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https://github.com/c64scene-ar/llvm-6502.git
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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@21618 91177308-0d34-0410-b5e6-96231b3b80d8
1102 lines
39 KiB
C++
1102 lines
39 KiB
C++
//===- SimplifyLibCalls.cpp - Optimize specific well-known library calls --===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file was developed by Reid Spencer and is distributed under the
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// University of Illinois Open Source License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file implements a variety of small optimizations for calls to specific
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// well-known (e.g. runtime library) function calls. For example, a call to the
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// function "exit(3)" that occurs within the main() function can be transformed
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// into a simple "return 3" instruction. Any optimization that takes this form
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// (replace call to library function with simpler code that provides same
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// result) belongs in this file.
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//
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//===----------------------------------------------------------------------===//
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#define DEBUG_TYPE "simplify-libcalls"
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#include "llvm/Constants.h"
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#include "llvm/DerivedTypes.h"
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#include "llvm/Instructions.h"
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#include "llvm/Module.h"
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#include "llvm/Pass.h"
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#include "llvm/ADT/hash_map"
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#include "llvm/ADT/Statistic.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Target/TargetData.h"
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#include "llvm/Transforms/IPO.h"
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#include <iostream>
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using namespace llvm;
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namespace {
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/// This statistic keeps track of the total number of library calls that have
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/// been simplified regardless of which call it is.
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Statistic<> SimplifiedLibCalls("simplify-libcalls",
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"Number of well-known library calls simplified");
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// Forward declarations
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class LibCallOptimization;
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class SimplifyLibCalls;
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/// @brief The list of optimizations deriving from LibCallOptimization
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hash_map<std::string,LibCallOptimization*> optlist;
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/// This class is the abstract base class for the set of optimizations that
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/// corresponds to one library call. The SimplifyLibCalls pass will call the
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/// ValidateCalledFunction method to ask the optimization if a given Function
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/// is the kind that the optimization can handle. If the subclass returns true,
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/// then SImplifyLibCalls will also call the OptimizeCall method to perform,
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/// or attempt to perform, the optimization(s) for the library call. Otherwise,
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/// OptimizeCall won't be called. Subclasses are responsible for providing the
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/// name of the library call (strlen, strcpy, etc.) to the LibCallOptimization
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/// constructor. This is used to efficiently select which call instructions to
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/// optimize. The criteria for a "lib call" is "anything with well known
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/// semantics", typically a library function that is defined by an international
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/// standard. Because the semantics are well known, the optimizations can
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/// generally short-circuit actually calling the function if there's a simpler
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/// way (e.g. strlen(X) can be reduced to a constant if X is a constant global).
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/// @brief Base class for library call optimizations
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class LibCallOptimization
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{
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public:
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/// The \p fname argument must be the name of the library function being
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/// optimized by the subclass.
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/// @brief Constructor that registers the optimization.
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LibCallOptimization(const char * fname )
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: func_name(fname)
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#ifndef NDEBUG
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, stat_name(std::string("simplify-libcalls:")+fname)
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, stat_desc(std::string("Number of ")+fname+"(...) calls simplified")
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, occurrences(stat_name.c_str(),stat_desc.c_str())
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#endif
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{
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// Register this call optimizer in the optlist (a hash_map)
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optlist[func_name] = this;
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}
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/// @brief Deregister from the optlist
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virtual ~LibCallOptimization() { optlist.erase(func_name); }
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/// The implementation of this function in subclasses should determine if
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/// \p F is suitable for the optimization. This method is called by
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/// SimplifyLibCalls::runOnModule to short circuit visiting all the call
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/// sites of such a function if that function is not suitable in the first
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/// place. If the called function is suitabe, this method should return true;
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/// false, otherwise. This function should also perform any lazy
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/// initialization that the LibCallOptimization needs to do, if its to return
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/// true. This avoids doing initialization until the optimizer is actually
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/// going to be called upon to do some optimization.
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/// @brief Determine if the function is suitable for optimization
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virtual bool ValidateCalledFunction(
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const Function* F, ///< The function that is the target of call sites
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SimplifyLibCalls& SLC ///< The pass object invoking us
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) = 0;
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/// The implementations of this function in subclasses is the heart of the
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/// SimplifyLibCalls algorithm. Sublcasses of this class implement
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/// OptimizeCall to determine if (a) the conditions are right for optimizing
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/// the call and (b) to perform the optimization. If an action is taken
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/// against ci, the subclass is responsible for returning true and ensuring
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/// that ci is erased from its parent.
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/// @brief Optimize a call, if possible.
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virtual bool OptimizeCall(
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CallInst* ci, ///< The call instruction that should be optimized.
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SimplifyLibCalls& SLC ///< The pass object invoking us
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) = 0;
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/// @brief Get the name of the library call being optimized
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const char * getFunctionName() const { return func_name; }
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#ifndef NDEBUG
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/// @brief Called by SimplifyLibCalls to update the occurrences statistic.
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void succeeded() { ++occurrences; }
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#endif
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private:
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const char* func_name; ///< Name of the library call we optimize
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#ifndef NDEBUG
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std::string stat_name; ///< Holder for debug statistic name
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std::string stat_desc; ///< Holder for debug statistic description
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Statistic<> occurrences; ///< debug statistic (-debug-only=simplify-libcalls)
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#endif
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};
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/// This class is an LLVM Pass that applies each of the LibCallOptimization
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/// instances to all the call sites in a module, relatively efficiently. The
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/// purpose of this pass is to provide optimizations for calls to well-known
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/// functions with well-known semantics, such as those in the c library. The
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/// class provides the basic infrastructure for handling runOnModule. Whenever /// this pass finds a function call, it asks the appropriate optimizer to
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/// validate the call (ValidateLibraryCall). If it is validated, then
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/// the OptimizeCall method is also called.
