From dd1a005dbcafaea5f138e357e56d9b52215a1436 Mon Sep 17 00:00:00 2001
From: Robin Salen <salenrobin@gmail.com>
Date: Fri, 6 Oct 2023 20:00:41 -0400
Subject: [PATCH] Compute the helper inverse of the shift high limbs

---
 evm/src/witness/operation.rs | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/evm/src/witness/operation.rs b/evm/src/witness/operation.rs
index 568fe4b181..f4dc03e806 100644
--- a/evm/src/witness/operation.rs
+++ b/evm/src/witness/operation.rs
@@ -497,6 +497,10 @@ fn append_shift<F: Field>(
         channel.addr_context = F::from_canonical_usize(lookup_addr.context);
         channel.addr_segment = F::from_canonical_usize(lookup_addr.segment);
         channel.addr_virtual = F::from_canonical_usize(lookup_addr.virt);
+
+        // Extra field required by the constraints for large shifts.
+        let high_limb_sum = row.mem_channels[0].value[1..].iter().copied().sum::<F>();
+        row.general.shift_mut().high_limb_sum_inv = high_limb_sum.inverse();
     }
 
     let operator = if is_shl {