if a loop contains any implicit control flow.
+struct LoopSafetyInfo {
+  bool MayThrow = false;       // The current loop contains an instruction which
+                               // may throw.
+  bool HeaderMayThrow = false; // Same as previous, but specific to loop header
+  // Used to update funclet bundle operands.
+  DenseMap<BasicBlock *, ColorVector> BlockColors;
+
+  LoopSafetyInfo() = default;
+};
+
+/// Computes safety information for a loop checks loop body & header for
+/// the possibility of may throw exception, it takes LoopSafetyInfo and loop as
+/// argument. Updates safety information in LoopSafetyInfo argument.
+/// Note: This is defined to clear and reinitialize an already initialized
+/// LoopSafetyInfo.  Some callers rely on this fact.
+void computeLoopSafetyInfo(LoopSafetyInfo *, Loop *);
+
+/// Returns true if the instruction in a loop is guaranteed to execute at least
+/// once (under the assumption that the loop is entered).
+bool isGuaranteedToExecute(const Instruction &Inst, const DominatorTree *DT,
+                           const Loop *CurLoop,
+                           const LoopSafetyInfo *SafetyInfo);
+  
+}
+
+#endif