|
| 1 | +//===-- WebAssemblyDebugFixup.cpp - Debug Fixup ------------------===// |
| 2 | +// |
| 3 | +// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| 4 | +// See https://llvm.org/LICENSE.txt for license information. |
| 5 | +// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| 6 | +// |
| 7 | +//===----------------------------------------------------------------------===// |
| 8 | +/// |
| 9 | +/// \file |
| 10 | +/// Several prior passes may "stackify" registers, here we ensure any references |
| 11 | +/// in such registers in debug_value instructions become stack relative also. |
| 12 | +/// This is done in a separate pass such that not all previous passes need to |
| 13 | +/// track stack depth when values get stackified. |
| 14 | +/// |
| 15 | +//===----------------------------------------------------------------------===// |
| 16 | + |
| 17 | +#include "MCTargetDesc/WebAssemblyMCTargetDesc.h" |
| 18 | +#include "WebAssembly.h" |
| 19 | +#include "WebAssemblyMachineFunctionInfo.h" |
| 20 | +#include "WebAssemblySubtarget.h" |
| 21 | +#include "WebAssemblyUtilities.h" |
| 22 | +#include "llvm/ADT/SCCIterator.h" |
| 23 | +#include "llvm/CodeGen/MachineFrameInfo.h" |
| 24 | +#include "llvm/CodeGen/MachineFunction.h" |
| 25 | +#include "llvm/CodeGen/MachineInstrBuilder.h" |
| 26 | +#include "llvm/CodeGen/MachineLoopInfo.h" |
| 27 | +#include "llvm/CodeGen/MachineRegisterInfo.h" |
| 28 | +#include "llvm/CodeGen/Passes.h" |
| 29 | +#include "llvm/Support/Debug.h" |
| 30 | +#include "llvm/Support/raw_ostream.h" |
| 31 | +using namespace llvm; |
| 32 | + |
| 33 | +#define DEBUG_TYPE "wasm-debug-fixup" |
| 34 | + |
| 35 | +namespace { |
| 36 | +class WebAssemblyDebugFixup final : public MachineFunctionPass { |
| 37 | + StringRef getPassName() const override { return "WebAssembly Debug Fixup"; } |
| 38 | + |
| 39 | + void getAnalysisUsage(AnalysisUsage &AU) const override { |
| 40 | + AU.setPreservesCFG(); |
| 41 | + MachineFunctionPass::getAnalysisUsage(AU); |
| 42 | + } |
| 43 | + |
| 44 | + bool runOnMachineFunction(MachineFunction &MF) override; |
| 45 | + |
| 46 | +public: |
| 47 | + static char ID; // Pass identification, replacement for typeid |
| 48 | + WebAssemblyDebugFixup() : MachineFunctionPass(ID) {} |
| 49 | +}; |
| 50 | +} // end anonymous namespace |
| 51 | + |
| 52 | +char WebAssemblyDebugFixup::ID = 0; |
| 53 | +INITIALIZE_PASS( |
| 54 | + WebAssemblyDebugFixup, DEBUG_TYPE, |
| 55 | + "Ensures debug_value's that have been stackified become stack relative", |
| 56 | + false, false) |
| 57 | + |
| 58 | +FunctionPass *llvm::createWebAssemblyDebugFixup() { |
| 59 | + return new WebAssemblyDebugFixup(); |
| 60 | +} |
| 61 | + |
| 62 | +bool WebAssemblyDebugFixup::runOnMachineFunction(MachineFunction &MF) { |
| 63 | + LLVM_DEBUG(dbgs() << "********** Debug Fixup **********\n" |
| 64 | + "********** Function: " |
| 65 | + << MF.getName() << '\n'); |
| 66 | + |
| 67 | + WebAssemblyFunctionInfo &MFI = *MF.getInfo<WebAssemblyFunctionInfo>(); |
| 68 | + const auto *TII = MF.getSubtarget<WebAssemblySubtarget>().getInstrInfo(); |
