forked from OSchip/llvm-project
84 lines
3.0 KiB
C++
84 lines
3.0 KiB
C++
//===-- WebAssemblyEHRestoreStackPointer.cpp - __stack_pointer restoration ===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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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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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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