From 7bf5118f69b1f36392c8e8865b44892a42af1fc0 Mon Sep 17 00:00:00 2001
From: wborgeaud <williamborgeaud@gmail.com>
Date: Thu, 7 Jul 2022 18:46:20 +0200
Subject: [PATCH] Test exp kernel function

---
 evm/src/cpu/kernel/aggregator.rs  | 36 +++++++++++++++++++++++++++++++
 evm/src/cpu/kernel/asm/exp.asm    |  3 +++
 evm/src/cpu/kernel/interpreter.rs |  8 +++----
 3 files changed, 43 insertions(+), 4 deletions(-)

diff --git a/evm/src/cpu/kernel/aggregator.rs b/evm/src/cpu/kernel/aggregator.rs
index d58208fd..a23e18b8 100644
--- a/evm/src/cpu/kernel/aggregator.rs
+++ b/evm/src/cpu/kernel/aggregator.rs
@@ -27,6 +27,7 @@ mod tests {
 
     use anyhow::Result;
     use ethereum_types::U256;
+    use rand::{thread_rng, Rng};
 
     use crate::cpu::kernel::aggregator::combined_kernel;
     use crate::cpu::kernel::interpreter::run;
@@ -43,6 +44,41 @@ mod tests {
             .map(U256::from_str)
             .collect::<Result<Vec<_>, _>>()?)
     }
+    #[test]
+    fn test_exp() -> Result<()> {
+        // Make sure we can parse and assemble the entire kernel.
+        let kernel = combined_kernel();
+        let exp = kernel.global_labels["exp"];
+        let mut rng = thread_rng();
+        let a = U256([0; 4].map(|_| rng.gen()));
+        let b = U256([0; 4].map(|_| rng.gen()));
+
+        // Random input
+        let initial_stack = vec![U256::from_str("0xdeadbeef")?, b, a];
+        let stack_with_kernel = run(&kernel.code, exp, initial_stack);
+        let initial_stack = vec![b, a];
+        let code = [0xa, 0x63, 0xde, 0xad, 0xbe, 0xef, 0x56]; // EXP, PUSH4 deadbeef, JUMP
+        let stack_with_opcode = run(&code, 0, initial_stack);
+        assert_eq!(stack_with_kernel, stack_with_opcode);
+
+        // 0 base
+        let initial_stack = vec![U256::from_str("0xdeadbeef")?, b, U256::zero()];
+        let stack_with_kernel = run(&kernel.code, exp, initial_stack);
+        let initial_stack = vec![b, U256::zero()];
+        let code = [0xa, 0x63, 0xde, 0xad, 0xbe, 0xef, 0x56]; // EXP, PUSH4 deadbeef, JUMP
+        let stack_with_opcode = run(&code, 0, initial_stack);
+        assert_eq!(stack_with_kernel, stack_with_opcode);
+
+        // 0 exponent
+        let initial_stack = vec![U256::from_str("0xdeadbeef")?, U256::zero(), a];
+        let stack_with_kernel = run(&kernel.code, exp, initial_stack);
+        let initial_stack = vec![U256::zero(), a];
+        let code = [0xa, 0x63, 0xde, 0xad, 0xbe, 0xef, 0x56]; // EXP, PUSH4 deadbeef, JUMP
+        let stack_with_opcode = run(&code, 0, initial_stack);
+        assert_eq!(stack_with_kernel, stack_with_opcode);
+
+        Ok(())
+    }
 
     #[test]
     fn test_ec_ops() -> Result<()> {
diff --git a/evm/src/cpu/kernel/asm/exp.asm b/evm/src/cpu/kernel/asm/exp.asm
index 3e3b0f6f..683e67c3 100644
--- a/evm/src/cpu/kernel/asm/exp.asm
+++ b/evm/src/cpu/kernel/asm/exp.asm
@@ -10,6 +10,7 @@
 /// Note that this correctly handles exp(0, 0) == 1.
 
 global exp:
+    jumpdest
     // stack: x, e, retdest
     dup2
     // stack: e, x, e, retdest
@@ -28,6 +29,7 @@ global exp:
     jump
 
 step_case:
+    jumpdest
     // stack: x, e, retdest
     push recursion_return
     // stack: recursion_return, x, e, retdest
@@ -45,6 +47,7 @@ step_case:
     // stack: exp, x * x, e / 2, recursion_return, x, e, retdest
     jump
 recursion_return:
+    jumpdest
     // stack: exp(x * x, e / 2), x, e, retdest
     push 2
     // stack: 2, exp(x * x, e / 2), x, e, retdest
diff --git a/evm/src/cpu/kernel/interpreter.rs b/evm/src/cpu/kernel/interpreter.rs
index a099a48b..97fb5209 100644
--- a/evm/src/cpu/kernel/interpreter.rs
+++ b/evm/src/cpu/kernel/interpreter.rs
@@ -127,21 +127,21 @@ impl<'a> Interpreter<'a> {
     fn run_add(&mut self) {
         let x = self.pop();
         let y = self.pop();
-        self.push(x + y);
+        self.push(x.overflowing_add(y).0);
         self.incr(1);
     }
 
     fn run_mul(&mut self) {
         let x = self.pop();
         let y = self.pop();
-        self.push(x * y);
+        self.push(x.overflowing_mul(y).0);
         self.incr(1);
     }
 
     fn run_sub(&mut self) {
         let x = self.pop();
         let y = self.pop();
-        self.push(x - y);
+        self.push(x.overflowing_sub(y).0);
         self.incr(1);
     }
 
@@ -180,7 +180,7 @@ impl<'a> Interpreter<'a> {
     fn run_exp(&mut self) {
         let x = self.pop();
         let y = self.pop();
-        self.push(x.pow(y));
+        self.push(x.overflowing_pow(y).0);
         self.incr(1);
     }