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Simplifying the justification.

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This commit is contained in:
Daniel Lemire 2022-11-18 15:38:21 -05:00
parent 8b7a55a03c
commit 003a983188
1 changed files with 5 additions and 12 deletions
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17
include/fast_float/parse_number.h
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@ -81,7 +81,7 @@ fastfloat_really_inline bool rounds_to_nearest() noexcept {
// There might be other ways to prevent compile-time optimizations (e.g., asm).
// The value does not need to be std::numeric_limits<float>::min(), any small
// value so that 1 + x should round to 1 would do (after accounting for excess
// precision, as in 387).
// precision, as in 387 instructions).
static volatile float fmin = std::numeric_limits<float>::min();
float fmini = fmin; // we copy it so that it gets loaded at most once.
//
@ -90,19 +90,12 @@ fastfloat_really_inline bool rounds_to_nearest() noexcept {
// fmin + 1.0f == 1.0f - fmin.
//
// FE_UPWARD:
// fmin + 1.0f = 0x1.00001 (1.00001)
// 1.0f - fmin = 0x1 (1)
// fmin + 1.0f > 1
// 1.0f - fmin == 1
//
// FE_DOWNWARD or FE_TOWARDZERO:
// fmin + 1.0f = 0x1 (1)
// 1.0f - fmin = 0x0.999999 (0.999999)
//
// fmin + 1.0f = 0x1 (1)
// 1.0f - fmin = 0x0.999999 (0.999999)
//
// FE_TONEAREST:
// fmin + 1.0f = 0x1 (1)
// 1.0f - fmin = 0x1 (1)
// fmin + 1.0f == 1
// 1.0f - fmin < 1
//
// Note: This may fail to be accurate if fast-math has been
// enabled, as rounding conventions may not apply.