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/// @brief A ModulePass for optimizing well-known function calls.
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class SimplifyLibCalls : public ModulePass
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{
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public:
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/// We need some target data for accurate signature details that are
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/// target dependent. So we require target data in our AnalysisUsage.
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/// @brief Require TargetData from AnalysisUsage.
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virtual void getAnalysisUsage(AnalysisUsage& Info) const
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{
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// Ask that the TargetData analysis be performed before us so we can use
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// the target data.
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Info.addRequired<TargetData>();
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}
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/// For this pass, process all of the function calls in the module, calling
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/// ValidateLibraryCall and OptimizeCall as appropriate.
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/// @brief Run all the lib call optimizations on a Module.
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virtual bool runOnModule(Module &M)
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{
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reset(M);
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bool result = false;
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// The call optimizations can be recursive. That is, the optimization might
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// generate a call to another function which can also be optimized. This way
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// we make the LibCallOptimization instances very specific to the case they
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// handle. It also means we need to keep running over the function calls in
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// the module until we don't get any more optimizations possible.
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bool found_optimization = false;
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do
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{
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found_optimization = false;
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for (Module::iterator FI = M.begin(), FE = M.end(); FI != FE; ++FI)
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{
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// All the "well-known" functions are external and have external linkage
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// because they live in a runtime library somewhere and were (probably)
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// not compiled by LLVM. So, we only act on external functions that have
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// external linkage and non-empty uses.
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if (!FI->isExternal() || !FI->hasExternalLinkage() || FI->use_empty())
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continue;
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// Get the optimization class that pertains to this function
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LibCallOptimization* CO = optlist[FI->getName().c_str()];
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if (!CO)
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continue;
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// Make sure the called function is suitable for the optimization
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if (!CO->ValidateCalledFunction(FI,*this))
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continue;
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// Loop over each of the uses of the function
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for (Value::use_iterator UI = FI->use_begin(), UE = FI->use_end();
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UI != UE ; )
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{
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// If the use of the function is a call instruction
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if (CallInst* CI = dyn_cast<CallInst>(*UI++))
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{
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// Do the optimization on the LibCallOptimization.
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if (CO->OptimizeCall(CI,*this))
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{
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++SimplifiedLibCalls;
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found_optimization = result = true;
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#ifndef NDEBUG
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CO->succeeded();
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#endif
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}
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}
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}
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}
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} while (found_optimization);
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return result;
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}
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/// @brief Return the *current* module we're working on.
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Module* getModule() const { return M; }
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/// @brief Return the *current* target data for the module we're working on.
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TargetData* getTargetData() const { return TD; }
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/// @brief Return the size_t type -- syntactic shortcut
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const Type* getIntPtrType() const { return TD->getIntPtrType(); }
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/// @brief Return a Function* for the fputc libcall
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Function* get_fputc()
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{
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if (!fputc_func)
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{
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std::vector<const Type*> args;
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args.push_back(Type::IntTy);
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const Type* FILE_type = M->getTypeByName("struct._IO_FILE");
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if (!FILE_type)
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FILE_type = M->getTypeByName("struct._FILE");
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if (!FILE_type)
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return 0;
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args.push_back(PointerType::get(FILE_type));
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FunctionType* fputc_type =
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FunctionType::get(Type::IntTy, args, false);
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fputc_func = M->getOrInsertFunction("fputc",fputc_type);
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}
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return fputc_func;
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}
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/// @brief Return a Function* for the fwrite libcall
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Function* get_fwrite()
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{
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if (!fwrite_func)
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{
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std::vector<const Type*> args;
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args.push_back(PointerType::get(Type::SByteTy));
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args.push_back(TD->getIntPtrType());
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args.push_back(TD->getIntPtrType());
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const Type* FILE_type = M->getTypeByName("struct._IO_FILE");
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if (!FILE_type)
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FILE_type = M->getTypeByName("struct._FILE");
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if (!FILE_type)
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return 0;
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args.push_back(PointerType::get(FILE_type));
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FunctionType* fwrite_type =
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FunctionType::get(TD->getIntPtrType(), args, false);
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fwrite_func = M->getOrInsertFunction("fwrite",fwrite_type);
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}
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return fwrite_func;
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}
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/// @brief Return a Function* for the sqrt libcall
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Function* get_sqrt()
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{
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if (!sqrt_func)
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{
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std::vector<const Type*> args;
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args.push_back(Type::DoubleTy);
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FunctionType* sqrt_type =
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FunctionType::get(Type::DoubleTy, args, false);
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sqrt_func = M->getOrInsertFunction("sqrt",sqrt_type);
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}
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return sqrt_func;
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}
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/// @brief Return a Function* for the strlen libcall
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Function* get_strlen()
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{
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if (!strlen_func)
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{
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std::vector<const Type*> args;
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args.push_back(PointerType::get(Type::SByteTy));
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FunctionType* strlen_type =
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FunctionType::get(TD->getIntPtrType(), args, false);
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strlen_func = M->getOrInsertFunction("strlen",strlen_type);
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}
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return strlen_func;
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}
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/// @brief Return a Function* for the memcpy libcall
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Function* get_memcpy()
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{
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if (!memcpy_func)
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{
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// Note: this is for llvm.memcpy intrinsic
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std::vector<const Type*> args;
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args.push_back(PointerType::get(Type::SByteTy));
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args.push_back(PointerType::get(Type::SByteTy));
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args.push_back(Type::IntTy);
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args.push_back(Type::IntTy);
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FunctionType* memcpy_type = FunctionType::get(Type::VoidTy, args, false);
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memcpy_func = M->getOrInsertFunction("llvm.memcpy",memcpy_type);
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}
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return memcpy_func;
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}
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private:
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/// @brief Reset our cached data for a new Module
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void reset(Module& mod)
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{
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M = &mod;
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TD = &getAnalysis<TargetData>();
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fputc_func = 0;
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fwrite_func = 0;
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memcpy_func = 0;
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sqrt_func = 0;
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strlen_func = 0;
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}
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private:
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Function* fputc_func; ///< Cached fputc function
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Function* fwrite_func; ///< Cached fwrite function
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Function* memcpy_func; ///< Cached llvm.memcpy function
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Function* sqrt_func; ///< Cached sqrt function
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Function* strlen_func; ///< Cached strlen function
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Module* M; ///< Cached Module
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TargetData* TD; ///< Cached TargetData
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};
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// Register the pass
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RegisterOpt<SimplifyLibCalls>
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X("simplify-libcalls","Simplify well-known library calls");
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} // anonymous namespace
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// The only public symbol in this file which just instantiates the pass object
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ModulePass *llvm::createSimplifyLibCallsPass()
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{
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return new SimplifyLibCalls();
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}
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// Classes below here, in the anonymous namespace, are all subclasses of the
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// LibCallOptimization class, each implementing all optimizations possible for a
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// single well-known library call. Each has a static singleton instance that
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// auto registers it into the "optlist" global above.
