|// Low-level VM code for ARM CPUs.
|// Bytecode interpreter, fast functions and helper functions.
|// Copyright (C) 2005-2011 Mike Pall. See Copyright Notice in luajit.h
|
|.arch arm
|.section code_op, code_sub
|
|.actionlist build_actionlist
|.globals GLOB_
|.globalnames globnames
|.externnames extnames
|
|// Note: The ragged indentation of the instructions is intentional.
|//       The starting columns indicate data dependencies.
|
|//-----------------------------------------------------------------------
|
|// Fixed register assignments for the interpreter.
|
|// The following must be C callee-save (but BASE is often refetched).
|.define BASE,		r4	// Base of current Lua stack frame.
|.define KBASE,		r5	// Constants of current Lua function.
|.define PC,		r6	// Next PC.
|.define DISPATCH,	r7	// Opcode dispatch table.
|.define LREG,		r8	// Register holding lua_State (also in SAVE_L).
|.define MASKR8,	r9	// 255*8 constant for fast bytecode decoding.
|
|// The following temporaries are not saved across C calls, except for RA/RC.
|.define RA,		r10	// Callee-save.
|.define RC,		r11	// Callee-save.
|.define RB,		r12
|.define OP,		r12	// Overlaps RB, must not be lr.
|.define INS,		lr
|
|// Calling conventions. Also used as temporaries.
|.define CARG1,		r0
|.define CARG2,		r1
|.define CARG3,		r2
|.define CARG4,		r3
|.define CARG12,	r0	// For 1st soft-fp double.
|.define CARG34,	r2	// For 2nd soft-fp double.
|
|.define CRET1,		r0
|.define CRET2,		r1
|
|// Stack layout while in interpreter. Must match with lj_frame.h.
|.define CFRAME_SPACE,	#28
|.define SAVE_ERRF,	[sp, #24]
|.define SAVE_NRES,	[sp, #20]
|.define SAVE_CFRAME,	[sp, #16]
|.define SAVE_L,	[sp, #12]
|.define SAVE_PC,	[sp, #8]
|.define SAVE_MULTRES,	[sp, #4]
|.define ARG5,		[sp]
|
|.macro saveregs
|  push {r4, r5, r6, r7, r8, r9, r10, r11, lr}
|  sub sp, sp, CFRAME_SPACE
|.endmacro
|.macro restoreregs_ret
|  add sp, sp, CFRAME_SPACE
|  pop {r4, r5, r6, r7, r8, r9, r10, r11, pc}
|.endmacro
|
|// Type definitions. Some of these are only used for documentation.
|.type L,		lua_State,	LREG
|.type GL,		global_State
|.type TVALUE,		TValue
|.type GCOBJ,		GCobj
|.type STR,		GCstr
|.type TAB,		GCtab
|.type LFUNC,		GCfuncL
|.type CFUNC,		GCfuncC
|.type PROTO,		GCproto
|.type UPVAL,		GCupval
|.type NODE,		Node
|.type NARGS8,		int
|.type TRACE,		GCtrace
|
|//-----------------------------------------------------------------------
|
|// Trap for not-yet-implemented parts.
|.macro NYI; ud; .endmacro
|
|//-----------------------------------------------------------------------
|
|// Access to frame relative to BASE.
|.define FRAME_FUNC,	#-8
|.define FRAME_PC,	#-4
|
|.macro decode_RA8, dst, ins; and dst, MASKR8, ins, lsr #5; .endmacro
