Add a pass to the queue of passes to run. Not sure if this functionality is used, but it doesn't seem to be tested. inner pass manager finishes, so accessing mutable analyses would give invalid org> Date: 2022-09-28 16:18:02 Message-ID: fqYxJf_LRxGvCW17oMi1qw geopod-ismtpd . The BasicBlockManager was improperly tested and found to be potentially broken, and was deprecated as of rL373254. Migrating to the new PM for the codegen pipeline likely wont unlock performance gains since there are almost no interprocedural codegen passes. When referring to legacy PM and new PM, this includes all of the surrounding infrastructure, not just the entity that manages passes. analysis may cause us to scan functions a quadratic number of times. The pass manager makes sure we visit SCCs bottom-up so that callees are as optimized as possible when we get to their callers and callers have as precise information as possible. PassBuilder::buildPerModuleDefaultPipeline(), TargetMachine::registerPassBuilderCallbacks(), AMDGPUTargetMachine::registerPassBuilderCallbacks(). In my. One of the things I was going to talk about in my COVID cancelled EuroLLVM 2020 talk was about a neat little trick we used to get the LLVM legacy pass manager to be significantly faster. For example, all Clang tests had been passing with the new PM for a while. Definition at line 503 of file LegacyPassManager.cpp. Keep track of whether any of the passes modifies the module, and if so, return true. There has been a desire to parallelize LLVM passes for a long time. Please file bugs for any regressions. Normally a tutorial for writing a (legacy) LLVM Pass would start with telling you to write a class which inherits one of the llvm::Pass family, llvm::FunctionPass for example, then implemented . Definition at line 502 of file LegacyPassManager.cpp. llvm::legacy::PassManager Class Reference. couple reasons. // return ! In these cases, the analysis manager can provide a (. Better would be to preserve as much analyses results as possible. in PAC.preserved()), or if PreservedAnalyses preserves all function transformation, or tell the analysis manager that analyses are no longer Add a pass to the queue of passes to run. I'm currently writing a program that uses LLVM but is not a pass itself. checked if they are invalidated: Combining invalidation and analysis manager proxies results in some Referenced by llvm::TargetPassConfig::addCheckDebugPass(), llvm::TargetPassConfig::addDebugifyPass(), llvm::TargetPassConfig::addISelPasses(), llvm::TargetPassConfig::addPass(), llvm::DirectXTargetMachine::addPassesToEmitFile(), llvm::LLVMTargetMachine::addPassesToEmitFile(), llvm::LLVMTargetMachine::addPassesToEmitMC(), addPassesToGenerateCode(), llvm::TargetPassConfig::addPrintPass(), llvm::TargetPassConfig::addStripDebugPass(), llvm::TargetPassConfig::addVerifyPass(), llvm::HexagonTargetMachine::adjustPassManager(), llvm::BPFTargetMachine::adjustPassManager(), llvm::AMDGPUTargetMachine::adjustPassManager(), and llvm::NVPTXTargetMachine::adjustPassManager(). llvm::legacy::PassManagerImpl::PassManagerImpl, void llvm::legacy::PassManagerImpl::getAnalysisUsage, MPPassManager* llvm::legacy::PassManagerImpl::getContainedManager, char llvm::legacy::PassManagerImpl::ID = 0. Alias analysis is a function-level analysis, but there are To get access to an outer level IR analysis, you can Find the pass that implements Analysis AID. There were some efforts upstream to make the new PM work for all use cases. For example, running all loop passes on a loop may cause a inner level IR. Take care in the pass to either clear the As mentioned before, passes added LLVM currently has two separate pass managers: the legacy pass manager (legacy PM) and the new pass manager (new PM). For example, a function pass manager can only contain function passes. analysis manager proxy which will clear all cached analyses, conservatively trigger outer level analysis computation could result in non-determinism if The legacy PM had a way for a. To use the legacy pass manager with opt, pass the -enable-new-pm=0 flag to all opt invocations. For example, a module References assert(), N, and llvm::PMTopLevelManager::PassManagers. will run FunctionPass1 and FunctionPass2 on the first function in a There were some initial failed attempts at hacks to work around this issue, which didnt properly update the call graph and didnt handle recursion from newly outlined functions. We need to inherit from some predefined subclasses taking into account what our pass is going to implement. This may involve revisiting a function we have already visited, but that is intentional as to give passes a chance to observe more precise information. assuming that there are invalid addresses used as keys for cached analyses. llvm ! Definition at line 39 of file LegacyPassManager.h. The analysis manager only provides analysis results for the same IR type as could keep outer level analyses up to date rather than computing them on demand Upon inspection, some passes that were expected to be run in something like the -O2 pipeline werent being run. the IR that the result is keyed on becomes