llvm-6502/include/llvm/Analysis/Passes.h
Hal Finkel 16fd27b2c3 Add scoped-noalias metadata
This commit adds scoped noalias metadata. The primary motivations for this
feature are:
  1. To preserve noalias function attribute information when inlining
  2. To provide the ability to model block-scope C99 restrict pointers

Neither of these two abilities are added here, only the necessary
infrastructure. In fact, there should be no change to existing functionality,
only the addition of new features. The logic that converts noalias function
parameters into this metadata during inlining will come in a follow-up commit.

What is added here is the ability to generally specify noalias memory-access
sets. Regarding the metadata, alias-analysis scopes are defined similar to TBAA
nodes:

!scope0 = metadata !{ metadata !"scope of foo()" }
!scope1 = metadata !{ metadata !"scope 1", metadata !scope0 }
!scope2 = metadata !{ metadata !"scope 2", metadata !scope0 }
!scope3 = metadata !{ metadata !"scope 2.1", metadata !scope2 }
!scope4 = metadata !{ metadata !"scope 2.2", metadata !scope2 }

Loads and stores can be tagged with an alias-analysis scope, and also, with a
noalias tag for a specific scope:

... = load %ptr1, !alias.scope !{ !scope1 }
... = load %ptr2, !alias.scope !{ !scope1, !scope2 }, !noalias !{ !scope1 }

When evaluating an aliasing query, if one of the instructions is associated
with an alias.scope id that is identical to the noalias scope associated with
the other instruction, or is a descendant (in the scope hierarchy) of the
noalias scope associated with the other instruction, then the two memory
accesses are assumed not to alias.

Note that is the first element of the scope metadata is a string, then it can
be combined accross functions and translation units. The string can be replaced
by a self-reference to create globally unqiue scope identifiers.

[Note: This overview is slightly stylized, since the metadata nodes really need
to just be numbers (!0 instead of !scope0), and the scope lists are also global
unnamed metadata.]

Existing noalias metadata in a callee is "cloned" for use by the inlined code.
This is necessary because the aliasing scopes are unique to each call site
(because of possible control dependencies on the aliasing properties). For
example, consider a function: foo(noalias a, noalias b) { *a = *b; } that gets
inlined into bar() { ... if (...) foo(a1, b1); ... if (...) foo(a2, b2); } --
now just because we know that a1 does not alias with b1 at the first call site,
and a2 does not alias with b2 at the second call site, we cannot let inlining
these functons have the metadata imply that a1 does not alias with b2.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@213864 91177308-0d34-0410-b5e6-96231b3b80d8
2014-07-24 14:25:39 +00:00

159 lines
5.4 KiB
C++

//===-- llvm/Analysis/Passes.h - Constructors for analyses ------*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This header file defines prototypes for accessor functions that expose passes
// in the analysis libraries.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_ANALYSIS_PASSES_H
#define LLVM_ANALYSIS_PASSES_H
namespace llvm {
class FunctionPass;
class ImmutablePass;
class LoopPass;
class ModulePass;
class Pass;
class PassInfo;
class LibCallInfo;
//===--------------------------------------------------------------------===//
//
// createGlobalsModRefPass - This pass provides alias and mod/ref info for
// global values that do not have their addresses taken.
//
Pass *createGlobalsModRefPass();
//===--------------------------------------------------------------------===//
//
// createAliasDebugger - This pass helps debug clients of AA
//
Pass *createAliasDebugger();
//===--------------------------------------------------------------------===//
//
// createAliasAnalysisCounterPass - This pass counts alias queries and how the
// alias analysis implementation responds.
//
ModulePass *createAliasAnalysisCounterPass();
//===--------------------------------------------------------------------===//
//
// createAAEvalPass - This pass implements a simple N^2 alias analysis
// accuracy evaluator.
//
FunctionPass *createAAEvalPass();
//===--------------------------------------------------------------------===//
//
// createNoAAPass - This pass implements a "I don't know" alias analysis.
//
ImmutablePass *createNoAAPass();
//===--------------------------------------------------------------------===//
//
// createBasicAliasAnalysisPass - This pass implements the stateless alias
// analysis.
//
ImmutablePass *createBasicAliasAnalysisPass();
//===--------------------------------------------------------------------===//
//
/// createLibCallAliasAnalysisPass - Create an alias analysis pass that knows
/// about the semantics of a set of libcalls specified by LCI. The newly
/// constructed pass takes ownership of the pointer that is provided.
///
FunctionPass *createLibCallAliasAnalysisPass(LibCallInfo *LCI);
//===--------------------------------------------------------------------===//
//
// createScalarEvolutionAliasAnalysisPass - This pass implements a simple
// alias analysis using ScalarEvolution queries.
//
FunctionPass *createScalarEvolutionAliasAnalysisPass();
//===--------------------------------------------------------------------===//
//
// createTypeBasedAliasAnalysisPass - This pass implements metadata-based
// type-based alias analysis.
//
ImmutablePass *createTypeBasedAliasAnalysisPass();
//===--------------------------------------------------------------------===//
//
// createScopedNoAliasAAPass - This pass implements metadata-based
// scoped noalias analysis.
//
ImmutablePass *createScopedNoAliasAAPass();
//===--------------------------------------------------------------------===//
//
// createObjCARCAliasAnalysisPass - This pass implements ObjC-ARC-based
// alias analysis.
//
ImmutablePass *createObjCARCAliasAnalysisPass();
//===--------------------------------------------------------------------===//
//
/// createLazyValueInfoPass - This creates an instance of the LazyValueInfo
/// pass.
FunctionPass *createLazyValueInfoPass();
//===--------------------------------------------------------------------===//
//
// createDependenceAnalysisPass - This creates an instance of the
// DependenceAnalysis pass.
//
FunctionPass *createDependenceAnalysisPass();
//===--------------------------------------------------------------------===//
//
// createCostModelAnalysisPass - This creates an instance of the
// CostModelAnalysis pass.
//
FunctionPass *createCostModelAnalysisPass();
//===--------------------------------------------------------------------===//
//
// createDelinearizationPass - This pass implements attempts to restore
// multidimensional array indices from linearized expressions.
//
FunctionPass *createDelinearizationPass();
//===--------------------------------------------------------------------===//
//
// Minor pass prototypes, allowing us to expose them through bugpoint and
// analyze.
FunctionPass *createInstCountPass();
//===--------------------------------------------------------------------===//
//
// createRegionInfoPass - This pass finds all single entry single exit regions
// in a function and builds the region hierarchy.
//
FunctionPass *createRegionInfoPass();
// Print module-level debug info metadata in human-readable form.
ModulePass *createModuleDebugInfoPrinterPass();
//===--------------------------------------------------------------------===//
//
// createMemDepPrinter - This pass exhaustively collects all memdep
// information and prints it with -analyze.
//
FunctionPass *createMemDepPrinter();
// createJumpInstrTableInfoPass - This creates a pass that stores information
// about the jump tables created by JumpInstrTables
ImmutablePass *createJumpInstrTableInfoPass();
}
#endif