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Fixing Huffman Encoding edge case failure for assembly x64 #662

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Merged
merged 2 commits into from
Dec 8, 2021
Merged

Fixing Huffman Encoding edge case failure for assembly x64 #662

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23a5444
Fixing huffman edge case failure for asm x64
Gathros Dec 23, 2019
b985f8d
Merge branch 'main' into x86huffman
Amaras Dec 8, 2021
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18 changes: 16 additions & 2 deletions contents/huffman_encoding/code/asm-x64/huffman.s
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Original file line number Diff line number Diff line change
Expand Up @@ -250,7 +250,7 @@ generate_codebook_recurse:
push rbp
push r12
push r13
test rdi, rdi # If we reached a null pointer we're done
test rsi, rsi # If we reached a null pointer we're done
jz generate_codebook_recurse_done
mov r12, rsi
cmp QWORD PTR [r12 + tree_left], 0 # If at least one of the children is not null
Expand Down Expand Up @@ -314,7 +314,7 @@ generate_tree_count_chars:
generate_tree_leaves_setup:
mov r12, 255 # The loop counter. We can only get here if the "test" on line 301 resulted in a zero so the next jl instruction will do the right thing
generate_tree_leaves:
jl generate_tree_branches # If not then it's time to generate the branches
jl generate_tree_one_leaf # If not then it's time to generate the branches
mov r13d, DWORD PTR [rsp + 4*r12] # Load the count at the ith position
test r13d, r13d # And check if it's zero
jz generate_tree_leaves_counters # If it is we can skip this iteration
Expand All @@ -329,6 +329,18 @@ generate_tree_leaves:
generate_tree_leaves_counters:
dec r12 # Decrement the loop counter and start over
jmp generate_tree_leaves
generate_tree_one_leaf:
cmp DWORD PTR [rsp + counts_size], 1 # Check if there is only one element in the heap
jne generate_tree_branches
lea rdi, [rsp + counts_size] # Get the element
call heap_pop
mov r12, rax
mov rdi, tree_size # Create the new tree node, the pointer to it will be in rax
call malloc
mov QWORD PTR [rax + tree_left], r12 # Save element in the left node
mov ecx, DWORD PTR [r12 + tree_count] # Save element count in branch
mov DWORD PTR [rax + tree_count], ecx
jmp generate_tree_ret # Returning
generate_tree_branches:
cmp DWORD PTR [rsp + counts_size], 1 # Check if there are still at least two elements in the heap
jle generate_tree_done # If not, we're done
Expand All @@ -352,6 +364,7 @@ generate_tree_branches:
generate_tree_done:
lea rdi, [rsp + counts_size] # The tree's root will be in rax after the pop
call heap_pop
generate_tree_ret:
add rsp, 5128
pop r13
pop r12
Expand Down Expand Up @@ -524,3 +537,4 @@ free_tree:
free_tree_done:
pop rbx
ret