From 83054b0ffee655d7fef4520a6a70d1450d091c64 Mon Sep 17 00:00:00 2001
From: Robin Salen <salenrobin@gmail.com>
Date: Mon, 23 Oct 2023 19:12:54 -0400
Subject: [PATCH] Handle empty case for memcpy_bytes

---
 evm/src/cpu/kernel/asm/memory/memcpy.asm | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/evm/src/cpu/kernel/asm/memory/memcpy.asm b/evm/src/cpu/kernel/asm/memory/memcpy.asm
index 108b7c6f..e9aea36f 100644
--- a/evm/src/cpu/kernel/asm/memory/memcpy.asm
+++ b/evm/src/cpu/kernel/asm/memory/memcpy.asm
@@ -57,6 +57,17 @@ memcpy_finish:
 // Similar logic to memcpy, but optimized for copying sequences of bytes.
 global memcpy_bytes:
     // stack: DST, SRC, count, retdest
+
+    // Handle empty case
+    DUP7
+    // stack: count, DST, SRC, count, retdest
+    ISZERO
+    // stack: count == 0, DST, SRC, count, retdest
+    %jumpi(memcpy_bytes_empty)
+
+    // stack: DST, SRC, count, retdest
+
+    // Handle small case
     DUP7
     // stack: count, DST, SRC, count, retdest
     %lt_const(0x20)
@@ -119,6 +130,12 @@ memcpy_bytes_finish:
     // stack: retdest
     JUMP
 
+memcpy_bytes_empty:
+    // stack: DST, SRC, count, retdest
+    %pop7
+    // stack: retdest
+    JUMP
+
 %macro memcpy_bytes
     %stack (dst: 3, src: 3, count) -> (dst, src, count, %%after)
     %jump(memcpy_bytes)