From a69d48dd19cb9f1b0f26795566b96969aba0d7eb Mon Sep 17 00:00:00 2001
From: Robert O'Callahan <rocallahan@google.com>
Date: Thu, 30 Oct 2025 11:24:00 +0000
Subject: [PATCH] Instead of using packing and hashing to compute SigSpec
 ordering and equality, just use the width and chunkwise comparisons

This avoids having to pack and compute hashes, and generally results in a
simpler ordering.
---
 kernel/rtlil.cc | 50 +++++++++++--------------------------------------
 1 file changed, 11 insertions(+), 39 deletions(-)

diff --git a/kernel/rtlil.cc b/kernel/rtlil.cc
index cc3714948..634269d9d 100644
--- a/kernel/rtlil.cc
+++ b/kernel/rtlil.cc
@@ -5345,23 +5345,12 @@ bool RTLIL::SigSpec::operator <(const RTLIL::SigSpec &other) const
 	if (width_ != other.width_)
 		return width_ < other.width_;
 
-	pack();
-	other.pack();
-
-	if (chunks_.size() != other.chunks_.size())
-		return chunks_.size() < other.chunks_.size();
-
-	updhash();
-	other.updhash();
-
-	if (hash_ != other.hash_)
-		return hash_ < other.hash_;
-
-	for (size_t i = 0; i < chunks_.size(); i++)
-		if (chunks_[i] != other.chunks_[i]) {
-			cover("kernel.rtlil.sigspec.comp_lt.hash_collision");
-			return chunks_[i] < other.chunks_[i];
-		}
+	auto other_it = other.chunks().begin();
+	for (const SigChunk &c : chunks()) {
+		if (c != *other_it)
+			return c < *other_it;
+		++other_it;
+	}
 
 	cover("kernel.rtlil.sigspec.comp_lt.equal");
 	return false;
@@ -5377,29 +5366,12 @@ bool RTLIL::SigSpec::operator ==(const RTLIL::SigSpec &other) const
 	if (width_ != other.width_)
 		return false;
 
-	// Without this, SigSpec() == SigSpec(State::S0, 0) will fail
-	//   since the RHS will contain one SigChunk of width 0 causing
-	//   the size check below to fail
-	if (width_ == 0)
-		return true;
-
-	pack();
-	other.pack();
-
-	if (chunks_.size() != other.chunks_.size())
-		return false;
-
-	updhash();
-	other.updhash();
-
-	if (hash_ != other.hash_)
-		return false;
-
-	for (size_t i = 0; i < chunks_.size(); i++)
-		if (chunks_[i] != other.chunks_[i]) {
-			cover("kernel.rtlil.sigspec.comp_eq.hash_collision");
+	auto other_it = other.chunks().begin();
+	for (const SigChunk &c : chunks()) {
+		if (c != *other_it)
 			return false;
-		}
+		++other_it;
+	}
 
 	cover("kernel.rtlil.sigspec.comp_eq.equal");
 	return true;