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91 lines
3.4 KiB
C++
91 lines
3.4 KiB
C++
//===- Local.h - Functions to perform local transformations -----*- C++ -*-===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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//
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// This family of functions perform various local transformations to the
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// program.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_ANALYSIS_UTILS_LOCAL_H
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#define LLVM_ANALYSIS_UTILS_LOCAL_H
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#include "llvm/IR/DataLayout.h"
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#include "llvm/IR/GetElementPtrTypeIterator.h"
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namespace llvm {
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/// Given a getelementptr instruction/constantexpr, emit the code necessary to
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/// compute the offset from the base pointer (without adding in the base
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/// pointer). Return the result as a signed integer of intptr size.
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/// When NoAssumptions is true, no assumptions about index computation not
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/// overflowing is made.
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template <typename IRBuilderTy>
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Value *EmitGEPOffset(IRBuilderTy *Builder, const DataLayout &DL, User *GEP,
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bool NoAssumptions = false) {
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GEPOperator *GEPOp = cast<GEPOperator>(GEP);
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Type *IntPtrTy = DL.getIntPtrType(GEP->getType());
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Value *Result = Constant::getNullValue(IntPtrTy);
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// If the GEP is inbounds, we know that none of the addressing operations will
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// overflow in an unsigned sense.
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bool isInBounds = GEPOp->isInBounds() && !NoAssumptions;
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// Build a mask for high order bits.
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unsigned IntPtrWidth = IntPtrTy->getScalarType()->getIntegerBitWidth();
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uint64_t PtrSizeMask =
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std::numeric_limits<uint64_t>::max() >> (64 - IntPtrWidth);
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gep_type_iterator GTI = gep_type_begin(GEP);
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for (User::op_iterator i = GEP->op_begin() + 1, e = GEP->op_end(); i != e;
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++i, ++GTI) {
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Value *Op = *i;
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uint64_t Size = DL.getTypeAllocSize(GTI.getIndexedType()) & PtrSizeMask;
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if (Constant *OpC = dyn_cast<Constant>(Op)) {
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if (OpC->isZeroValue())
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continue;
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// Handle a struct index, which adds its field offset to the pointer.
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if (StructType *STy = GTI.getStructTypeOrNull()) {
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if (OpC->getType()->isVectorTy())
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OpC = OpC->getSplatValue();
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uint64_t OpValue = cast<ConstantInt>(OpC)->getZExtValue();
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Size = DL.getStructLayout(STy)->getElementOffset(OpValue);
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if (Size)
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Result = Builder->CreateAdd(Result, ConstantInt::get(IntPtrTy, Size),
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GEP->getName()+".offs");
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continue;
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}
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Constant *Scale = ConstantInt::get(IntPtrTy, Size);
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Constant *OC = ConstantExpr::getIntegerCast(OpC, IntPtrTy, true /*SExt*/);
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Scale = ConstantExpr::getMul(OC, Scale, isInBounds/*NUW*/);
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// Emit an add instruction.
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Result = Builder->CreateAdd(Result, Scale, GEP->getName()+".offs");
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continue;
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}
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// Convert to correct type.
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if (Op->getType() != IntPtrTy)
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Op = Builder->CreateIntCast(Op, IntPtrTy, true, Op->getName()+".c");
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if (Size != 1) {
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// We'll let instcombine(mul) convert this to a shl if possible.
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Op = Builder->CreateMul(Op, ConstantInt::get(IntPtrTy, Size),
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GEP->getName()+".idx", isInBounds /*NUW*/);
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}
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// Emit an add instruction.
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Result = Builder->CreateAdd(Op, Result, GEP->getName()+".offs");
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}
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return Result;
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}
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}
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#endif // LLVM_TRANSFORMS_UTILS_LOCAL_H
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