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//===--- LLVMSwiftRCIdentity.cpp - LLVM RCIdentity Analysis for Swift -----===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See https://swift.org/LICENSE.txt for license information
// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
//
//===----------------------------------------------------------------------===//
#include "swift/LLVMPasses/Passes.h"
#include "LLVMARCOpts.h"
#include "llvm/IR/Module.h"
using namespace llvm;
using swift::SwiftRCIdentity;
llvm::Value *
SwiftRCIdentity::stripPointerCasts(llvm::Value *Val) {
return Val->stripPointerCasts();
}
llvm::Value *
SwiftRCIdentity::stripReferenceForwarding(llvm::Value *Val) {
auto Inst = dyn_cast<Instruction>(Val);
if (!Inst)
return Val;
auto Kind = classifyInstruction(*Inst);
switch(Kind) {
case RT_RetainN:
case RT_UnknownObjectRetainN:
case RT_BridgeRetainN:
case RT_ReleaseN:
case RT_UnknownObjectReleaseN:
case RT_BridgeReleaseN:
case RT_FixLifetime:
case RT_Retain:
case RT_UnknownObjectRetain:
case RT_Release:
case RT_UnknownObjectRelease:
case RT_Unknown:
case RT_AllocObject:
case RT_NoMemoryAccessed:
case RT_BridgeRelease:
case RT_BridgeRetain:
case RT_RetainUnowned:
case RT_CheckUnowned:
case RT_ObjCRelease:
case RT_EndBorrow:
break;
// ObjC forwards references.
case RT_ObjCRetain:
Val = cast<CallInst>(Inst)->getArgOperand(0);
break;
}
return Val;
}
llvm::Value *
SwiftRCIdentity::getSwiftRCIdentityRoot(llvm::Value *Val) {
// Only allow this method to go up a fixed number of levels to make sure
// we don't explode compile time.
llvm::Value *OldVal = Val;
unsigned levels = 0;
do {
llvm::Value *NewVal = Val;
// Try to strip off pointer casts and reference forwarding.
Val = stripPointerCasts(Val);
Val = stripReferenceForwarding(Val);
// Nothing was stripped off.
if (NewVal == Val)
break;
// Hit max number of levels.
if (++levels > MaxRecursionDepth)
return OldVal;
} while (true);
return Val;
}
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