WebAssemblyCallIndirectFixup.cpp revision 327952
1//===-- WebAssemblyCallIndirectFixup.cpp - Fix call_indirects -------------===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file is distributed under the University of Illinois Open Source 6// License. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9/// 10/// \file 11/// \brief This file converts pseudo call_indirect instructions into real 12/// call_indirects. 13/// 14/// The order of arguments for a call_indirect is the arguments to the function 15/// call, followed by the function pointer. There's no natural way to express 16/// a machineinstr with varargs followed by one more arg, so we express it as 17/// the function pointer followed by varargs, then rewrite it here. 18/// 19/// We need to rewrite the order of the arguments on the machineinstrs 20/// themselves so that register stackification knows the order they'll be 21/// executed in. 22/// 23//===----------------------------------------------------------------------===// 24 25#include "MCTargetDesc/WebAssemblyMCTargetDesc.h" // for WebAssembly::ARGUMENT_* 26#include "WebAssembly.h" 27#include "WebAssemblyMachineFunctionInfo.h" 28#include "WebAssemblySubtarget.h" 29#include "llvm/Analysis/AliasAnalysis.h" 30#include "llvm/CodeGen/LiveIntervals.h" 31#include "llvm/CodeGen/MachineBlockFrequencyInfo.h" 32#include "llvm/CodeGen/MachineDominators.h" 33#include "llvm/CodeGen/MachineInstrBuilder.h" 34#include "llvm/CodeGen/MachineRegisterInfo.h" 35#include "llvm/CodeGen/Passes.h" 36#include "llvm/Support/Debug.h" 37#include "llvm/Support/raw_ostream.h" 38using namespace llvm; 39 40#define DEBUG_TYPE "wasm-call-indirect-fixup" 41 42namespace { 43class WebAssemblyCallIndirectFixup final : public MachineFunctionPass { 44 StringRef getPassName() const override { 45 return "WebAssembly CallIndirect Fixup"; 46 } 47 48 bool runOnMachineFunction(MachineFunction &MF) override; 49 50public: 51 static char ID; // Pass identification, replacement for typeid 52 WebAssemblyCallIndirectFixup() : MachineFunctionPass(ID) {} 53}; 54} // end anonymous namespace 55 56char WebAssemblyCallIndirectFixup::ID = 0; 57FunctionPass *llvm::createWebAssemblyCallIndirectFixup() { 58 return new WebAssemblyCallIndirectFixup(); 59} 60 61static unsigned GetNonPseudoCallIndirectOpcode(const MachineInstr &MI) { 62 switch (MI.getOpcode()) { 63 using namespace WebAssembly; 64 case PCALL_INDIRECT_VOID: return CALL_INDIRECT_VOID; 65 case PCALL_INDIRECT_I32: return CALL_INDIRECT_I32; 66 case PCALL_INDIRECT_I64: return CALL_INDIRECT_I64; 67 case PCALL_INDIRECT_F32: return CALL_INDIRECT_F32; 68 case PCALL_INDIRECT_F64: return CALL_INDIRECT_F64; 69 case PCALL_INDIRECT_v16i8: return CALL_INDIRECT_v16i8; 70 case PCALL_INDIRECT_v8i16: return CALL_INDIRECT_v8i16; 71 case PCALL_INDIRECT_v4i32: return CALL_INDIRECT_v4i32; 72 case PCALL_INDIRECT_v4f32: return CALL_INDIRECT_v4f32; 73 default: return INSTRUCTION_LIST_END; 74 } 75} 76 77static bool IsPseudoCallIndirect(const MachineInstr &MI) { 78 return GetNonPseudoCallIndirectOpcode(MI) != 79 WebAssembly::INSTRUCTION_LIST_END; 80} 81 82bool WebAssemblyCallIndirectFixup::runOnMachineFunction(MachineFunction &MF) { 83 DEBUG(dbgs() << "********** Fixing up CALL_INDIRECTs **********\n" 84 << MF.getName() << '\n'); 85 86 bool Changed = false; 87 const WebAssemblyInstrInfo *TII = 88 MF.getSubtarget<WebAssemblySubtarget>().getInstrInfo(); 89 90 for (MachineBasicBlock &MBB : MF) { 91 for (MachineInstr &MI : MBB) { 92 if (IsPseudoCallIndirect(MI)) { 93 DEBUG(dbgs() << "Found call_indirect: " << MI << '\n'); 94 95 // Rewrite pseudo to non-pseudo 96 const MCInstrDesc &Desc = TII->get(GetNonPseudoCallIndirectOpcode(MI)); 97 MI.setDesc(Desc); 98 99 // Rewrite argument order 100 SmallVector<MachineOperand, 8> Ops; 101 102 // Set up a placeholder for the type signature immediate. 103 Ops.push_back(MachineOperand::CreateImm(0)); 104 105 // Set up the flags immediate, which currently has no defined flags 106 // so it's always zero. 107 Ops.push_back(MachineOperand::CreateImm(0)); 108 109 for (const MachineOperand &MO : 110 make_range(MI.operands_begin() + 111 MI.getDesc().getNumDefs() + 1, 112 MI.operands_begin() + 113 MI.getNumExplicitOperands())) 114 Ops.push_back(MO); 115 Ops.push_back(MI.getOperand(MI.getDesc().getNumDefs())); 116 117 // Replace the instructions operands. 118 while (MI.getNumOperands() > MI.getDesc().getNumDefs()) 119 MI.RemoveOperand(MI.getNumOperands() - 1); 120 for (const MachineOperand &MO : Ops) 121 MI.addOperand(MO); 122 123 DEBUG(dbgs() << " After transform: " << MI); 124 Changed = true; 125 } 126 } 127 } 128 129 DEBUG(dbgs() << "\nDone fixing up CALL_INDIRECTs\n\n"); 130 131 return Changed; 132} 133 134