ia32_emitter.c

/*
 * This file is part of libFirm.
 * Copyright (C) 2012 University of Karlsruhe.
 */

/**
 * @file
 * @brief       This file implements the ia32 node emitter.
 * @author      Christian Wuerdig, Matthias Braun
 *
 * Summary table for x86 floatingpoint compares:
 * (remember effect of unordered on x86: ZF=1, PF=1, CF=1)
 *
 *   pnc_Eq  => !P && E
 *   pnc_Lt  => !P && B
 *   pnc_Le  => !P && BE
 *   pnc_Gt  => A
 *   pnc_Ge  => AE
 *   pnc_Lg  => NE
 *   pnc_Leg => NP  (ordered)
 *   pnc_Uo  => P
 *   pnc_Ue  => E
 *   pnc_Ul  => B
 *   pnc_Ule => BE
 *   pnc_Ug  => P || A
 *   pnc_Uge => P || AE
 *   pnc_Ne  => P || NE
 */
#include <inttypes.h>

#include "be_t.h"
#include "bearch_ia32_t.h"
#include "beasm.h"
#include "beblocksched.h"
#include "bediagnostic.h"
#include "begnuas.h"
#include "besched.h"
#include "bestack.h"
#include "beutil.h"
#include "debug.h"
#include "execfreq.h"
#include "gen_ia32_emitter.h"
#include "gen_ia32_regalloc_if.h"
#include "ia32_architecture.h"
#include "ia32_emitter.h"
#include "ia32_new_nodes.h"
#include "irgwalk.h"
#include "irtools.h"
#include "lc_opts.h"
#include "lc_opts_enum.h"
#include "panic.h"

DEBUG_ONLY(static firm_dbg_module_t *dbg = NULL;)

static char       pic_base_label[128];
static ir_label_t exc_label_id;
static bool       mark_spill_reload;

static bool       sp_relative;
static int        frame_type_size;
static int        callframe_offset;
static ir_entity *thunks[N_ia32_gp_REGS];
static ir_type   *thunk_type;

typedef enum get_ip_style_t {
	IA32_GET_IP_POP,
	IA32_GET_IP_THUNK,
} get_ip_style_t;

static int get_ip_style = IA32_GET_IP_THUNK;

/** Return the next block in Block schedule */
static ir_node *get_prev_block_sched(const ir_node *block)
{
	return (ir_node*)get_irn_link(block);
}

/** Checks if the current block is a fall-through target. */
static bool is_fallthrough(const ir_node *cfgpred)
{
	if (!is_Proj(cfgpred))
		return true;
	ir_node *pred = get_Proj_pred(cfgpred);
	if (is_ia32_SwitchJmp(pred))
		return false;
	return true;
}

/**
 * returns non-zero if the given block needs a label
 * because of being a jump-target (and not a fall-through)
 */
static bool block_needs_label(const ir_node *block)
{
	if (get_Block_entity(block) != NULL)
		return true;

	int  n_cfgpreds = get_Block_n_cfgpreds(block);
	bool need_label = true;
	if (n_cfgpreds == 0) {
		need_label = 0;
	} else if (n_cfgpreds == 1) {
		ir_node *cfgpred       = get_Block_cfgpred(block, 0);
		ir_node *cfgpred_block = get_nodes_block(cfgpred);
		if (get_prev_block_sched(block) == cfgpred_block
		    && is_fallthrough(cfgpred)) {
			need_label = 0;
		}
	}

	return need_label;
}

/**
 * Add a number to a prefix. This number will not be used a second time.
 */
static char *get_unique_label(char *buf, size_t buflen, const char *prefix)
{
	static unsigned long id = 0;
	snprintf(buf, buflen, "%s%s%lu", be_gas_get_private_prefix(), prefix, ++id);
	return buf;
}

static const char *get_register_name_8bit_low(const arch_register_t *reg)
{
	switch (reg->global_index) {
	case REG_EAX: return "al";
	case REG_EBX: return "bl";
	case REG_ECX: return "cl";
	case REG_EDX: return "dl";
	}
	panic("unexpected register");
}

static const char *get_register_name_8bit_high(const arch_register_t *reg)
{
	switch (reg->global_index) {
	case REG_EAX: return "ah";
	case REG_EBX: return "bh";
	case REG_ECX: return "ch";
	case REG_EDX: return "dh";
	}
	panic("unexpected register");
}

