From 5996c3f6f50ce0924a0b65bd97ad0a2a2705c95b Mon Sep 17 00:00:00 2001
From: 0xlny <lenny@419labs.io>
Date: Mon, 17 Oct 2022 17:56:30 +0200
Subject: [PATCH] :sparkles: Implement SLT

---
 src/kakarot/instructions.cairo                |  4 +-
 .../instructions/comparison_operations.cairo  | 40 ++++++++++++++++++-
 tests/cases/003_slt.json                      |  6 +++
 tests/units/kakarot/test_basic.cairo          | 13 +++++-
 4 files changed, 60 insertions(+), 3 deletions(-)
 create mode 100644 tests/cases/003_slt.json

diff --git a/src/kakarot/instructions.cairo b/src/kakarot/instructions.cairo
index 8ea86fc2b..e82ace0f9 100644
--- a/src/kakarot/instructions.cairo
+++ b/src/kakarot/instructions.cairo
@@ -184,8 +184,10 @@ namespace EVMInstructions {
         // Comparison & bitwise logic operations
         // 0x10 - LT
         add_instruction(instructions, 0x10, ComparisonOperations.exec_lt);
-        // 0x1 - GT
+        // 0x11 - GT
         add_instruction(instructions, 0x11, ComparisonOperations.exec_gt);
+        // 0x12 - SLT
+        add_instruction(instructions, 0x12, ComparisonOperations.exec_slt);
 
         // 0x52 - MSTORE
         add_instruction(instructions, 0x52, MemoryOperations.exec_store);
diff --git a/src/kakarot/instructions/comparison_operations.cairo b/src/kakarot/instructions/comparison_operations.cairo
index 33039bcdc..5cecfef22 100644
--- a/src/kakarot/instructions/comparison_operations.cairo
+++ b/src/kakarot/instructions/comparison_operations.cairo
@@ -4,7 +4,7 @@
 
 // Starkware dependencies
 from starkware.cairo.common.cairo_builtins import HashBuiltin
-from starkware.cairo.common.uint256 import Uint256, uint256_lt
+from starkware.cairo.common.uint256 import Uint256, uint256_lt, uint256_signed_lt
 
 // Internal dependencies
 from kakarot.model import model
@@ -19,6 +19,7 @@ namespace ComparisonOperations {
     // Define constants.
     const GAS_COST_LT = 3;
     const GAS_COST_GT = 3;
+    const GAS_COST_SLT = 3;
 
     // @notice 0x10 - LT
     // @dev Comparison operation
@@ -93,4 +94,41 @@ namespace ComparisonOperations {
         let ctx = ExecutionContext.increment_gas_used(ctx, GAS_COST_GT);
         return ctx;
     }
+
+    // @notice 0x12 - SLT
+    // @dev Comparison operation
+    // @custom:since Frontier
+    // @custom:group Comparison & Bitwise Logic Operations
+    // @custom:gas 3
+    // @custom:stack_consumed_elements 2
+    // @custom:stack_produced_elements 1
+    // @param ctx The pointer to the execution context.
+    // @return The pointer to the execution context.
+    func exec_slt{syscall_ptr: felt*, pedersen_ptr: HashBuiltin*, range_check_ptr}(
+        ctx: model.ExecutionContext*
+    ) -> model.ExecutionContext* {
+        alloc_locals;
+        %{ print("0x12 - SLT") %}
+
+        let stack = ctx.stack;
+
+        // Stack input:
+        // 0 - a: left side signed integer.
+        // 1 - b: right side signed integer.
+        let (stack, a) = Stack.pop(stack);
+        let (stack, b) = Stack.pop(stack);
+
+        // Compute the comparison
+        let (result) = uint256_signed_lt(a, b);
+
+        // Stack output:
+        // a < b: integer result of comparison a less than b
+        let stack: model.Stack* = Stack.push(stack, Uint256(result, 0));
+
+        // Update context stack.
+        let ctx = ExecutionContext.update_stack(ctx, stack);
+        // Increment gas used.
+        let ctx = ExecutionContext.increment_gas_used(ctx, GAS_COST_SLT);
+        return ctx;
+    }
 }
diff --git a/tests/cases/003_slt.json b/tests/cases/003_slt.json
new file mode 100644
index 000000000..b4f46f584
--- /dev/null
+++ b/tests/cases/003_slt.json
@@ -0,0 +1,6 @@
+{
+  "name": "Comparison & bitwise logic operations - SLT",
+  "code": "60ff600112",
+  "calldata": "",
+  "expected_return_data": ""
+}
\ No newline at end of file
diff --git a/tests/units/kakarot/test_basic.cairo b/tests/units/kakarot/test_basic.cairo
index 58500ed53..f67f7d39f 100644
--- a/tests/units/kakarot/test_basic.cairo
+++ b/tests/units/kakarot/test_basic.cairo
@@ -67,7 +67,7 @@ func test_comparison_operations{syscall_ptr: felt*, pedersen_ptr: HashBuiltin*,
     // Assert value on the top of the stack
     test_utils.assert_top_stack(ctx, 0);
 
-    // Load test case for LT
+    // Load test case for GT
     let (evm_test_case: EVMTestCase) = test_utils.load_evm_test_case_from_file(
         './tests/cases/003_gt.json'
     );
@@ -75,6 +75,17 @@ func test_comparison_operations{syscall_ptr: felt*, pedersen_ptr: HashBuiltin*,
     // Run EVM execution
     let ctx: model.ExecutionContext* = Kakarot.execute(evm_test_case.code, evm_test_case.calldata);
 
+    // Assert value on the top of the stack
+    test_utils.assert_top_stack(ctx, 1);
+
+     // Load test case for SLT
+    let (evm_test_case: EVMTestCase) = test_utils.load_evm_test_case_from_file(
+        './tests/cases/003_slt.json'
+    );
+
+    // Run EVM execution
+    let ctx: model.ExecutionContext* = Kakarot.execute(evm_test_case.code, evm_test_case.calldata);
+
     // Assert value on the top of the stack
     test_utils.assert_top_stack(ctx, 1);