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//===-- WebAssemblyOptimizeReturned.cpp - Optimize "returned" attributes --===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
///
/// \file
/// Optimize calls with "returned" attributes for WebAssembly.
///
//===----------------------------------------------------------------------===//
#include "WebAssembly.h"
#include "llvm/IR/Dominators.h"
#include "llvm/IR/InstVisitor.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
using namespace llvm;
#define DEBUG_TYPE "wasm-optimize-returned"
namespace {
class OptimizeReturned final : public FunctionPass,
public InstVisitor<OptimizeReturned> {
StringRef getPassName() const override {
return "WebAssembly Optimize Returned";
}
void getAnalysisUsage(AnalysisUsage &AU) const override {
AU.setPreservesCFG();
AU.addRequired<DominatorTreeWrapperPass>();
AU.addPreserved<DominatorTreeWrapperPass>();
FunctionPass::getAnalysisUsage(AU);
}
bool runOnFunction(Function &F) override;
DominatorTree *DT = nullptr;
public:
static char ID;
OptimizeReturned() : FunctionPass(ID) {}
void visitCallSite(CallSite CS);
};
} // End anonymous namespace
char OptimizeReturned::ID = 0;
INITIALIZE_PASS(OptimizeReturned, DEBUG_TYPE,
"Optimize calls with \"returned\" attributes for WebAssembly",
false, false)
FunctionPass *llvm::createWebAssemblyOptimizeReturned() {
return new OptimizeReturned();
}
void OptimizeReturned::visitCallSite(CallSite CS) {
for (unsigned I = 0, E = CS.getNumArgOperands(); I < E; ++I)
if (CS.paramHasAttr(I, Attribute::Returned)) {
Instruction *Inst = CS.getInstruction();
Value *Arg = CS.getArgOperand(I);
// Ignore constants, globals, undef, etc.
if (isa<Constant>(Arg))
continue;
// Like replaceDominatedUsesWith but using Instruction/Use dominance.
Arg->replaceUsesWithIf(Inst,
[&](Use &U) { return DT->dominates(Inst, U); });
}
}
bool OptimizeReturned::runOnFunction(Function &F) {
LLVM_DEBUG(dbgs() << "********** Optimize returned Attributes **********\n"
"********** Function: "
<< F.getName() << '\n');
DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
visit(F);
return true;
}
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