static const char *get_register_name_16bit(const arch_register_t *reg)
{
	switch (reg->global_index) {
	case REG_EAX: return "ax";
	case REG_EBX: return "bx";
	case REG_ECX: return "cx";
	case REG_EDX: return "dx";
	case REG_ESI: return "si";
	case REG_EDI: return "di";
	case REG_ESP: return "sp";
	case REG_EBP: return "bp";
	}
	panic("unexpected register");
}

static const char *get_register_name_mode(const arch_register_t *reg,
                                          ir_mode *mode)
{
	if (mode == NULL)
		return reg->name;
	if (mode == ia32_mode_8h)
		return get_register_name_8bit_high(reg);
	unsigned size = get_mode_size_bits(mode);
	if (size == 8)
		return get_register_name_8bit_low(reg);
	else if (size == 16)
		return get_register_name_16bit(reg);
	else
		return reg->name;
}

/**
 * emit a register, possible shortened by a mode
 * @param reg   the register
 * @param mode  the mode of the register or NULL for full register
 */
static void emit_register(const arch_register_t *reg, ir_mode *mode)
{
	const char *name = get_register_name_mode(reg, mode);
	be_emit_char('%');
	be_emit_string(name);
}

static void ia32_emit_relocation(x86_imm32_t const *const imm)
{
	ir_entity *entity = imm->entity;
	be_gas_emit_entity(entity);
	switch (imm->kind) {
	case X86_IMM_ADDR:
	case X86_IMM_PCREL:
		return;
	case X86_IMM_TLS_IE: be_emit_cstring("@INDNTPOFF"); return;
	case X86_IMM_TLS_LE: be_emit_cstring("@NTPOFF");    return;
	case X86_IMM_GOT:    be_emit_cstring("@GOT");       return;
	case X86_IMM_GOTOFF: be_emit_cstring("@GOTOFF");    return;
	case X86_IMM_PLT:    be_emit_cstring("@PLT");       return;
	case X86_IMM_PICBASE_REL:
		be_emit_char('-');
		be_emit_string(pic_base_label);
		return;
	case X86_IMM_FRAMEOFFSET:
	case X86_IMM_GOTPCREL:
	case X86_IMM_VALUE:
		break;
	}
	panic("Unexpected immediate kind");
}

static void emit_ia32_immediate(bool const prefix, x86_imm32_t const *const imm)
{
	if (prefix)
		be_emit_char('$');
	ir_entity const *const entity = imm->entity;
	int32_t          const offset = imm->offset;
	if (entity != NULL) {
		assert(imm->kind != X86_IMM_VALUE);
		ia32_emit_relocation(imm);
		if (offset != 0)
			be_emit_irprintf("%+"PRId32, offset);
	} else {
		assert(imm->kind == X86_IMM_VALUE);
		be_emit_irprintf("0x%"PRIX32, (uint32_t)offset);
	}
}

static void emit_ia32_immediate_attr(bool const prefix, ir_node const *const node)
{
	ia32_immediate_attr_t const *const attr = get_ia32_immediate_attr_const(node);
	emit_ia32_immediate(prefix, &attr->imm);
}

static void ia32_emit_mode_suffix_mode(const ir_mode *mode)
{
	assert(mode_is_int(mode) || mode_is_reference(mode) || mode == ia32_mode_8h);
	switch (get_mode_size_bits(mode)) {
		case 8:  be_emit_char('b');     return;
		case 16: be_emit_char('w');     return;
		case 32: be_emit_char('l');     return;
		/* gas docu says q is the suffix but gcc, objdump and icc use ll
		 * apparently */
		case 64: be_emit_cstring("ll"); return;
	}
	panic("cannot output mode_suffix for %+F", mode);
}

static void ia32_emit_x87_mode_suffix(ir_node const *const node)
{
	/* we only need to emit the mode on address mode */
	if (get_ia32_op_type(node) == ia32_Normal)
		return;

	ir_mode *mode = get_ia32_ls_mode(node);
	assert(mode != NULL);