| 69 | + |
| 70 | + struct StackElem { |
| 71 | + unsigned Reg; |
| 72 | + MachineInstr *DebugValue; |
| 73 | + }; |
| 74 | + std::vector<StackElem> Stack; |
| 75 | + for (MachineBasicBlock &MBB : MF) { |
| 76 | + // We may insert into this list. |
| 77 | + for (auto MII = MBB.begin(); MII != MBB.end(); ++MII) { |
| 78 | + MachineInstr &MI = *MII; |
| 79 | + if (MI.isDebugValue()) { |
| 80 | + auto &MO = MI.getOperand(0); |
| 81 | + // Also check if not a $noreg: likely a DBG_VALUE we just inserted. |
| 82 | + if (MO.isReg() && MO.getReg().isValid() && |
| 83 | + MFI.isVRegStackified(MO.getReg())) { |
| 84 | + // Found a DBG_VALUE with a stackified register we will |
| 85 | + // change into a stack operand. |
| 86 | + // Search for register rather than assume it is on top (which it |
| 87 | + // typically is if it appears right after the def), since |
| 88 | + // DBG_VALUE's may shift under some circumstances. |
| 89 | + size_t Depth = 0; |
| 90 | + for (auto &Elem : Stack) { |
| 91 | + if (MO.getReg() == Elem.Reg) { |
| 92 | + LLVM_DEBUG(dbgs() << "Debug Value VReg " << MO.getReg() |
| 93 | + << " -> Stack Relative " << Depth << "\n"); |
| 94 | + MO.ChangeToTargetIndex(WebAssembly::TI_OPERAND_STACK, Depth); |
| 95 | + // Save the DBG_VALUE instruction that defined this stackified |
| 96 | + // variable since later we need it to construct another one on |
| 97 | + // pop. |
| 98 | + Elem.DebugValue = &MI; |
| 99 | + break; |
| 100 | + } |
| 101 | + Depth++; |
| 102 | + } |
| 103 | + // If the Reg was not found, we have a DBG_VALUE outside of its |
| 104 | + // def-use range, and we leave it unmodified as reg, which means |
| 105 | + // it will be culled later. |
| 106 | + } |
| 107 | + } else { |
| 108 | + // Track stack depth. |
| 109 | + for (MachineOperand &MO : reverse(MI.explicit_uses())) { |
| 110 | + if (MO.isReg() && MFI.isVRegStackified(MO.getReg())) { |
| 111 | + auto Prev = Stack.back(); |
| 112 | + Stack.pop_back(); |
| 113 | + assert(Prev.Reg == MO.getReg() && |
| 114 | + "WebAssemblyDebugFixup: Pop: Register not matched!"); |
| 115 | + if (Prev.DebugValue) { |
| 116 | + // This stackified reg is a variable that started life at |
| 117 | + // Prev.DebugValue, so now that we're popping it we must insert |
| 118 | + // a $noreg DBG_VALUE for the variable to end it, right after |
| 119 | + // the current instruction. |
| 120 | + BuildMI(*Prev.DebugValue->getParent(), std::next(MII), |
| 121 | + MI.getDebugLoc(), TII->get(WebAssembly::DBG_VALUE), false, |
| 122 | + Register(), Prev.DebugValue->getOperand(2).getMetadata(), |
| 123 | + Prev.DebugValue->getOperand(3).getMetadata()); |
| 124 | + } |
| 125 | + } |
| 126 | + } |
| 127 | + for (MachineOperand &MO : MI.defs()) { |
| 128 | + if (MO.isReg() && MFI.isVRegStackified(MO.getReg())) { |
| 129 | + Stack.push_back({MO.getReg(), nullptr}); |
| 130 | + } |
| 131 | + } |
| 132 | + } |
| 133 | + } |
| 134 | + assert(Stack.empty() && |
| 135 | + "WebAssemblyDebugFixup: Stack not empty at end of basic block!"); |
| 136 | + } |
| 137 | + |
| 138 | + return true; |
| 139 | +} |
0 commit comments