|.macro decode_RB8, dst, ins; and dst, MASKR8, ins, lsr #21; .endmacro
|.macro decode_RC8, dst, ins; and dst, MASKR8, ins, lsr #13; .endmacro
|.macro decode_RD, dst, ins; lsr dst, ins, #16; .endmacro
|
|// Instruction fetch.
|.macro ins_NEXT1
|  ldrb OP, [PC]
|.endmacro
|.macro ins_NEXT2
|   ldr INS, [PC], #4
|.endmacro
|// Instruction decode+dispatch.
|.macro ins_NEXT3
|  ldr OP, [DISPATCH, OP, lsl #2]
|   decode_RA8 RA, INS
|   decode_RD RC, INS
|  bx OP
|.endmacro
|.macro ins_NEXT
|  ins_NEXT1
|  ins_NEXT2
|  ins_NEXT3
|.endmacro
|
|// Instruction footer.
|.if 1
|  // Replicated dispatch. Less unpredictable branches, but higher I-Cache use.
|  .define ins_next, ins_NEXT
|  .define ins_next_, ins_NEXT
|  .define ins_next1, ins_NEXT1
|  .define ins_next2, ins_NEXT2
|  .define ins_next3, ins_NEXT3
|.else
|  // Common dispatch. Lower I-Cache use, only one (very) unpredictable branch.
|  // Affects only certain kinds of benchmarks (and only with -j off).
|  .macro ins_next
|    b ->ins_next
|  .endmacro
|  .macro ins_next1
|  .endmacro
|  .macro ins_next2
|  .endmacro
|  .macro ins_next3
|    b ->ins_next
|  .endmacro
|  .macro ins_next_
|  ->ins_next:
|    ins_NEXT
|  .endmacro
|.endif
|
|// Avoid register name substitution for field name.
#define field_pc	pc
|
|// Call decode and dispatch.
|.macro ins_callt
|  // BASE = new base, CARG3 = LFUNC/CFUNC, RC = nargs*8, FRAME_PC(BASE) = PC
|  ldr PC, LFUNC:CARG3->field_pc
|  ldrb OP, [PC]
|   ldr INS, [PC], #4
|  ldr OP, [DISPATCH, OP, lsl #2]
|   decode_RA8 RA, INS
|   add RA, RA, BASE
|  bx OP
|.endmacro
|
|.macro ins_call
|  // BASE = new base, CARG3 = LFUNC/CFUNC, RC = nargs*8, PC = caller PC
|  str PC, [BASE, FRAME_PC]
|  ins_callt
|.endmacro
|
|//-----------------------------------------------------------------------
|
|// Macros to test operand types.
|.macro checktp, reg, tp; cmn reg, #-tp; .endmacro
|.macro checkstr, reg, target; checktp reg, LJ_TSTR; bne target; .endmacro
|.macro checktab, reg, target; checktp reg, LJ_TTAB; bne target; .endmacro
|.macro checkfunc, reg, target; checktp reg, LJ_TFUNC; bne target; .endmacro
|
|// Assumes DISPATCH is relative to GL.
#define DISPATCH_GL(field)	(GG_DISP2G + (int)offsetof(global_State, field))
#define DISPATCH_J(field)	(GG_DISP2J + (int)offsetof(jit_State, field))
|
#define PC2PROTO(field)  ((int)offsetof(GCproto, field)-(int)sizeof(GCproto))
|
|.macro hotloop
|  NYI
|.endmacro
|
|.macro hotcall
|  NYI
|.endmacro
|
|// Set current VM state.
|.macro mv_vmstate, reg, st; mvn reg, #LJ_VMST_..st; .endmacro
|.macro st_vmstate, reg; str reg, [DISPATCH, #DISPATCH_GL(vmstate)]; .endmacro
|
|//-----------------------------------------------------------------------