	if (mode_is_float(mode)) {
		switch (get_mode_size_bits(mode)) {
			case  32: be_emit_char('s'); return;
			case  64: be_emit_char('l'); return;
			/* long doubles have different sizes due to alignment on different
			 * platforms. */
			case  80:
			case  96:
			case 128: be_emit_char('t'); return;
		}
	} else {
		assert(mode_is_int(mode) || mode_is_reference(mode));
		switch (get_mode_size_bits(mode)) {
			case 16: be_emit_char('s');     return;
			case 32: be_emit_char('l');     return;
			/* gas docu says q is the suffix but gcc, objdump and icc use ll
			 * apparently */
			case 64: be_emit_cstring("ll"); return;
		}
	}
	panic("cannot output mode_suffix for %+F", mode);
}

static char get_xmm_mode_suffix(ir_mode *mode)
{
	assert(mode_is_float(mode));
	switch (get_mode_size_bits(mode)) {
	case 32: return 's';
	case 64: return 'd';
	default: panic("invalid XMM mode");
	}
}

static void ia32_emit_xmm_mode_suffix(ir_node const *const node)
{
	ir_mode *mode = get_ia32_ls_mode(node);
	assert(mode != NULL);
	be_emit_char(get_xmm_mode_suffix(mode));
}

/**
 * Returns the target block for a control flow node.
 */
static ir_node *get_cfop_target_block(const ir_node *irn)
{
	assert(get_irn_mode(irn) == mode_X);
	return (ir_node*)get_irn_link(irn);
}

/**
 * Emits the target label for a control flow node.
 */
static void ia32_emit_cfop_target(const ir_node *node)
{
	ir_node *block = get_cfop_target_block(node);
	be_gas_emit_block_name(block);
}

void x86_emit_condition_code(x86_condition_code_t cc)
{
	switch (cc) {
	case x86_cc_overflow:      be_emit_cstring("o");  return;
	case x86_cc_not_overflow:  be_emit_cstring("no"); return;
	case x86_cc_float_below:
	case x86_cc_float_unordered_below:
	case x86_cc_below:         be_emit_cstring("b");  return;
	case x86_cc_float_above_equal:
	case x86_cc_float_unordered_above_equal:
	case x86_cc_above_equal:   be_emit_cstring("ae"); return;
	case x86_cc_float_equal:
	case x86_cc_equal:         be_emit_cstring("e");  return;
	case x86_cc_float_not_equal:
	case x86_cc_not_equal:     be_emit_cstring("ne"); return;
	case x86_cc_float_below_equal:
	case x86_cc_float_unordered_below_equal:
	case x86_cc_below_equal:   be_emit_cstring("be"); return;
	case x86_cc_float_above:
	case x86_cc_float_unordered_above:
	case x86_cc_above:         be_emit_cstring("a");  return;
	case x86_cc_sign:          be_emit_cstring("s");  return;
	case x86_cc_not_sign:      be_emit_cstring("ns"); return;
	case x86_cc_parity:        be_emit_cstring("p");  return;
	case x86_cc_not_parity:    be_emit_cstring("np"); return;
	case x86_cc_less:          be_emit_cstring("l");  return;
	case x86_cc_greater_equal: be_emit_cstring("ge"); return;
	case x86_cc_less_equal:    be_emit_cstring("le"); return;
	case x86_cc_greater:       be_emit_cstring("g");  return;
	case x86_cc_float_parity_cases:
	case x86_cc_additional_float_cases:
		break;
	}
	panic("invalid ia32 condition code");
}

typedef enum ia32_emit_mod_t {
	EMIT_NONE         = 0,
	EMIT_ALTERNATE_AM = 1U << 0,
	EMIT_LONG         = 1U << 1,
	EMIT_LOW_REG      = 1U << 2,
	EMIT_HIGH_REG     = 1U << 3,
	EMIT_16BIT_REG    = 1U << 4,
	EMIT_32BIT_REG    = 1U << 5,
	EMIT_SHIFT_COMMA  = 1U << 6,
} ia32_emit_mod_t;
ENUM_BITSET(ia32_emit_mod_t)

static ir_node const *get_irn_n_reg(ir_node const *const node, int const pos)
{
	ir_node *const in = get_irn_n(node, pos);
	return is_ia32_NoReg_GP(in) ? NULL : in;
}

