1 //===- PtrUseVisitor.cpp - InstVisitors over a pointers uses --------------===//
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 /// \file
10 /// Implementation of the pointer use visitors.
11 ///
12 //===----------------------------------------------------------------------===//
13 
14 #include "llvm/Analysis/PtrUseVisitor.h"
15 
16 using namespace llvm;
17 
18 void detail::PtrUseVisitorBase::enqueueUsers(Instruction &I) {
19   for (Value::use_iterator UI = I.use_begin(), UE = I.use_end();
20        UI != UE; ++UI) {
21     if (VisitedUses.insert(&UI.getUse())) {
22       UseToVisit NewU = {
23         UseToVisit::UseAndIsOffsetKnownPair(&UI.getUse(), IsOffsetKnown),
24         Offset
25       };
26       Worklist.push_back(llvm_move(NewU));
27     }
28   }
29 }
30 
31 bool detail::PtrUseVisitorBase::adjustOffsetForGEP(GetElementPtrInst &GEPI) {
32   if (!IsOffsetKnown)
33     return false;
34 
35   for (gep_type_iterator GTI = gep_type_begin(GEPI), GTE = gep_type_end(GEPI);
36        GTI != GTE; ++GTI) {
37     ConstantInt *OpC = dyn_cast<ConstantInt>(GTI.getOperand());
38     if (!OpC)
39       return false;
40     if (OpC->isZero())
41       continue;
42 
43     // Handle a struct index, which adds its field offset to the pointer.
44     if (StructType *STy = dyn_cast<StructType>(*GTI)) {
45       unsigned ElementIdx = OpC->getZExtValue();
46       const StructLayout *SL = DL.getStructLayout(STy);
47       Offset += APInt(Offset.getBitWidth(),
48                          SL->getElementOffset(ElementIdx));
49       continue;
50     }
51 
52     // For array or vector indices, scale the index by the size of the type.
53     APInt Index = OpC->getValue().sextOrTrunc(Offset.getBitWidth());
54     Offset += Index * APInt(Offset.getBitWidth(),
55                                DL.getTypeAllocSize(GTI.getIndexedType()));
56   }
57   return true;
58 }
59