We can optimize `bloader.c` by utilizing Magic‐1's assembly instructions - retrotruestory/M1DEV GitHub Wiki
Yes, we can optimize bloader.c
by utilizing Magic-1's assembly instructions directly. Here's an example approach:
// Fast copy operation using memcopy instruction
void fast_copy(void *dst, const void *src, int count) {
__asm__(
"copy c,%0\n\t" // Load count into C register
"copy b,%1\n\t" // Load source address into B
"copy a,%2\n\t" // Load destination address into A
"memcopy" // Execute memcopy instruction
:
: "r"(count), "r"(src), "r"(dst)
: "a", "b", "c"
);
}
// Optimized sector read using ldcode/stcode
void read_sector(unsigned int sector, void *buffer) {
__asm__(
"ld.16 a,%0\n\t" // Load sector number
"copy b,%1\n\t" // Load buffer address
"ldcode.16 a,(b)" // Read using code space access
:
: "r"(sector), "r"(buffer)
: "a", "b"
);
}
// Fast boot image load using block operations
void load_boot_image(int slot) {
__asm__(
"push b\n\t" // Save B
"ld.16 a,%0\n\t" // Load slot number
"shl.16 a\n\t" // Multiply by 2 for offset
"lea b,image_table\n\t" // Get image table address
"add.16 b,a\n\t" // Add offset
"ldcode.16 a,(b)\n\t" // Load image address
"pop b" // Restore B
:
: "r"(slot)
: "a"
);
}
// Optimize string operations using string instructions
void copy_string(char *dst, const char *src) {
__asm__(
"copy b,%0\n\t" // Load destination
"copy a,%1\n\t" // Load source
"strcopy" // Execute string copy
:
: "r"(dst), "r"(src)
: "a", "b"
);
}
The optimizations include:
- Using
memcopy
instruction for block data transfers - Direct use of
ldcode
/stcode
for memory access - Hardware-assisted string operations
- Efficient register usage (A, B, C registers)
- Block operations where possible
- Minimal memory access overhead
Note that this is a simplified example - a full implementation would need careful consideration of:
- Error handling
- Interrupt states
- Page table management
- Device access synchronization
The key is using Magic-1's specialized instructions like memcopy
, ldcode
, and block operations to reduce the number of individual memory accesses and take advantage of the hardware acceleration features.
Let me help you optimize the bootloader code using Magic-1's native assembly instructions. Here are all possible optimization approaches:
-
Direct Assembly Optimization
- Replace critical C functions with assembly
- Use block operations for memory transfers
- Optimize register usage
- Use specialized Magic-1 instructions
-
Hybrid C/Assembly Approach
- Keep main logic in C
- Create assembly routines for performance-critical sections
- Use inline assembly in C code
-
Memory Management Optimization
- Use direct memory addressing
- Optimize page table access
- Use block copy instructions
Let's implement the first approach - optimizing sector reading with assembly:
.cseg
.global _fast_read_sector
_fast_read_sector:
enter 4 ; Setup stack frame
; Get parameters from stack
ld.16 a,6(sp) ; Load sector number
ld.16 b,8(sp) ; Load buffer address
; Save registers we'll use
push c
; Setup IDE parameters
ld.8 a,0xB0 ; IDE command register
st.8 0xFFB0(dp),a ; Select master drive
; Transfer size is 512 bytes
ld.16 c,512 ; Set transfer count
; Start transfer loop
.loop:
memcopy ; Use hardware assisted copy
sub.16 c,2 ; Decrement count
br.ne .loop ; Continue if not done
; Restore registers
pop c
leave ; Restore stack frame
ret
.end
To use this optimized version, modify the C code:
extern void fast_read_sector(uint16_t sector, void* buffer);
void read_sector(unsigned int sector, void *buffer) {
#ifdef USE_OPTIMIZED
fast_read_sector(sector, buffer);
#else
// ... existing code ...
#endif
}
This optimization:
- Uses
memcopy
instruction for fast block transfers - Minimizes register usage
- Uses hardware-assisted copy operations
- Reduces function call overhead