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remove bugs from float_fix

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Scott Beamer 2015-09-23 16:11:47 -07:00
parent 56daea793a
commit fbc6e695d3
1 changed files with 9 additions and 9 deletions
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14
csrc/float_fix.cc
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@ -22,7 +22,7 @@
// Returns the bits in x[high:low] in the lowest positions // Returns the bits in x[high:low] in the lowest positions
uint64_t BitRange(uint64_t x, int high, int low) { uint64_t BitRange(uint64_t x, int high, int low) {
int high_gap = 64 - high; int high_gap = 63 - high;
return x << high_gap >> (low + high_gap); return x << high_gap >> (low + high_gap);
} }
@ -56,27 +56,27 @@ bool NestedFloatPossible(uint64_t raw_input) {
// logic from berkeley-hardfloat/src/main/scala/recodedFloatNToFloatN.scala // logic from berkeley-hardfloat/src/main/scala/recodedFloatNToFloatN.scala
uint64_t UnrecodeFloatFromDouble(uint64_t raw_input) { uint64_t UnrecodeFloatFromDouble(uint64_t raw_input) {
uint64_t recoded_float = raw_input & 0x1ffffffff; // lower 33 bits uint64_t recoded_float = raw_input & 0x1ffffffff; // lower 33 bits
uint64_t sign = BitRange(recoded_float, 31, 31); uint64_t sign = BitRange(recoded_float, 32, 32);
uint64_t exp_in = BitRange(recoded_float, 30, 22); uint64_t exp_in = BitRange(recoded_float, 31, 23);
uint64_t sig_in = BitRange(recoded_float, 21, 0); uint64_t sig_in = BitRange(recoded_float, 22, 0);
bool is_high_subnormal_in = BitRange(exp_in, 6, 0) < 2; bool is_high_subnormal_in = BitRange(exp_in, 6, 0) < 2;
bool is_subnormal = (BitRange(exp_in, 8, 6) == 1) || bool is_subnormal = (BitRange(exp_in, 8, 6) == 1) ||
((BitRange(exp_in, 8, 7) == 1) && is_high_subnormal_in); ((BitRange(exp_in, 8, 7) == 1) && is_high_subnormal_in);
bool is_normal = ((BitRange(exp_in, 8, 7) == 1) && !is_high_subnormal_in) || bool is_normal = (BitRange(exp_in, 8, 7) == 1) && !is_high_subnormal_in ||
(BitRange(exp_in, 8, 7) == 2); (BitRange(exp_in, 8, 7) == 2);
bool is_special = BitRange(exp_in, 8, 7) == 3; bool is_special = BitRange(exp_in, 8, 7) == 3;
bool is_NaN = is_special && BitRange(exp_in, 6, 6); bool is_NaN = is_special && BitRange(exp_in, 6, 6);
uint64_t denorm_shift_dist = 2 - BitRange(exp_in, 4, 0); uint64_t denorm_shift_dist = 2 - BitRange(exp_in, 4, 0);
uint64_t subnormal_sig_out = (0x400000 | sig_in) >> denorm_shift_dist; uint64_t subnormal_sig_out = (0x400000 | sig_in) >> denorm_shift_dist;
uint64_t normal_exp_out = BitRange(exp_in, 7, 0) - 129; uint8_t normal_exp_out = BitRange(exp_in, 7, 0) - 129;
uint64_t exp_out = is_normal ? normal_exp_out : (is_special ? 255 : 0); uint64_t exp_out = is_normal ? normal_exp_out : (is_special ? 255 : 0);
uint64_t sig_out = is_normal || is_NaN ? sig_in : uint64_t sig_out = is_normal || is_NaN ? sig_in :
is_subnormal ? subnormal_sig_out : 0; is_subnormal ? subnormal_sig_out : 0;
uint64_t raw_output64 = (sign << 63) | (exp_out << 23) | sig_out; uint64_t raw_output64 = (sign << 31) | (exp_out << 23) | sig_out;
// assert((raw_output64 & 0xffffffff00000000) == uint64_t(0)); // assert((raw_output64 & 0xffffffff00000000) == uint64_t(0));
// If this is not a recoded float, this will return gibberish, however, // If this is not a recoded float, this will return gibberish, however,
// the output will not match spike and thus the replacement will not happen. // the output will not match spike and thus the replacement will not happen.