mirror of
https://github.com/revng/revng
synced 2026-06-21 14:07:57 +00:00
Giacomo Vercesi
798af62b87
Re-organize the variants of `libtcg-helpers-*.bc` as such: * `libtcg-helpers-full-$ARCH.bc`: unchanged, contains all helper function with their bodies and all CSVs. * `libtcg-helpers-declarations-only-$ARCH.bc`: all helper functions have been turned to declarations. All CSVs (except a couple of special ones) have been dropped. * `libtcg-helpers-to-inline-$ARCH.bc`: only functions with the `revng_inline` section retain their body. Only CSVs that are used by these functions are present. Lift now loads only the `declarations-only` variant of helpers, as their body is not required until `inline-helpers`. In `inline-helpers` the `to-inline` variant is loaded and linked, which then allows the helpers to be inlined.
83 lines
2.8 KiB
C++
83 lines
2.8 KiB
C++
//
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// This file is distributed under the MIT License. See LICENSE.md for details.
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//
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#include "llvm/IR/Module.h"
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#include "llvm/Pass.h"
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#include "revng/Model/FunctionTags.h"
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#include "PostProcessingHelpers.h"
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using namespace llvm;
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class HelpersModuleToDeclarations : public llvm::ModulePass {
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public:
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static char ID;
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public:
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HelpersModuleToDeclarations() : llvm::ModulePass(ID) {}
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bool runOnModule(llvm::Module &M) override {
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for (Function &F : M) {
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// Only the full module requires debugging information. Remove the !dbg
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// tag and the body of the functions. Later `-globaldce` and
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// `-strip-dead-debug-info` will take care of dropping all the unused
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// data.
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F.eraseMetadata(LLVMContext::MD_dbg);
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deleteOnlyBody(F);
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}
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// The global variables are not needed in this module. Drop their debug info
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// and their initializer. GlobalDCE will be run later to remove them. This
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// is except a couple of special ones that are always needed.
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for (GlobalVariable &GV : M.globals()) {
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GV.eraseMetadata(LLVMContext::MD_dbg);
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if (not isSpecialGV(GV))
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GV.setInitializer(nullptr);
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}
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// Assume the module M already contains the functions.
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// Collect all functions whose name starts with "helper_" to prevent DCE
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llvm::DenseSet<Function *> Helpers;
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for (Function &F : M)
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if (isHelper(F))
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Helpers.insert(&F);
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PointerType *PointerType = PointerType::get(M.getContext(), 0);
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// Create constant array initializer with function pointers to the helpers
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// functions. Since all the helper functions are declarations they might be
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// removed by a globaldce, to prevent that store their pointer in a global
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// variable with external linkage.
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std::vector<Constant *> FunctionPointers;
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for (Function *F : Helpers)
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FunctionPointers.push_back(ConstantExpr::getBitCast(F, PointerType));
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// Create array type: [N x <function pointer type>]
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ArrayType *FunctionArray = ArrayType::get(PointerType,
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FunctionPointers.size());
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Constant *Initializer = ConstantArray::get(FunctionArray, FunctionPointers);
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new GlobalVariable(M,
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FunctionArray,
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true,
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GlobalValue::ExternalLinkage,
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Initializer,
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HelpersListName);
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// Tag all globals
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tagQEMUGlobalsAndFunctions(M);
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return true;
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}
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};
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char HelpersModuleToDeclarations::ID = 0;
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using Register = RegisterPass<HelpersModuleToDeclarations>;
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static Register X("helpers-module-to-declarations",
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"Purge all helper functions but keep their "
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"declarations alive in a array of pointers.",
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true,
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true);
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