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namespace {
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// Forward declare a utility function.
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bool getConstantStringLength(Value* V, uint64_t& len );
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/// This LibCallOptimization will find instances of a call to "exit" that occurs
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/// within the "main" function and change it to a simple "ret" instruction with
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/// the same value passed to the exit function. When this is done, it splits the
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/// basic block at the exit(3) call and deletes the call instruction.
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/// @brief Replace calls to exit in main with a simple return
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struct ExitInMainOptimization : public LibCallOptimization
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{
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ExitInMainOptimization() : LibCallOptimization("exit") {}
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virtual ~ExitInMainOptimization() {}
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// Make sure the called function looks like exit (int argument, int return
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// type, external linkage, not varargs).
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virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC)
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{
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if (f->arg_size() >= 1)
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if (f->arg_begin()->getType()->isInteger())
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return true;
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return false;
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}
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virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& SLC)
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{
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// To be careful, we check that the call to exit is coming from "main", that
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// main has external linkage, and the return type of main and the argument
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// to exit have the same type.
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Function *from = ci->getParent()->getParent();
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if (from->hasExternalLinkage())
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if (from->getReturnType() == ci->getOperand(1)->getType())
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if (from->getName() == "main")
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{
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// Okay, time to actually do the optimization. First, get the basic
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// block of the call instruction
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BasicBlock* bb = ci->getParent();
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// Create a return instruction that we'll replace the call with.
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// Note that the argument of the return is the argument of the call
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// instruction.
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ReturnInst* ri = new ReturnInst(ci->getOperand(1), ci);
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// Split the block at the call instruction which places it in a new
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// basic block.
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bb->splitBasicBlock(ci);
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// The block split caused a branch instruction to be inserted into
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// the end of the original block, right after the return instruction
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// that we put there. That's not a valid block, so delete the branch
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// instruction.
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bb->getInstList().pop_back();
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// Now we can finally get rid of the call instruction which now lives
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// in the new basic block.
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ci->eraseFromParent();
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// Optimization succeeded, return true.
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return true;
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}
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// We didn't pass the criteria for this optimization so return false
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return false;
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}
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} ExitInMainOptimizer;
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/// This LibCallOptimization will simplify a call to the strcat library
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/// function. The simplification is possible only if the string being
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/// concatenated is a constant array or a constant expression that results in
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/// a constant string. In this case we can replace it with strlen + llvm.memcpy
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/// of the constant string. Both of these calls are further reduced, if possible
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/// on subsequent passes.
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/// @brief Simplify the strcat library function.
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struct StrCatOptimization : public LibCallOptimization
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{
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public:
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/// @brief Default constructor
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StrCatOptimization() : LibCallOptimization("strcat") {}
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public:
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/// @breif Destructor
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virtual ~StrCatOptimization() {}
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/// @brief Make sure that the "strcat" function has the right prototype
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virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC)
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{
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if (f->getReturnType() == PointerType::get(Type::SByteTy))
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if (f->arg_size() == 2)
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{
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Function::const_arg_iterator AI = f->arg_begin();
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if (AI++->getType() == PointerType::get(Type::SByteTy))
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if (AI->getType() == PointerType::get(Type::SByteTy))
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{
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// Indicate this is a suitable call type.
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return true;
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}
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}
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return false;
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}
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/// @brief Optimize the strcat library function
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virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& SLC)
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{
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// Extract some information from the instruction
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Module* M = ci->getParent()->getParent()->getParent();
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Value* dest = ci->getOperand(1);
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Value* src = ci->getOperand(2);
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// Extract the initializer (while making numerous checks) from the
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// source operand of the call to strcat. If we get null back, one of
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// a variety of checks in get_GVInitializer failed
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uint64_t len = 0;
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if (!getConstantStringLength(src,len))
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return false;
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// Handle the simple, do-nothing case
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if (len == 0)
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{
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ci->replaceAllUsesWith(dest);
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ci->eraseFromParent();
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return true;
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}
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// Increment the length because we actually want to memcpy the null
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// terminator as well.