/* Generate subroutines used by opcodes and other parts of the VM. */
/* The .code_sub section should be last to help static branch prediction. */
static void build_subroutines(BuildCtx *ctx)
{
  |.code_sub
  |
  |//-----------------------------------------------------------------------
  |//-- Return handling ----------------------------------------------------
  |//-----------------------------------------------------------------------
  |
  |->vm_returnp:
  |  // See vm_return. Also: RB = previous base.
  |  tst PC, #FRAME_P
  |  beq ->cont_dispatch
  |
  |  // Return from pcall or xpcall fast func.
  |  ldr PC, [RB, FRAME_PC]		// Fetch PC of previous frame.
  |   mvn CARG2, #~LJ_TTRUE
  |  mov BASE, RB
  |  // Prepending may overwrite the pcall frame, so do it at the end.
  |   str CARG2, [RA, FRAME_PC]		// Prepend true to results.
  |  sub RA, RA, #8
  |
  |->vm_returnc:
  |  add RC, RC, #8			// RC = (nresults+1)*8.
  |   ands CARG1, PC, #FRAME_TYPE
  |  str RC, SAVE_MULTRES
  |   beq ->BC_RET_Z			// Handle regular return to Lua.
  |
  |->vm_return:
  |  // BASE = base, RA = resultptr, RC/MULTRES = (nresults+1)*8, PC = return
  |  // CARG1 = PC & FRAME_TYPE
  |  bic RB, PC, #FRAME_TYPEP
  |   cmp CARG1, #FRAME_C
  |  sub RB, BASE, RB			// RB = previous base.
  |   bne ->vm_returnp
  |
  |  str RB, L->base
  |   ldr KBASE, SAVE_NRES
  |    mv_vmstate CARG4, C
  |   sub BASE, BASE, #8
  |  subs CARG3, RC, #8
  |   lsl KBASE, KBASE, #3		// KBASE = (nresults_wanted+1)*8
  |    st_vmstate CARG4
  |  beq >2
  |1:
  |  subs CARG3, CARG3, #8
  |   ldrd CARG12, [RA], #8
  |   strd CARG12, [BASE], #8
  |  bne <1
  |2:
  |  cmp KBASE, RC			// More/less results wanted?
  |  bne >6
  |3:
  |  str BASE, L->top			// Store new top.
  |
  |->vm_leave_cp:
  |  ldr RC, SAVE_CFRAME		// Restore previous C frame.
  |   mov CRET1, #0			// Ok return status for vm_pcall.
  |  str RC, L->cframe
  |
  |->vm_leave_unw:
  |  restoreregs_ret
  |
  |6:
  |  blt >7				// Less results wanted?
  |  // More results wanted. Check stack size and fill up results with nil.
  |  ldr CARG3, L->maxstack
  |   mvn CARG2, #~LJ_TNIL
  |  cmp BASE, CARG3
  |  bhs >8
  |   str CARG2, [BASE, #4]
  |  add RC, RC, #8
  |  add BASE, BASE, #8
  |  b <2
  |
  |7:  // Less results wanted.
  |  sub CARG1, RC, KBASE
  |  cmp KBASE, #0			// LUA_MULTRET+1 case?
  |  subne BASE, BASE, CARG1		// Either keep top or shrink it.
  |  b <3
  |
  |8:  // Corner case: need to grow stack for filling up results.
  |  // This can happen if:
  |  // - A C function grows the stack (a lot).
  |  // - The GC shrinks the stack in between.
  |  // - A return back from a lua_call() with (high) nresults adjustment.
  |  str BASE, L->top			// Save current top held in BASE (yes).
  |  mov CARG2, KBASE
  |  mov CARG1, L
  |  bl extern lj_state_growstack	// (lua_State *L, int n)
  |  ldr BASE, L->top			// Need the (realloced) L->top in BASE.
  |  b <2
  |
  |->vm_unwind_c:			// Unwind C stack, return from vm_pcall.
  |  NYI
  |->vm_unwind_c_eh:			// Landing pad for external unwinder.
  |  NYI
  |
  |->vm_unwind_ff:			// Unwind C stack, return from ff pcall.
  |  NYI
  |->vm_unwind_ff_eh:			// Landing pad for external unwinder.
  |  NYI
  |
  |//-----------------------------------------------------------------------
  |//-- Grow stack for calls -----------------------------------------------
  |//-----------------------------------------------------------------------
  |
  |->vm_growstack_c:			// Grow stack for C function.
  |  NYI
  |
  |->vm_growstack_l:			// Grow stack for Lua function.
  |  NYI
  |
  |//-----------------------------------------------------------------------
  |//-- Entry points into the assembler VM ---------------------------------
