mirror of
https://github.com/revng/revng
synced 2026-06-21 14:07:57 +00:00
Pietro Fezzardi
e2791443fb
Now extractvalue instruction are replaced by dedicated OpaqueExtractValue custom opcode, that prevents LLVM from doing strange things with extractvalues during optimizations (such as e.g. sinking). This is important since extractvalue instructions and struct-typed values in general in our LLVM IR are not real first-class citizens, but only a byproduct of the binary lifting process, and they actually represent bundles of registers that are returned from isolated functions.
82 lines
2.7 KiB
C++
82 lines
2.7 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/ADT/SmallVector.h"
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#include "llvm/IR/Constants.h"
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#include "llvm/IR/Function.h"
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#include "llvm/IR/IRBuilder.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/Type.h"
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#include "llvm/Transforms/Utils/Local.h"
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#include "revng/Support/Assert.h"
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#include "revng/Support/FunctionTags.h"
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#include "revng/Support/IRHelpers.h"
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#include "revng/Support/OpaqueFunctionsPool.h"
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#include "revng-c/RemoveExtractValues/RemoveExtractValuesPass.h"
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#include "revng-c/Support/FunctionTags.h"
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using namespace llvm;
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char RemoveExtractValues::ID = 0;
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using Reg = RegisterPass<RemoveExtractValues>;
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static Reg X("remove-extractvalues",
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"Substitute extractvalues with opaque calls so that they don't "
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"get optimized",
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true,
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true);
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bool RemoveExtractValues::runOnFunction(llvm::Function &F) {
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using namespace llvm;
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// Collect all ExtractValues
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SmallVector<ExtractValueInst *, 16> ToReplace;
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for (auto &BB : F)
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for (auto &I : BB)
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if (auto *ExtractVal = llvm::dyn_cast<llvm::ExtractValueInst>(&I))
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ToReplace.push_back(ExtractVal);
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if (ToReplace.empty())
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return false;
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// Create a pool of functions with the same behavior: we will need a different
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// function for each different struct
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OpaqueFunctionsPool<TypePair> OpaqueEVPool(F.getParent(),
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/* PurgeOnDestruction */ false);
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initOpaqueEVPool(OpaqueEVPool, F.getParent());
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llvm::LLVMContext &LLVMCtx = F.getContext();
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IRBuilder<> Builder(LLVMCtx);
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for (ExtractValueInst *I : ToReplace) {
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Builder.SetInsertPoint(I);
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// Collect arguments of the ExtractValue
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SmallVector<Value *, 8> ArgValues = { I->getAggregateOperand() };
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revng_assert(I->getNumIndices() == 1);
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for (auto Idx : I->indices()) {
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auto *IndexVal = ConstantInt::get(IntegerType::getInt64Ty(LLVMCtx), Idx);
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ArgValues.push_back(IndexVal);
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}
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// Get or generate the function
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auto *EVFunctionType = getOpaqueEVFunctionType(I);
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const TypePair &Key = { I->getType(), I->getAggregateOperand()->getType() };
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auto *ExtractValueFunction = OpaqueEVPool.get(Key,
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EVFunctionType,
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"OpaqueExtractvalue");
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// Emit a call to the new function
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CallInst *InjectedCall = Builder.CreateCall(ExtractValueFunction,
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ArgValues);
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I->replaceAllUsesWith(InjectedCall);
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InjectedCall->copyMetadata(*I);
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llvm::RecursivelyDeleteTriviallyDeadInstructions(I);
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}
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return true;
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}
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