1 //===-- OrderedInstructions.cpp - Instruction dominance function ---------===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This file defines utility to check dominance relation of 2 instructions.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #include "llvm/Analysis/OrderedInstructions.h"
15 using namespace llvm;
16 
17 bool OrderedInstructions::localDominates(const Instruction *InstA,
18                                          const Instruction *InstB) const {
19   assert(InstA->getParent() == InstB->getParent() &&
20          "Instructions must be in the same basic block");
21 
22   const BasicBlock *IBB = InstA->getParent();
23   auto OBB = OBBMap.find(IBB);
24   if (OBB == OBBMap.end())
25     OBB = OBBMap.insert({IBB, make_unique<OrderedBasicBlock>(IBB)}).first;
26   return OBB->second->dominates(InstA, InstB);
27 }
28 
29 /// Given 2 instructions, use OrderedBasicBlock to check for dominance relation
30 /// if the instructions are in the same basic block, Otherwise, use dominator
31 /// tree.
32 bool OrderedInstructions::dominates(const Instruction *InstA,
33                                     const Instruction *InstB) const {
34   // Use ordered basic block to do dominance check in case the 2 instructions
35   // are in the same basic block.
36   if (InstA->getParent() == InstB->getParent())
37     return localDominates(InstA, InstB);
38   return DT->dominates(InstA->getParent(), InstB->getParent());
39 }
40 
41 bool OrderedInstructions::dfsBefore(const Instruction *InstA,
42                                     const Instruction *InstB) const {
43   // Use ordered basic block in case the 2 instructions are in the same basic
44   // block.
45   if (InstA->getParent() == InstB->getParent())
46     return localDominates(InstA, InstB);
47 
48   DomTreeNode *DA = DT->getNode(InstA->getParent());
49   DomTreeNode *DB = DT->getNode(InstB->getParent());
50   return DA->getDFSNumIn() < DB->getDFSNumIn();
51 }
52