From a24c1b84dc70476d4c7e8ccde36db83f5b0dbcfa Mon Sep 17 00:00:00 2001
From: Ohad Nir <141617878+ohad-nir-starkware@users.noreply.github.com>
Date: Wed, 12 Feb 2025 21:01:39 +0200
Subject: [PATCH] remove NonZeroReservedBits from VirtualMachineError (#1948)

---
 CHANGELOG.md                  | 2 ++
 vm/src/vm/decoding/decoder.rs | 8 +-------
 vm/src/vm/errors/vm_errors.rs | 2 --
 3 files changed, 3 insertions(+), 9 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 0497cac9cf..8c655c11d3 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,8 @@
 
 #### Upcoming Changes
 
+* feat: remove `NonZeroReservedBits` from `VirtualMachineError` [#1948](https://github.com/lambdaclass/cairo-vm/pull/1948)
+
 * feat: set `encoded_instruction` to be u128 for opcode_extensions to come [#1940](https://github.com/lambdaclass/cairo-vm/pull/1940)
 
 * feat: add `get_u32_range` to `impl VirtualMachine` add `get_u32` and `get_u32_range` to `impl Memory` [#1936](https://github.com/lambdaclass/cairo-vm/pull/1936)
diff --git a/vm/src/vm/decoding/decoder.rs b/vm/src/vm/decoding/decoder.rs
index 70049cc2f5..5f78a81e02 100644
--- a/vm/src/vm/decoding/decoder.rs
+++ b/vm/src/vm/decoding/decoder.rs
@@ -13,8 +13,6 @@ use crate::{
 /// opcode_extension_num=0 means the instruction is a Stone instruction.
 /// opcode_extension_num>0 is for new Stwo opcodes.
 pub fn decode_instruction(encoded_instr: u128) -> Result<Instruction, VirtualMachineError> {
-    // HIGH_BITS_MASK is a mask to extract the high bits that are yet to be used in any opcode extension.
-    const HIGH_BITS_MASK: u128 = ((1 << 127) - (1 << 64)) << 1;
     const DST_REG_MASK: u128 = 0x0001;
     const DST_REG_OFF: u128 = 0;
     const OP0_REG_MASK: u128 = 0x0002;
@@ -38,10 +36,6 @@ pub fn decode_instruction(encoded_instr: u128) -> Result<Instruction, VirtualMac
     const OFF2_OFF: u128 = 32;
     const OFFX_MASK: u128 = 0xFFFF;
 
-    if (encoded_instr & HIGH_BITS_MASK) != 0 {
-        return Err(VirtualMachineError::NonZeroReservedBits);
-    }
-
     // Grab offsets and convert them from little endian format.
     let off0 = decode_offset(encoded_instr >> OFF0_OFF & OFFX_MASK);
     let off1 = decode_offset(encoded_instr >> OFF1_OFF & OFFX_MASK);
@@ -189,7 +183,7 @@ mod decoder_test {
         let error = decode_instruction(0x214a7800080008000);
         assert_eq!(
             error.unwrap_err().to_string(),
-            "Reserved instruction bits must be 0",
+            "Invalid opcode extension value: 4",
         )
     }
 
diff --git a/vm/src/vm/errors/vm_errors.rs b/vm/src/vm/errors/vm_errors.rs
index 3733c12270..e225f96d5f 100644
--- a/vm/src/vm/errors/vm_errors.rs
+++ b/vm/src/vm/errors/vm_errors.rs
@@ -34,8 +34,6 @@ pub enum VirtualMachineError {
     MainScopeError(#[from] ExecScopeError),
     #[error(transparent)]
     Other(anyhow::Error),
-    #[error("Reserved instruction bits must be 0")]
-    NonZeroReservedBits,
     #[error("Instruction should be an int")]
     InvalidInstructionEncoding,
     #[error("Invalid op1_register value: {0}")]