/**
 * Emits address mode.
 */
static void ia32_emit_am(ir_node const *const node)
{
	if (get_ia32_am_tls_segment(node))
		be_emit_cstring("%gs:");

	ir_node const *const base = get_irn_n_reg(node, n_ia32_base);
	ir_node const *const idx  = get_irn_n_reg(node, n_ia32_index);

	/* emit offset */
	ia32_attr_t const *const attr = get_ia32_attr_const(node);
	int32_t          const offset = attr->am_imm.offset;
	ir_entity const *const entity = attr->am_imm.entity;
	if (entity) {
		assert(attr->am_imm.kind != X86_IMM_VALUE);
		const ia32_attr_t *attr = get_ia32_attr_const(node);
		ia32_emit_relocation(&attr->am_imm);
		if (offset != 0)
			be_emit_irprintf("%+"PRId32, offset);
	} else if (offset != 0 || (!base && !idx)) {
		assert(attr->am_imm.kind == X86_IMM_VALUE);
		/* also handle special case if nothing is set */
		be_emit_irprintf("%"PRId32, offset);
	}

	if (base || idx) {
		be_emit_char('(');

		/* emit base */
		if (base) {
			arch_register_t const *const reg = arch_get_irn_register(base);
			emit_register(reg, NULL);
		}

		/* emit index + scale */
		if (idx) {
			be_emit_char(',');
			arch_register_t const *const reg = arch_get_irn_register(idx);
			emit_register(reg, NULL);

			int const scale = get_ia32_am_scale(node);
			if (scale > 0)
				be_emit_irprintf(",%d", 1 << scale);
		}
		be_emit_char(')');
	}
}

static x86_condition_code_t determine_final_cc(ir_node const *node, int flags_pos);

void ia32_emitf(ir_node const *const node, char const *fmt, ...)
{
	va_list ap;
	va_start(ap, fmt);

	be_emit_char('\t');
	for (;;) {
		const char      *start = fmt;
		ia32_emit_mod_t  mod   = EMIT_NONE;

		while (*fmt != '%' && *fmt != '\n' && *fmt != '\0')
			++fmt;
		if (fmt != start) {
			be_emit_string_len(start, fmt - start);
		}

		if (*fmt == '\n') {
			be_emit_char('\n');
			be_emit_write_line();
			be_emit_char('\t');
			++fmt;
			if (*fmt == '\0')
				break;
			continue;
		}

		if (*fmt == '\0')
			break;

		++fmt;
		for (;;) {
			switch (*fmt) {
			case '*': mod |= EMIT_ALTERNATE_AM; break;
			case 'l': mod |= EMIT_LONG;         break;
			case '<': mod |= EMIT_LOW_REG;      break;
			case '>': mod |= EMIT_HIGH_REG;     break;
			case '^': mod |= EMIT_16BIT_REG;    break;
			case '#': mod |= EMIT_32BIT_REG;    break;
			case ',': mod |= EMIT_SHIFT_COMMA;  break;
			default:
				goto end_of_mods;
			}
			++fmt;
		}
end_of_mods:

		switch (*fmt++) {
			arch_register_t const *reg;
			ir_node         const *imm;

			case '%':
				be_emit_char('%');
				break;

			case 'A': {
				switch (*fmt++) {
					case 'F':
						if (get_ia32_op_type(node) == ia32_Normal) {
							ia32_x87_attr_t const *const attr = get_ia32_x87_attr_const(node);
							char            const *const fmt  = attr->x87.res_in_reg ? "%%st, %%%s" : "%%%s, %%st";
							be_emit_irprintf(fmt, attr->x87.reg->name);
							break;
						} else {
							goto emit_AM;
						}

emit_AM:
					case 'M':
						if (mod & EMIT_ALTERNATE_AM)
							be_emit_char('*');
						ia32_emit_am(node);
						break;

					case 'R':
						reg = va_arg(ap, const arch_register_t*);
						if (get_ia32_op_type(node) == ia32_Normal) {
							goto emit_R;
						} else {
							goto emit_AM;
						}

					case 'S':
						if (get_ia32_op_type(node) == ia32_Normal) {
							goto emit_S;
						} else {
							++fmt;
							goto emit_AM;
						}

