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FPA: added to_fp_unsigned

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Signed-off-by: Christoph M. Wintersteiger <cwinter@microsoft.com>
This commit is contained in:
Christoph M. Wintersteiger 2014-12-28 15:26:52 +00:00
parent 1aae53f48c
commit 4d1f71775d
2 changed files with 134 additions and 9 deletions
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140
src/ast/fpa/fpa2bv_converter.cpp
View file

@ -2171,11 +2171,6 @@ void fpa2bv_converter::mk_to_fp_signed(func_decl * f, unsigned num, expr * const
unsigned bv_sz = m_bv_util.get_bv_size(x);
SASSERT(m_bv_util.get_bv_size(rm) == 3);
//if (bv_sz < f_sz) {
// x = m_bv_util.mk_zero_extend(f_sz - bv_sz, x);
// bv_sz = f_sz;
//}
expr_ref bv0_1(m), bv1_1(m), bv0_sz(m), bv1_sz(m);
bv0_1 = m_bv_util.mk_numeral(0, 1);
bv1_1 = m_bv_util.mk_numeral(1, 1);
@ -2245,12 +2240,14 @@ void fpa2bv_converter::mk_to_fp_signed(func_decl * f, unsigned num, expr * const
unsigned exp_sz = ebits + 2; // (+2 for rounder)
exp_2 = m_bv_util.mk_extract(exp_sz - 1, 0, s_exp);
// the remaining bits are 0 if ebits is large enough.
exp_too_large = m.mk_false(); // This is always in range.
exp_too_large = m.mk_false();
// The exponent is at most bv_sz, i.e., we need ld(bv_sz)+1 ebits.
// exp < bv_sz (+sign bit which is [0])
unsigned exp_worst_case_sz = (unsigned)((log((double)bv_sz) / log((double)2)) + 1.0);
TRACE("fpa2bv_to_fp_signed", tout << "exp worst case sz: " << exp_worst_case_sz << std::endl;);
if (exp_sz < exp_worst_case_sz) {
// exp_sz < exp_worst_case_sz and exp >= 0.
// Take the maximum legal exponent; this
@ -2266,7 +2263,7 @@ void fpa2bv_converter::mk_to_fp_signed(func_decl * f, unsigned num, expr * const
sig_4 = m.mk_ite(exp_too_large, m_bv_util.mk_numeral(0, sig_sz), sig_4);
exp_2 = m.mk_ite(exp_too_large, max_exp, exp_2);
}
dbg_decouple("fpa2bv_to_fp_signed_exp_too_large", exp_too_large);
dbg_decouple("fpa2bv_to_fp_signed_exp_too_large", exp_too_large);
expr_ref sgn(m), sig(m), exp(m);
sgn = is_neg_bit;
@ -2290,7 +2287,134 @@ void fpa2bv_converter::mk_to_fp_unsigned(func_decl * f, unsigned num, expr * con
TRACE("fpa2bv_to_fp_unsigned", for (unsigned i = 0; i < num; i++)
tout << "arg" << i << " = " << mk_ismt2_pp(args[i], m) << std::endl;);
NOT_IMPLEMENTED_YET();
// This is a conversion from unsigned bitvector to float:
// ((_ to_fp_unsigned eb sb) RoundingMode(_ BitVec m) (_ FloatingPoint eb sb))
// Semantics:
// Let b in[[(_ BitVec m)]] and let n be the unsigned integer represented by b.
// [[(_ to_fp_unsigned eb sb)]](r, x) = +infinity if n is too large to be
// represented as a finite number of[[(_ FloatingPoint eb sb)]];
// [[(_ to_fp_unsigned eb sb)]](r, x) = y otherwise, where y is the finite number
// such that[[fp.to_real]](y) is closest to n according to rounding mode r.
SASSERT(num == 2);
SASSERT(m_util.is_float(f->get_range()));
SASSERT(m_bv_util.is_bv(args[0]));
SASSERT(m_bv_util.is_bv(args[1]));
expr_ref rm(m), x(m);
rm = args[0];
x = args[1];
dbg_decouple("fpa2bv_to_fp_unsigned_x", x);
unsigned ebits = m_util.get_ebits(f->get_range());
unsigned sbits = m_util.get_sbits(f->get_range());
unsigned f_sz = sbits + ebits;
unsigned bv_sz = m_bv_util.get_bv_size(x);
SASSERT(m_bv_util.get_bv_size(rm) == 3);
expr_ref bv0_1(m), bv1_1(m), bv0_sz(m), bv1_sz(m);
bv0_1 = m_bv_util.mk_numeral(0, 1);
bv1_1 = m_bv_util.mk_numeral(1, 1);
bv0_sz = m_bv_util.mk_numeral(0, bv_sz);
bv1_sz = m_bv_util.mk_numeral(1, bv_sz);
expr_ref is_zero(m), nzero(m), pzero(m), ninf(m), pinf(m);
is_zero = m.mk_eq(x, bv0_sz);
mk_nzero(f, nzero);
mk_pzero(f, pzero);
mk_ninf(f, ninf);
mk_pinf(f, pinf);
// Special case: x == 0 -> p/n zero
expr_ref c1(m), v1(m), rm_is_to_neg(m);
c1 = is_zero;
mk_is_rm(rm, BV_RM_TO_NEGATIVE, rm_is_to_neg);
mk_ite(rm_is_to_neg, nzero, pzero, v1);
// Special case: x != 0
expr_ref exp_too_large(m), sig_4(m), exp_2(m);
// x is [bv_sz-1] . [bv_sz-2 ... 0] * 2^(bv_sz-1)
// bv_sz-1 is the "1.0" bit for the rounder.
expr_ref lz(m), e_bv_sz(m), e_rest_sz(m);
mk_leading_zeros(x, bv_sz, lz);
e_bv_sz = m_bv_util.mk_numeral(bv_sz, bv_sz);
e_rest_sz = m_bv_util.mk_bv_sub(e_bv_sz, lz);
SASSERT(m_bv_util.get_bv_size(lz) == m_bv_util.get_bv_size(e_bv_sz));
dbg_decouple("fpa2bv_to_fp_unsigned_lz", lz);
expr_ref shifted_sig(m);
shifted_sig = m_bv_util.mk_bv_shl(x, lz);
expr_ref sticky(m);
// shifted_sig is [bv_sz-1] . [bv_sz-2 ... 0] * 2^(bv_sz-1) * 2^(-lz)
unsigned sig_sz = sbits + 4; // we want extra rounding bits.
if (sig_sz <= bv_sz) {
expr_ref sig_rest(m);
sig_4 = m_bv_util.mk_extract(bv_sz - 1, bv_sz - sig_sz + 1, shifted_sig); // one short
sig_rest = m_bv_util.mk_extract(bv_sz - sig_sz, 0, shifted_sig);
sticky = m.mk_app(m_bv_util.get_fid(), OP_BREDOR, sig_rest);
sig_4 = m_bv_util.mk_concat(sig_4, sticky);
}
else {
unsigned extra_bits = sig_sz - bv_sz;
expr_ref extra_zeros(m);
extra_zeros = m_bv_util.mk_numeral(0, extra_bits);
sig_4 = m_bv_util.mk_concat(shifted_sig, extra_zeros);
lz = m_bv_util.mk_bv_add(m_bv_util.mk_concat(extra_zeros, lz),
m_bv_util.mk_numeral(extra_bits, sig_sz));
bv_sz = bv_sz + extra_bits;
SASSERT(is_well_sorted(m, lz));
}
SASSERT(m_bv_util.get_bv_size(sig_4) == sig_sz);
expr_ref s_exp(m), exp_rest(m);
s_exp = m_bv_util.mk_bv_sub(m_bv_util.mk_numeral(bv_sz - 2, bv_sz), lz);
// s_exp = (bv_sz-2) + (-lz) signed
SASSERT(m_bv_util.get_bv_size(s_exp) == bv_sz);
unsigned exp_sz = ebits + 2; // (+2 for rounder)
exp_2 = m_bv_util.mk_extract(exp_sz - 1, 0, s_exp);
// the remaining bits are 0 if ebits is large enough.
exp_too_large = m.mk_false(); // This is always in range.
// The exponent is at most bv_sz, i.e., we need ld(bv_sz)+1 ebits.
// exp < bv_sz (+sign bit which is [0])
unsigned exp_worst_case_sz = (unsigned)((log((double)bv_sz) / log((double)2)) + 1.0);
if (exp_sz < exp_worst_case_sz) {
// exp_sz < exp_worst_case_sz and exp >= 0.
// Take the maximum legal exponent; this
// allows us to keep the most precision.
expr_ref max_exp(m), max_exp_bvsz(m);
mk_max_exp(exp_sz, max_exp);
max_exp_bvsz = m_bv_util.mk_zero_extend(bv_sz - exp_sz, max_exp);
exp_too_large = m_bv_util.mk_ule(m_bv_util.mk_bv_add(
max_exp_bvsz,
m_bv_util.mk_numeral(1, bv_sz)),
s_exp);
sig_4 = m.mk_ite(exp_too_large, m_bv_util.mk_numeral(0, sig_sz), sig_4);
exp_2 = m.mk_ite(exp_too_large, max_exp, exp_2);
}
dbg_decouple("fpa2bv_to_fp_unsigned_exp_too_large", exp_too_large);
expr_ref sgn(m), sig(m), exp(m);
sgn = bv0_1;
sig = sig_4;
exp = exp_2;
dbg_decouple("fpa2bv_to_fp_unsigned_sgn", sgn);
dbg_decouple("fpa2bv_to_fp_unsigned_sig", sig);
dbg_decouple("fpa2bv_to_fp_unsigned_exp", exp);
SASSERT(m_bv_util.get_bv_size(sig) == sbits + 4);
SASSERT(m_bv_util.get_bv_size(exp) == ebits + 2);
expr_ref v2(m);
round(f->get_range(), rm, sgn, sig, exp, v2);
mk_ite(c1, v1, v2, result);
}
void fpa2bv_converter::mk_to_ieee_bv(func_decl * f, unsigned num, expr * const * args, expr_ref & result) {

