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In the process of fixing the noalias parameter -> metadata conversion process that will take place during inlining (which will be committed soon, but not turned on by default), I have come to realize that the semantics provided by yesterday's commit are not really what we want. Here's why: void foo(noalias a, noalias b, noalias c, bool x) { *q = x ? a : b; *c = *q; } Generically, we know that *c does not alias with *a and with *b (so there is an 'and' in what we know we're not), and we know that *q might be derived from *a or from *b (so there is an 'or' in what we know that we are). So we do not want the semantics currently, where any noalias scope matching any alias.scope causes a NoAlias return. What we want to know is that the noalias scopes form a superset of the alias.scope list (meaning that all the things we know we're not is a superset of all of things the other instruction might be). Making that change, however, introduces a composibility problem. If we inline once, adding the noalias metadata, and then inline again adding more, and we append new scopes onto the noalias and alias.scope lists each time. But, this means that we could change what was a NoAlias result previously into a MayAlias result because we appended an additional scope onto one of the alias.scope lists. So, instead of giving scopes the ability to have parents (which I had borrowed from the TBAA implementation, but seems increasingly unlikely to be useful in practice), I've given them domains. The subset/superset condition now applies within each domain independently, and we only need it to hold in one domain. Each time we inline, we add the new scopes in a new scope domain, and everything now composes nicely. In addition, this simplifies the implementation. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@213948 91177308-0d34-0410-b5e6-96231b3b80d8
151 lines
5.6 KiB
C++
151 lines
5.6 KiB
C++
//===---- llvm/MDBuilder.h - Builder for LLVM metadata ----------*- C++ -*-===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file defines the MDBuilder class, which is used as a convenient way to
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// create LLVM metadata with a consistent and simplified interface.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_IR_MDBUILDER_H
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#define LLVM_IR_MDBUILDER_H
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#include "llvm/ADT/StringRef.h"
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#include "llvm/Support/DataTypes.h"
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#include <utility>
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namespace llvm {
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class APInt;
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template <typename T> class ArrayRef;
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class LLVMContext;
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class MDNode;
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class MDString;
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class MDBuilder {
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LLVMContext &Context;
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public:
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MDBuilder(LLVMContext &context) : Context(context) {}
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/// \brief Return the given string as metadata.
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MDString *createString(StringRef Str);
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//===------------------------------------------------------------------===//
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// FPMath metadata.
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//===------------------------------------------------------------------===//
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/// \brief Return metadata with the given settings. The special value 0.0
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/// for the Accuracy parameter indicates the default (maximal precision)
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/// setting.
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MDNode *createFPMath(float Accuracy);
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//===------------------------------------------------------------------===//
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// Prof metadata.
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//===------------------------------------------------------------------===//
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/// \brief Return metadata containing two branch weights.
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MDNode *createBranchWeights(uint32_t TrueWeight, uint32_t FalseWeight);
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/// \brief Return metadata containing a number of branch weights.
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MDNode *createBranchWeights(ArrayRef<uint32_t> Weights);
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//===------------------------------------------------------------------===//
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// Range metadata.
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//===------------------------------------------------------------------===//
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/// \brief Return metadata describing the range [Lo, Hi).
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MDNode *createRange(const APInt &Lo, const APInt &Hi);
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//===------------------------------------------------------------------===//
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// AA metadata.
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//===------------------------------------------------------------------===//
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protected:
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/// \brief Return metadata appropriate for a AA root node (scope or TBAA).
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/// Each returned node is distinct from all other metadata and will never
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/// be identified (uniqued) with anything else.
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MDNode *createAnonymousAARoot(StringRef Name = StringRef(),
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MDNode *Extra = nullptr);
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public:
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/// \brief Return metadata appropriate for a TBAA root node. Each returned
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/// node is distinct from all other metadata and will never be identified
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/// (uniqued) with anything else.
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MDNode *createAnonymousTBAARoot() {
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return createAnonymousAARoot();
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}
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/// \brief Return metadata appropriate for an alias scope domain node.
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/// Each returned node is distinct from all other metadata and will never
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/// be identified (uniqued) with anything else.
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MDNode *createAnonymousAliasScopeDomain(StringRef Name = StringRef()) {
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return createAnonymousAARoot(Name);
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}
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/// \brief Return metadata appropriate for an alias scope root node.
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/// Each returned node is distinct from all other metadata and will never
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/// be identified (uniqued) with anything else.
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MDNode *createAnonymousAliasScope(MDNode *Domain,
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StringRef Name = StringRef()) {
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return createAnonymousAARoot(Name, Domain);
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}
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/// \brief Return metadata appropriate for a TBAA root node with the given
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/// name. This may be identified (uniqued) with other roots with the same
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/// name.
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MDNode *createTBAARoot(StringRef Name);
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/// \brief Return metadata appropriate for an alias scope domain node with
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/// the given name. This may be identified (uniqued) with other roots with
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/// the same name.
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MDNode *createAliasScopeDomain(StringRef Name);
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/// \brief Return metadata appropriate for an alias scope node with
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/// the given name. This may be identified (uniqued) with other scopes with
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/// the same name and domain.
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MDNode *createAliasScope(StringRef Name, MDNode *Domain);
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/// \brief Return metadata for a non-root TBAA node with the given name,
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/// parent in the TBAA tree, and value for 'pointsToConstantMemory'.
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MDNode *createTBAANode(StringRef Name, MDNode *Parent,
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bool isConstant = false);
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struct TBAAStructField {
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uint64_t Offset;
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uint64_t Size;
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MDNode *TBAA;
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TBAAStructField(uint64_t Offset, uint64_t Size, MDNode *TBAA) :
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Offset(Offset), Size(Size), TBAA(TBAA) {}
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};
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/// \brief Return metadata for a tbaa.struct node with the given
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/// struct field descriptions.
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MDNode *createTBAAStructNode(ArrayRef<TBAAStructField> Fields);
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/// \brief Return metadata for a TBAA struct node in the type DAG
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/// with the given name, a list of pairs (offset, field type in the type DAG).
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MDNode *
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createTBAAStructTypeNode(StringRef Name,
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ArrayRef<std::pair<MDNode *, uint64_t>> Fields);
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/// \brief Return metadata for a TBAA scalar type node with the
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/// given name, an offset and a parent in the TBAA type DAG.
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MDNode *createTBAAScalarTypeNode(StringRef Name, MDNode *Parent,
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uint64_t Offset = 0);
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/// \brief Return metadata for a TBAA tag node with the given
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/// base type, access type and offset relative to the base type.
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MDNode *createTBAAStructTagNode(MDNode *BaseType, MDNode *AccessType,
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uint64_t Offset);
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};
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} // end namespace llvm
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#endif
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