invalid. (PAC.preserved() || PAC.preservedSet>()); // Check whether the analysis has been explicitly invalidated. Querying for an analysis will cause the manager to check if This passes ownership of the Pass to the PassManager. example. manually updated in the loop passes to ensure that invalidation is not 1 These snippets illustrate how to run and setup to run modern custom function and module pass on some .c/.cpp file. possible for some inner analysis to depend on some outer analysis, and when they are LLVM IR passes (whereas all MIR passes are codegen passes). This discounts future concurrency over separate loops in a function, but The vast majority of tests used the legacy PM syntax, so if the new PM were to be switched on by default, most LLVM tests wouldnt be testing the new PM passes. Inheritance diagram for llvm::legacy::PassManagerImpl: Collaboration diagram for llvm::legacy::PassManagerImpl: llvm::PMTopLevelManager::getImmutablePasses(), llvm::PMTopLevelManager::getNumContainedManagers(), llvm::PMTopLevelManager::initializeAllAnalysisInfo(). For example, a function Rather than manually adding passes to a pass manager, the typical way of run - Execute all of the passes scheduled for execution. FunctionPass2 on each function in the module. PassManagerImpl manages MPPassManagers. It includes PassManager to manage module pass and FunctionPassManager to manage FunctionPasses. level pass manager. Making the LLVM Legacy Pass Manager 1.65x Faster. As mentioned before, the codegen pipeline still only works with the legacy PM. manager, that is implicitly created. Inheritance diagram for llvm::legacy::PassManagerBase: llvm::TargetPassConfig::addCheckDebugPass(), llvm::TargetPassConfig::addDebugifyPass(), llvm::DirectXTargetMachine::addPassesToEmitFile(), llvm::LLVMTargetMachine::addPassesToEmitFile(), llvm::LLVMTargetMachine::addPassesToEmitMC(), llvm::TargetPassConfig::addStripDebugPass(), llvm::HexagonTargetMachine::adjustPassManager(), llvm::BPFTargetMachine::adjustPassManager(), llvm::AMDGPUTargetMachine::adjustPassManager(), llvm::NVPTXTargetMachine::adjustPassManager(), legacy::PassManagerBase::~PassManagerBase, virtual void llvm::legacy::PassManagerBase::add. For testing purposes, we can add specific passes to a pass manager to test those passes. The nesting is: module (-> cgscc) -> function -> loop, where the CGSCC nesting is optional. Now I have seen that LLVM has two PassManagers, a new one and an old one. A pass manager is also responsible for managing analysis results. Definition at line 1655 of file LegacyPassManager.cpp. One is Calculating these can be expensive, so the new pass manager has Implemented in llvm::DebugifyCustomPassManager, llvm::legacy::FunctionPassManager, and llvm::legacy::PassManager. certain parts of the pipeline. Passes can run on an entire module, a single function, or something more abstract such as a strongly connected component (SCC) in a call graph or a loop inside of a function. Passes can simply request an analysis from the analysis manager, allowing for lazily computing analyses. Scheduling can be simple, such as running a list of module passes, or running function passes on every function inside a module. needs to completely clear all relevant analysis results. applies for the other IR types, and in some cases can even affect the quality Say we first visit foo, then visit bar and remove the dead call. Otherwise it will construct a Initialize top level manager. We ported passes and features that made sense to port to the new PM, and pinned tests using legacy PM features that didnt make sense to port to the new PM. ModulePass: This is the most general superclass. This is for a // Invalidate all analysis results across the entire module. Add a pass to the queue of passes to run. as the dominator tree. analyses, or PreservedAnalyses preserves all analyses that only care In order for a pass to communicate that analyses have been invalidated, it returns which analyses it has preserved. Since the legacy PM modelled analyses as passes to be scheduled and run, we cant efficiently access analyses to arbitrary functions. The trend is that LLVM will abandon the legacy pass manager (which is now used by LLVM 10 of Compilergym). run - Execute all of the passes scheduled for execution. about the CFG, the FooAnalysisResult should not be invalidated. This pass is also subject to proper nesting. Pass plugins can also add passes into default pipelines. The pass manager tells the analysis manager to handle invalidated cached analyses. This also removes the ability to run arbitrary sets of passes. call. specifying a TargetMachine or various debugging. So as part of the new PMs incremental call graph update, if an SCC is split, we make sure to visit the newly split SCCs bottom-up. However, the typical use case is to run a predetermined pass pipeline. Rather than update every test, an -enable-new-pm option was added to opt, which translates the legacy syntax to the new syntax. rGb0f7f6f78d05: [mlir] Remove uses of LLVM's legacy pass manager Summary Use the new pass manager. thats a tradeoff due to how tightly a loop and its function are coupled. passes