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len++;
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// We need to find the end of the destination string. That's where the
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// memory is to be moved to. We just generate a call to strlen (further
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// optimized in another pass). Note that the SLC.get_strlen() call
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// caches the Function* for us.
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CallInst* strlen_inst =
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new CallInst(SLC.get_strlen(), dest, dest->getName()+".len",ci);
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// Now that we have the destination's length, we must index into the
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// destination's pointer to get the actual memcpy destination (end of
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// the string .. we're concatenating).
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std::vector<Value*> idx;
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idx.push_back(strlen_inst);
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GetElementPtrInst* gep =
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new GetElementPtrInst(dest,idx,dest->getName()+".indexed",ci);
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// We have enough information to now generate the memcpy call to
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// do the concatenation for us.
|
|
std::vector<Value*> vals;
|
|
vals.push_back(gep); // destination
|
|
vals.push_back(ci->getOperand(2)); // source
|
|
vals.push_back(ConstantSInt::get(Type::IntTy,len)); // length
|
|
vals.push_back(ConstantSInt::get(Type::IntTy,1)); // alignment
|
|
new CallInst(SLC.get_memcpy(), vals, "", ci);
|
|
|
|
// Finally, substitute the first operand of the strcat call for the
|
|
// strcat call itself since strcat returns its first operand; and,
|
|
// kill the strcat CallInst.
|
|
ci->replaceAllUsesWith(dest);
|
|
ci->eraseFromParent();
|
|
return true;
|
|
}
|
|
} StrCatOptimizer;
|
|
|
|
/// This LibCallOptimization will simplify a call to the strcpy library
|
|
/// function. Two optimizations are possible:
|
|
/// (1) If src and dest are the same and not volatile, just return dest
|
|
/// (2) If the src is a constant then we can convert to llvm.memmove
|
|
/// @brief Simplify the strcpy library function.
|
|
struct StrCpyOptimization : public LibCallOptimization
|
|
{
|
|
public:
|
|
StrCpyOptimization() : LibCallOptimization("strcpy") {}
|
|
virtual ~StrCpyOptimization() {}
|
|
|
|
/// @brief Make sure that the "strcpy" function has the right prototype
|
|
virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC)
|
|
{
|
|
if (f->getReturnType() == PointerType::get(Type::SByteTy))
|
|
if (f->arg_size() == 2)
|
|
{
|
|
Function::const_arg_iterator AI = f->arg_begin();
|
|
if (AI++->getType() == PointerType::get(Type::SByteTy))
|
|
if (AI->getType() == PointerType::get(Type::SByteTy))
|
|
{
|
|
// Indicate this is a suitable call type.
|
|
return true;
|
|
}
|
|
}
|
|
return false;
|
|
}
|
|
|
|
/// @brief Perform the strcpy optimization
|
|
virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& SLC)
|
|
{
|
|
// First, check to see if src and destination are the same. If they are,
|
|
// then the optimization is to replace the CallInst with the destination
|
|
// because the call is a no-op. Note that this corresponds to the
|
|
// degenerate strcpy(X,X) case which should have "undefined" results
|
|
// according to the C specification. However, it occurs sometimes and
|
|
// we optimize it as a no-op.
|
|
Value* dest = ci->getOperand(1);
|
|
Value* src = ci->getOperand(2);
|
|
if (dest == src)
|
|
{
|
|
ci->replaceAllUsesWith(dest);
|
|
ci->eraseFromParent();
|
|
return true;
|
|
}
|
|
|
|
// Get the length of the constant string referenced by the second operand,
|
|
// the "src" parameter. Fail the optimization if we can't get the length
|
|
// (note that getConstantStringLength does lots of checks to make sure this
|
|
// is valid).
|
|
uint64_t len = 0;
|
|
if (!getConstantStringLength(ci->getOperand(2),len))
|
|
return false;
|
|
|
|
// If the constant string's length is zero we can optimize this by just
|
|
// doing a store of 0 at the first byte of the destination
|
|
if (len == 0)
|
|
{
|
|
new StoreInst(ConstantInt::get(Type::SByteTy,0),ci->getOperand(1),ci);
|
|
ci->replaceAllUsesWith(dest);
|
|
ci->eraseFromParent();
|
|
return true;
|
|
}
|
|
|
|
// Increment the length because we actually want to memcpy the null
|
|
// terminator as well.
|
|
len++;
|
|
|
|
// Extract some information from the instruction
|
|
Module* M = ci->getParent()->getParent()->getParent();
|
|
|
|
// We have enough information to now generate the memcpy call to
|
|
// do the concatenation for us.
|
|
std::vector<Value*> vals;
|
|
vals.push_back(dest); // destination
|
|
vals.push_back(src); // source
|
|
vals.push_back(ConstantSInt::get(Type::IntTy,len)); // length
|
|
vals.push_back(ConstantSInt::get(Type::IntTy,1)); // alignment
|
|
new CallInst(SLC.get_memcpy(), vals, "", ci);
|
|
|
|
// Finally, substitute the first operand of the strcat call for the
|
|
// strcat call itself since strcat returns its first operand; and,
|
|
// kill the strcat CallInst.
|
|
ci->replaceAllUsesWith(dest);
|
|
ci->eraseFromParent();
|
|
return true;
|
|
}
|
|
} StrCpyOptimizer;
|
|
|
|
/// This LibCallOptimization will simplify a call to the strlen library
|
|
/// function by replacing it with a constant value if the string provided to
|
|
/// it is a constant array.