					default: goto unknown;
				}
				break;
			}

			case 'B': {
				ir_node const *const src = get_irn_n(node, n_ia32_binary_right);
				if (is_ia32_Immediate(src)) {
					emit_ia32_immediate_attr(true, src);
					be_emit_cstring(", ");
					if (get_ia32_op_type(node) == ia32_Normal) {
						goto destination_operand;
					} else {
						ia32_emit_am(node);
					}
				} else {
					if (get_ia32_op_type(node) == ia32_Normal) {
						reg = arch_get_irn_register(src);
						emit_register(reg, get_ia32_ls_mode(node));
					} else {
						ia32_emit_am(node);
					}
					be_emit_cstring(", ");
destination_operand:
					reg = arch_get_irn_register_in(node, n_ia32_binary_left);
					emit_register(reg, get_ia32_ls_mode(node));
				}
				break;
			}

			case 'D':
				if (!is_digit(*fmt))
					goto unknown;
				reg = arch_get_irn_register_out(node, *fmt++ - '0');
				goto emit_R;

			case 'E': {
				const ir_entity *const entity = va_arg(ap, const ir_entity*);
				be_gas_emit_entity(entity);
				break;
			}

			case 'F':
				if (*fmt == 'M') {
					ia32_emit_x87_mode_suffix(node);
				} else if (*fmt == 'P') {
					ia32_x87_attr_t const *const attr = get_ia32_x87_attr_const(node);
					if (attr->x87.pop)
						be_emit_char('p');
				} else if (*fmt == 'R') {
					/* NOTE: Work around a gas quirk for non-commutative operations if the
					 * destination register is not %st0.  In this case r/non-r is swapped.
					 * %st0 = %st0 - %st1 -> fsub  %st1, %st0 (as expected)
					 * %st0 = %st1 - %st0 -> fsubr %st1, %st0 (as expected)
					 * %st1 = %st0 - %st1 -> fsub  %st0, %st1 (expected: fsubr)
					 * %st1 = %st1 - %st0 -> fsubr %st0, %st1 (expected: fsub)
					 * In fact this corresponds to the encoding of the instruction:
					 * - The r suffix selects whether %st0 is on the left (no r) or on the
					 *   right (r) side of the executed operation.
					 * - The placement of %st0 selects whether the result is written to
					 *   %st0 (right) or the other register (left).
					 * This means that it is sufficient to test whether the operands are
					 * permuted.  In particular it is not necessary to consider wether the
					 * result is to be placed into the explicit register operand. */
					if (get_ia32_x87_attr_const(node)->x87.reverse)
						be_emit_char('r');
				} else if (*fmt == 'X') {
					ia32_emit_xmm_mode_suffix(node);
				} else if (*fmt == '0') {
					be_emit_char('%');
					be_emit_string(get_ia32_x87_attr_const(node)->x87.reg->name);
				} else {
					goto unknown;
				}
				++fmt;
				break;

			case 'I':
				imm = node;
emit_I:
				if (mod & EMIT_SHIFT_COMMA) {
					const ia32_immediate_attr_t *attr
						= get_ia32_immediate_attr_const(imm);
					if (attr->imm.entity == NULL && attr->imm.offset == 1)
						break;
				}
				emit_ia32_immediate_attr(!(mod & EMIT_ALTERNATE_AM), imm);
				if (mod & EMIT_SHIFT_COMMA) {
					be_emit_char(',');
				}
				break;

			case 'L':
				ia32_emit_cfop_target(node);
				break;

			case 'M': {
				ir_mode *mode = get_ia32_ls_mode(node);
				if (!mode)
					mode = ia32_mode_gp;
				if (mod & EMIT_32BIT_REG) {
					if (get_mode_size_bits(mode) == 32)
						break;
					be_emit_char(mode_is_signed(mode) ? 's' : 'z');
				}
				ia32_emit_mode_suffix_mode(mode);
				break;
			}

			case 'P': {
				x86_condition_code_t cc;
				if (*fmt == 'X') {
					++fmt;
					cc = (x86_condition_code_t)va_arg(ap, int);
				} else if (is_digit(*fmt)) {
					cc = determine_final_cc(node, *fmt - '0');
					++fmt;
				} else {
					goto unknown;
				}
				x86_emit_condition_code(cc);
				break;
			}

