From 324d9c8f3cfd6cec2ab2a7064b700c3c72604241 Mon Sep 17 00:00:00 2001
From: Alexe Adelina Maria <adelina_maria.alexe@stud.acs.upb.ro>
Date: Wed, 12 Mar 2025 00:01:50 +0200
Subject: [PATCH] readme - part 2
---
README.md | 107 +++++++++++++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 106 insertions(+), 1 deletion(-)
diff --git a/README.md b/README.md
index d6c60a8..30054ca 100644
--- a/README.md
+++ b/README.md
@@ -13,7 +13,7 @@ The translation should be as simple as possible while covering basic arithmetic
## Conventions and Guidelines
-Because we want to prevent you from having to juggle with registers and
+Because we want to prevent you from having to juggle with registers and allocate memory for vectors.
- **Basic Register Mapping:**
- `A` â `eax`
@@ -103,3 +103,108 @@ When multiplying with MUL, the multiplication will actually take EAX and source2
The last 3 rows represent the second operation.
**Note**: For simplicity, we will never use eax as source2, and we will never never use the value from EDX.
+
+### Shift operations
+
+SHL (Shift left) and SHR (Shift right) are bitwise shift instructions.
+
+### Usage - shl, shr
+
+`SHL destination, no_bits_shifted`
+
+`SHR destination, no_bits_shifted`
+
+- SHL: Moves bits to the left, filling the rightmost bits with zeros. Each shift effectively **multiplies** the value by 2.
+ - Example: `00001100` (`12` in decimal) shifted left by 1 becomes `00011000` (`24` in decimal).
+
+
+- SHR: Moves bits to the right, filling the leftmost bits with zeros. Each shift effectively **divides** the value by 2.
+ - Example: `00001100` (`12` in decimal) shifted left by 1 becomes `00000110` (`6` in decimal).
+
+
+| **C Code** | **ASM Code** |
+|------------- |---------------- |
+| `a = a << 1` | `SHL eax, 1` |
+| `b = b >> 2` | `SHR ebx, 2` |
+
+
+### Conditional Statements
+
+### CMP Instrunction
+
+`CMP` instruction compares two values by substracting the second operand from the first. It updates CPU flags, but does not store the result.
+
+### Usage - cmp
+
+`CMP operand1, operand2`
+
+- Example:
+
+ `MOV eax, 3`
+
+ `CMP eax, 3` ; Compares eax with 3
+
+ `JE equal_label` ; Jumps to label "equal_label" if eax == 3 (Zero flag is set)
+
+
+### Jumps
+
+Here's a short description of each conditional jump:
+
+- **JMP** (Jump): Jumps to the given label.
+- **JE** (Jump if Equal): Jumps to the given label if the two compared values are equal (e.g.: `CMP` sets the Zero Flag).
+- **JNE** (Jump if Not Equal): Jumps if the two values are not equal (Zero Flag is not set).
+- **JG** (Jump if Greater): Jumps if the first value is greater than the second (Signed comparison).
+- **JGE** (Jump if Greater or Equal): Jumps if the first value is greater than or equal to the second.
+- **JL** (Jump if Less): Jumps if the first value is less than the second.
+- **JLE** (Jump if Less or Equal): Jumps if the first value is less than or equal to the second.
+
+### Usage
+
+`JMP label`
+
+`JE label`
+
+`JNE label`
+
+`JG label`
+
+`JL label`
+
+### C - ASM translation
+
+| **C Code** | **ASM Code** |
+|------------- |---------------- |
+| `if (a == b) {` | `CMP eax, ebx` |
+| | `JNE else_label` |
+| `// some code here` | `; some code here` |
+| | `JMP end_if` |
+| `} else {` | `else_label:` |
+| `some other code here` | `; some other code here`|
+| `}` | `end_if:` |
+
+### Loops - for, while
+
+### `for` loop
+
+| **C Code** | **ASM Code** |
+|------------- |---------------- |
+| `for (a = 0; a < 10; a++) {` | `MOV eax, 0` |
+| | `start_loop:` |
+| | `CMP eax, 10` |
+| | `JGE end_loop` |
+| `// some code here` | `; some code here` |
+| | `ADD eax, 1` |
+| | `JMP start_loop` |
+| `}` | `end_loop:` |
+
+### `while` loop
+
+| **C Code** | **ASM Code** |
+|------------- |---------------- |
+| `while (b < 5) {` | `start_loop:` |
+| | `CMP ebx, 5` |
+| | `JGE end_loop` |
+| `// some code here` | `; some code that makes b greater or equal than 5` |
+| | `JMP start_loop` |
+| `}` | `end_loop:` |
\ No newline at end of file
--
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