## 1. Fast Memory Copy Implementation - retrotruestory/M1DEV GitHub Wiki
Optimized Assembly Routines for Magic-1
After reviewing the Magic-1 architecture documentation, I can provide some optimized assembly routines for performance-critical sections. These routines take advantage of Magic-1's unique instruction set and register architecture to maximize efficiency.
1. Fast Memory Copy Implementation
Here's an optimized implementation of a memory copy function using Magic-1's native features:
.cseg
.global _fast_memcpy
; Fast memory copy routine
; void fast_memcpy(void* dest, void* src, unsigned int count)
; Parameters:
; dest - destination address (passed in 4(sp))
; src - source address (passed in 6(sp))
; count - number of bytes to copy (passed in 8(sp))
_fast_memcpy:
enter 4 ; Setup stack frame
ld.16 a,4(sp) ; Load destination address
ld.16 b,6(sp) ; Load source address
ld.16 c,8(sp) ; Load count
cmp.16 c,#0 ; Check if count is zero
br.eq .done ; If so, we're done
; Check if count >= 8 for memcopy optimization
cmp.16 c,#8
br.ge .use_memcopy
.byte_loop: ; Fallback for small copies
ld.8 a,(b) ; Load byte from source
st.8 (--sp),a ; Save it temporarily
ld.16 a,6(sp) ; Reload destination address
ld.8 b,(sp++) ; Get saved byte
st.8 (a),b ; Store byte to destination
ld.16 a,6(sp) ; Reload source address
add.16 a,#1 ; Increment source
st.16 6(sp),a ; Store back
ld.16 a,4(sp) ; Reload destination address
add.16 a,#1 ; Increment destination
st.16 4(sp),a ; Store back
ld.16 c,8(sp) ; Reload count
sub.16 c,#1 ; Decrement count
st.16 8(sp),c ; Store back
cmp.16 c,#0 ; Check if count is zero
br.ne .byte_loop ; Continue if not zero
br .done ; Otherwise, we're done
.use_memcopy: ; Use hardware memcopy for larger blocks
; Setup registers for memcopy
ld.16 a,4(sp) ; Load destination to A
ld.16 b,6(sp) ; Load source to B
ld.16 c,8(sp) ; Load count to C (memcopy uses C as count)
memcopy ; Use hardware-assisted memcopy
.done:
leave ; Restore frame pointer
ret ; Return to caller
2. Optimized String Length Function
Here's an efficient implementation of strlen that uses Magic-1's architecture features:
.cseg
.global _fast_strlen
; Fast string length calculation
; unsigned int fast_strlen(const char* str)
; Parameter:
; str - string pointer (4(sp))
; Returns length in A register
_fast_strlen:
enter 4 ; Setup stack frame
ld.16 b,4(sp) ; Load string pointer to B
ld.16 a,#0 ; Initialize length counter to 0
.loop:
ld.8 c,(b) ; Load current character
cmp.8 c,#0 ; Check if null terminator
br.eq .done ; If null, we're done
add.16 a,#1 ; Increment length counter
add.16 b,#1 ; Move to next character
br .loop ; Continue loop
.done:
leave ; Restore frame pointer
ret ; Return to caller (result already in A)
3. Fast 16-bit Integer Square Root
This routine implements an efficient integer square root calculation for 16-bit values:
.cseg
.global _fast_sqrt16
; Fast 16-bit integer square root
; unsigned int fast_sqrt16(unsigned int val)
; Parameter:
; val - unsigned 16-bit value (4(sp))
; Returns square root in A register
_fast_sqrt16:
enter 4 ; Setup stack frame
ld.16 b,4(sp) ; Load value
ld.16 c,#0 ; Clear C register
; Check if input is 0 or 1
cmp.16 b,#1
br.le .return_b ; If 0 or 1, return input
; Use Newton's method: x = (x + n/x)/2
ld.16 a,#1 ; Initial guess x = 1
.loop:
copy c,a ; Save old guess in C
; Calculate n/x (using divide routine)
copy a,b ; Load n (value) into A
call _divu16 ; A / B -> A (result)
; Add previous guess (C) to quotient (A)
add.16 a,c ; A = A + C
; Divide by 2 (shift right)
shr.16 a ; A = A / 2
; Check if we've converged (new guess == old guess)
cmp.16 a,c
br.eq .done ; If equal, we're done
copy b,c ; Set up for next iteration
br .loop ; Continue loop
.return_b:
copy a,b ; For 0 or 1, return the input
.done:
leave ; Restore frame pointer
ret ; Return to caller
4. Fast In-Place Array Reversal
This routine efficiently reverses an array of 16-bit values in place:
.cseg
.global _reverse_array16
; Fast in-place array reversal for 16-bit values
; void reverse_array16(uint16_t* arr, unsigned int count)
; Parameters:
; arr - array pointer (4(sp))
; count - number of elements (6(sp))
_reverse_array16:
enter 4 ; Setup stack frame
ld.16 b,4(sp) ; Load array pointer
ld.16 c,6(sp) ; Load count
cmp.16 c,#1 ; Check if count <= 1
br.le .done ; Nothing to reverse
; Calculate end pointer: end = arr + count - 1
ld.16 a,c ; Load count
sub.16 a,#1 ; Subtract 1
shl.16 a ; Multiply by 2 (16-bit elements)
add.16 a,b ; A now points to last element