			case 'R':
				reg = va_arg(ap, const arch_register_t*);
emit_R:
				if (mod & EMIT_ALTERNATE_AM)
					be_emit_char('*');
				const char *name;
				if (mod & EMIT_HIGH_REG) {
					name = get_register_name_8bit_high(reg);
				} else if (mod & EMIT_LOW_REG) {
					name = get_register_name_8bit_low(reg);
				} else if (mod & EMIT_16BIT_REG) {
					name = get_register_name_16bit(reg);
				} else if (mod & EMIT_32BIT_REG) {
					name = reg->name;
				} else {
					name = get_register_name_mode(reg, get_ia32_ls_mode(node));
				}
				be_emit_char('%');
				be_emit_string(name);
				if (mod & EMIT_SHIFT_COMMA) {
					be_emit_char(',');
				}
				break;

emit_S:
			case 'S': {
				if (!is_digit(*fmt))
					goto unknown;

				unsigned pos = *fmt++ - '0';
				ir_node const *const src = get_irn_n(node, pos);
				if (is_ia32_Immediate(src)) {
					imm = src;
					goto emit_I;
				} else {
					reg = arch_get_irn_register(src);
					goto emit_R;
				}
			}

			case 's': {
				const char *str = va_arg(ap, const char*);
				be_emit_string(str);
				break;
			}

			case 'u':
				if (mod & EMIT_LONG) {
					unsigned long num = va_arg(ap, unsigned long);
					be_emit_irprintf("%lu", num);
				} else {
					unsigned num = va_arg(ap, unsigned);
					be_emit_irprintf("%u", num);
				}
				break;

			case 'd':
				if (mod & EMIT_LONG) {
					long num = va_arg(ap, long);
					be_emit_irprintf("%ld", num);
				} else {
					int num = va_arg(ap, int);
					be_emit_irprintf("%d", num);
				}
				break;

			default:
unknown:
				panic("unknown format conversion");
		}
	}

	be_emit_finish_line_gas(node);
	va_end(ap);
}

/**
 * walks up a tree of copies/perms/spills/reloads to find the original value
 * that is moved around
 */
static ir_node *find_original_value(ir_node *node)
{
	if (irn_visited(node))
		return NULL;

	mark_irn_visited(node);
	if (be_is_Copy(node)) {
		return find_original_value(be_get_Copy_op(node));
	} else if (be_is_CopyKeep(node)) {
		return find_original_value(be_get_CopyKeep_op(node));
	} else if (is_Proj(node)) {
		ir_node *pred = get_Proj_pred(node);
		if (be_is_Perm(pred)) {
			return find_original_value(get_irn_n(pred, get_Proj_num(node)));
		} else if (be_is_MemPerm(pred)) {
			return find_original_value(get_irn_n(pred, get_Proj_num(node)));
		} else if (is_ia32_Load(pred)) {
			return find_original_value(get_irn_n(pred, n_ia32_Load_mem));
		} else if (is_ia32_Store(pred)) {
			return find_original_value(get_irn_n(pred, n_ia32_Store_val));
		} else {
			return node;
		}
	} else if (is_Phi(node)) {
		foreach_irn_in(node, i, in) {
			ir_node *res = find_original_value(in);
			if (res != NULL)
				return res;
		}
		return NULL;
	} else {
		return node;
	}
}

static x86_condition_code_t determine_final_cc(ir_node const *const node, int const flags_pos)
{
	ia32_condcode_attr_t const *const attr = get_ia32_condcode_attr_const(node);
	x86_condition_code_t              cc   = attr->condition_code;
	if (attr->attr.ins_permuted)
		cc = x86_negate_condition_code(cc);

	ir_node *flags = skip_Proj(get_irn_n(node, flags_pos));

	/* Permuted operands of a test instruction do not change the result. */
	if (is_ia32_Test(flags))
		return cc;

	if (is_ia32_Sahf(flags)) {
		flags = get_irn_n(flags, n_ia32_Sahf_val);
		if (!is_ia32_FucomFnstsw(flags) && !is_ia32_FucomppFnstsw(flags) && !is_ia32_FtstFnstsw(flags)) {
			ir_graph *const irg = get_irn_irg(node);
			inc_irg_visited(irg);
			flags = find_original_value(flags);
			assert(is_ia32_FucomFnstsw(flags) || is_ia32_FucomppFnstsw(flags) || is_ia32_FtstFnstsw(flags));
		}
	}

	ia32_attr_t const *const flags_attr = get_ia32_attr_const(flags);
	if (flags_attr->ins_permuted)
		cc = x86_invert_condition_code(cc);
	return cc;
}

