Xargon/Duckstation
1
0
Fork 0
mirror of https://github.com/RetroDECK/Duckstation.git synced 2024-11-25 15:15:40 +00:00
Code Issues Actions Packages Projects Releases Wiki Activity

GTE: Use intrinsic CountLeadingZeros()

Browse source 
Super tiny micro-optimization.
This commit is contained in:
Connor McLaughlin 2020-04-26 18:33:35 +10:00
parent 28a022547f
commit d1e841f55d
1 changed files with 7 additions and 33 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

40
src/core/gte.cpp
View file

@ -1,41 +1,15 @@
#include "gte.h"
#include "common/bitutils.h"
#include <algorithm>
#include <array>
// TODO: Optimize, intrinsics?
static inline constexpr u32 CountLeadingZeros(u16 value)
ALWAYS_INLINE u32 CountLeadingBits(u32 value)
{
u32 count = 0;
for (u32 i = 0; i < 16 && (value & UINT16_C(0x8000)) == 0; i++)
{
count++;
value <<= 1;
}
// if top-most bit is set, we want to count ones not zeros
if (value & UINT32_C(0x80000000))
value ^= UINT32_C(0xFFFFFFFF);
return count;
}
static inline constexpr u32 CountLeadingBits(u32 value)
{
u32 count = 0;
if ((value & UINT32_C(0x80000000)) != 0)
{
for (u32 i = 0; i < 32 && ((value & UINT32_C(0x80000000)) != 0); i++)
{
count++;
value <<= 1;
}
}
else
{
for (u32 i = 0; i < 32 && (value & UINT32_C(0x80000000)) == 0; i++)
{
count++;
value <<= 1;
}
}
return count;
return (value == 0u) ? 32 : CountLeadingZeros(value);
}
namespace GTE {
@ -365,7 +339,7 @@ u32 Core::UNRDivide(u32 lhs, u32 rhs)
return 0x1FFFF;
}
const u32 shift = CountLeadingZeros(static_cast<u16>(rhs));
const u32 shift = (rhs == 0) ? 16 : CountLeadingZeros(static_cast<u16>(rhs));
lhs <<= shift;
rhs <<= shift;