| ... | ... | @@ -202,18 +202,19 @@ pub fn parseHexFloat(comptime T: type, s: []const u8) !T { |
| 202 | 202 | exponent += 1; |
| 203 | 203 | } |
| 204 | 204 | |
| 205 | | // There are two cases to handle: |
| 206 | | // - We've truncated more than 0.5ULP (R=S=1), increase the mantissa. |
| 207 | | // - We've truncated exactly 0.5ULP (R=1 S=0), increase the mantissa if the |
| 208 | | // result is odd (G=1). |
| 209 | | // The two checks can be neatly folded as follows. |
| 210 | | mantissa |= @boolToInt(mantissa & 0b100 != 0); |
| 211 | | mantissa += 1; |
| 212 | | |
| 205 | // Whenever the guard bit is one (G=1) and: |
| 206 | // - we've truncated more than 0.5ULP (R=S=1) |
| 207 | // - we've truncated exactly 0.5ULP (R=1 S=0) |
| 208 | // Were are going to increase the mantissa (round up) |
| 209 | const guard_bit_and_half_or_more = (mantissa & 0b110) == 0b110; |
| 213 | 210 | mantissa >>= 2; |
| 214 | 211 | exponent += 2; |
| 215 | 212 | |
| 216 | | if (mantissa & (1 << (mantissa_bits + 1)) != 0) { |
| 213 | if (guard_bit_and_half_or_more) { |
| 214 | mantissa += 1; |
| 215 | } |
| 216 | |
| 217 | if (mantissa == (1 << (mantissa_bits + 1))) { |
| 217 | 218 | // Renormalize, if the exponent overflows we'll catch that below. |
| 218 | 219 | mantissa >>= 1; |
| 219 | 220 | exponent += 1; |
| ... | ... | @@ -338,6 +339,7 @@ test "f128" { |
| 338 | 339 | // // Min denormalized value. |
| 339 | 340 | .{ .s = "0x1p-16494", .v = math.f128_true_min }, |
| 340 | 341 | .{ .s = "-0x1p-16494", .v = -math.f128_true_min }, |
| 342 | .{ .s = "0x1.edcb34a235253948765432134674fp-1", .v = 0x1.edcb34a235253948765432134674fp-1 }, |
| 341 | 343 | }; |
| 342 | 344 | |
| 343 | 345 | for (cases) |case| { |
Andrew Kelley <andrew@ziglang.org> 2022-01-31 22:59:49-05:00
lib