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System: Add new 'Type 1B' fast boot

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This saves approximately 2 seconds of boot time, as it no longer copies
the shell from ROM to RAM. The actual byte reads only take in the order
of 75ms, but because the BIOS executes the memcpy() out of uncached ROM,
the repeated instruction fetches take it up to almost 2 seconds...

It would be faster to read it from the CD-ROM...
This commit is contained in:
Stenzek 2024-09-26 16:28:45 +10:00
parent d1eed89292
commit a26c3e5620
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1 changed files with 22 additions and 2 deletions
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24
src/core/bios.cpp
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@ -251,8 +251,28 @@ bool BIOS::PatchBIOSFastBoot(u8* image, u32 image_size, ImageInfo::FastBootPatch
u32 patch_offset;
if (type == ImageInfo::FastBootPatch::Type1)
{
patch_offset = 0x18000;
INFO_LOG("Using Type 1 fast boot patch at offset 0x{:08X}.", patch_offset);
// Try the "new" fast boot (Type 1B), where we patch the routine that copies/decompresses the shell.
// This saves approximately 2 seconds of fast boot time, because the memcpy() executes out of uncached ROM...
static constexpr const char* search_pattern = "e0 ff bd 27" // add sp, sp, -20
"1c 00 bf af" // sw ra, 0xc(sp)
"20 00 a4 af" // sw a0, 0x20(sp)
"?? ?? 05 3c" // lui a1, 0xbfc1
"?? ?? 06 3c" // lui a2, 0x6
"?? ?? c6 34" // ori a2, a2, 0x7ff0
"?? ?? a5 34" // ori a1, a1, 0x8000
"?? ?? ?? 0f"; // jal 0xbfc02b50
const std::optional<size_t> offset =
StringUtil::BytePatternSearch(std::span<const u8>(image, image_size), search_pattern);
if (offset.has_value())
{
patch_offset = static_cast<u32>(offset.value());
VERBOSE_LOG("Found Type 1B pattern at offset 0x{:08X}", patch_offset);
}
else
{
patch_offset = 0x18000;
INFO_LOG("Using Type 1A fast boot patch at offset 0x{:08X}.", patch_offset);
}
}
else if (type == ImageInfo::FastBootPatch::Type2)
{