text: /*
   * local-propagation.c: Local constant, copy and tree propagation.
   *
   * To make some sense of the tree mover, read mono/docs/tree-mover.txt
   *
   * Author:
   *   Paolo Molaro (lupus@ximian.com)
   *   Dietmar Maurer (dietmar@ximian.com)
   *   Massimiliano Mantione (massi@ximian.com)
   *
   * (C) 2006 Novell, Inc.  http://www.novell.com
   * Copyright 2011 Xamarin, Inc (http://www.xamarin.com)
   */
  
  
  #include <string.h>
  #include <stdio.h>
  #ifdef HAVE_ALLOCA_H
  #include <alloca.h>
  #endif
  
  #include <mono/metadata/debug-helpers.h>
  #include <mono/metadata/mempool.h>
  #include <mono/metadata/opcodes.h>
  #include "mini.h"
  #include "ir-emit.h"
  
  #ifndef MONO_ARCH_IS_OP_MEMBASE
  #define MONO_ARCH_IS_OP_MEMBASE(opcode) FALSE
  #endif
  
  static inline MonoBitSet* 
  mono_bitset_mp_new_noinit (MonoMemPool *mp,  guint32 max_size)
  {
  	int size = mono_bitset_alloc_size (max_size, 0);
  	gpointer mem;
  
  	mem = mono_mempool_alloc (mp, size);
  	return mono_bitset_mem_new (mem, max_size, MONO_BITSET_DONT_FREE);
  }
  
  /*
   * mono_local_cprop:
   *
   *  A combined local copy and constant propagation pass.
   */
  void
  mono_local_cprop (MonoCompile *cfg)
  {
  	MonoBasicBlock *bb;
  	MonoInst **defs;
  	gint32 *def_index;
  	int max;
  
  restart:
  
  	max = cfg->next_vreg;
  	defs = mono_mempool_alloc (cfg->mempool, sizeof (MonoInst*) * (cfg->next_vreg + 1));
  	def_index = mono_mempool_alloc (cfg->mempool, sizeof (guint32) * (cfg->next_vreg + 1));
  
  	for (bb = cfg->bb_entry; bb; bb = bb->next_bb) {
  		MonoInst *ins;
  		int ins_index;
  		int last_call_index;
  
  		/* Manually init the defs entries used by the bblock */
  		MONO_BB_FOR_EACH_INS (bb, ins) {
  			int sregs [MONO_MAX_SRC_REGS];
  			int num_sregs, i;
  
  			if ((ins->dreg != -1) && (ins->dreg < max)) {
  				defs [ins->dreg] = NULL;
  #if SIZEOF_REGISTER == 4
  				defs [ins->dreg + 1] = NULL;
  #endif
  			}
  
  			num_sregs = mono_inst_get_src_registers (ins, sregs);
  			for (i = 0; i < num_sregs; ++i) {
  				int sreg = sregs [i];
  				if (sreg < max) {
  					defs [sreg] = NULL;
  #if SIZEOF_REGISTER == 4
  					defs [sreg + 1] = NULL;
  #endif
  				}
  			}
  		}
  
  		ins_index = 0;
  		last_call_index = -1;
  		MONO_BB_FOR_EACH_INS (bb, ins) {
  			const char *spec = INS_INFO (ins->opcode);
  			int regtype, srcindex, sreg;
  			int num_sregs;
  			int sregs [MONO_MAX_SRC_REGS];
  
  			if (ins->opcode == OP_NOP) {
  				MONO_DELETE_INS (bb, ins);
  				continue;
  			}
  
  			g_assert (ins->opcode > MONO_CEE_LAST);
  
