From 2e16ab04898880e8f3ea48c54e29c6f7596f0892 Mon Sep 17 00:00:00 2001
From: Hamish Ivey-Law <426294+unzvfu@users.noreply.github.com>
Date: Thu, 20 Apr 2023 01:34:04 +1000
Subject: [PATCH] Replace %stack calls with equivalent opcodes. (#994)

---
 .../kernel/asm/core/precompiles/rip160.asm    | 30 +++++++++++++-----
 .../kernel/asm/core/precompiles/sha256.asm    | 31 ++++++++++++++-----
 2 files changed, 47 insertions(+), 14 deletions(-)

diff --git a/evm/src/cpu/kernel/asm/core/precompiles/rip160.asm b/evm/src/cpu/kernel/asm/core/precompiles/rip160.asm
index c7137f9b..2f7b2c32 100644
--- a/evm/src/cpu/kernel/asm/core/precompiles/rip160.asm
+++ b/evm/src/cpu/kernel/asm/core/precompiles/rip160.asm
@@ -20,13 +20,29 @@ global precompile_rip160:
     // Copy the call data to the kernel general segment (ripemd expects it there) and call ripemd.
     %calldatasize
     GET_CONTEXT
-    %stack (ctx, size) ->
-        (
-        0, @SEGMENT_KERNEL_GENERAL, 200, // DST
-        ctx, @SEGMENT_CALLDATA, 0,       // SRC
-        size, ripemd,                    // count, retdest
-        200, size, rip160_contd          // ripemd input: virt, num_bytes, retdest
-        )
+
+    // The next block of code is equivalent to the following %stack macro call
+    // (unfortunately the macro call takes too long to expand dynamically).
+    //
+    //    %stack (ctx, size) ->
+    //        (
+    //        0, @SEGMENT_KERNEL_GENERAL, 200, // DST
+    //        ctx, @SEGMENT_CALLDATA, 0,       // SRC
+    //        size, ripemd,                    // count, retdest
+    //        200, size, rip160_contd          // ripemd input: virt, num_bytes, retdest
+    //        )
+    PUSH 200
+    PUSH ripemd
+    DUP4
+    PUSH 0
+    PUSH @SEGMENT_CALLDATA
+    PUSH rip160_contd
+    SWAP7
+    SWAP6
+    PUSH 200
+    PUSH @SEGMENT_KERNEL_GENERAL
+    PUSH 0
+
     %jump(memcpy)
 
 rip160_contd:
diff --git a/evm/src/cpu/kernel/asm/core/precompiles/sha256.asm b/evm/src/cpu/kernel/asm/core/precompiles/sha256.asm
index 9bfd544e..86461a59 100644
--- a/evm/src/cpu/kernel/asm/core/precompiles/sha256.asm
+++ b/evm/src/cpu/kernel/asm/core/precompiles/sha256.asm
@@ -23,13 +23,30 @@ global precompile_sha256:
     // Copy the call data to the kernel general segment (sha2 expects it there) and call sha2.
     %calldatasize
     GET_CONTEXT
-    %stack (ctx, size) ->
-        (
-        0, @SEGMENT_KERNEL_GENERAL, 1, // DST
-        ctx, @SEGMENT_CALLDATA, 0,     // SRC
-        size, sha2,                    // count, retdest
-        0, size, sha256_contd          // sha2 input: virt, num_bytes, retdest
-        )
+
+    // The next block of code is equivalent to the following %stack macro call
+    // (unfortunately the macro call takes too long to expand dynamically).
+    //
+    //    %stack (ctx, size) ->
+    //        (
+    //        0, @SEGMENT_KERNEL_GENERAL, 1, // DST
+    //        ctx, @SEGMENT_CALLDATA, 0,     // SRC
+    //        size, sha2,                    // count, retdest
+    //        0, size, sha256_contd          // sha2 input: virt, num_bytes, retdest
+    //        )
+    //
+    PUSH 0
+    PUSH sha2
+    DUP4
+    PUSH 0
+    PUSH @SEGMENT_CALLDATA
+    PUSH sha256_contd
+    SWAP7
+    SWAP6
+    PUSH 1
+    PUSH @SEGMENT_KERNEL_GENERAL
+    PUSH 0
+
     %jump(memcpy)
 
 sha256_contd: