piwalker/dolphin
1
0
Fork 0
mirror of https://github.com/dolphin-emu/dolphin.git synced 2024-11-14 21:37:52 -07:00
Code Issues Actions Packages Projects Releases Wiki Activity

Arm64Emitter: Simplify LogicalImm further

Browse Source 
h/t @dougallj
This commit is contained in:
Merry 2022-07-07 23:04:56 +01:00
parent 20ccc38f0f
commit 0d947ed6fe
1 changed files with 12 additions and 26 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

38
Source/Core/Common/Arm64Emitter.h
View File

@ -538,38 +538,26 @@ struct LogicalImm
value |= value >> kWRegSizeInBits;
}
// Identify the smallest repeating element size.
size_t esize = 0;
for (size_t i = 64; i > 1; i /= 2)
{
if (value != Common::RotateRight(value, i / 2))
{
esize = i;
break;
}
}
if (value == 0 || (~value) == 0 || esize == 0 || esize > width)
if (value == 0 || (~value) == 0)
{
valid = false;
return;
}
const u64 emask = (~u64{0}) >> (64 - esize);
// Extract the repeating element, rotating it such that the LSB is 1:
// Normalize value, rotating it such that the LSB is 1:
// If LSB is already one, we mask away the trailing sequence of ones and
// pick the next sequence of ones. This ensures we get a complete element
// that has not been cut-in-half due to rotation across the word boundary.
const u64 inverse_mask_from_trailing_ones = ~value | (value + 1);
const size_t rotation = Common::LeastSignificantSetBit(value & inverse_mask_from_trailing_ones);
const u64 element = Common::RotateRight(value, rotation) & emask;
const size_t rotation = Common::CountTrailingZeros(value & (value + 1));
const u64 normalized = Common::RotateRight(value, rotation);
// In order to be a valid element of an AArch64 logical immediate, it must
// be contiguous.
const size_t element_size = Common::CountTrailingZeros(normalized & (normalized + 1));
const size_t ones = Common::CountTrailingZeros(~normalized);
if (!Common::IsValidLowMask(element))
// Check the value is repeating; also ensures element size is a power of two.
if (Common::RotateRight(value, element_size) != value)
{
valid = false;
return;
@ -579,11 +567,9 @@ struct LogicalImm
// it gives both the number of set bits and the length of the repeated
// segment.
const size_t tmp = ((~esize + 1) << 1) | (Common::CountSetBits(element) - 1);
r = static_cast<u8>((esize - rotation) & (esize - 1));
s = tmp & 0x3f;
n = (~tmp >> 6) & 1;
r = static_cast<u8>((element_size - rotation) & (element_size - 1));
s = (((~element_size + 1) << 1) | (ones - 1)) & 0x3f;
n = (element_size >> 6) & 1;
valid = true;
}