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Misc: use native crc32 instructions on SEE 4.2 targets. (#8169, #4933)

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Teselka
2024-11-20 13:10:36 +02:00
committed by ocornut
parent e6dd8f626a
commit 326dc95f9c
3 changed files with 23 additions and 0 deletions
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18
imgui.cpp
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@@ -2150,6 +2150,7 @@ void ImFormatStringToTempBufferV(const char** out_buf, const char** out_buf_end,
}
}
#ifndef IMGUI_ENABLE_SSE4_2
// CRC32 needs a 1KB lookup table (not cache friendly)
// Although the code to generate the table is simple and shorter than the table itself, using a const table allows us to easily:
// - avoid an unnecessary branch/memory tap, - keep the ImHashXXX functions usable by static constructors, - make it thread-safe.
@@ -2173,6 +2174,7 @@ static const ImU32 GCrc32LookupTable[256] =
0xE330A81A,0x115B2B19,0x020BD8ED,0xF0605BEE,0x24AA3F05,0xD6C1BC06,0xC5914FF2,0x37FACCF1,0x69E9F0D5,0x9B8273D6,0x88D28022,0x7AB90321,0xAE7367CA,0x5C18E4C9,0x4F48173D,0xBD23943E,
0xF36E6F75,0x0105EC76,0x12551F82,0xE03E9C81,0x34F4F86A,0xC69F7B69,0xD5CF889D,0x27A40B9E,0x79B737BA,0x8BDCB4B9,0x988C474D,0x6AE7C44E,0xBE2DA0A5,0x4C4623A6,0x5F16D052,0xAD7D5351
};
#endif
// Known size hash
// It is ok to call ImHashData on a string with known length but the ### operator won't be supported.
@@ -2181,10 +2183,16 @@ ImGuiID ImHashData(const void* data_p, size_t data_size, ImGuiID seed)
{
ImU32 crc = ~seed;
const unsigned char* data = (const unsigned char*)data_p;
#ifndef IMGUI_ENABLE_SSE4_2
const ImU32* crc32_lut = GCrc32LookupTable;
while (data_size-- != 0)
crc = (crc >> 8) ^ crc32_lut[(crc & 0xFF) ^ *data++];
return ~crc;
#else
while (data_size-- != 0)
crc = _mm_crc32_u8(crc, *data++);
return ~crc;
#endif
}
// Zero-terminated string hash, with support for ### to reset back to seed value
@@ -2198,7 +2206,9 @@ ImGuiID ImHashStr(const char* data_p, size_t data_size, ImGuiID seed)
seed = ~seed;
ImU32 crc = seed;
const unsigned char* data = (const unsigned char*)data_p;
#ifndef IMGUI_ENABLE_SSE4_2
const ImU32* crc32_lut = GCrc32LookupTable;
#endif
if (data_size != 0)
{
while (data_size-- != 0)
@@ -2206,7 +2216,11 @@ ImGuiID ImHashStr(const char* data_p, size_t data_size, ImGuiID seed)
unsigned char c = *data++;
if (c == '#' && data_size >= 2 && data[0] == '#' && data[1] == '#')
crc = seed;
#ifndef IMGUI_ENABLE_SSE4_2
crc = (crc >> 8) ^ crc32_lut[(crc & 0xFF) ^ c];
#else
crc = _mm_crc32_u8(crc, c);
#endif
}
}
else
@@ -2215,7 +2229,11 @@ ImGuiID ImHashStr(const char* data_p, size_t data_size, ImGuiID seed)
{
if (c == '#' && data[0] == '#' && data[1] == '#')
crc = seed;
#ifndef IMGUI_ENABLE_SSE4_2
crc = (crc >> 8) ^ crc32_lut[(crc & 0xFF) ^ c];
#else
crc = _mm_crc32_u8(crc, c);
#endif
}
}
return ~crc;