1 //===- MustExecute.h - Is an instruction known to execute--------*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 /// Contains a collection of routines for determining if a given instruction is
11 /// guaranteed to execute if a given point in control flow is reached. The most
12 /// common example is an instruction within a loop being provably executed if we
13 /// branch to the header of it's containing loop.
15 //===----------------------------------------------------------------------===//
17 #ifndef LLVM_ANALYSIS_MUSTEXECUTE_H
18 #define LLVM_ANALYSIS_MUSTEXECUTE_H
20 #include "llvm/ADT/DenseMap.h"
21 #include "llvm/Analysis/EHPersonalities.h"
22 #include "llvm/Analysis/LoopInfo.h"
23 #include "llvm/IR/BasicBlock.h"
24 #include "llvm/IR/Dominators.h"
25 #include "llvm/IR/Instruction.h"
33 /// Captures loop safety information.
34 /// It keep information for loop & its header may throw exception or otherwise
35 /// exit abnormaly on any iteration of the loop which might actually execute
36 /// at runtime. The primary way to consume this infromation is via
37 /// isGuaranteedToExecute below, but some callers bailout or fallback to
38 /// alternate reasoning if a loop contains any implicit control flow.
39 struct LoopSafetyInfo {
40 bool MayThrow = false; // The current loop contains an instruction which
42 bool HeaderMayThrow = false; // Same as previous, but specific to loop header
43 // Used to update funclet bundle operands.
44 DenseMap<BasicBlock *, ColorVector> BlockColors;
46 LoopSafetyInfo() = default;
49 /// Computes safety information for a loop checks loop body & header for
50 /// the possibility of may throw exception, it takes LoopSafetyInfo and loop as
51 /// argument. Updates safety information in LoopSafetyInfo argument.
52 /// Note: This is defined to clear and reinitialize an already initialized
53 /// LoopSafetyInfo. Some callers rely on this fact.
54 void computeLoopSafetyInfo(LoopSafetyInfo *, Loop *);
56 /// Returns true if the instruction in a loop is guaranteed to execute at least
57 /// once (under the assumption that the loop is entered).
58 bool isGuaranteedToExecute(const Instruction &Inst, const DominatorTree *DT,
60 const LoopSafetyInfo *SafetyInfo);