  			/* FIXME: Optimize this */
  			if (ins->opcode == OP_LDADDR) {
  				MonoInst *var = ins->inst_p0;
  
  				defs [var->dreg] = NULL;
  				/*
  				if (!MONO_TYPE_ISSTRUCT (var->inst_vtype))
  					break;
  				*/
  			}
  
  			if (MONO_IS_STORE_MEMBASE (ins)) {
  				sreg = ins->dreg;
  				regtype = 'i';
  
  				if ((regtype == 'i') && (sreg != -1) && defs [sreg]) {
  					MonoInst *def = defs [sreg];
  
  					if ((def->opcode == OP_MOVE) && (!defs [def->sreg1] || (def_index [def->sreg1] < def_index [sreg])) && !vreg_is_volatile (cfg, def->sreg1)) {
  						int vreg = def->sreg1;
  						if (cfg->verbose_level > 2) printf ("CCOPY: R%d -> R%d\n", sreg, vreg);
  						ins->dreg = vreg;
  					}
  				}
  			}
  
  			num_sregs = mono_inst_get_src_registers (ins, sregs);
  			for (srcindex = 0; srcindex < num_sregs; ++srcindex) {
  				MonoInst *def;
  				int nregs;
  
  				nregs = mono_inst_get_src_registers (ins, sregs);
  
  				regtype = spec [MONO_INST_SRC1 + srcindex];
  				sreg = sregs [srcindex];
  
  				if ((regtype == ' ') || (sreg == -1) || (!defs [sreg]))
  					continue;
  
  				def = defs [sreg];
  
  				/* Copy propagation */
  				/* 
  				 * The first check makes sure the source of the copy did not change since 
  				 * the copy was made.
  				 * The second check avoids volatile variables.
  				 * The third check avoids copy propagating local vregs through a call, 
  				 * since the lvreg will be spilled 
  				 * The fourth check avoids copy propagating a vreg in cases where
  				 * it would be eliminated anyway by reverse copy propagation later,
  				 * because propagating it would create another use for it, thus making 
  				 * it impossible to use reverse copy propagation.
  				 */
  				/* Enabling this for floats trips up the fp stack */
  				/* 
  				 * Enabling this for floats on amd64 seems to cause a failure in 
  				 * basic-math.cs, most likely because it gets rid of some r8->r4 
  				 * conversions.
  				 */
  				if (MONO_IS_MOVE (def) &&
  					(!defs [def->sreg1] || (def_index [def->sreg1] < def_index [sreg])) &&
  					!vreg_is_volatile (cfg, def->sreg1) &&
  					/* This avoids propagating local vregs across calls */
  					((get_vreg_to_inst (cfg, def->sreg1) || !defs [def->sreg1] || (def_index [def->sreg1] >= last_call_index) || (def->opcode == OP_VMOVE))) &&
  					!(defs [def->sreg1] && defs [def->sreg1]->next == def) &&
  					(!MONO_ARCH_USE_FPSTACK || (def->opcode != OP_FMOVE)) &&
  					(def->opcode != OP_FMOVE)) {
  					int vreg = def->sreg1;
  
  					if (cfg->verbose_level > 2) printf ("CCOPY/2: R%d -> R%d\n", sreg, vreg);
  					sregs [srcindex] = vreg;
  					mono_inst_set_src_registers (ins, sregs);
  
  					/* Allow further iterations */
  					srcindex = -1;
  					continue;
  				}
  
  				/* Constant propagation */
  				/* FIXME: Make is_inst_imm a macro */
  				/* FIXME: Make is_inst_imm take an opcode argument */
  				/* is_inst_imm is only needed for binops */
  				if ((((def->opcode == OP_ICONST) || ((sizeof (gpointer) == 8) && (def->opcode == OP_I8CONST))) &&
  					 (((srcindex == 0) && (ins->sreg2 == -1)) || mono_arch_is_inst_imm (def->inst_c0))) || 
  					(!MONO_ARCH_USE_FPSTACK && (def->opcode == OP_R8CONST))) {
  					guint32 opcode2;
  
