include/llvm/Transforms/IPO/FunctionAttrs.h

   1 //===- FunctionAttrs.h - Compute function attributes ------------*- C++ -*-===//
   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 /// \file
  10 /// Provides passes for computing function attributes based on interprocedural
  11 /// analyses.
  12 //
  13 //===----------------------------------------------------------------------===//
  14
  15 #ifndef LLVM_TRANSFORMS_IPO_FUNCTIONATTRS_H
  16 #define LLVM_TRANSFORMS_IPO_FUNCTIONATTRS_H
  17
  18 #include "llvm/Analysis/CGSCCPassManager.h"
  19 #include "llvm/Analysis/LazyCallGraph.h"
  20 #include "llvm/IR/PassManager.h"
  21
  22 namespace llvm {
  23
  24 class AAResults;
  25 class Function;
  26 class Module;
  27 class Pass;
  28
  29 /// The three kinds of memory access relevant to 'readonly' and
  30 /// 'readnone' attributes.
  31 enum MemoryAccessKind {
  32   MAK_ReadNone = 0,
  33   MAK_ReadOnly = 1,
  34   MAK_MayWrite = 2,
  35   MAK_WriteOnly = 3
  36 };
  37
  38 /// Returns the memory access properties of this copy of the function.
  39 MemoryAccessKind computeFunctionBodyMemoryAccess(Function &F, AAResults &AAR);
  40
  41 /// Computes function attributes in post-order over the call graph.
  42 ///
  43 /// By operating in post-order, this pass computes precise attributes for
  44 /// called functions prior to processsing their callers. This "bottom-up"
  45 /// approach allows powerful interprocedural inference of function attributes
  46 /// like memory access patterns, etc. It can discover functions that do not
  47 /// access memory, or only read memory, and give them the readnone/readonly
  48 /// attribute. It also discovers function arguments that are not captured by
  49 /// the function and marks them with the nocapture attribute.
  50 struct PostOrderFunctionAttrsPass : PassInfoMixin<PostOrderFunctionAttrsPass> {
  51   PreservedAnalyses run(LazyCallGraph::SCC &C, CGSCCAnalysisManager &AM,
  52                         LazyCallGraph &CG, CGSCCUpdateResult &UR);
  53 };
  54
  55 /// Create a legacy pass manager instance of a pass to compute function attrs
  56 /// in post-order.
  57 Pass *createPostOrderFunctionAttrsLegacyPass();
  58
  59 /// A pass to do RPO deduction and propagation of function attributes.
  60 ///
  61 /// This pass provides a general RPO or "top down" propagation of
  62 /// function attributes. For a few (rare) cases, we can deduce significantly
  63 /// more about function attributes by working in RPO, so this pass
  64 /// provides the complement to the post-order pass above where the majority of
  65 /// deduction is performed.
  66 // FIXME: Currently there is no RPO CGSCC pass structure to slide into and so
  67 // this is a boring module pass, but eventually it should be an RPO CGSCC pass
  68 // when such infrastructure is available.
  69 class ReversePostOrderFunctionAttrsPass
  70     : public PassInfoMixin<ReversePostOrderFunctionAttrsPass> {
  71 public:
  72   PreservedAnalyses run(Module &M, ModuleAnalysisManager &AM);
  73 };
  74
  75 } // end namespace llvm
  76
  77 #endif // LLVM_TRANSFORMS_IPO_FUNCTIONATTRS_H