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to reflect the new license. We understand that people may be surprised that we're moving the header entirely to discuss the new license. We checked this carefully with the Foundation's lawyer and we believe this is the correct approach. Essentially, all code in the project is now made available by the LLVM project under our new license, so you will see that the license headers include that license only. Some of our contributors have contributed code under our old license, and accordingly, we have retained a copy of our old license notice in the top-level files in each project and repository. llvm-svn: 351636
87 lines
3.1 KiB
C++
87 lines
3.1 KiB
C++
//===-- WebAssemblyEHRestoreStackPointer.cpp - __stack_pointer restoration ===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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///
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/// \file
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/// After the stack is unwound due to a thrown exception, the __stack_pointer
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/// global can point to an invalid address. This inserts instructions that
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/// restore __stack_pointer global.
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///
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//===----------------------------------------------------------------------===//
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#include "MCTargetDesc/WebAssemblyMCTargetDesc.h"
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#include "WebAssembly.h"
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#include "WebAssemblySubtarget.h"
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#include "WebAssemblyUtilities.h"
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#include "llvm/CodeGen/MachineFrameInfo.h"
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#include "llvm/MC/MCAsmInfo.h"
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using namespace llvm;
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#define DEBUG_TYPE "wasm-eh-restore-stack-pointer"
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namespace {
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class WebAssemblyEHRestoreStackPointer final : public MachineFunctionPass {
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public:
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static char ID; // Pass identification, replacement for typeid
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WebAssemblyEHRestoreStackPointer() : MachineFunctionPass(ID) {}
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StringRef getPassName() const override {
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return "WebAssembly Restore Stack Pointer for Exception Handling";
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}
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void getAnalysisUsage(AnalysisUsage &AU) const override {
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AU.setPreservesCFG();
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MachineFunctionPass::getAnalysisUsage(AU);
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}
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bool runOnMachineFunction(MachineFunction &MF) override;
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};
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} // end anonymous namespace
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char WebAssemblyEHRestoreStackPointer::ID = 0;
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INITIALIZE_PASS(WebAssemblyEHRestoreStackPointer, DEBUG_TYPE,
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"Restore Stack Pointer for Exception Handling", true, false)
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FunctionPass *llvm::createWebAssemblyEHRestoreStackPointer() {
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return new WebAssemblyEHRestoreStackPointer();
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}
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bool WebAssemblyEHRestoreStackPointer::runOnMachineFunction(
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MachineFunction &MF) {
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LLVM_DEBUG(dbgs() << "********** EH Restore Stack Pointer **********\n"
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"********** Function: "
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<< MF.getName() << '\n');
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const auto *FrameLowering = static_cast<const WebAssemblyFrameLowering *>(
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MF.getSubtarget().getFrameLowering());
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if (!FrameLowering->needsPrologForEH(MF))
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return false;
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bool Changed = false;
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for (auto &MBB : MF) {
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if (!MBB.isEHPad())
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continue;
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Changed = true;
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// Insert __stack_pointer restoring instructions at the beginning of each EH
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// pad, after the catch instruction. (Catch instructions may have been
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// reordered, and catch_all instructions have not been inserted yet, but
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// those cases are handled in LateEHPrepare).
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//
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// Here it is safe to assume that SP32 holds the latest value of
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// __stack_pointer, because the only exception for this case is when a
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// function uses the red zone, but that only happens with leaf functions,
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// and we don't restore __stack_pointer in leaf functions anyway.
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auto InsertPos = MBB.begin();
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if (WebAssembly::isCatch(*MBB.begin()))
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InsertPos++;
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FrameLowering->writeSPToGlobal(WebAssembly::SP32, MF, MBB, InsertPos,
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MBB.begin()->getDebugLoc());
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}
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return Changed;
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}
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