Suyu/dynarmic
1
0
Fork 0
mirror of https://git.suyu.dev/suyu/dynarmic.git synced 2026-01-05 22:18:16 +01:00
Code Issues Projects Releases Packages Wiki Activity Actions

ir: Add opcodes for unsigned reciprocal estimate

Browse source
This commit is contained in:
Lioncash 2018-09-07 22:45:00 -04:00 • committed by MerryMage
parent d46dea136f
commit af83360f89
8 changed files with 71 additions and 29 deletions
Download patch file Download diff file Expand all files Collapse all files

27
src/common/fp/op/FPRecipEstimate.cpp
View file

@ -4,7 +4,6 @@
* General Public License version 2 or any later version.
*/
#include <array>
#include <tuple>
#include "common/assert.h"
@ -16,32 +15,10 @@
#include "common/fp/process_exception.h"
#include "common/fp/process_nan.h"
#include "common/fp/unpacked.h"
#include "common/math_util.h"
namespace Dynarmic::FP {
constexpr u64 lut_offset = 256;
/// Input is a u0.9 fixed point number. Only values in [0.5, 1.0) are valid.
/// Output is a u0.8 fixed point number, with an implied 1 prefixed.
/// i.e.: The output is a value in [1.0, 2.0).
static u8 RecipEstimate(u64 a) {
using LUT = std::array<u8, 256>;
static const LUT lut = [] {
LUT result{};
for (u64 i = 0; i < result.size(); i++) {
u64 a = i + lut_offset;
a = a * 2 + 1;
u64 b = (1u << 19) / a;
result[i] = static_cast<u8>((b + 1) / 2);
}
return result;
}();
return lut[a - lut_offset];
}
template<typename FPT>
FPT FPRecipEstimate(FPT op, FPCR fpcr, FPSR& fpsr) {
FPType type;
@ -92,7 +69,7 @@ FPT FPRecipEstimate(FPT op, FPCR fpcr, FPSR& fpsr) {
}
const u64 scaled = value.mantissa >> (normalized_point_position - 8);
u64 estimate = static_cast<u64>(RecipEstimate(scaled)) << (FPInfo<FPT>::explicit_mantissa_width - 8);
u64 estimate = static_cast<u64>(Common::RecipEstimate(scaled)) << (FPInfo<FPT>::explicit_mantissa_width - 8);
int result_exponent = -(value.exponent + 1);
if (result_exponent < FPInfo<FPT>::exponent_min) {
switch (result_exponent) {