  |//-----------------------------------------------------------------------
  |
  |->vm_resume:				// Setup C frame and resume thread.
  |  NYI
  |
  |->vm_pcall:				// Setup protected C frame and enter VM.
  |  // (lua_State *L, TValue *base, int nres1, ptrdiff_t ef)
  |  saveregs
  |  mov PC, #FRAME_CP
  |  str CARG4, SAVE_ERRF
  |  b >1
  |
  |->vm_call:				// Setup C frame and enter VM.
  |  // (lua_State *L, TValue *base, int nres1)
  |  saveregs
  |  mov PC, #FRAME_C
  |
  |1:  // Entry point for vm_pcall above (PC = ftype).
  |  ldr RC, L:CARG1->cframe
  |   str CARG3, SAVE_NRES
  |    mov L, CARG1
  |   str CARG1, SAVE_L
  |    mov BASE, CARG2
  |  str sp, L->cframe			// Add our C frame to cframe chain.
  |    ldr DISPATCH, L->glref		// Setup pointer to dispatch table.
  |   str CARG1, SAVE_PC		// Any value outside of bytecode is ok.
  |  str RC, SAVE_CFRAME
  |    add DISPATCH, DISPATCH, #GG_G2DISP
  |
  |3:  // Entry point for vm_cpcall/vm_resume (BASE = base, PC = ftype).
  |  ldr RB, L->base			// RB = old base (for vmeta_call).
  |   ldr CARG1, L->top
  |    mov MASKR8, #255
  |  add PC, PC, BASE
  |    lsl MASKR8, MASKR8, #3		// MASKR8 = 255*8.
  |  sub PC, PC, RB			// PC = frame delta + frame type
  |    mv_vmstate CARG2, INTERP
  |   sub NARGS8:RC, CARG1, BASE
  |    st_vmstate CARG2
  |
  |->vm_call_dispatch:
  |  // RB = old base, BASE = new base, RC = nargs*8, PC = caller PC
  |  ldrd CARG34, [BASE, FRAME_FUNC]
  |  checkfunc CARG4, ->vmeta_call
  |
  |->vm_call_dispatch_f:
  |  ins_call
  |  // BASE = new base, RC = nargs*8
  |
  |->vm_cpcall:				// Setup protected C frame, call C.
  |  // (lua_State *L, lua_CFunction func, void *ud, lua_CPFunction cp)
  |  saveregs
  |  mov L, CARG1
  |   ldr RA, L:CARG1->stack
  |  str CARG1, SAVE_L
  |   ldr RB, L->top
  |  str CARG1, SAVE_PC			// Any value outside of bytecode is ok.
  |  ldr RC, L->cframe
  |   sub RA, RA, RB			// Compute -savestack(L, L->top).
  |  str sp, L->cframe			// Add our C frame to cframe chain.
  |  mov RB, #0
  |   str RA, SAVE_NRES			// Neg. delta means cframe w/o frame.
  |  str RB, SAVE_ERRF			// No error function.
  |  str RC, SAVE_CFRAME
  |  blx CARG4			// (lua_State *L, lua_CFunction func, void *ud)
  |   ldr DISPATCH, L->glref		// Setup pointer to dispatch table.
  |  movs BASE, CRET1
  |    mov PC, #FRAME_CP
  |   add DISPATCH, DISPATCH, #GG_G2DISP
  |  bne <3				// Else continue with the call.
  |  b ->vm_leave_cp			// No base? Just remove C frame.
  |
  |//-----------------------------------------------------------------------
  |//-- Metamethod handling ------------------------------------------------
  |//-----------------------------------------------------------------------
  |
  |//-- Continuation dispatch ----------------------------------------------
  |
  |->cont_dispatch:
  |  NYI
  |
  |->cont_cat:
  |  NYI
  |
  |//-- Table indexing metamethods -----------------------------------------
  |
  |->vmeta_tgets:
  |  NYI
  |
  |->vmeta_tgetb:
  |  NYI
  |
  |->vmeta_tgetv:
  |  NYI
  |
  |//-----------------------------------------------------------------------
  |
  |->vmeta_tsets:
  |  NYI
  |
  |->vmeta_tsetb:
  |  NYI
  |
  |->vmeta_tsetv:
  |  NYI
  |
  |//-- Comparison metamethods ---------------------------------------------
  |
  |->vmeta_comp:
  |  NYI
  |
  |->cont_nop:
  |  NYI
  |
  |->cont_ra:				// RA = resultptr
  |  NYI
  |
  |->cont_condt:			// RA = resultptr
  |  NYI
  |
  |->cont_condf:			// RA = resultptr
  |  NYI
  |
  |->vmeta_equal:
  |  NYI
  |
  |//-- Arithmetic metamethods ---------------------------------------------
  |
  |->vmeta_arith_vn:
  |  NYI
  |
  |->vmeta_arith_nv:
  |  NYI
  |
  |->vmeta_unm:
  |  NYI
  |
  |->vmeta_arith_vv:
  |  NYI