  					/* srcindex == 1 -> binop, ins->sreg2 == -1 -> unop */
  					if ((srcindex == 1) && (ins->sreg1 != -1) && defs [ins->sreg1] && (defs [ins->sreg1]->opcode == OP_ICONST) && defs [ins->sreg2]) {
  						/* Both arguments are constants, perform cfold */
  						mono_constant_fold_ins (cfg, ins, defs [ins->sreg1], defs [ins->sreg2], TRUE);
  					} else if ((srcindex == 0) && (ins->sreg2 != -1) && defs [ins->sreg2]) {
  						/* Arg 1 is constant, swap arguments if possible */
  						int opcode = ins->opcode;
  						mono_constant_fold_ins (cfg, ins, defs [ins->sreg1], defs [ins->sreg2], TRUE);
  						if (ins->opcode != opcode) {
  							/* Allow further iterations */
  							srcindex = -1;
  							continue;
  						}
  					} else if ((srcindex == 0) && (ins->sreg2 == -1)) {
  						/* Constant unop, perform cfold */
  						mono_constant_fold_ins (cfg, ins, defs [ins->sreg1], NULL, TRUE);
  					}
  
  					opcode2 = mono_op_to_op_imm (ins->opcode);
  					if ((opcode2 != -1) && mono_arch_is_inst_imm (def->inst_c0) && ((srcindex == 1) || (ins->sreg2 == -1))) {
  						ins->opcode = opcode2;
  						if ((def->opcode == OP_I8CONST) && (sizeof (gpointer) == 4)) {
  							ins->inst_ls_word = def->inst_ls_word;
  							ins->inst_ms_word = def->inst_ms_word;
  						} else {
  							ins->inst_imm = def->inst_c0;
  						}
  						sregs [srcindex] = -1;
  						mono_inst_set_src_registers (ins, sregs);
  
  						if ((opcode2 == OP_VOIDCALL) || (opcode2 == OP_CALL) || (opcode2 == OP_LCALL) || (opcode2 == OP_FCALL))
  							((MonoCallInst*)ins)->fptr = (gpointer)ins->inst_imm;
  
  						/* Allow further iterations */
  						srcindex = -1;
  						continue;
  					}
  					else {
  						/* Special cases */
  #if defined(TARGET_X86) || defined(TARGET_AMD64)
  						if ((ins->opcode == OP_X86_LEA) && (srcindex == 1)) {
  #if SIZEOF_REGISTER == 8
  							/* FIXME: Use OP_PADD_IMM when the new JIT is done */
  							ins->opcode = OP_LADD_IMM;
  #else
  							ins->opcode = OP_ADD_IMM;
  #endif
  							ins->inst_imm += def->inst_c0 << ins->backend.shift_amount;
  							ins->sreg2 = -1;
  						}
  #endif
  						opcode2 = mono_load_membase_to_load_mem (ins->opcode);
  						if ((srcindex == 0) && (opcode2 != -1) && mono_arch_is_inst_imm (def->inst_c0)) {
  							ins->opcode = opcode2;
  							ins->inst_imm = def->inst_c0 + ins->inst_offset;
  							ins->sreg1 = -1;
  						}
  					}
  				}
  				else if (((def->opcode == OP_ADD_IMM) || (def->opcode == OP_LADD_IMM)) && (MONO_IS_LOAD_MEMBASE (ins) || MONO_ARCH_IS_OP_MEMBASE (ins->opcode))) {
  					/* ADD_IMM is created by spill_global_vars */
  					/* 
  					 * We have to guarantee that def->sreg1 haven't changed since def->dreg
  					 * was defined. cfg->frame_reg is assumed to remain constant.
  					 */
  					if ((def->sreg1 == cfg->frame_reg) || ((def->next == ins) && (def->dreg != def->sreg1))) {
  						ins->inst_basereg = def->sreg1;
  						ins->inst_offset += def->inst_imm;
  					}
  				} else if ((ins->opcode == OP_ISUB_IMM) && (def->opcode == OP_IADD_IMM) && (def->next == ins) && (def->dreg != def->sreg1)) {
  					ins->sreg1 = def->sreg1;
  					ins->inst_imm -= def->inst_imm;
  				} else if ((ins->opcode == OP_IADD_IMM) && (def->opcode == OP_ISUB_IMM) && (def->next == ins) && (def->dreg != def->sreg1)) {
  					ins->sreg1 = def->sreg1;
  					ins->inst_imm -= def->inst_imm;
  				} else if (ins->opcode == OP_STOREI1_MEMBASE_REG &&
  						   (def->opcode == OP_ICONV_TO_U1 || def->opcode == OP_ICONV_TO_I1 || def->opcode == OP_SEXT_I4 || (SIZEOF_REGISTER == 8 && def->opcode == OP_LCONV_TO_U1)) &&
  						   (!defs [def->sreg1] || (def_index [def->sreg1] < def_index [sreg]))) {
  					/* Avoid needless sign extension */
  					ins->sreg1 = def->sreg1;
  				} else if (ins->opcode == OP_STOREI2_MEMBASE_REG &&
  						   (def->opcode == OP_ICONV_TO_U2 || def->opcode == OP_ICONV_TO_I2 || def->opcode == OP_SEXT_I4 || (SIZEOF_REGISTER == 8 && def->opcode == OP_LCONV_TO_I2)) &&
  						   (!defs [def->sreg1] || (def_index [def->sreg1] < def_index [sreg]))) {
  					/* Avoid needless sign extension */
  					ins->sreg1 = def->sreg1;
  				}
  			}
  