|
|
/// @brief Simplify the strlen library function.
|
|
struct StrLenOptimization : public LibCallOptimization
|
|
{
|
|
StrLenOptimization() : LibCallOptimization("strlen") {}
|
|
virtual ~StrLenOptimization() {}
|
|
|
|
/// @brief Make sure that the "strlen" function has the right prototype
|
|
virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC)
|
|
{
|
|
if (f->getReturnType() == SLC.getTargetData()->getIntPtrType())
|
|
if (f->arg_size() == 1)
|
|
if (Function::const_arg_iterator AI = f->arg_begin())
|
|
if (AI->getType() == PointerType::get(Type::SByteTy))
|
|
return true;
|
|
return false;
|
|
}
|
|
|
|
/// @brief Perform the strlen optimization
|
|
virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& SLC)
|
|
{
|
|
// Get the length of the string
|
|
uint64_t len = 0;
|
|
if (!getConstantStringLength(ci->getOperand(1),len))
|
|
return false;
|
|
|
|
ci->replaceAllUsesWith(
|
|
ConstantInt::get(SLC.getTargetData()->getIntPtrType(),len));
|
|
ci->eraseFromParent();
|
|
return true;
|
|
}
|
|
} StrLenOptimizer;
|
|
|
|
/// This LibCallOptimization will simplify a call to the memcpy library
|
|
/// function by expanding it out to a single store of size 0, 1, 2, 4, or 8
|
|
/// bytes depending on the length of the string and the alignment. Additional
|
|
/// optimizations are possible in code generation (sequence of immediate store)
|
|
/// @brief Simplify the memcpy library function.
|
|
struct MemCpyOptimization : public LibCallOptimization
|
|
{
|
|
/// @brief Default Constructor
|
|
MemCpyOptimization() : LibCallOptimization("llvm.memcpy") {}
|
|
protected:
|
|
/// @brief Subclass Constructor
|
|
MemCpyOptimization(const char* fname) : LibCallOptimization(fname) {}
|
|
public:
|
|
/// @brief Destructor
|
|
virtual ~MemCpyOptimization() {}
|
|
|
|
/// @brief Make sure that the "memcpy" function has the right prototype
|
|
virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& TD)
|
|
{
|
|
// Just make sure this has 4 arguments per LLVM spec.
|
|
return (f->arg_size() == 4);
|
|
}
|
|
|
|
/// Because of alignment and instruction information that we don't have, we
|
|
/// leave the bulk of this to the code generators. The optimization here just
|
|
/// deals with a few degenerate cases where the length of the string and the
|
|
/// alignment match the sizes of our intrinsic types so we can do a load and
|
|
/// store instead of the memcpy call.
|
|
/// @brief Perform the memcpy optimization.
|
|
virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& TD)
|
|
{
|
|
// Make sure we have constant int values to work with
|
|
ConstantInt* LEN = dyn_cast<ConstantInt>(ci->getOperand(3));
|
|
if (!LEN)
|
|
return false;
|
|
ConstantInt* ALIGN = dyn_cast<ConstantInt>(ci->getOperand(4));
|
|
if (!ALIGN)
|
|
return false;
|
|
|
|
// If the length is larger than the alignment, we can't optimize
|
|
uint64_t len = LEN->getRawValue();
|
|
uint64_t alignment = ALIGN->getRawValue();
|
|
if (len > alignment)
|
|
return false;
|
|
|
|
// Get the type we will cast to, based on size of the string
|
|
Value* dest = ci->getOperand(1);
|
|
Value* src = ci->getOperand(2);
|
|
Type* castType = 0;
|
|
switch (len)
|
|
{
|
|
case 0:
|
|
// memcpy(d,s,0,a) -> noop
|
|
ci->eraseFromParent();
|
|
return true;
|
|
case 1: castType = Type::SByteTy; break;
|
|
case 2: castType = Type::ShortTy; break;
|
|
case 4: castType = Type::IntTy; break;
|
|
case 8: castType = Type::LongTy; break;
|
|
default:
|
|
return false;
|
|
}
|
|
|
|
// Cast source and dest to the right sized primitive and then load/store
|
|
CastInst* SrcCast =
|
|
new CastInst(src,PointerType::get(castType),src->getName()+".cast",ci);
|
|
CastInst* DestCast =
|
|
new CastInst(dest,PointerType::get(castType),dest->getName()+".cast",ci);
|
|
LoadInst* LI = new LoadInst(SrcCast,SrcCast->getName()+".val",ci);
|
|
StoreInst* SI = new StoreInst(LI, DestCast, ci);
|
|
ci->eraseFromParent();
|
|
return true;
|
|
}
|
|
} MemCpyOptimizer;
|
|
|
|
/// This LibCallOptimization will simplify a call to the memmove library
|
|
/// function. It is identical to MemCopyOptimization except for the name of
|
|
/// the intrinsic.
|
|
/// @brief Simplify the memmove library function.
|
|
struct MemMoveOptimization : public MemCpyOptimization
|
|
{
|
|
/// @brief Default Constructor
|
|
MemMoveOptimization() : MemCpyOptimization("llvm.memmove") {}
|
|
|
|
} MemMoveOptimizer;
|
|
|
|
/// This LibCallOptimization will simplify calls to the "pow" library
|
|
/// function. It looks for cases where the result of pow is well known and
|
|
/// substitutes the appropriate value.
|
|
/// @brief Simplify the pow library function.