  |
  |->vmeta_binop:
  |  NYI
  |
  |->vmeta_len:
  |  NYI
  |
  |//-- Call metamethod ----------------------------------------------------
  |
  |->vmeta_call:			// Resolve and call __call metamethod.
  |  NYI
  |
  |->vmeta_callt:			// Resolve __call for BC_CALLT.
  |  NYI
  |
  |//-- Argument coercion for 'for' statement ------------------------------
  |
  |->vmeta_for:
  |  NYI
  |
  |//-----------------------------------------------------------------------
  |//-- Fast functions -----------------------------------------------------
  |//-----------------------------------------------------------------------
  |
  |.macro .ffunc, name
  |->ff_ .. name:
  |.endmacro
  |
  |.macro .ffunc_1, name
  |->ff_ .. name:
  |  NYI
  |.endmacro
  |
  |.macro .ffunc_2, name
  |->ff_ .. name:
  |  NYI
  |.endmacro
  |
  |.macro .ffunc_n, name
  |  .ffunc_1 name
  |  NYI
  |.endmacro
  |
  |.macro .ffunc_nn, name
  |  .ffunc_2 name
  |  NYI
  |.endmacro
  |
  |.macro ffgccheck
  |  NYI
  |.endmacro
  |
  |//-- Base library: checks -----------------------------------------------
  |
  |.ffunc assert
  |  NYI
  |
  |.ffunc type
  |  NYI
  |
  |//-- Base library: getters and setters ---------------------------------
  |
  |.ffunc_1 getmetatable
  |  NYI
  |
  |.ffunc_2 setmetatable
  |  NYI
  |
  |.ffunc rawget
  |  NYI
  |
  |//-- Base library: conversions ------------------------------------------
  |
  |.ffunc tonumber
  |  NYI
  |
  |.ffunc_1 tostring
  |  NYI
  |
  |//-- Base library: iterators -------------------------------------------
  |
  |.ffunc next
  |  NYI
  |
  |.ffunc_1 pairs
  |  NYI
  |
  |.ffunc_2 ipairs_aux
  |  NYI
  |
  |.ffunc_1 ipairs
  |  NYI
  |
  |//-- Base library: catch errors ----------------------------------------
  |
  |.ffunc pcall
  |  NYI
  |
  |.ffunc_2 xpcall
  |  NYI
  |
  |//-- Coroutine library --------------------------------------------------
  |
  |.macro coroutine_resume_wrap, resume
  |.if resume
  |.ffunc_1 coroutine_resume
  |.else
  |.ffunc coroutine_wrap_aux
  |.endif
  |  NYI
  |.endmacro
  |
  |  coroutine_resume_wrap 1		// coroutine.resume
  |  coroutine_resume_wrap 0		// coroutine.wrap
  |
  |.ffunc coroutine_yield
  |  NYI
  |
  |//-- Math library -------------------------------------------------------
  |
  |.ffunc_n math_abs
  |  NYI
  |
  |->fff_restv:
  |  NYI
  |
  |->fff_res1:
  |  NYI
  |
  |->fff_res:
  |  NYI
  |
  |.macro math_extern, func
  |  .ffunc math_ .. func
  |  NYI
  |.endmacro
  |
  |.macro math_extern2, func
  |  .ffunc math_ .. func
  |  NYI
  |.endmacro
  |
  |.macro math_round, func
  |  .ffunc math_ .. func
  |  NYI
  |.endmacro
  |
  |  math_round floor
  |  math_round ceil
  |
  |  math_extern sqrt
  |  math_extern log
  |  math_extern log10
  |  math_extern exp
  |  math_extern sin
  |  math_extern cos
  |  math_extern tan
  |  math_extern asin
  |  math_extern acos
  |  math_extern atan
  |  math_extern sinh
  |  math_extern cosh
  |  math_extern tanh
  |  math_extern2 pow
  |  math_extern2 atan2
  |  math_extern2 fmod
  |
  |->ff_math_deg:
  |.ffunc_n math_rad
  |  NYI
  |
  |.ffunc math_ldexp
  |  NYI
  |
  |.ffunc math_frexp
  |  NYI
  |
  |.ffunc math_modf
  |  NYI
  |
  |.macro math_minmax, name, cmpop
  |  .ffunc_1 name
  |  NYI
  |.endmacro
  |
  |  math_minmax math_min, NYI
  |  math_minmax math_max, NYI
  |
  |//-- String library -----------------------------------------------------
  |
  |.ffunc_1 string_len
  |  NYI
  |
  |.ffunc string_byte			// Only handle the 1-arg case here.
  |  NYI
  |
  |.ffunc string_char			// Only handle the 1-arg case here.
  |  NYI
  |
  |.ffunc string_sub
  |  NYI
  |
  |.ffunc string_rep			// Only handle the 1-char case inline.
  |  NYI
  |
  |.ffunc string_reverse