  			/* Do strength reduction here */
  			/* FIXME: Add long/float */
  			switch (ins->opcode) {
  			case OP_MOVE:
  			case OP_XMOVE:
  				if (ins->dreg == ins->sreg1) {
  					MONO_DELETE_INS (bb, ins);
  					spec = INS_INFO (ins->opcode);
  				}
  				break;
  			case OP_ADD_IMM:
  			case OP_IADD_IMM:
  			case OP_SUB_IMM:
  			case OP_ISUB_IMM:
  #if SIZEOF_REGISTER == 8
  			case OP_LADD_IMM:
  			case OP_LSUB_IMM:
  #endif
  				if (ins->inst_imm == 0) {
  					ins->opcode = OP_MOVE;
  					spec = INS_INFO (ins->opcode);
  				}
  				break;
  			case OP_MUL_IMM:
  			case OP_IMUL_IMM:
  #if SIZEOF_REGISTER == 8
  			case OP_LMUL_IMM:
  #endif
  				if (ins->inst_imm == 0) {
  					ins->opcode = (ins->opcode == OP_LMUL_IMM) ? OP_I8CONST : OP_ICONST;
  					ins->inst_c0 = 0;
  					ins->sreg1 = -1;
  				} else if (ins->inst_imm == 1) {
  					ins->opcode = OP_MOVE;
  				} else if ((ins->opcode == OP_IMUL_IMM) && (ins->inst_imm == -1)) {
  					ins->opcode = OP_INEG;
  				} else if ((ins->opcode == OP_LMUL_IMM) && (ins->inst_imm == -1)) {
  					ins->opcode = OP_LNEG;
  				} else {
  					int power2 = mono_is_power_of_two (ins->inst_imm);
  					if (power2 >= 0) {
  						ins->opcode = (ins->opcode == OP_MUL_IMM) ? OP_SHL_IMM : ((ins->opcode == OP_LMUL_IMM) ? OP_LSHL_IMM : OP_ISHL_IMM);
  						ins->inst_imm = power2;
  					}
  				}
  				spec = INS_INFO (ins->opcode);
  				break;
  			case OP_IREM_UN_IMM:
  			case OP_IDIV_UN_IMM: {
  				int c = ins->inst_imm;
  				int power2 = mono_is_power_of_two (c);
  
  				if (power2 >= 0) {
  					if (ins->opcode == OP_IREM_UN_IMM) {
  						ins->opcode = OP_IAND_IMM;
  						ins->sreg2 = -1;
  						ins->inst_imm = (1 << power2) - 1;
  					} else if (ins->opcode == OP_IDIV_UN_IMM) {
  						ins->opcode = OP_ISHR_UN_IMM;
  						ins->sreg2 = -1;
  						ins->inst_imm = power2;
  					}
  				}
  				spec = INS_INFO (ins->opcode);
  				break;
  			}
  			case OP_IDIV_IMM: {
  				int c = ins->inst_imm;
  				int power2 = mono_is_power_of_two (c);
  				MonoInst *tmp1, *tmp2, *tmp3, *tmp4;
  