|
|
struct PowOptimization : public LibCallOptimization
|
|
{
|
|
public:
|
|
/// @brief Default Constructor
|
|
PowOptimization() : LibCallOptimization("pow") {}
|
|
/// @brief Destructor
|
|
virtual ~PowOptimization() {}
|
|
|
|
/// @brief Make sure that the "pow" function has the right prototype
|
|
virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC)
|
|
{
|
|
// Just make sure this has 2 arguments
|
|
return (f->arg_size() == 2);
|
|
}
|
|
|
|
/// @brief Perform the pow optimization.
|
|
virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& SLC)
|
|
{
|
|
const Type *Ty = cast<Function>(ci->getOperand(0))->getReturnType();
|
|
Value* base = ci->getOperand(1);
|
|
Value* expn = ci->getOperand(2);
|
|
if (ConstantFP *Op1 = dyn_cast<ConstantFP>(base)) {
|
|
double Op1V = Op1->getValue();
|
|
if (Op1V == 1.0)
|
|
{
|
|
// pow(1.0,x) -> 1.0
|
|
ci->replaceAllUsesWith(ConstantFP::get(Ty,1.0));
|
|
ci->eraseFromParent();
|
|
return true;
|
|
}
|
|
}
|
|
else if (ConstantFP* Op2 = dyn_cast<ConstantFP>(expn))
|
|
{
|
|
double Op2V = Op2->getValue();
|
|
if (Op2V == 0.0)
|
|
{
|
|
// pow(x,0.0) -> 1.0
|
|
ci->replaceAllUsesWith(ConstantFP::get(Ty,1.0));
|
|
ci->eraseFromParent();
|
|
return true;
|
|
}
|
|
else if (Op2V == 0.5)
|
|
{
|
|
// pow(x,0.5) -> sqrt(x)
|
|
CallInst* sqrt_inst = new CallInst(SLC.get_sqrt(), base,
|
|
ci->getName()+".pow",ci);
|
|
ci->replaceAllUsesWith(sqrt_inst);
|
|
ci->eraseFromParent();
|
|
return true;
|
|
}
|
|
else if (Op2V == 1.0)
|
|
{
|
|
// pow(x,1.0) -> x
|
|
ci->replaceAllUsesWith(base);
|
|
ci->eraseFromParent();
|
|
return true;
|
|
}
|
|
else if (Op2V == -1.0)
|
|
{
|
|
// pow(x,-1.0) -> 1.0/x
|
|
BinaryOperator* div_inst= BinaryOperator::create(Instruction::Div,
|
|
ConstantFP::get(Ty,1.0), base, ci->getName()+".pow", ci);
|
|
ci->replaceAllUsesWith(div_inst);
|
|
ci->eraseFromParent();
|
|
return true;
|
|
}
|
|
}
|
|
return false; // opt failed
|
|
}
|
|
} PowOptimizer;
|
|
|
|
/// This LibCallOptimization will simplify calls to the "fputs" library
|
|
/// function. It looks for cases where the result of fputs is not used and the
|
|
/// operation can be reduced to something simpler.
|
|
/// @brief Simplify the pow library function.
|
|
struct PutsOptimization : public LibCallOptimization
|
|
{
|
|
public:
|
|
/// @brief Default Constructor
|
|
PutsOptimization() : LibCallOptimization("fputs") {}
|
|
|
|
/// @brief Destructor
|
|
virtual ~PutsOptimization() {}
|
|
|
|
/// @brief Make sure that the "fputs" function has the right prototype
|
|
virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC)
|
|
{
|
|
// Just make sure this has 2 arguments
|
|
return (f->arg_size() == 2);
|
|
}
|
|
|
|
/// @brief Perform the fputs optimization.
|
|
virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& SLC)
|
|
{
|
|
// If the result is used, none of these optimizations work
|
|
if (!ci->hasNUses(0))
|
|
return false;
|
|
|
|
// All the optimizations depend on the length of the first argument and the
|
|
// fact that it is a constant string array. Check that now
|
|
uint64_t len = 0;
|
|
if (!getConstantStringLength(ci->getOperand(1), len))
|
|
return false;
|
|
|
|
switch (len)
|
|
{
|
|
case 0:
|
|
// fputs("",F) -> noop
|
|
break;
|
|
case 1:
|
|
{
|
|
// fputs(s,F) -> fputc(s[0],F) (if s is constant and strlen(s) == 1)
|
|
Function* fputc_func = SLC.get_fputc();
|
|
if (!fputc_func)
|
|
return false;
|
|
LoadInst* loadi = new LoadInst(ci->getOperand(1),
|
|
ci->getOperand(1)->getName()+".byte",ci);
|
|
CastInst* casti = new CastInst(loadi,Type::IntTy,
|
|
loadi->getName()+".int",ci);
|
|
new CallInst(fputc_func,casti,ci->getOperand(2),"",ci);
|
|
break;
|
|
}
|
|
default:
|
|
{
|
|
// fputs(s,F) -> fwrite(s,1,len,F) (if s is constant and strlen(s) > 1)
|
|
Function* fwrite_func = SLC.get_fwrite();
|
|
if (!fwrite_func)
|
|
return false;
|
|
std::vector<Value*> parms;
|
|
parms.push_back(ci->getOperand(1));
|
|
parms.push_back(ConstantUInt::get(SLC.getIntPtrType(),len));
|
|
parms.push_back(ConstantUInt::get(SLC.getIntPtrType(),1));
|
|
parms.push_back(ci->getOperand(2));
|
|
new CallInst(fwrite_func,parms,"",ci);
|
|
break;
|
|
}
|
|
}
|
|
ci->eraseFromParent();
|
|
return true; // success
|
|
}
|
|
} PutsOptimizer;
|
|
|
|
/// A function to compute the length of a null-terminated constant array of
|
|
/// integers. This function can't rely on the size of the constant array
|
|
/// because there could be a null terminator in the middle of the array.
