path: root/js/src/jit/mips32/Assembler-mips32.h

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
 * vim: set ts=8 sts=2 et sw=2 tw=80:
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#ifndef jit_mips32_Assembler_mips32_h
#define jit_mips32_Assembler_mips32_h

#include <iterator>

#include "jit/mips-shared/Assembler-mips-shared.h"

#include "jit/mips32/Architecture-mips32.h"

namespace js {
namespace jit {

static constexpr Register CallTempReg4 = t4;
static constexpr Register CallTempReg5 = t5;

static constexpr Register CallTempNonArgRegs[] = {t0, t1, t2, t3, t4};
static const uint32_t NumCallTempNonArgRegs = std::size(CallTempNonArgRegs);

class ABIArgGenerator {
  unsigned usedArgSlots_;
  unsigned firstArgFloatSize_;
  // Note: This is not compliant with the system ABI.  The Lowering phase
  // expects to lower an MWasmParameter to only one register.
  bool useGPRForFloats_;
  ABIArg current_;

 public:
  ABIArgGenerator();
  ABIArg next(MIRType argType);
  ABIArg& current() { return current_; }

  void enforceO32ABI() { useGPRForFloats_ = true; }

  uint32_t stackBytesConsumedSoFar() const {
    if (usedArgSlots_ <= 4) {
      return ShadowStackSpace;
    }

    return usedArgSlots_ * sizeof(intptr_t);
  }

  void increaseStackOffset(uint32_t bytes) { MOZ_CRASH("NYI"); }
};

// These registers may be volatile or nonvolatile.
static constexpr Register ABINonArgReg0 = t0;
static constexpr Register ABINonArgReg1 = t1;
static constexpr Register ABINonArgReg2 = t2;
static constexpr Register ABINonArgReg3 = t3;

// This register may be volatile or nonvolatile. Avoid f18 which is the
// ScratchDoubleReg.
static constexpr FloatRegister ABINonArgDoubleReg{FloatRegisters::f16,
                                                  FloatRegister::Double};

// These registers may be volatile or nonvolatile.
// Note: these three registers are all guaranteed to be different
static constexpr Register ABINonArgReturnReg0 = t0;
static constexpr Register ABINonArgReturnReg1 = t1;
static constexpr Register ABINonVolatileReg = s0;

// This register is guaranteed to be clobberable during the prologue and
// epilogue of an ABI call which must preserve both ABI argument, return
// and non-volatile registers.
static constexpr Register ABINonArgReturnVolatileReg = t0;

// TLS pointer argument register for WebAssembly functions. This must not alias
// any other register used for passing function arguments or return values.
// Preserved by WebAssembly functions.
static constexpr Register WasmTlsReg = s5;

// Registers used for asm.js/wasm table calls. These registers must be disjoint
// from the ABI argument registers, WasmTlsReg and each other.
static constexpr Register WasmTableCallScratchReg0 = ABINonArgReg0;
static constexpr Register WasmTableCallScratchReg1 = ABINonArgReg1;
static constexpr Register WasmTableCallSigReg = ABINonArgReg2;
static constexpr Register WasmTableCallIndexReg = ABINonArgReg3;

// Register used as a scratch along the return path in the fast js -> wasm stub
// code. This must not overlap ReturnReg, JSReturnOperand, or WasmTlsReg. It
// must be a volatile register.
static constexpr Register WasmJitEntryReturnScratch = t1;

static constexpr Register InterpreterPCReg = t5;

static constexpr Register JSReturnReg_Type = a3;
static constexpr Register JSReturnReg_Data = a2;
static constexpr Register64 ReturnReg64(v1, v0);
static constexpr FloatRegister ReturnFloat32Reg = {FloatRegisters::f0,
                                                   FloatRegister::Single};
static constexpr FloatRegister ReturnDoubleReg = {FloatRegisters::f0,
                                                  FloatRegister::Double};
static constexpr FloatRegister ScratchFloat32Reg = {FloatRegisters::f18,
                                                    FloatRegister::Single};
static constexpr FloatRegister ScratchDoubleReg = {FloatRegisters::f18,
                                                   FloatRegister::Double};

struct ScratchFloat32Scope : public AutoFloatRegisterScope {
  explicit ScratchFloat32Scope(MacroAssembler& masm)
      : AutoFloatRegisterScope(masm, ScratchFloat32Reg) {}
};

struct ScratchDoubleScope : public AutoFloatRegisterScope {
  explicit ScratchDoubleScope(MacroAssembler& masm)
      : AutoFloatRegisterScope(masm, ScratchDoubleReg) {}
};

static constexpr FloatRegister f0 = {FloatRegisters::f0, FloatRegister::Double};
static constexpr FloatRegister f2 = {FloatRegisters::f2, FloatRegister::Double};
static constexpr FloatRegister f4 = {FloatRegisters::f4, FloatRegister::Double};
static constexpr FloatRegister f6 = {FloatRegisters::f6, FloatRegister::Double};
static constexpr FloatRegister f8 = {FloatRegisters::f8, FloatRegister::Double};
static constexpr FloatRegister f10 = {FloatRegisters::f10,
                                      FloatRegister::Double};
static constexpr FloatRegister f12 = {FloatRegisters::f12,
                                      FloatRegister::Double};
static constexpr FloatRegister f14 = {FloatRegisters::f14,
                                      FloatRegister::Double};
static constexpr FloatRegister f16 = {FloatRegisters::f16,
                                      FloatRegister::Double};
static constexpr FloatRegister f18 = {FloatRegisters::f18,
                                      FloatRegister::Double};
static constexpr FloatRegister f20 = {FloatRegisters::f20,
                                      FloatRegister::Double};
static constexpr FloatRegister f22 = {FloatRegisters::f22,
                                      FloatRegister::Double};
static constexpr FloatRegister f24 = {FloatRegisters::f24,
                                      FloatRegister::Double};
static constexpr FloatRegister f26 = {FloatRegisters::f26,
                                      FloatRegister::Double};
static constexpr FloatRegister f28 = {FloatRegisters::f28,
                                      FloatRegister::Double};
static constexpr FloatRegister f30 = {FloatRegisters::f30,
                                      FloatRegister::Double};