  |  NYI
  |
  |.macro ffstring_case, name, lo
  |  .ffunc name
  |  NYI
  |.endmacro
  |
  |ffstring_case string_lower, 65
  |ffstring_case string_upper, 97
  |
  |//-- Table library ------------------------------------------------------
  |
  |.ffunc_1 table_getn
  |  NYI
  |
  |//-- Bit library --------------------------------------------------------
  |
  |.macro .ffunc_bit, name
  |  .ffunc_n bit_..name
  |  NYI
  |.endmacro
  |
  |.ffunc_bit tobit
  |  NYI
  |->fff_resbit:
  |  NYI
  |
  |.macro .ffunc_bit_op, name, ins
  |  .ffunc_bit name
  |  NYI
  |.endmacro
  |
  |.ffunc_bit_op band, and
  |.ffunc_bit_op bor, or
  |.ffunc_bit_op bxor, xor
  |
  |.ffunc_bit bswap
  |  NYI
  |
  |.ffunc_bit bnot
  |  NYI
  |
  |.macro .ffunc_bit_sh, name, ins, shmod
  |  .ffunc_nn bit_..name
  |  NYI
  |.endmacro
  |
  |.ffunc_bit_sh lshift, NYI, 1
  |.ffunc_bit_sh rshift, NYI, 1
  |.ffunc_bit_sh arshift, NYI, 1
  |.ffunc_bit_sh rol, NYI, 2
  |.ffunc_bit_sh ror, NYI, 0
  |
  |//-----------------------------------------------------------------------
  |
  |->fff_fallback:			// Call fast function fallback handler.
  |  NYI
  |
  |->fff_gcstep:			// Call GC step function.
  |  NYI
  |
  |//-----------------------------------------------------------------------
  |//-- Special dispatch targets -------------------------------------------
  |//-----------------------------------------------------------------------
  |
  |->vm_record:				// Dispatch target for recording phase.
#if LJ_HASJIT
  |  NYI
#endif
  |
  |->vm_rethook:			// Dispatch target for return hooks.
  |  NYI
  |
  |->vm_inshook:			// Dispatch target for instr/line hooks.
  |  NYI
  |
  |->cont_hook:				// Continue from hook yield.
  |  NYI
  |
  |->vm_hotloop:			// Hot loop counter underflow.
#if LJ_HASJIT
  |  NYI
#endif
  |
  |->vm_callhook:			// Dispatch target for call hooks.
  |  NYI
  |
  |->vm_hotcall:			// Hot call counter underflow.
  |  NYI
  |
  |//-----------------------------------------------------------------------
  |//-- Trace exit handler -------------------------------------------------
  |//-----------------------------------------------------------------------
  |
  |->vm_exit_handler:
#if LJ_HASJIT
  |  NYI
#endif
  |->vm_exit_interp:
#if LJ_HASJIT
  |  NYI
#endif
  |
  |//-----------------------------------------------------------------------
  |//-- Math helper functions ----------------------------------------------
  |//-----------------------------------------------------------------------
  |
  |// FP value rounding. Called by math.floor/math.ceil fast functions
  |// and from JIT code.
  |//
  |.macro vm_round, name, mode
  |->name:
  |  NYI
  |.endmacro
  |
  |  vm_round vm_floor, 0
  |  vm_round vm_ceil,  1
#if LJ_HASJIT
  |  vm_round vm_trunc, 2
#else
  |->vm_trunc:
#endif
  |
  |->vm_powi:
#if LJ_HASJIT
  |  NYI
#endif
  |
  |->vm_foldfpm:
#if LJ_HASJIT
  |  NYI
#endif
  |
  |// Callable from C: double lj_vm_foldarith(double x, double y, int op)
  |// Compute x op y for basic arithmetic operators (+ - * / % ^ and unary -)
  |// and basic math functions. ORDER ARITH
  |->vm_foldarith:
  |  NYI
  |
  |//-----------------------------------------------------------------------
  |//-- Miscellaneous functions --------------------------------------------
  |//-----------------------------------------------------------------------
  |
  |//-----------------------------------------------------------------------
  |//-- FFI helper functions -----------------------------------------------
  |//-----------------------------------------------------------------------
  |
  |->vm_ffi_call:
#if LJ_HASFFI
  |  NYI
#endif
  |
  |//-----------------------------------------------------------------------
}

