Download MIPS Assembly: Translating C Code, Delayed Loads, and Branches and more Schemes and Mind Maps Computer Programming in PDF only on Docsity! Practice Translate the C code into assembly: for(i = 0; i < 100; i++) { sum+=A[i]; } Assume int is 32 bits $s0 = &A[0] $v0 = sum; $t0 = i; and $t0, $t0, $zero #let i = 0 addi $t1, $zero, 100 #temp = 100 lw $t3, 0($s0) #temp1 = A[i] add $v0, $v0, $t3 #sum += temp addi $s0, $s0, 4 #addr of A[i+1] addi $t0, $t0, 1 #i = i+ bne $t1, $t0, LOOP #if i < 100
LOOP: label 1. initialization 2. load A[i] from memory to register 3. add the value of A[i] to sum 4. increase by 1 5. check if i still < 100 To implement the following C code, what are the instructions that we should put in the box? A: lw $t0, 0($s2) addi $s2, $s2, 4 C: sw $t0, 0($s2) addi $s2, $s2, 4 B: sw $t1, 0($s2) addi $s2, $s2, 4 D: sw $t1, 0($s2) addi $s2, $s2, 1 add $t0, $zero, $zero addi $t1, $zero, 100 LOOP: addi $t0, $t0, 1 beq $t0, $t1, LOOP for(i = 0; i < 100; i++) A[i] = i;
MIPS Mystery 2: Delayed Branches
The instruction after the branch executes even if the branch is taken. All jumps and branches are delayed -- the next instruction always executes Example ori $t0, $zero, 4 beq $t0, $t0, foo ori $t0, $zero, 5 foo: $t0 == 5 file: delayed_branch.s Why? We’ll talk about it in a few weeks.
Pseudo Instructions Assembly language programming is repetitive Some code is not very readable The assembler provides some simple shorthand for common operations Register $at is reserved for implementing them. Assembly Shorthand Description or $s1, $zero, $s2 mov $s1, $s2 move beq $zero, $zero, b unconditional branch Homework? li $s2, load 32 bit constant Homework? nop do nothing Homework? div d, s1, s2 dst = src1/src Homework? mulou d, s1, s2 dst = low32bits(src1*src2) From C to MIPS Compiling: C to bits Architecture- independent Architecture- dependent In the Compiler Abstract Syntax Tree C-Code
In the Compiler Abstract Syntax Tree (^) Control Flow Graph
In the Compiler C-Code Assembly
In the Assembler Assembly Executable Binary