|
|
/// We also have to bail out if we find a non-integer constant initializer
|
|
/// of one of the elements or if there is no null-terminator. The logic
|
|
/// below checks each of these conditions and will return true only if all
|
|
/// conditions are met. In that case, the \p len parameter is set to the length
|
|
/// of the null-terminated string. If false is returned, the conditions were
|
|
/// not met and len is set to 0.
|
|
/// @brief Get the length of a constant string (null-terminated array).
|
|
bool getConstantStringLength(Value* V, uint64_t& len )
|
|
{
|
|
assert(V != 0 && "Invalid args to getConstantStringLength");
|
|
len = 0; // make sure we initialize this
|
|
User* GEP = 0;
|
|
// If the value is not a GEP instruction nor a constant expression with a
|
|
// GEP instruction, then return false because ConstantArray can't occur
|
|
// any other way
|
|
if (GetElementPtrInst* GEPI = dyn_cast<GetElementPtrInst>(V))
|
|
GEP = GEPI;
|
|
else if (ConstantExpr* CE = dyn_cast<ConstantExpr>(V))
|
|
if (CE->getOpcode() == Instruction::GetElementPtr)
|
|
GEP = CE;
|
|
else
|
|
return false;
|
|
else
|
|
return false;
|
|
|
|
// Make sure the GEP has exactly three arguments.
|
|
if (GEP->getNumOperands() != 3)
|
|
return false;
|
|
|
|
// Check to make sure that the first operand of the GEP is an integer and
|
|
// has value 0 so that we are sure we're indexing into the initializer.
|
|
if (ConstantInt* op1 = dyn_cast<ConstantInt>(GEP->getOperand(1)))
|
|
{
|
|
if (!op1->isNullValue())
|
|
return false;
|
|
}
|
|
else
|
|
return false;
|
|
|
|
// Ensure that the second operand is a ConstantInt. If it isn't then this
|
|
// GEP is wonky and we're not really sure what were referencing into and
|
|
// better of not optimizing it. While we're at it, get the second index
|
|
// value. We'll need this later for indexing the ConstantArray.
|
|
uint64_t start_idx = 0;
|
|
if (ConstantInt* CI = dyn_cast<ConstantInt>(GEP->getOperand(2)))
|
|
start_idx = CI->getRawValue();
|
|
else
|
|
return false;
|
|
|
|
// The GEP instruction, constant or instruction, must reference a global
|
|
// variable that is a constant and is initialized. The referenced constant
|
|
// initializer is the array that we'll use for optimization.
|
|
GlobalVariable* GV = dyn_cast<GlobalVariable>(GEP->getOperand(0));
|
|
if (!GV || !GV->isConstant() || !GV->hasInitializer())
|
|
return false;
|
|
|
|
// Get the initializer.
|
|
Constant* INTLZR = GV->getInitializer();
|
|
|
|
// Handle the ConstantAggregateZero case
|
|
if (ConstantAggregateZero* CAZ = dyn_cast<ConstantAggregateZero>(INTLZR))
|
|
{
|
|
// This is a degenerate case. The initializer is constant zero so the
|
|
// length of the string must be zero.
|
|
len = 0;
|
|
return true;
|
|
}
|
|
|
|
// Must be a Constant Array
|
|
ConstantArray* A = dyn_cast<ConstantArray>(INTLZR);
|
|
if (!A)
|
|
return false;
|
|
|
|
// Get the number of elements in the array
|
|
uint64_t max_elems = A->getType()->getNumElements();
|
|
|
|
// Traverse the constant array from start_idx (derived above) which is
|
|
// the place the GEP refers to in the array.
|
|
for ( len = start_idx; len < max_elems; len++)
|
|
{
|
|
if (ConstantInt* CI = dyn_cast<ConstantInt>(A->getOperand(len)))
|
|
{
|
|
// Check for the null terminator
|
|
if (CI->isNullValue())
|
|
break; // we found end of string
|
|
}
|
|
else
|
|
return false; // This array isn't suitable, non-int initializer
|
|
}
|
|
if (len >= max_elems)
|
|
return false; // This array isn't null terminated
|
|
|
|
// Subtract out the initial value from the length
|
|
len -= start_idx;
|
|
return true; // success!