3
src/ast/fpa/fpa2bv_rewriter.h
View file

@ -144,7 +144,8 @@ struct fpa2bv_rewriter_cfg : public default_rewriter_cfg {
case OP_FLOAT_IS_SUBNORMAL: m_conv.mk_is_subnormal(f, num, args, result); return BR_DONE;
case OP_FLOAT_IS_POSITIVE: m_conv.mk_is_positive(f, num, args, result); return BR_DONE;
case OP_FLOAT_IS_NEGATIVE: m_conv.mk_is_negative(f, num, args, result); return BR_DONE;
case OP_FLOAT_TO_FP: m_conv.mk_to_fp(f, num, args, result); return BR_DONE;
case OP_FLOAT_TO_FP: m_conv.mk_to_fp(f, num, args, result); return BR_DONE;
case OP_FLOAT_TO_FP_UNSIGNED: m_conv.mk_to_fp_unsigned(f, num, args, result); return BR_DONE;
case OP_FLOAT_FP: m_conv.mk_fp(f, num, args, result); return BR_DONE;
case OP_FLOAT_TO_UBV: m_conv.mk_to_ubv(f, num, args, result); return BR_DONE;
case OP_FLOAT_TO_SBV: m_conv.mk_to_sbv(f, num, args, result); return BR_DONE;