/* Generate the code for a single instruction. */
static void build_ins(BuildCtx *ctx, BCOp op, int defop)
{
  int vk = 0;
  |=>defop:

  switch (op) {

  /* -- Comparison ops ---------------------------------------------------- */

  /* Remember: all ops branch for a true comparison, fall through otherwise. */

  case BC_ISLT: case BC_ISGE: case BC_ISLE: case BC_ISGT:
    |  NYI
    break;

  case BC_ISEQV: case BC_ISNEV:
    vk = op == BC_ISEQV;
    |  NYI
    break;

  case BC_ISEQS: case BC_ISNES:
    vk = op == BC_ISEQS;
    |  NYI
    break;

  case BC_ISEQN: case BC_ISNEN:
    vk = op == BC_ISEQN;
    |  NYI
    break;

  case BC_ISEQP: case BC_ISNEP:
    vk = op == BC_ISEQP;
    |  NYI
    break;

  /* -- Unary test and copy ops ------------------------------------------- */

  case BC_ISTC: case BC_ISFC: case BC_IST: case BC_ISF:
    |  NYI
    break;

  /* -- Unary ops --------------------------------------------------------- */

  case BC_MOV:
    |  NYI
    break;
  case BC_NOT:
    |  NYI
    break;
  case BC_UNM:
    |  NYI
    break;
  case BC_LEN:
    |  NYI
    break;

  /* -- Binary ops -------------------------------------------------------- */

  case BC_ADDVN: case BC_ADDNV: case BC_ADDVV:
    |  NYI
    break;
  case BC_SUBVN: case BC_SUBNV: case BC_SUBVV:
    |  NYI
    break;
  case BC_MULVN: case BC_MULNV: case BC_MULVV:
    |  NYI
    break;
  case BC_DIVVN: case BC_DIVNV: case BC_DIVVV:
    |  NYI
    break;
  case BC_MODVN:
    |  NYI
    break;
  case BC_MODNV: case BC_MODVV:
    |  NYI
    break;
  case BC_POW:
    |  NYI
    break;

  case BC_CAT:
    |  NYI
    break;

  /* -- Constant ops ------------------------------------------------------ */

  case BC_KSTR:
    |  NYI
    break;
  case BC_KCDATA:
#if LJ_HASFFI
    |  NYI
#endif
    break;
  case BC_KSHORT:
    |  NYI
    break;
  case BC_KNUM:
    |  NYI
    break;
  case BC_KPRI:
    |  NYI
    break;
  case BC_KNIL:
    |  NYI
    break;

  /* -- Upvalue and function ops ------------------------------------------ */

  case BC_UGET:
    |  NYI
    break;
  case BC_USETV:
    |  NYI
    break;
  case BC_USETS:
    |  NYI
    break;
  case BC_USETN:
    |  NYI
    break;
  case BC_USETP:
    |  NYI
    break;

  case BC_UCLO:
    |  NYI
    break;

  case BC_FNEW:
    |  NYI
    break;

  /* -- Table ops --------------------------------------------------------- */

  case BC_TNEW:
  case BC_TDUP:
    |  NYI
    break;

  case BC_GGET:
  case BC_GSET:
    |  NYI
    break;

  case BC_TGETV:
    |  NYI
    break;
  case BC_TGETS:
    |  NYI
    break;
  case BC_TGETB:
    |  NYI
    break;

  case BC_TSETV:
    |  NYI
    break;
  case BC_TSETS:
    |  NYI
    break;
  case BC_TSETB:
    |  NYI
    break;

  case BC_TSETM:
    |  NYI
    break;

  /* -- Calls and vararg handling ----------------------------------------- */

  case BC_CALLM:
    |  NYI
    break;
  case BC_CALL:
    |  NYI
    break;

  case BC_CALLMT:
    |  NYI
    break;
  case BC_CALLT:
    |  NYI
    break;

  case BC_ITERC:
    |  NYI
    break;

  case BC_ITERN:
    |  NYI
    break;

  case BC_ISNEXT:
    |  NYI
    break;

  case BC_VARG:
    |  NYI
    break;

