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optimizations for float to float conversions

Signed-off-by: Christoph M. Wintersteiger <cwinter@microsoft.com>
This commit is contained in:
Christoph M. Wintersteiger 2013-11-14 16:56:13 +00:00
parent 4b0c00969c
commit 6a2f987fb7
2 changed files with 120 additions and 114 deletions

View file

@ -1825,146 +1825,150 @@ void fpa2bv_converter::mk_to_float(func_decl * f, unsigned num, expr * const * a
mk_triple(args[0], args[1], args[2], result);
}
else if (num == 2 && is_app(args[1]) && m_util.is_float(m.get_sort(args[1]))) {
// We also support float to float conversion
// We also support float to float conversion
sort * s = f->get_range();
expr_ref rm(m), x(m);
rm = args[0];
x = args[1];
expr_ref c1(m), c2(m), c3(m), c4(m), c5(m);
expr_ref v1(m), v2(m), v3(m), v4(m), v5(m), v6(m);
expr_ref one1(m);
one1 = m_bv_util.mk_numeral(1, 1);
expr_ref ninf(m), pinf(m);
mk_plus_inf(f, pinf);
mk_minus_inf(f, ninf);
// NaN -> NaN
mk_is_nan(x, c1);
mk_nan(f, v1);
// +0 -> +0
mk_is_pzero(x, c2);
mk_pzero(f, v2);
// -0 -> -0
mk_is_nzero(x, c3);
mk_nzero(f, v3);
// +oo -> +oo
mk_is_pinf(x, c4);
v4 = pinf;
// -oo -> -oo
mk_is_ninf(x, c5);
v5 = ninf;
// otherwise: the actual conversion with rounding.
sort * s = f->get_range();
expr_ref sgn(m), sig(m), exp(m), lz(m);
unpack(x, sgn, sig, exp, lz, true);
dbg_decouple("fpa2bv_to_float_x_sig", sig);
dbg_decouple("fpa2bv_to_float_x_exp", exp);
dbg_decouple("fpa2bv_to_float_lz", lz);
expr_ref res_sgn(m), res_sig(m), res_exp(m);
res_sgn = sgn;
unsigned from_sbits = m_util.get_sbits(m.get_sort(args[1]));
unsigned from_ebits = m_util.get_ebits(m.get_sort(args[1]));
unsigned to_sbits = m_util.get_sbits(s);
unsigned to_ebits = m_util.get_ebits(s);
SASSERT(m_bv_util.get_bv_size(sgn) == 1);
SASSERT(m_bv_util.get_bv_size(sig) == from_sbits);
SASSERT(m_bv_util.get_bv_size(exp) == from_ebits);
SASSERT(m_bv_util.get_bv_size(lz) == from_ebits);
if (from_sbits == to_sbits && from_ebits == to_ebits)
result = x;
else {
expr_ref c1(m), c2(m), c3(m), c4(m), c5(m);
expr_ref v1(m), v2(m), v3(m), v4(m), v5(m), v6(m);
expr_ref one1(m);
if (from_sbits < (to_sbits + 3))
{
// make sure that sig has at least to_sbits + 3
res_sig = m_bv_util.mk_concat(sig, m_bv_util.mk_numeral(0, to_sbits+3-from_sbits));
}
else if (from_sbits > (to_sbits + 3))
{
// collapse the extra bits into a sticky bit.
expr_ref sticky(m), low(m), high(m);
low = m_bv_util.mk_extract(from_sbits - to_sbits - 3, 0, sig);
high = m_bv_util.mk_extract(from_sbits - 1, from_sbits - to_sbits - 2, sig);
sticky = m.mk_app(m_bv_util.get_fid(), OP_BREDOR, low.get());
res_sig = m_bv_util.mk_concat(high, sticky);
}
else
res_sig = sig;
one1 = m_bv_util.mk_numeral(1, 1);
expr_ref ninf(m), pinf(m);
mk_plus_inf(f, pinf);
mk_minus_inf(f, ninf);
res_sig = m_bv_util.mk_zero_extend(1, res_sig); // extra zero in the front for the rounder.
unsigned sig_sz = m_bv_util.get_bv_size(res_sig);
SASSERT(sig_sz == to_sbits+4);
// NaN -> NaN
mk_is_nan(x, c1);
mk_nan(f, v1);
expr_ref exponent_overflow(m);
exponent_overflow = m.mk_false();
// +0 -> +0
mk_is_pzero(x, c2);
mk_pzero(f, v2);
if (from_ebits < (to_ebits + 2))
{
res_exp = m_bv_util.mk_sign_extend(to_ebits-from_ebits+2, exp);
}
else if (from_ebits > (to_ebits + 2))
{
expr_ref high(m), low(m), lows(m), high_red_or(m), high_red_and(m), h_or_eq(m), h_and_eq(m);
expr_ref no_ovf(m), zero1(m), s_is_one(m), s_is_zero(m);
high = m_bv_util.mk_extract(from_ebits - 1, to_ebits + 2, exp);
low = m_bv_util.mk_extract(to_ebits+1, 0, exp);
lows = m_bv_util.mk_extract(to_ebits+1, to_ebits+1, low);
// -0 -> -0
mk_is_nzero(x, c3);
mk_nzero(f, v3);
// +oo -> +oo
mk_is_pinf(x, c4);
v4 = pinf;
// -oo -> -oo
mk_is_ninf(x, c5);
v5 = ninf;
high_red_or = m.mk_app(m_bv_util.get_fid(), OP_BREDOR, high.get());
high_red_and = m.mk_app(m_bv_util.get_fid(), OP_BREDAND, high.get());
// otherwise: the actual conversion with rounding.
expr_ref sgn(m), sig(m), exp(m), lz(m);
unpack(x, sgn, sig, exp, lz, true);
zero1 = m_bv_util.mk_numeral(0, 1);
m_simp.mk_eq(high_red_and, one1, h_and_eq);
m_simp.mk_eq(high_red_or, zero1, h_or_eq);
m_simp.mk_eq(lows, zero1, s_is_zero);
m_simp.mk_eq(lows, one1, s_is_one);
dbg_decouple("fpa2bv_to_float_x_sig", sig);
dbg_decouple("fpa2bv_to_float_x_exp", exp);
dbg_decouple("fpa2bv_to_float_lz", lz);
expr_ref res_sgn(m), res_sig(m), res_exp(m);
res_sgn = sgn;
SASSERT(m_bv_util.get_bv_size(sgn) == 1);
SASSERT(m_bv_util.get_bv_size(sig) == from_sbits);
SASSERT(m_bv_util.get_bv_size(exp) == from_ebits);
SASSERT(m_bv_util.get_bv_size(lz) == from_ebits);
if (from_sbits < (to_sbits + 3))
{
// make sure that sig has at least to_sbits + 3
res_sig = m_bv_util.mk_concat(sig, m_bv_util.mk_numeral(0, to_sbits+3-from_sbits));
}
else if (from_sbits > (to_sbits + 3))
{
// collapse the extra bits into a sticky bit.
expr_ref sticky(m), low(m), high(m);
low = m_bv_util.mk_extract(from_sbits - to_sbits - 3, 0, sig);
high = m_bv_util.mk_extract(from_sbits - 1, from_sbits - to_sbits - 2, sig);
sticky = m.mk_app(m_bv_util.get_fid(), OP_BREDOR, low.get());
res_sig = m_bv_util.mk_concat(high, sticky);
}
else
res_sig = sig;
res_sig = m_bv_util.mk_zero_extend(1, res_sig); // extra zero in the front for the rounder.
unsigned sig_sz = m_bv_util.get_bv_size(res_sig);
SASSERT(sig_sz == to_sbits+4);
expr_ref exponent_overflow(m);
exponent_overflow = m.mk_false();
if (from_ebits < (to_ebits + 2))
{
res_exp = m_bv_util.mk_sign_extend(to_ebits-from_ebits+2, exp);
}
else if (from_ebits > (to_ebits + 2))
{
expr_ref high(m), low(m), lows(m), high_red_or(m), high_red_and(m), h_or_eq(m), h_and_eq(m);
expr_ref no_ovf(m), zero1(m), s_is_one(m), s_is_zero(m);
high = m_bv_util.mk_extract(from_ebits - 1, to_ebits + 2, exp);
