From 6610ec44877740da4eba56019c764d57d7417701 Mon Sep 17 00:00:00 2001
From: Daniel Lubarov <daniel@lubarov.com>
Date: Mon, 18 Jul 2022 14:55:15 -0700
Subject: [PATCH 1/3] Implement memcpy

This can be used, for example, to copy `CALL` data (which is a slice of the caller's main memory) to the callee's `CALLDATA` segment.
---
 evm/src/cpu/kernel/asm/basic_macros.asm | 18 ++++++++
 evm/src/cpu/kernel/asm/memory.asm       | 56 ++++++++++++++++++++++++-
 2 files changed, 72 insertions(+), 2 deletions(-)

diff --git a/evm/src/cpu/kernel/asm/basic_macros.asm b/evm/src/cpu/kernel/asm/basic_macros.asm
index 7bf001b4..854e0a1a 100644
--- a/evm/src/cpu/kernel/asm/basic_macros.asm
+++ b/evm/src/cpu/kernel/asm/basic_macros.asm
@@ -26,6 +26,24 @@
     %endrep
 %endmacro
 
+%macro pop5
+    %rep 5
+        pop
+    %endrep
+%endmacro
+
+%macro pop6
+    %rep 6
+        pop
+    %endrep
+%endmacro
+
+%macro pop7
+    %rep 7
+        pop
+    %endrep
+%endmacro
+
 %macro add_const(c)
     // stack: input, ...
     PUSH $c
diff --git a/evm/src/cpu/kernel/asm/memory.asm b/evm/src/cpu/kernel/asm/memory.asm
index e3af9954..0bf0fbd1 100644
--- a/evm/src/cpu/kernel/asm/memory.asm
+++ b/evm/src/cpu/kernel/asm/memory.asm
@@ -1,4 +1,4 @@
-// Load a byte from the given segment of the current context's memory space.
+// Load a value from the given segment of the current context's memory space.
 // Note that main memory values are one byte each, but in general memory values
 // can be 256 bits. This macro deals with a single address (unlike MLOAD), so
 // if it is used with main memory, it will load a single byte.
@@ -12,7 +12,7 @@
     // stack: value
 %endmacro
 
-// Store a byte to the given segment of the current context's memory space.
+// Store a value to the given segment of the current context's memory space.
 // Note that main memory values are one byte each, but in general memory values
 // can be 256 bits. This macro deals with a single address (unlike MSTORE), so
 // if it is used with main memory, it will store a single byte.
@@ -25,3 +25,55 @@
     MSTORE_GENERAL
     // stack: (empty)
 %endmacro
+
+// Copies `count` values from
+//     SRC = (src_ctx, src_segment, src_addr)
+// to
+//     DST = (dst_ctx, dst_segment, dst_addr).
+// These tuple definitions are used for brevity in the stack comments below.
+global memcpy:
+    JUMPDEST
+    // stack: DST, SRC, count, retdest
+    DUP7
+    // stack: count, DST, SRC, count, retdest
+    ISZERO
+    // stack: count == 0, DST, SRC, count, retdest
+    %jumpi memcpy_finish
+    // stack: DST, SRC, count, retdest
+
+    // Copy the next value.
+    DUP6
+    DUP6
+    DUP6
+    // stack: SRC, DST, SRC, count, retdest
+    MLOAD_GENERAL
+    // stack: value, DST, SRC, count, retdest
+    DUP4
+    DUP4
+    DUP4
+    // stack: DST, value, DST, SRC, count, retdest
+    MSTORE_GENERAL
+    // stack: DST, SRC, count, retdest
+
+    // Increment dst_addr.
+    SWAP2
+    %add_const(1)
+    SWAP2
+    // Increment src_addr.
+    SWAP5
+    %add_const(1)
+    SWAP5
+    // Decrement count.
+    SWAP6
+    %sub_const(1)
+    SWAP6
+
+    // Recurse!
+    JUMP memcpy
+
+memcpy_finish:
+    JUMPDEST
+    // stack: DST, SRC, count, retdest
+    %pop7
+    // stack: retdest
+    JUMP

From 80d32f89b6cac50c57f0a76728cbd48b852bee55 Mon Sep 17 00:00:00 2001
From: Daniel Lubarov <daniel@lubarov.com>
Date: Mon, 18 Jul 2022 15:58:12 -0700
Subject: [PATCH 2/3] fixes

---
 evm/src/cpu/kernel/aggregator.rs  | 1 +
 evm/src/cpu/kernel/asm/memory.asm | 4 ++--
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/evm/src/cpu/kernel/aggregator.rs b/evm/src/cpu/kernel/aggregator.rs
index c6c47387..8784e337 100644
--- a/evm/src/cpu/kernel/aggregator.rs
+++ b/evm/src/cpu/kernel/aggregator.rs
@@ -28,6 +28,7 @@ pub(crate) fn combined_kernel() -> Kernel {
         include_str!("asm/exp.asm"),
         include_str!("asm/curve_mul.asm"),
         include_str!("asm/curve_add.asm"),
+        include_str!("asm/memory.asm"),
         include_str!("asm/moddiv.asm"),
         include_str!("asm/secp256k1/curve_mul.asm"),
         include_str!("asm/secp256k1/curve_add.asm"),
diff --git a/evm/src/cpu/kernel/asm/memory.asm b/evm/src/cpu/kernel/asm/memory.asm
index 0bf0fbd1..42368af5 100644
--- a/evm/src/cpu/kernel/asm/memory.asm
+++ b/evm/src/cpu/kernel/asm/memory.asm
@@ -38,7 +38,7 @@ global memcpy:
     // stack: count, DST, SRC, count, retdest
     ISZERO
     // stack: count == 0, DST, SRC, count, retdest
-    %jumpi memcpy_finish
+    %jumpi(memcpy_finish)
     // stack: DST, SRC, count, retdest
 
     // Copy the next value.
@@ -69,7 +69,7 @@ global memcpy:
     SWAP6
 
     // Recurse!
-    JUMP memcpy
+    %jump(memcpy)
 
 memcpy_finish:
     JUMPDEST

From 5b1f5640398132105f996ce093b90d43cb4d7e12 Mon Sep 17 00:00:00 2001
From: Daniel Lubarov <daniel@lubarov.com>
Date: Tue, 19 Jul 2022 07:20:57 -0700
Subject: [PATCH 3/3] Feedback

---
 evm/src/cpu/kernel/asm/memory.asm | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/evm/src/cpu/kernel/asm/memory.asm b/evm/src/cpu/kernel/asm/memory.asm
index 42368af5..88748a3e 100644
--- a/evm/src/cpu/kernel/asm/memory.asm
+++ b/evm/src/cpu/kernel/asm/memory.asm
@@ -68,7 +68,7 @@ global memcpy:
     %sub_const(1)
     SWAP6
 
-    // Recurse!
+    // Continue the loop.
     %jump(memcpy)
 
 memcpy_finish: