Question

Write a full MIPS that behaves exactly like the following C program.

The following C code shows the proposed algorithm. The string is traversed with two indices, called old_index and new_index, where the latter always takes a value less or equal to the former. When a non-space character is found, the character at position old_index is copied to position new_index, and both indices are incremented. When a space is found, the current character is not copied, and only old_index is incremented. The algorithm stops when a null character is found.

#include <stdio.h> int main() // Read string char s1001; printf("Enter string: "); gets (s); //Remove spaces char c; int old-index = 0; int new-index = 0; do //Read character c = s[old-index]; // old position moves ahead old_index++; // If it's a space, ignore if(c=-'') continue; /7 Copy character new-index] = c; // New position moves ahead new_index++; } while (c); // Print result printf("New string: %s\n", s);

Answer 1

main: # @main

push RBP

mov RBP, RSP

sub RSP, 144

lea RDI, QWORD PTR [.L.str]

mov DWORD PTR [RBP - 4], 0

mov DWORD PTR [RBP - 120], 0

mov DWORD PTR [RBP - 124], 0

mov AL, 0

call printf

lea RDI, QWORD PTR [RBP - 112]

mov DWORD PTR [RBP - 128], EAX # 4-byte Spill

call gets

mov QWORD PTR [RBP - 136], RAX # 8-byte Spill

.LBB0_1: # =>This Inner Loop Header: Depth=1

movsxd RAX, DWORD PTR [RBP - 120]

mov CL, BYTE PTR [RBP + RAX - 112]

mov BYTE PTR [RBP - 113], CL

mov EDX, DWORD PTR [RBP - 120]

add EDX, 1

mov DWORD PTR [RBP - 120], EDX

movsx EDX, BYTE PTR [RBP - 113]

cmp EDX, 32

jne .LBB0_3

jmp .LBB0_4

.LBB0_3: # in Loop: Header=BB0_1 Depth=1

mov AL, BYTE PTR [RBP - 113]

movsxd RCX, DWORD PTR [RBP - 124]

mov BYTE PTR [RBP + RCX - 112], AL

mov EDX, DWORD PTR [RBP - 124]

add EDX, 1

mov DWORD PTR [RBP - 124], EDX

.LBB0_4: # in Loop: Header=BB0_1 Depth=1

cmp BYTE PTR [RBP - 113], 0

jne .LBB0_1

lea RDI, QWORD PTR [.L.str1]

lea RSI, QWORD PTR [RBP - 112]

mov AL, 0

call printf

mov ECX, 0

mov DWORD PTR [RBP - 140], EAX # 4-byte Spill

mov EAX, ECX

add RSP, 144

pop RBP

ret

.L.str:

.asciz "Enter String:"

.L.str1:

.asciz "New string: %s \n"