LLVM  8.0.0svn
StripGCRelocates.cpp
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1 //===- StripGCRelocates.cpp - Remove gc.relocates inserted by RewriteStatePoints===//
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 is a little utility pass that removes the gc.relocates inserted by
11 // RewriteStatepointsForGC. Note that the generated IR is incorrect,
12 // but this is useful as a single pass in itself, for analysis of IR, without
13 // the GC.relocates. The statepoint and gc.result instrinsics would still be
14 // present.
15 //===----------------------------------------------------------------------===//
16 
17 #include "llvm/IR/Function.h"
18 #include "llvm/IR/InstIterator.h"
19 #include "llvm/IR/Instructions.h"
20 #include "llvm/IR/Statepoint.h"
21 #include "llvm/IR/Type.h"
22 #include "llvm/Pass.h"
24 
25 using namespace llvm;
26 
27 namespace {
28 struct StripGCRelocates : public FunctionPass {
29  static char ID; // Pass identification, replacement for typeid
30  StripGCRelocates() : FunctionPass(ID) {
32  }
33 
34  void getAnalysisUsage(AnalysisUsage &Info) const override {}
35 
36  bool runOnFunction(Function &F) override;
37 
38 };
39 char StripGCRelocates::ID = 0;
40 }
41 
43  // Nothing to do for declarations.
44  if (F.isDeclaration())
45  return false;
47  // TODO: We currently do not handle gc.relocates that are in landing pads,
48  // i.e. not bound to a single statepoint token.
49  for (Instruction &I : instructions(F)) {
50  if (auto *GCR = dyn_cast<GCRelocateInst>(&I))
51  if (isStatepoint(GCR->getOperand(0)))
52  GCRelocates.push_back(GCR);
53  }
54  // All gc.relocates are bound to a single statepoint token. The order of
55  // visiting gc.relocates for deletion does not matter.
56  for (GCRelocateInst *GCRel : GCRelocates) {
57  Value *OrigPtr = GCRel->getDerivedPtr();
58  Value *ReplaceGCRel = OrigPtr;
59 
60  // All gc_relocates are i8 addrspace(1)* typed, we need a bitcast from i8
61  // addrspace(1)* to the type of the OrigPtr, if the are not the same.
62  if (GCRel->getType() != OrigPtr->getType())
63  ReplaceGCRel = new BitCastInst(OrigPtr, GCRel->getType(), "cast", GCRel);
64 
65  // Replace all uses of gc.relocate and delete the gc.relocate
66  // There maybe unncessary bitcasts back to the OrigPtr type, an instcombine
67  // pass would clear this up.
68  GCRel->replaceAllUsesWith(ReplaceGCRel);
69  GCRel->eraseFromParent();
70  }
71  return !GCRelocates.empty();
72 }
73 
74 INITIALIZE_PASS(StripGCRelocates, "strip-gc-relocates",
75  "Strip gc.relocates inserted through RewriteStatepointsForGC",
76  true, false)
static PassRegistry * getPassRegistry()
getPassRegistry - Access the global registry object, which is automatically initialized at applicatio...
Compute iterated dominance frontiers using a linear time algorithm.
Definition: AllocatorList.h:24
F(f)
Type * getType() const
All values are typed, get the type of this value.
Definition: Value.h:245
This class represents a no-op cast from one type to another.
void replaceAllUsesWith(Value *V)
Change all uses of this to point to a new Value.
Definition: Value.cpp:439
static bool runOnFunction(Function &F, bool PostInlining)
Represent the analysis usage information of a pass.
void initializeStripGCRelocatesPass(PassRegistry &)
FunctionPass class - This class is used to implement most global optimizations.
Definition: Pass.h:285
#define INITIALIZE_PASS(passName, arg, name, cfg, analysis)
Definition: PassSupport.h:34
This is a &#39;vector&#39; (really, a variable-sized array), optimized for the case when the array is small...
Definition: SmallVector.h:847
#define I(x, y, z)
Definition: MD5.cpp:58
bool isDeclaration() const
Return true if the primary definition of this global value is outside of the current translation unit...
Definition: Globals.cpp:206
bool isStatepoint(ImmutableCallSite CS)
Definition: Statepoint.cpp:27
Represents calls to the gc.relocate intrinsic.
Definition: Statepoint.h:374
LLVM Value Representation.
Definition: Value.h:73
inst_range instructions(Function *F)
Definition: InstIterator.h:134