; B points to first element, A points to last element
; while (B < A) { swap(*B, *A); B++; A--; }
.loop:
cmp.16 b,a ; Compare pointers
br.ge .done ; Done if B >= A
; Swap elements - first load both values
ld.16 c,(b) ; C = *B (first element)
st.16 (--sp),c ; Save C temporarily
ld.16 c,(a) ; C = *A (last element)
; Now store them back in opposite positions
st.16 (b),c ; *B = C (former last element)
ld.16 c,(sp++) ; Restore original first element
st.16 (a),c ; *A = C (former first element)
; Advance pointers
add.16 b,#2 ; B++ (16-bit elements)
sub.16 a,#2 ; A-- (16-bit elements)
br .loop ; Continue loop
.done:
leave ; Restore frame pointer
ret ; Return to caller
5. Optimized Block Clear Function
Here's an efficient implementation for clearing a block of memory:
.cseg
.global _fast_memset
; Fast memory set with optimized word operations
; void fast_memset(void* dest, unsigned char value, unsigned int count)
; Parameters:
; dest - destination address (4(sp))
; value - byte value to set (6(sp))
; count - number of bytes (8(sp))
_fast_memset:
enter 4 ; Setup stack frame
ld.16 b,4(sp) ; Load destination address
ld.8 a,6(sp) ; Load byte value
ld.16 c,8(sp) ; Load count
cmp.16 c,#0 ; Check if count is zero
br.eq .done ; If so, we're done
; Duplicate the byte value in both halves of A for word operations
ld.16 a,a ; Sign extends, but that's not what we want
and.16 a,#0x00ff ; Mask to keep only the lower byte
shl.16 a,#8 ; Shift to upper byte
ld.8 c,6(sp) ; Reload byte value
or.16 a,c ; Combine - now A has byte value in both bytes
; Check alignment for possible word operations
copy c,b ; Copy destination address
and.16 c,#1 ; Check if odd alignment
br.eq .aligned_path ; Jump if even alignment
; Handle initial unaligned byte if needed
ld.8 c,a ; Get byte value
st.8 (b),c ; Store first byte
add.16 b,#1 ; Advance destination
ld.16 c,8(sp) ; Reload count
sub.16 c,#1 ; Decrement count
st.16 8(sp),c ; Save updated count
cmp.16 c,#0 ; Check if we're done
br.eq .done ; If count is now 0, we're done
.aligned_path:
; Now B is aligned and we can use word operations
ld.16 c,8(sp) ; Reload count
shr.16 c ; Divide by 2 to get word count
cmp.16 c,#0 ; Check if any full words
br.eq .remain ; Skip if no full words
.word_loop:
st.16 (b),a ; Store word (two bytes)
add.16 b,#2 ; Advance destination by 2
sub.16 c,#1 ; Decrement word count
cmp.16 c,#0 ; Check if more words
br.ne .word_loop ; Continue if more words
.remain:
; Handle remaining odd byte if needed
ld.16 c,8(sp) ; Reload original count
and.16 c,#1 ; Check for odd byte
br.eq .done ; Skip if even count
; Handle final byte
ld.8 c,a ; Get byte value
st.8 (b),c ; Store final byte
.done:
leave ; Restore frame pointer
ret ; Return to caller
Usage Examples
Here's how you would call these optimized functions from C:
// Include the function declarations
extern void fast_memcpy(void* dest, void* src, unsigned int count);
extern unsigned int fast_strlen(const char* str);
extern unsigned int fast_sqrt16(unsigned int val);
extern void reverse_array16(uint16_t* arr, unsigned int count);
extern void fast_memset(void* dest, unsigned char value, unsigned int count);
// Example usage
void example_function(void) {
char buffer1[128], buffer2[128];
uint16_t numbers[10] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
// Fast memory copy
fast_memcpy(buffer1, "Hello Magic-1!", 14);
// Get string length
unsigned int len = fast_strlen(buffer1);
// Calculate square root
unsigned int sqrt_result = fast_sqrt16(256); // Should be 16
// Reverse an array
reverse_array16(numbers, 10);
// Clear a memory block
fast_memset(buffer2, 0, 128);
}
Key Optimization Techniques
These routines demonstrate several important optimization techniques for Magic-1:
-
Use of hardware acceleration: The
memcopyinstruction provides significant performance gains for block transfers. -
Register usage optimization: Careful management of A, B, and C registers to minimize memory access.
-
Word operations: Processing 16-bit words instead of bytes where possible for better throughput.
-
Handling alignment: Special handling for unaligned cases to ensure correctness while still optimizing aligned operations.
-
Minimal stack usage: Limited use of the stack to reduce memory overhead and improve speed.
-
Loop unrolling: For very tight loops, consider unrolling further to reduce branch overhead.
These optimized routines should provide excellent performance for your Magic-1 system. You can integrate them into your codebase by assembling them separately and linking with your C programs.