LLVM  9.0.0svn
StripGCRelocates.cpp
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1 //===- StripGCRelocates.cpp - Remove gc.relocates inserted by RewriteStatePoints===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // This is a little utility pass that removes the gc.relocates inserted by
10 // RewriteStatepointsForGC. Note that the generated IR is incorrect,
11 // but this is useful as a single pass in itself, for analysis of IR, without
12 // the GC.relocates. The statepoint and gc.result instrinsics would still be
13 // present.
14 //===----------------------------------------------------------------------===//
15 
16 #include "llvm/IR/Function.h"
17 #include "llvm/IR/InstIterator.h"
18 #include "llvm/IR/Instructions.h"
19 #include "llvm/IR/Statepoint.h"
20 #include "llvm/IR/Type.h"
21 #include "llvm/Pass.h"
23 
24 using namespace llvm;
25 
26 namespace {
27 struct StripGCRelocates : public FunctionPass {
28  static char ID; // Pass identification, replacement for typeid
29  StripGCRelocates() : FunctionPass(ID) {
31  }
32 
33  void getAnalysisUsage(AnalysisUsage &Info) const override {}
34 
35  bool runOnFunction(Function &F) override;
36 
37 };
38 char StripGCRelocates::ID = 0;
39 }
40 
42  // Nothing to do for declarations.
43  if (F.isDeclaration())
44  return false;
46  // TODO: We currently do not handle gc.relocates that are in landing pads,
47  // i.e. not bound to a single statepoint token.
48  for (Instruction &I : instructions(F)) {
49  if (auto *GCR = dyn_cast<GCRelocateInst>(&I))
50  if (isStatepoint(GCR->getOperand(0)))
51  GCRelocates.push_back(GCR);
52  }
53  // All gc.relocates are bound to a single statepoint token. The order of
54  // visiting gc.relocates for deletion does not matter.
55  for (GCRelocateInst *GCRel : GCRelocates) {
56  Value *OrigPtr = GCRel->getDerivedPtr();
57  Value *ReplaceGCRel = OrigPtr;
58 
59  // All gc_relocates are i8 addrspace(1)* typed, we need a bitcast from i8
60  // addrspace(1)* to the type of the OrigPtr, if the are not the same.
61  if (GCRel->getType() != OrigPtr->getType())
62  ReplaceGCRel = new BitCastInst(OrigPtr, GCRel->getType(), "cast", GCRel);
63 
64  // Replace all uses of gc.relocate and delete the gc.relocate
65  // There maybe unncessary bitcasts back to the OrigPtr type, an instcombine
66  // pass would clear this up.
67  GCRel->replaceAllUsesWith(ReplaceGCRel);
68  GCRel->eraseFromParent();
69  }
70  return !GCRelocates.empty();
71 }
72 
73 INITIALIZE_PASS(StripGCRelocates, "strip-gc-relocates",
74  "Strip gc.relocates inserted through RewriteStatepointsForGC",
75  true, false)
static PassRegistry * getPassRegistry()
getPassRegistry - Access the global registry object, which is automatically initialized at applicatio...
This class represents lattice values for constants.
Definition: AllocatorList.h:23
F(f)
Type * getType() const
All values are typed, get the type of this value.
Definition: Value.h:244
bool isStatepoint(const CallBase *Call)
Definition: Statepoint.cpp:20
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:429
Analysis containing CSE Info
Definition: CSEInfo.cpp:20
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:284
#define INITIALIZE_PASS(passName, arg, name, cfg, analysis)
Definition: PassSupport.h:33
This is a &#39;vector&#39; (really, a variable-sized array), optimized for the case when the array is small...
Definition: SmallVector.h:841
#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:205
Represents calls to the gc.relocate intrinsic.
Definition: Statepoint.h:363
LLVM Value Representation.
Definition: Value.h:72
inst_range instructions(Function *F)
Definition: InstIterator.h:133