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/AliasAnalysis.h" 19 #include "llvm/Analysis/CGSCCPassManager.h" 20 #include "llvm/Analysis/LazyCallGraph.h" 21 #include "llvm/IR/PassManager.h" 22 23 namespace llvm { 24 25 class GlobalValueSummary; 26 class ModuleSummaryIndex; 27 class Function; 28 class Module; 29 class Pass; 30 31 /// Returns the memory access properties of this copy of the function. 32 FunctionModRefBehavior computeFunctionBodyMemoryAccess(Function &F, 33 AAResults &AAR); 34 35 /// Propagate function attributes for function summaries along the index's 36 /// callgraph during thinlink 37 bool thinLTOPropagateFunctionAttrs( 38 ModuleSummaryIndex &Index, 39 function_ref<bool(GlobalValue::GUID, const GlobalValueSummary *)> 40 isPrevailing); 41 42 /// Computes function attributes in post-order over the call graph. 43 /// 44 /// By operating in post-order, this pass computes precise attributes for 45 /// called functions prior to processsing their callers. This "bottom-up" 46 /// approach allows powerful interprocedural inference of function attributes 47 /// like memory access patterns, etc. It can discover functions that do not 48 /// access memory, or only read memory, and give them the readnone/readonly 49 /// attribute. It also discovers function arguments that are not captured by 50 /// the function and marks them with the nocapture attribute. 51 struct PostOrderFunctionAttrsPass : PassInfoMixin<PostOrderFunctionAttrsPass> { 52 PreservedAnalyses run(LazyCallGraph::SCC &C, CGSCCAnalysisManager &AM, 53 LazyCallGraph &CG, CGSCCUpdateResult &UR); 54 }; 55 56 /// Create a legacy pass manager instance of a pass to compute function attrs 57 /// in post-order. 58 Pass *createPostOrderFunctionAttrsLegacyPass(); 59 60 /// A pass to do RPO deduction and propagation of function attributes. 61 /// 62 /// This pass provides a general RPO or "top down" propagation of 63 /// function attributes. For a few (rare) cases, we can deduce significantly 64 /// more about function attributes by working in RPO, so this pass 65 /// provides the complement to the post-order pass above where the majority of 66 /// deduction is performed. 67 // FIXME: Currently there is no RPO CGSCC pass structure to slide into and so 68 // this is a boring module pass, but eventually it should be an RPO CGSCC pass 69 // when such infrastructure is available. 70 class ReversePostOrderFunctionAttrsPass 71 : public PassInfoMixin<ReversePostOrderFunctionAttrsPass> { 72 public: 73 PreservedAnalyses run(Module &M, ModuleAnalysisManager &AM); 74 }; 75 76 } // end namespace llvm 77 78 #endif // LLVM_TRANSFORMS_IPO_FUNCTIONATTRS_H 79