From 4e736b63b8c712940b24842e934ca6aa73d77952 Mon Sep 17 00:00:00 2001
From: Nicholas Ward <npward@berkeley.edu>
Date: Wed, 15 Mar 2023 23:05:44 -0700
Subject: [PATCH] fixes

---
 evm/src/cpu/kernel/asm/bignum/add.asm | 19 ++++++++-----------
 evm/src/cpu/kernel/tests/bignum.rs    |  7 ++++++-
 2 files changed, 14 insertions(+), 12 deletions(-)

diff --git a/evm/src/cpu/kernel/asm/bignum/add.asm b/evm/src/cpu/kernel/asm/bignum/add.asm
index 7f646097..09b405e8 100644
--- a/evm/src/cpu/kernel/asm/bignum/add.asm
+++ b/evm/src/cpu/kernel/asm/bignum/add.asm
@@ -29,25 +29,22 @@ add_loop:
     // stack: (a[cur] + b[cur] + carry) // 2^128, a[cur] + b[cur] + carry, i, a_cur_loc, b_cur_loc, retdest
     SWAP1
     // stack: a[cur] + b[cur] + carry, (a[cur] + b[cur] + carry) // 2^128, i, a_cur_loc, b_cur_loc, retdest
-    %shl_const(128)
-    %shr_const(128)
+    %mod_const(0x100000000000000000000000000000000)
     // stack: c[cur] = (a[cur] + b[cur] + carry) % 2^128, carry_new = (a[cur] + b[cur] + carry) // 2^128, i, a_cur_loc, b_cur_loc, retdest
     DUP4
     // stack: a_cur_loc, c[cur], carry_new, i, a_cur_loc, b_cur_loc, retdest
     %mstore_kernel_general
     // stack: carry_new, i, a_cur_loc, b_cur_loc, retdest
-    %stack (c, i, a, b) -> (a, b, c, i)
-    // stack: a_cur_loc, b_cur_loc, carry_new, i, retdest
+    SWAP2
     %increment
-    // stack: a_cur_loc + 1, b_cur_loc, carry_new, i, retdest
+    SWAP2
+    // stack: carry_new, i, a_cur_loc + 1, b_cur_loc, retdest
+    SWAP3
+    %increment
+    SWAP3
+    // stack: carry_new, i, a_cur_loc + 1, b_cur_loc + 1, retdest
     SWAP1
-    // stack: b_cur_loc, a_cur_loc + 1, carry_new, i, retdest
-    %increment
-    // stack: b_cur_loc + 1, a_cur_loc + 1, carry_new, i, retdest
-    %stack (b, a, c, i) -> (i, c, a, b)
-    // stack: i, carry_new, a_cur_loc + 1, b_cur_loc + 1, retdest
     %decrement
-    // stack: i - 1, carry_new, a_cur_loc + 1, b_cur_loc + 1, retdest
     SWAP1
     // stack: carry_new, i - 1, a_cur_loc + 1, b_cur_loc + 1, retdest
     DUP2
diff --git a/evm/src/cpu/kernel/tests/bignum.rs b/evm/src/cpu/kernel/tests/bignum.rs
index 1d4196b2..bd3daa95 100644
--- a/evm/src/cpu/kernel/tests/bignum.rs
+++ b/evm/src/cpu/kernel/tests/bignum.rs
@@ -20,6 +20,8 @@ fn test_data() -> Vec<BigUint> {
         0u128.into(),
         1u128.into(),
         u128::MAX.into(),
+
+        // Generated by GMP's mpz_rrandomb for bit lengths 5, 10, 100, 255, 256, 257, 500, 511, 512, 513, 1000, and 1500.
         21u128.into(),
         908u128.into(),
         1267650597867046177654064545792u128.into(),
@@ -266,6 +268,7 @@ where
     F: Fn(usize) -> (BigUint, BigUint, U256, Vec<U256>),
 {
     let (a, b, length, memory) = prepare_two_bignums_fn(1000);
+    let len: usize = length.try_into().unwrap();
 
     // Determine expected sum.
     let sum = a + b;
@@ -288,7 +291,9 @@ where
     interpreter.run()?;
 
     // Determine actual sum.
-    let new_memory = interpreter.get_kernel_general_memory();
+    let carry_limb = interpreter.stack()[0];
+    let mut new_memory = interpreter.get_kernel_general_memory();
+    new_memory[len] = carry_limb;
     let actual_sum: Vec<_> = new_memory[..expected_sum.len()].into();
 
     // Compare.