  				/* FIXME: Move this elsewhere cause its hard to implement it here */
  				if (power2 == 1) {
  					int r1 = mono_alloc_ireg (cfg);
  
  					NEW_BIALU_IMM (cfg, tmp1, OP_ISHR_UN_IMM, r1, ins->sreg1, 31);
  					mono_bblock_insert_after_ins (bb, ins, tmp1);
  					NEW_BIALU (cfg, tmp2, OP_IADD, r1, r1, ins->sreg1);
  					mono_bblock_insert_after_ins (bb, tmp1, tmp2);
  					NEW_BIALU_IMM (cfg, tmp3, OP_ISHR_IMM, ins->dreg, r1, 1);
  					mono_bblock_insert_after_ins (bb, tmp2, tmp3);
  
  					NULLIFY_INS (ins);
  
  					// We allocated a new vreg, so need to restart
  					goto restart;
  				} else if (power2 > 0) {
  					int r1 = mono_alloc_ireg (cfg);
  
  					NEW_BIALU_IMM (cfg, tmp1, OP_ISHR_IMM, r1, ins->sreg1, 31);
  					mono_bblock_insert_after_ins (bb, ins, tmp1);
  					NEW_BIALU_IMM (cfg, tmp2, OP_ISHR_UN_IMM, r1, r1, (32 - power2));
  					mono_bblock_insert_after_ins (bb, tmp1, tmp2);
  					NEW_BIALU (cfg, tmp3, OP_IADD, r1, r1, ins->sreg1);
  					mono_bblock_insert_after_ins (bb, tmp2, tmp3);
  					NEW_BIALU_IMM (cfg, tmp4, OP_ISHR_IMM, ins->dreg, r1, power2);
  					mono_bblock_insert_after_ins (bb, tmp3, tmp4);
  
  					NULLIFY_INS (ins);
  
  					// We allocated a new vreg, so need to restart
  					goto restart;
  				}
  				break;
  			}
  			}
  			
  			if (spec [MONO_INST_DEST] != ' ') {
  				MonoInst *def = defs [ins->dreg];
  
  				if (def && (def->opcode == OP_ADD_IMM) && (def->sreg1 == cfg->frame_reg) && (MONO_IS_STORE_MEMBASE (ins))) {
  					/* ADD_IMM is created by spill_global_vars */
  					/* cfg->frame_reg is assumed to remain constant */
  					ins->inst_destbasereg = def->sreg1;
  					ins->inst_offset += def->inst_imm;
  				}
  			}
  			
  			if ((spec [MONO_INST_DEST] != ' ') && !MONO_IS_STORE_MEMBASE (ins) && !vreg_is_volatile (cfg, ins->dreg)) {
  				defs [ins->dreg] = ins;
  				def_index [ins->dreg] = ins_index;
  			}
  
  			if (MONO_IS_CALL (ins))
  				last_call_index = ins_index;
  
  			ins_index ++;
  		}
  	}
  }
  
  static inline gboolean
  reg_is_softreg_no_fpstack (int reg, const char spec)
  {
  	return (spec == 'i' && reg >= MONO_MAX_IREGS)
  		|| ((spec == 'f' && reg >= MONO_MAX_FREGS) && !MONO_ARCH_USE_FPSTACK)
  #ifdef MONO_ARCH_SIMD_INTRINSICS
  		|| (spec == 'x' && reg >= MONO_MAX_XREGS)
  #endif
  		|| (spec == 'v');
  }
  		