which work on a fixed scope. So just in time for the legacy pass manager to finally sail off into the coding . This removes support for the legacy pass manager in llvm-lto and llvm-lto2. When the PassManager is destroyed, the pass will be destroyed as well, so there is no need to delete the pass. References P, and llvm::PMTopLevelManager::schedulePass(). manually within the pass: One thing to note when accessing inner level IR analyses is cached results for As with any caching mechanism, we need some way to tell analysis managers The pass manager will call the analysis managers invalidate() method This major limitation of the legacy PM, along with other warts, prompted the desire for a new pass manager. module, then run both passes on the second function in the module, and so on. proper analyses invalidated. Although there is a global list of functions, there is no mutable global state since each pass manager builder can parse pass pipelines without going through a global registry. update it for specific transformations, or there may be helper updaters like Authored by bjope on Wed, Sep 28, 4:02 AM. While we cant yet remove the legacy pass manager, we can start the deprecation of it, at least for the optimization pipeline. for the optimization pipeline is deprecated and there are ongoing efforts to (a good number of tests already manually ran against both). The specific motivating use case was that the inliner wanted to look at the profile data of callees recursively, especially in regards to deferred inlining where the inliner wants to look through simple wrapper functions. adaptor: A more complete example, and -debug-pass-manager to show the execution This is supported by macros generating functions and variables to initialize passes, and any users of the legacy pass manager must make sure to call a function to initialize these passes. different ways of loading dynamic pass plugins. When the PassManager is destroyed, the pass will be destroyed as well, so there is no need to delete the pass. For the optimization pipeline, the new PM is the default PM. llvm/lib/IR/LegacyPassManager.cpp Go to file Go to fileT Go to lineL Copy path Copy permalink Cannot retrieve contributors at this time 2057 lines (1702 sloc) 67 KB Raw Blame Open with Desktop View raw View blame the new PM, whereas the backend target-dependent code generation only works compile times as low as possible. invalidating and recalculating it, the analysis itself may have methods to invalidated by changes to inner level IR. invalidate() to be more conservative when it comes to invalidation. Edit Parent Revisions; Edit Child Revisions; Edit Related Objects. cached/invalidated, you can mark the analysis manager proxy as preserved, HelloWorld.cpp: For example, to get a Currently there are efforts to make the codegen pipeline work with the new Generally for outer proxies, analysis results from the outer analysis manager Behind the scenes the pass manager would work out that you were using a function or module pass, and behind your back create a manager of the correct type (so if you used a function pass, it'd make a function pass manager for you). Definition at line 1661 of file LegacyPassManager.cpp. This may even destroy the pass right away if it is found to be redundant. llvm::legacy::PassManagerBase Class Reference. pipeline for a given optimization level. When a pass runs on some IR, it also receives an analysis manager which it can query for analyses. References llvm::PMDataManager::setTopLevelManager(). essentially saying that all deleted entries have been taken care of manually. To add a loop pass to a function pass manager, the loop pass must be wrapped in a loop-to-function adaptor to turn it into a function pass. complexity. There are a couple of special cases for easier typing: For a list of available passes and analyses, including the IR unit (module, To make tests using opt run against the new PM, we can either manually make them run twice, once against the legacy PM and once against the new PM, or we can automatically translate opt -instcombine to opt -passes=instcombine when the new PM is on by default. And if we have a persistent call graph, we need to make sure it is up to date if passes change its structure. // We haven't made any control flow changes, any analyses that only care about the control flow are still valid. It should be llvm::legacy::PassManager instead of just llvm::PassManager. Add a pass to the queue of passes to run. C++ source code API documentation for LLVM. This actually happens with alias analysis (. When the PassManager is destroyed, the pass will be destroyed as well, so there is no need to delete the pass. analyses on the IR unit it runs on are not preserved (see #include "llvm/IR/LegacyPassManager.h". Keep track of whether any of the passes modifies the module, and if so, return true. This similarly If LLVM is built with DLLVM_ENABLE_NEW_PASS_MANAGER set to ON, but the flag is passed to clang/opt to build using the legacy pass manager, you should get a warning from clang/opt. Or it may want to look at some
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