|
|
}
|
|
|
|
// TODO:
|
|
// Additional cases that we need to add to this file:
|
|
//
|
|
// cbrt:
|
|
// * cbrt(expN(X)) -> expN(x/3)
|
|
// * cbrt(sqrt(x)) -> pow(x,1/6)
|
|
// * cbrt(sqrt(x)) -> pow(x,1/9)
|
|
//
|
|
// cos, cosf, cosl:
|
|
// * cos(-x) -> cos(x)
|
|
//
|
|
// exp, expf, expl:
|
|
// * exp(log(x)) -> x
|
|
//
|
|
// ffs, ffsl, ffsll:
|
|
// * ffs(cnst) -> cnst'
|
|
//
|
|
// fprintf:
|
|
// * fprintf(file,fmt) -> fputs(fmt,file)
|
|
// (if fmt is constant and constains no % characters)
|
|
// * fprintf(file,"%s",str) -> fputs(orig,str)
|
|
// (only if the fprintf result is not used)
|
|
// * fprintf(file,"%c",chr) -> fputc(chr,file)
|
|
//
|
|
// isascii:
|
|
// * isascii(c) -> ((c & ~0x7f) == 0)
|
|
//
|
|
// isdigit:
|
|
// * isdigit(c) -> (unsigned)(c) - '0' <= 9
|
|
//
|
|
// log, logf, logl:
|
|
// * log(exp(x)) -> x
|
|
// * log(x**y) -> y*log(x)
|
|
// * log(exp(y)) -> y*log(e)
|
|
// * log(exp2(y)) -> y*log(2)
|
|
// * log(exp10(y)) -> y*log(10)
|
|
// * log(sqrt(x)) -> 0.5*log(x)
|
|
// * log(pow(x,y)) -> y*log(x)
|
|
//
|
|
// lround, lroundf, lroundl:
|
|
// * lround(cnst) -> cnst'
|
|
//
|
|
// memcmp:
|
|
// * memcmp(s1,s2,0) -> 0
|
|
// * memcmp(x,x,l) -> 0
|
|
// * memcmp(x,y,l) -> cnst
|
|
// (if all arguments are constant and strlen(x) <= l and strlen(y) <= l)
|
|
// * memcpy(x,y,1) -> *x - *y
|
|
//
|
|
// memmove:
|
|
// * memmove(d,s,l,a) -> memcpy(d,s,l,a)
|
|
// (if s is a global constant array)
|
|
//
|
|
// memset:
|
|
// * memset(s,c,0) -> noop
|
|
// * memset(s,c,n) -> store s, c
|
|
// (for n=1,2,4,8)
|
|
//
|
|
// pow, powf, powl:
|
|
// * pow(exp(x),y) -> exp(x*y)
|
|
// * pow(sqrt(x),y) -> pow(x,y*0.5)
|
|
// * pow(pow(x,y),z)-> pow(x,y*z)
|
|
//
|
|
// puts:
|
|
// * puts("") -> fputc("\n",stdout) (how do we get "stdout"?)
|
|
//
|
|
// round, roundf, roundl:
|
|
// * round(cnst) -> cnst'
|
|
//
|
|
// signbit:
|
|
// * signbit(cnst) -> cnst'
|
|
// * signbit(nncst) -> 0 (if pstv is a non-negative constant)
|
|
//
|
|
// sprintf:
|
|
// * sprintf(dest,fmt) -> strcpy(dest,fmt)
|
|
// (if fmt is constant and constains no % characters)
|
|
// * sprintf(dest,"%s",orig) -> strcpy(dest,orig)
|
|
// (only if the sprintf result is not used)
|
|
//
|
|
// sqrt, sqrtf, sqrtl:
|
|
// * sqrt(expN(x)) -> expN(x*0.5)
|
|
// * sqrt(Nroot(x)) -> pow(x,1/(2*N))
|
|
// * sqrt(pow(x,y)) -> pow(|x|,y*0.5)
|
|
//
|
|
// strchr, strrchr:
|
|
// * strchr(s,c) -> offset_of_in(c,s)
|
|
// (if c is a constant integer and s is a constant string)
|
|
// * strrchr(s,c) -> reverse_offset_of_in(c,s)
|
|
// (if c is a constant integer and s is a constant string)
|
|
// * strrchr(s1,0) -> strchr(s1,0)
|
|
//
|
|
// strcmp:
|
|
// * strcmp(x,x) -> 0
|
|
// * strcmp(x,"") -> *x
|
|
// * strcmp("",x) -> *x
|
|
// * strcmp(x,y) -> cnst (if both x and y are constant strings)
|
|
//
|
|
// strncat:
|
|
// * strncat(x,y,0) -> x
|
|
// * strncat(x,y,0) -> x (if strlen(y) = 0)
|
|
// * strncat(x,y,l) -> strcat(x,y) (if y and l are constants an l > strlen(y))
|
|
//
|
|
// strncmp:
|
|
// * strncmp(x,y,0) -> 0
|
|
// * strncmp(x,x,l) -> 0
|
|
// * strncmp(x,"",l) -> *x
|
|
// * strncmp("",x,l) -> *x
|
|
// * strncmp(x,y,1) -> *x - *y
|
|
//
|
|
// strncpy:
|
|
// * strncpy(d,s,0) -> d
|
|
// * strncpy(d,s,l) -> memcpy(d,s,l,1)
|
|
// (if s and l are constants)
|
|
//
|
|
// strpbrk:
|
|
// * strpbrk(s,a) -> offset_in_for(s,a)
|
|
// (if s and a are both constant strings)
|
|
// * strpbrk(s,"") -> 0
|
|
// * strpbrk(s,a) -> strchr(s,a[0]) (if a is constant string of length 1)
|
|
//
|
|
// strspn, strcspn:
|
|
// * strspn(s,a) -> const_int (if both args are constant)
|
|
// * strspn("",a) -> 0
|
|
// * strspn(s,"") -> 0
|
|
// * strcspn(s,a) -> const_int (if both args are constant)
|
|
// * strcspn("",a) -> 0
|
|
// * strcspn(s,"") -> strlen(a)
|
|
//
|
|
// strstr:
|
|
// * strstr(x,x) -> x
|
|
// * strstr(s1,s2) -> offset_of_s2_in(s1)
|
|
// (if s1 and s2 are constant strings)
|
|
//
|
|
// tan, tanf, tanl:
|
|
// * tan(atan(x)) -> x
|
|
//
|
|
// toascii:
|
|
// * toascii(c) -> (c & 0x7f)
|
|
//
|
|
// trunc, truncf, truncl:
|
|
// * trunc(cnst) -> cnst'
|
|
//
|
|
//
|
|
}
|