  static inline gboolean
  reg_is_softreg (int reg, const char spec)
  {
  	return (spec == 'i' && reg >= MONO_MAX_IREGS)
  		|| (spec == 'f' && reg >= MONO_MAX_FREGS)
  #ifdef MONO_ARCH_SIMD_INTRINSICS
  		|| (spec == 'x' && reg >= MONO_MAX_XREGS)
  #endif
  		|| (spec == 'v');
  }
  
  static inline gboolean
  mono_is_simd_accessor (MonoInst *ins)
  {
  	switch (ins->opcode) {
  #ifdef MONO_ARCH_SIMD_INTRINSICS
  	case OP_INSERT_I1:
  	case OP_INSERT_I2:
  	case OP_INSERT_I4:
  	case OP_INSERT_I8:
  	case OP_INSERT_R4:
  	case OP_INSERT_R8:
  
  	case OP_INSERTX_U1_SLOW:
  	case OP_INSERTX_I4_SLOW:
  	case OP_INSERTX_R4_SLOW:
  	case OP_INSERTX_R8_SLOW:
  	case OP_INSERTX_I8_SLOW:
  		return TRUE;
  #endif
  	default:
  		return FALSE;
  	}
  }
  
  /**
   * mono_local_deadce:
   *
   *   Get rid of the dead assignments to local vregs like the ones created by the 
   * copyprop pass.
   */
  void
  mono_local_deadce (MonoCompile *cfg)
  {
  	MonoBasicBlock *bb;
  	MonoInst *ins, *prev;
  	MonoBitSet *used, *defined;
  
  	//mono_print_code (cfg, "BEFORE LOCAL-DEADCE");
  
  	/*
  	 * Assignments to global vregs can't be eliminated so this pass must come
  	 * after the handle_global_vregs () pass.
  	 */
  
  	used = mono_bitset_mp_new_noinit (cfg->mempool, cfg->next_vreg + 1);
  	defined = mono_bitset_mp_new_noinit (cfg->mempool, cfg->next_vreg + 1);
  
  	/* First pass: collect liveness info */
  	for (bb = cfg->bb_entry; bb; bb = bb->next_bb) {
  		/* Manually init the defs entries used by the bblock */
  		MONO_BB_FOR_EACH_INS (bb, ins) {
  			const char *spec = INS_INFO (ins->opcode);
  			int sregs [MONO_MAX_SRC_REGS];
  			int num_sregs, i;
  
  			if (spec [MONO_INST_DEST] != ' ') {
  				mono_bitset_clear_fast (used, ins->dreg);
  				mono_bitset_clear_fast (defined, ins->dreg);
  #if SIZEOF_REGISTER == 4
  				/* Regpairs */
  				mono_bitset_clear_fast (used, ins->dreg + 1);
  				mono_bitset_clear_fast (defined, ins->dreg + 1);
  #endif
  			}
  			num_sregs = mono_inst_get_src_registers (ins, sregs);
  			for (i = 0; i < num_sregs; ++i) {
  				mono_bitset_clear_fast (used, sregs [i]);
  #if SIZEOF_REGISTER == 4
  				mono_bitset_clear_fast (used, sregs [i] + 1);
  #endif
  			}
  		}
  
  		/*
  		 * Make a reverse pass over the instruction list
  		 */
  		MONO_BB_FOR_EACH_INS_REVERSE_SAFE (bb, prev, ins) {
  			const char *spec = INS_INFO (ins->opcode);
  			int sregs [MONO_MAX_SRC_REGS];
  			int num_sregs, i;
  
  			if (ins->opcode == OP_NOP) {
  				MONO_DELETE_INS (bb, ins);
  				continue;
  			}
  
  			g_assert (ins->opcode > MONO_CEE_LAST);
  
  			if (MONO_IS_NON_FP_MOVE (ins) && ins->prev) {
  				MonoInst *def;
  				const char *spec2;
  
  				def = ins->prev;
  				while (def->prev && (def->opcode == OP_NOP))
  					def = def->prev;
  				spec2 = INS_INFO (def->opcode);
  