/**
 * Emits an exception label for a given node.
 */
static void ia32_emit_exc_label(const ir_node *node)
{
	be_emit_string(be_gas_insn_label_prefix());
	be_emit_irprintf("%lu", get_ia32_exc_label_id(node));
}

static bool fallthrough_possible(const ir_node *block, const ir_node *target)
{
	return get_prev_block_sched(target) == block;
}

/**
 * Emits the jump sequence for a conditional jump (cmp + jmp_true + jmp_false)
 */
static void emit_ia32_Jcc(const ir_node *node)
{
	x86_condition_code_t cc = determine_final_cc(node, n_ia32_Jcc_eflags);

	/* get both Projs */
	ir_node const *proj_true   = get_Proj_for_pn(node, pn_ia32_Jcc_true);
	ir_node const *target_true = get_cfop_target_block(proj_true);
	ir_node const *proj_false  = get_Proj_for_pn(node, pn_ia32_Jcc_false);
	ir_node const *block       = get_nodes_block(node);
	if (fallthrough_possible(block, target_true)) {
		/* exchange both proj's so the second one can be omitted */
		const ir_node *t = proj_true;

		proj_true  = proj_false;
		proj_false = t;
		cc         = x86_negate_condition_code(cc);
	}
	const ir_node *target_false = get_cfop_target_block(proj_false);
	bool           fallthrough  = fallthrough_possible(block, target_false);
	/* if we can't have a fallthrough anyway, put the more likely case first */
	if (!fallthrough) {
		/* We would need execfreq for the concrete edge, but don't have it
		 * available here, so we use the block execfreq :-( */
		double freq_true  = get_block_execfreq(target_true);
		double freq_false = get_block_execfreq(target_false);
		if (freq_false > freq_true) {
			const ir_node *t = proj_true;
			proj_true  = proj_false;
			proj_false = t;
			cc         = x86_negate_condition_code(cc);
		}
	}

	bool need_parity_label = false;
	if (cc & x86_cc_float_parity_cases) {
		/* Some floating point comparisons require a test of the parity flag,
		 * which indicates that the result is unordered */
		if (cc & x86_cc_negated) {
			ia32_emitf(proj_true, "jp %L");
		} else {
			/* we need a local label if the false proj is a fallthrough
			 * as the falseblock might have no label emitted then */
			if (fallthrough) {
				need_parity_label = true;
				ia32_emitf(proj_false, "jp 1f");
			} else {
				ia32_emitf(proj_false, "jp %L");
			}
		}
	}
	ia32_emitf(proj_true, "j%PX %L", (int)cc);
	if (need_parity_label) {
		be_emit_cstring("1:\n");
		be_emit_write_line();
	}

	/* the second Proj might be a fallthrough */
	if (fallthrough) {
		if (be_options.verbose_asm)
			ia32_emitf(proj_false, "/* fallthrough to %L */");
	} else {
		ia32_emitf(proj_false, "jmp %L");
	}
}

/**
 * Emits an ia32 Setcc. This is mostly easy but some floating point compares
 * are tricky.
 */
static void emit_ia32_Setcc(const ir_node *node)
{
	const arch_register_t *dreg = arch_get_irn_register_out(node, pn_ia32_Setcc_res);

	x86_condition_code_t const cc = determine_final_cc(node, n_ia32_Setcc_eflags);
	if (cc & x86_cc_float_parity_cases) {
		if (cc & x86_cc_negated) {
			ia32_emitf(node, "set%PX %<R", (int)cc, dreg);
			ia32_emitf(node, "setp %>R", dreg);
			ia32_emitf(node, "orb %>R, %<R", dreg, dreg);
		} else {
			ia32_emitf(node, "set%PX %<R", (int)cc, dreg);
			ia32_emitf(node, "setnp %>R", dreg);
			ia32_emitf(node, "andb %>R, %<R", dreg, dreg);
		}