low = m_bv_util.mk_extract(to_ebits+1, 0, exp);
lows = m_bv_util.mk_extract(to_ebits+1, to_ebits+1, low);
expr_ref c2(m);
m_simp.mk_ite(h_or_eq, s_is_one, m.mk_false(), c2);
m_simp.mk_ite(h_and_eq, s_is_zero, c2, exponent_overflow);
high_red_or = m.mk_app(m_bv_util.get_fid(), OP_BREDOR, high.get());
high_red_and = m.mk_app(m_bv_util.get_fid(), OP_BREDAND, high.get());
zero1 = m_bv_util.mk_numeral(0, 1);
m_simp.mk_eq(high_red_and, one1, h_and_eq);
m_simp.mk_eq(high_red_or, zero1, h_or_eq);
m_simp.mk_eq(lows, zero1, s_is_zero);
m_simp.mk_eq(lows, one1, s_is_one);
// Note: Upon overflow, we _could_ try to shift the significand around...
expr_ref c2(m);
m_simp.mk_ite(h_or_eq, s_is_one, m.mk_false(), c2);
m_simp.mk_ite(h_and_eq, s_is_zero, c2, exponent_overflow);
// Note: Upon overflow, we _could_ try to shift the significand around...
res_exp = low;
}
else
res_exp = exp;
res_exp = low;
}
else
res_exp = exp;
// subtract lz for subnormal numbers.
expr_ref lz_ext(m);
lz_ext = m_bv_util.mk_zero_extend(to_ebits-from_ebits+2, lz);
res_exp = m_bv_util.mk_bv_sub(res_exp, lz_ext);
SASSERT(m_bv_util.get_bv_size(res_exp) == to_ebits+2);
// subtract lz for subnormal numbers.
expr_ref lz_ext(m);
lz_ext = m_bv_util.mk_zero_extend(to_ebits-from_ebits+2, lz);
res_exp = m_bv_util.mk_bv_sub(res_exp, lz_ext);
SASSERT(m_bv_util.get_bv_size(res_exp) == to_ebits+2);
dbg_decouple("fpa2bv_to_float_res_sig", res_sig);
dbg_decouple("fpa2bv_to_float_res_exp", res_exp);
dbg_decouple("fpa2bv_to_float_res_sig", res_sig);
dbg_decouple("fpa2bv_to_float_res_exp", res_exp);
expr_ref rounded(m);
round(s, rm, res_sgn, res_sig, res_exp, rounded);
expr_ref rounded(m);
round(s, rm, res_sgn, res_sig, res_exp, rounded);
expr_ref is_neg(m), sig_inf(m);
m_simp.mk_eq(sgn, one1, is_neg);
mk_ite(is_neg, ninf, pinf, sig_inf);
expr_ref is_neg(m), sig_inf(m);
m_simp.mk_eq(sgn, one1, is_neg);
mk_ite(is_neg, ninf, pinf, sig_inf);
dbg_decouple("fpa2bv_to_float_exp_ovf", exponent_overflow);
dbg_decouple("fpa2bv_to_float_exp_ovf", exponent_overflow);
mk_ite(exponent_overflow, sig_inf, rounded, v6);
mk_ite(exponent_overflow, sig_inf, rounded, v6);
// And finally, we tie them together.
mk_ite(c5, v5, v6, result);
mk_ite(c4, v4, result, result);
mk_ite(c3, v3, result, result);
mk_ite(c2, v2, result, result);
mk_ite(c1, v1, result, result);
// And finally, we tie them together.
mk_ite(c5, v5, v6, result);
mk_ite(c4, v4, result, result);
mk_ite(c3, v3, result, result);
mk_ite(c2, v2, result, result);
mk_ite(c1, v1, result, result);
}
}
else {
// .. other than that, we only support rationals for asFloat

View file

@ -360,6 +360,8 @@ void mpf_manager::set(mpf & o, unsigned ebits, unsigned sbits, mpf_rounding_mode
mk_inf(ebits, sbits, x.sign, o);
else if (is_zero(x))
mk_zero(ebits, sbits, x.sign, o);
else if (x.ebits == ebits && x.sbits == sbits)
set(o, x);
else {
set(o, x);
unpack(o, true);