  				/* 
  				 * Perform a limited kind of reverse copy propagation, i.e.
  				 * transform B <- FOO; A <- B into A <- FOO
  				 * This isn't copyprop, not deadce, but it can only be performed
  				 * after handle_global_vregs () has run.
  				 */
  				if (!get_vreg_to_inst (cfg, ins->sreg1) && (spec2 [MONO_INST_DEST] != ' ') && (def->dreg == ins->sreg1) && !mono_bitset_test_fast (used, ins->sreg1) && !MONO_IS_STORE_MEMBASE (def) && reg_is_softreg (ins->sreg1, spec [MONO_INST_DEST]) && !mono_is_simd_accessor (def)) {
  					if (cfg->verbose_level > 2) {
  						printf ("\tReverse copyprop in BB%d on ", bb->block_num);
  						mono_print_ins (ins);
  					}
  
  					def->dreg = ins->dreg;
  					MONO_DELETE_INS (bb, ins);
  					spec = INS_INFO (ins->opcode);
  				}
  			}
  
  			/* Enabling this on x86 could screw up the fp stack */
  			if (reg_is_softreg_no_fpstack (ins->dreg, spec [MONO_INST_DEST])) {
  				/* 
  				 * Assignments to global vregs can only be eliminated if there is another
  				 * assignment to the same vreg later in the same bblock.
  				 */
  				if (!mono_bitset_test_fast (used, ins->dreg) && 
  					(!get_vreg_to_inst (cfg, ins->dreg) || (!bb->extended && !vreg_is_volatile (cfg, ins->dreg) && mono_bitset_test_fast (defined, ins->dreg))) &&
  					MONO_INS_HAS_NO_SIDE_EFFECT (ins)) {
  					/* Happens with CMOV instructions */
  					if (ins->prev && ins->prev->opcode == OP_ICOMPARE_IMM) {
  						MonoInst *prev = ins->prev;
  						/* 
  						 * Can't use DELETE_INS since that would interfere with the
  						 * FOR_EACH_INS loop.
  						 */
  						NULLIFY_INS (prev);
  					}
  					//printf ("DEADCE: "); mono_print_ins (ins);
  					MONO_DELETE_INS (bb, ins);
  					spec = INS_INFO (ins->opcode);
  				}
  
  				if (spec [MONO_INST_DEST] != ' ')
  					mono_bitset_clear_fast (used, ins->dreg);
  			}
  
  			if (spec [MONO_INST_DEST] != ' ')
  				mono_bitset_set_fast (defined, ins->dreg);
  			num_sregs = mono_inst_get_src_registers (ins, sregs);
  			for (i = 0; i < num_sregs; ++i)
  				mono_bitset_set_fast (used, sregs [i]);
  			if (MONO_IS_STORE_MEMBASE (ins))
  				mono_bitset_set_fast (used, ins->dreg);
  
  			if (MONO_IS_CALL (ins)) {
  				MonoCallInst *call = (MonoCallInst*)ins;
  				GSList *l;
  
  				if (call->out_ireg_args) {
  					for (l = call->out_ireg_args; l; l = l->next) {
  						guint32 regpair, reg;
  
  						regpair = (guint32)(gssize)(l->data);
  						reg = regpair & 0xffffff;
  					
  						mono_bitset_set_fast (used, reg);
  					}
  				}
  
  				if (call->out_freg_args) {
  					for (l = call->out_freg_args; l; l = l->next) {
  						guint32 regpair, reg;
  
  						regpair = (guint32)(gssize)(l->data);
  						reg = regpair & 0xffffff;
  					
  						mono_bitset_set_fast (used, reg);
  					}
  				}
  			}
  		}
  	}
  
  	//mono_print_code (cfg, "AFTER LOCAL-DEADCE");
  }
  