  /* -- Returns ----------------------------------------------------------- */

  case BC_RETM:
    |  NYI
    break;

  case BC_RET:
    |  NYI
    break;

  case BC_RET0: case BC_RET1:
    |  NYI
    break;

  /* -- Loops and branches ------------------------------------------------ */

  case BC_FORL:
#if LJ_HASJIT
    |  hotloop
#endif
    |  // Fall through. Assumes BC_IFORL follows.
    break;

  case BC_JFORI:
  case BC_JFORL:
#if !LJ_HASJIT
    break;
#endif
  case BC_FORI:
  case BC_IFORL:
    vk = (op == BC_IFORL || op == BC_JFORL);
    |  NYI
    break;

  case BC_ITERL:
#if LJ_HASJIT
    |  hotloop
#endif
    |  // Fall through. Assumes BC_IITERL follows.
    break;

  case BC_JITERL:
#if !LJ_HASJIT
    break;
#endif
  case BC_IITERL:
    |  NYI
    break;

  case BC_LOOP:
    |  NYI
    break;

  case BC_ILOOP:
    |  NYI
    break;

  case BC_JLOOP:
#if LJ_HASJIT
    |  NYI
#endif
    break;

  case BC_JMP:
    |  NYI
    break;

  /* -- Function headers -------------------------------------------------- */

  case BC_FUNCF:
#if LJ_HASJIT
    |  hotcall
#endif
  case BC_FUNCV:  /* NYI: compiled vararg functions. */
    |  // Fall through. Assumes BC_IFUNCF/BC_IFUNCV follow.
    break;

  case BC_JFUNCF:
#if !LJ_HASJIT
    break;
#endif
  case BC_IFUNCF:
    |  NYI
    break;

  case BC_JFUNCV:
#if !LJ_HASJIT
    break;
#endif
    |  NYI  // NYI: compiled vararg functions
    break;  /* NYI: compiled vararg functions. */

  case BC_IFUNCV:
    |  NYI
    break;

  case BC_FUNCC:
  case BC_FUNCCW:
    |  NYI
    break;

  /* ---------------------------------------------------------------------- */

  default:
    fprintf(stderr, "Error: undefined opcode BC_%s\n", bc_names[op]);
    exit(2);
    break;
  }
}

static int build_backend(BuildCtx *ctx)
{
  int op;

  dasm_growpc(Dst, BC__MAX);

  build_subroutines(ctx);

  |.code_op
  for (op = 0; op < BC__MAX; op++)
    build_ins(ctx, (BCOp)op, op);

  return BC__MAX;
}

/* Emit pseudo frame-info for all assembler functions. */
static void emit_asm_debug(BuildCtx *ctx)
{
  int i;
  switch (ctx->mode) {
  case BUILD_elfasm:
    fprintf(ctx->fp, "\t.section .debug_frame,\"\",%%progbits\n");
    fprintf(ctx->fp,
	".Lframe0:\n"
	"\t.long .LECIE0-.LSCIE0\n"
	".LSCIE0:\n"
	"\t.long 0xffffffff\n"
	"\t.byte 0x1\n"
	"\t.string \"\"\n"
	"\t.uleb128 0x1\n"
	"\t.sleb128 -4\n"
	"\t.byte 0xe\n"				/* Return address is in lr. */
	"\t.byte 0xc\n\t.uleb128 0xd\n\t.uleb128 0\n"	/* def_cfa sp */
	"\t.align 2\n"
	".LECIE0:\n\n");
    fprintf(ctx->fp,
	".LSFDE0:\n"
	"\t.long .LEFDE0-.LASFDE0\n"
	".LASFDE0:\n"
	"\t.long .Lframe0\n"
	"\t.long .Lbegin\n"
	"\t.long %d\n"
	"\t.byte 0xe\n\t.uleb128 %d\n"		/* def_cfa_offset */
	"\t.byte 0x8e\n\t.uleb128 1\n",		/* Restore lr. */
	(int)ctx->codesz, CFRAME_SIZE);
    for (i = 11; i >= 4; i--)  /* Restore r4-r11. */
      fprintf(ctx->fp, "\t.byte %d\n\t.uleb128 %d\n", 0x80+i, 2+(11-i));
    fprintf(ctx->fp,
	"\t.align 2\n"
	".LEFDE0:\n\n");
    /* NYI: emit ARM.exidx. */
    break;
  default:
    break;
  }
}