// MIPS CPUs can only load multibyte data that is "naturally"
// four-byte-aligned, sp register should be eight-byte-aligned.
static constexpr uint32_t ABIStackAlignment = 8;
static constexpr uint32_t JitStackAlignment = 8;

static constexpr uint32_t JitStackValueAlignment =
    JitStackAlignment / sizeof(Value);
static_assert(JitStackAlignment % sizeof(Value) == 0 &&
                  JitStackValueAlignment >= 1,
              "Stack alignment should be a non-zero multiple of sizeof(Value)");

// TODO this is just a filler to prevent a build failure. The MIPS SIMD
// alignment requirements still need to be explored.
// TODO Copy the static_asserts from x64/x86 assembler files.
static constexpr uint32_t SimdMemoryAlignment = 8;
static constexpr uint32_t WasmStackAlignment = SimdMemoryAlignment;
static const uint32_t WasmTrapInstructionLength = 4;

// The offsets are dynamically asserted during
// code generation in the prologue/epilogue.
static constexpr uint32_t WasmCheckedCallEntryOffset = 0u;
static constexpr uint32_t WasmCheckedTailEntryOffset = 16u;

static constexpr Scale ScalePointer = TimesFour;

class Assembler : public AssemblerMIPSShared {
 public:
  Assembler() : AssemblerMIPSShared() {}

  static Condition UnsignedCondition(Condition cond);
  static Condition ConditionWithoutEqual(Condition cond);

  static uintptr_t GetPointer(uint8_t*);

 protected:
  // This is used to access the odd register form the pair of single
  // precision registers that make one double register.
  FloatRegister getOddPair(FloatRegister reg) {
    MOZ_ASSERT(reg.isDouble());
    MOZ_ASSERT(reg.id() % 2 == 0);
    FloatRegister odd(reg.id() | 1, FloatRegister::Single);
    return odd;
  }

 public:
  using AssemblerMIPSShared::bind;

  static void Bind(uint8_t* rawCode, const CodeLabel& label);

  void processCodeLabels(uint8_t* rawCode);

  static void TraceJumpRelocations(JSTracer* trc, JitCode* code,
                                   CompactBufferReader& reader);
  static void TraceDataRelocations(JSTracer* trc, JitCode* code,
                                   CompactBufferReader& reader);

  void bind(InstImm* inst, uintptr_t branch, uintptr_t target);

  // Copy the assembly code to the given buffer, and perform any pending
  // relocations relying on the target address.
  void executableCopy(uint8_t* buffer);

  static uint32_t PatchWrite_NearCallSize();

  static uint32_t ExtractLuiOriValue(Instruction* inst0, Instruction* inst1);
  static void WriteLuiOriInstructions(Instruction* inst, Instruction* inst1,
                                      Register reg, uint32_t value);

  static void PatchWrite_NearCall(CodeLocationLabel start,
                                  CodeLocationLabel toCall);
  static void PatchDataWithValueCheck(CodeLocationLabel label, ImmPtr newValue,
                                      ImmPtr expectedValue);
  static void PatchDataWithValueCheck(CodeLocationLabel label,
                                      PatchedImmPtr newValue,
                                      PatchedImmPtr expectedValue);

  static uint32_t ExtractInstructionImmediate(uint8_t* code);

  static void ToggleCall(CodeLocationLabel inst_, bool enabled);
};  // Assembler

static const uint32_t NumIntArgRegs = 4;

static inline bool GetIntArgReg(uint32_t usedArgSlots, Register* out) {
  if (usedArgSlots < NumIntArgRegs) {
    *out = Register::FromCode(a0.code() + usedArgSlots);
    return true;
  }
  return false;
}

// Get a register in which we plan to put a quantity that will be used as an
// integer argument. This differs from GetIntArgReg in that if we have no more
// actual argument registers to use we will fall back on using whatever
// CallTempReg* don't overlap the argument registers, and only fail once those
// run out too.
static inline bool GetTempRegForIntArg(uint32_t usedIntArgs,
                                       uint32_t usedFloatArgs, Register* out) {
  // NOTE: We can't properly determine which regs are used if there are
  // float arguments. If this is needed, we will have to guess.
  MOZ_ASSERT(usedFloatArgs == 0);

  if (GetIntArgReg(usedIntArgs, out)) {
    return true;
  }
  // Unfortunately, we have to assume things about the point at which
  // GetIntArgReg returns false, because we need to know how many registers it
  // can allocate.
  usedIntArgs -= NumIntArgRegs;
  if (usedIntArgs >= NumCallTempNonArgRegs) {
    return false;
  }
  *out = CallTempNonArgRegs[usedIntArgs];
  return true;
}

}  // namespace jit
}  // namespace js

#endif /* jit_mips32_Assembler_mips32_h */