mirror of
https://github.com/revng/revng
synced 2026-06-21 14:07:57 +00:00
Pietro Fezzardi
3016c2ad41
This commit enables to emit accesses with the square bracket array access operator on pointers. This is accomplished by adding an additional mandatory argument to ModelGEP (AND NOT to ModelGEPRef) to represent this case. MakeModelGEPPass is updated to take this into account, together with all the other passes that handle ModelGEPs.
125 lines
4.1 KiB
C++
125 lines
4.1 KiB
C++
//
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// Copyright rev.ng Labs Srl. See LICENSE.md for details.
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//
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#include "llvm/IR/DerivedTypes.h"
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#include "llvm/IR/IRBuilder.h"
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#include "llvm/IR/Instruction.h"
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#include "llvm/IR/Instructions.h"
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#include "llvm/IR/Module.h"
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#include "llvm/IR/Value.h"
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#include "llvm/Pass.h"
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#include "revng/Model/IRHelpers.h"
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#include "revng/Model/LoadModelPass.h"
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#include "revng/Model/QualifiedType.h"
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#include "revng/Model/RawFunctionType.h"
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#include "revng/Support/Assert.h"
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#include "revng/Support/OpaqueFunctionsPool.h"
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#include "revng-c/Support/DecompilationHelpers.h"
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#include "revng-c/Support/FunctionTags.h"
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#include "revng-c/Support/ModelHelpers.h"
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struct RemoveRefDeref : public llvm::FunctionPass {
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public:
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static char ID;
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RemoveRefDeref() : FunctionPass(ID) {}
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// Remove `ModelGEPRef` functions with no arguments
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bool runOnFunction(llvm::Function &F) override;
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void getAnalysisUsage(llvm::AnalysisUsage &AU) const override {
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AU.setPreservesCFG();
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}
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};
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using llvm::CallInst;
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using llvm::dyn_cast;
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static llvm::CallInst *isRefDeref(llvm::Value *V) {
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if (auto *Call = getCallToTagged(V, FunctionTags::ModelGEPRef))
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if (Call->arg_size() == 2)
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return Call;
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return nullptr;
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}
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bool RemoveRefDeref::runOnFunction(llvm::Function &F) {
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// Skip non-isolated functions
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auto FTags = FunctionTags::TagsSet::from(&F);
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if (not FTags.contains(FunctionTags::Isolated))
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return false;
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// Initialize the IR builder to inject functions
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llvm::LLVMContext &LLVMCtx = F.getContext();
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llvm::IRBuilder<> Builder(LLVMCtx);
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bool Modified = false;
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for (auto &BB : F) {
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for (auto &I : llvm::make_early_inc_range(BB)) {
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if (auto *Call = isRefDeref(&I)) {
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Builder.SetInsertPoint(&I);
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auto *BasePtrArg = Call->getArgOperand(1);
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llvm::Type *BasePtrType = BasePtrArg->getType();
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llvm::Type *CallRetType = Call->getType();
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if (BasePtrType != CallRetType) {
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// We consider pointers and integers on the LLVM IR interchangeable,
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// since it's the model who decides whether a values is a pointer or
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// not
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if (BasePtrType->isPointerTy() and CallRetType->isIntegerTy()) {
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BasePtrArg = Builder.CreatePtrToInt(BasePtrArg, CallRetType);
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} else if (BasePtrType->isIntegerTy()
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and CallRetType->isPointerTy()) {
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BasePtrArg = Builder.CreateIntToPtr(BasePtrArg, CallRetType);
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} else if (BasePtrType->isIntegerTy()
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and CallRetType->isIntegerTy()) {
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// A ModelGEPRef with no arguments and model type T takes a
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// reference of type T as argument and returns a reference of type
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// T.
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// Since by constructions references have the size of the
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// referenced value in LLVM IR, when simplifying a ModelGEPRef
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// with no arguments we should always be substituting a value
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// with size sizeof(T) with a value of the same size.
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//
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// The only possible exception is the use of booleans in the IR
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// (i1). In that case, the smallest model type we can assign to
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// them is a byte, and they are loaded and stored as bytes, but
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// when we use them in the IR the actual size of the type is 1.
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auto BaseSize = BasePtrType->getScalarSizeInBits();
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auto RetSize = CallRetType->getScalarSizeInBits();
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revng_assert((RetSize == 8 and BaseSize == 1)
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or (RetSize == 1 and BaseSize == 8));
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BasePtrArg = Builder.CreateZExtOrTrunc(BasePtrArg, Call->getType());
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} else {
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revng_abort("Incompatible types between ModelGEPRef and its base.");
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}
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}
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Call->replaceAllUsesWith(BasePtrArg);
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Call->eraseFromParent();
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Modified = true;
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}
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}
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}
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return Modified;
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}
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char RemoveRefDeref::ID = 0;
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static llvm::RegisterPass<RemoveRefDeref> X("remove-ref-deref",
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"Remove all dereferences of "
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"reference values",
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false,
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false);
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