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AK: Add trunc and rint to AK/Math.h

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These are useful in some algorithms, which require specific rounding.
This commit is contained in:
Hediadyoin1 2023-05-11 12:09:47 +02:00 committed by Andreas Kling
parent 6573ace8f1
commit 594369121a
Notes: sideshowbarker 2024-07-17 04:03:27 +09:00 
Author: https://github.com/Hendiadyoin1
Commit: https://github.com/SerenityOS/serenity/commit/594369121a
Pull-request: https://github.com/SerenityOS/serenity/pull/18998
Reviewed-by: https://github.com/kleinesfilmroellchen ✅
Reviewed-by: https://github.com/linusg ✅
1 changed files with 64 additions and 0 deletions
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64
AK/Math.h
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@ -85,6 +85,7 @@ namespace Rounding {
template<FloatingPoint T>
constexpr T ceil(T num)
{
// FIXME: SSE4.1 rounds[sd] num, res, 0b110
if (is_constant_evaluated()) {
if (num < NumericLimits<i64>::min() || num > NumericLimits<i64>::max())
return num;
@ -102,6 +103,7 @@ constexpr T ceil(T num)
template<FloatingPoint T>
constexpr T floor(T num)
{
// FIXME: SSE4.1 rounds[sd] num, res, 0b101
if (is_constant_evaluated()) {
if (num < NumericLimits<i64>::min() || num > NumericLimits<i64>::max())
return num;
@ -116,6 +118,66 @@ constexpr T floor(T num)
#endif
}
template<FloatingPoint T>
constexpr T trunc(T num)
{
#if ARCH(AARCH64)
if (is_constant_evaluated()) {
if (num < NumericLimits<i64>::min() || num > NumericLimits<i64>::max())
return num;
return static_cast<T>(static_cast<i64>(num));
}
AARCH64_INSTRUCTION(frintz, num);
#endif
// FIXME: Use dedicated instruction in the non constexpr case
// SSE4.1: rounds[sd] %num, %res, 0b111
if (num < NumericLimits<i64>::min() || num > NumericLimits<i64>::max())
return num;
return static_cast<T>(static_cast<i64>(num));
}
template<FloatingPoint T>
constexpr T rint(T x)
{
CONSTEXPR_STATE(rint, x);
// Note: This does break tie to even
// But the behavior of frndint/rounds[ds]/frintx can be configured
// through the floating point control registers.
// FIXME: We should decide if we rename this to allow us to get away from
// the configurability "burden" rint has
// this would make us use `rounds[sd] %num, %res, 0b100`
// and `frintn` respectively,
// no such guaranteed round exists for x87 `frndint`
#if ARCH(X86_64)
# ifdef __SSE4_1__
if constexpr (IsSame<T, double>) {
T r;
asm(
"roundsd %1, %0"
: "=x"(r)
: "x"(x));
return r;
}
if constexpr (IsSame<T, float>) {
T r;
asm(
"roundss %1, %0"
: "=x"(r)
: "x"(x));
return r;
}
# else
asm(
"frndint"
: "+t"(x));
return x;
# endif
#elif ARCH(AARCH64)
AARCH64_INSTRUCTION(frintx, x);
#endif
TODO();
}
template<FloatingPoint T>
constexpr T round(T x)
{
@ -286,8 +348,10 @@ ALWAYS_INLINE I round_to(P value)
using Rounding::ceil;
using Rounding::floor;
using Rounding::rint;
using Rounding::round;
using Rounding::round_to;
using Rounding::trunc;
namespace Division {
template<FloatingPoint T>