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Correct hex-float parsing

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Unblocks #495.
This commit is contained in:
Marc Tiehuis 2018-06-28 20:12:03 +12:00
parent 2fa588e81d
commit 4a35d7eeeb
2 changed files with 17 additions and 2 deletions
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11
src/tokenizer.cpp
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@ -357,12 +357,19 @@ static void end_float_token(Tokenize *t) {
// Mask the sign bit to 0 since always non-negative lex
const uint64_t exp_mask = 0xffffull << exp_shift;
if (shift >= 64) {
// must be special-cased to avoid undefined behavior on shift == 64
if (shift == 128) {
f_bits.repr[0] = 0;
f_bits.repr[1] = sig_bits[0];
} else if (shift == 0) {
f_bits.repr[0] = sig_bits[0];
f_bits.repr[1] = sig_bits[1];
} else if (shift >= 64) {
f_bits.repr[0] = 0;
f_bits.repr[1] = sig_bits[0] << (shift - 64);
} else {
f_bits.repr[0] = sig_bits[0] << shift;
f_bits.repr[1] = ((sig_bits[1] << shift) | (sig_bits[0] >> (64 - shift)));
f_bits.repr[1] = (sig_bits[1] << shift) | (sig_bits[0] >> (64 - shift));
}
f_bits.repr[1] &= ~exp_mask;

8
test/cases/math.zig
View File

@ -296,6 +296,14 @@ test "quad hex float literal parsing in range" {
const d = 0x1.edcbff8ad76ab5bf46463233214fp-435;
}
test "quad hex float literal parsing accurate" {
const a: f128 = 0x1.1111222233334444555566667777p+0;
// implied 1 is dropped, with an exponent of 0 (0x3fff) after biasing.
const expected: u128 = 0x3fff1111222233334444555566667777;
assert(@bitCast(u128, a) == expected);
}
test "hex float literal within range" {
const a = 0x1.0p16383;
const b = 0x0.1p16387;