From 953508f6d208b17740f08cea673f2d4bacc292f2 Mon Sep 17 00:00:00 2001
From: "Emil J. Tywoniak" <emil@tywoniak.eu>
Date: Tue, 1 Oct 2024 16:02:41 +0200
Subject: [PATCH] driver: add --hash-seed

---
 kernel/driver.cc     |  7 +++++++
 kernel/drivertools.h | 32 --------------------------------
 kernel/hashlib.h     |  9 ++++++++-
 kernel/scopeinfo.h   |  7 +++++--
 kernel/yosys.cc      |  1 +
 5 files changed, 21 insertions(+), 35 deletions(-)

diff --git a/kernel/driver.cc b/kernel/driver.cc
index 6565c472c..a3d85bd90 100644
--- a/kernel/driver.cc
+++ b/kernel/driver.cc
@@ -18,6 +18,7 @@
  */
 
 #include "kernel/yosys.h"
+#include "kernel/hashlib.h"
 #include "libs/sha1/sha1.h"
 #include "libs/cxxopts/include/cxxopts.hpp"
 #include <iostream>
@@ -282,6 +283,8 @@ int main(int argc, char **argv)
 		("M,randomize-pointers", "will slightly randomize allocated pointer addresses. for debugging")
 		("autoidx", "start counting autoidx up from <seed>, similar effect to --hash-seed",
 			cxxopts::value<uint64_t>(), "<idx>")
+		("hash-seed", "mix up hashing values with <seed>, for extreme optimization and testing",
+			cxxopts::value<uint64_t>(), "<seed>")
 		("A,abort", "will call abort() at the end of the script. for debugging")
 		("x,experimental", "do not print warnings for the experimental <feature>",
 			cxxopts::value<std::vector<std::string>>(), "<feature>")
@@ -437,6 +440,10 @@ int main(int argc, char **argv)
 			int idx = result["autoidx"].as<uint64_t>();
 			autoidx = idx;
 		}
+		if (result.count("hash-seed")) {
+			int seed = result["hash-seed"].as<uint64_t>();
+			Hasher::set_fudge((Hasher::hash_t)seed);
+		}
 
 		if (log_errfile == NULL) {
 			log_files.push_back(stdout);
diff --git a/kernel/drivertools.h b/kernel/drivertools.h
index fdead5c36..0e7b872e4 100644
--- a/kernel/drivertools.h
+++ b/kernel/drivertools.h
@@ -863,39 +863,7 @@ public:
 	bool try_append(DriveBit const &bit);
 	bool try_append(DriveChunk const &chunk);
 
-<<<<<<< HEAD
-	unsigned int hash() const
-	{
-		unsigned int inner = 0;
-		switch (type_)
-		{
-			case DriveType::NONE:
-				inner = 0;
-				break;
-			case DriveType::CONSTANT:
-				inner = constant_.hash();
-				break;
-			case DriveType::WIRE:
-				inner = wire_.hash();
-				break;
-			case DriveType::PORT:
-				inner = port_.hash();
-				break;
-			case DriveType::MARKER:
-				inner = marker_.hash();
-				break;
-			case DriveType::MULTIPLE:
-				inner = multiple_.hash();
-				break;
-			default:
-				log_abort();
-				break;
-		}
-		return mkhash((unsigned int)type_, inner);
-	}
-=======
 	Hasher hash_acc(Hasher h) const;
->>>>>>> 898d04260 (hashlib: redo interface for flexibility)
 
 	bool operator==(const DriveChunk &other) const
 	{
diff --git a/kernel/hashlib.h b/kernel/hashlib.h
index 21e4e155b..15c2c1afb 100644
--- a/kernel/hashlib.h
+++ b/kernel/hashlib.h
@@ -81,13 +81,20 @@ class Hasher {
 		// traditionally 5381 is used as starting value for the djb2 hash
 		state = 5381;
 	}
+	static void set_fudge(uint32_t f) {
+		fudge = f;
+	}
 
 	private:
 	uint32_t state;
+	static uint32_t fudge;
 	// The XOR version of DJB2
 	[[nodiscard]]
 	static uint32_t mkhash(uint32_t a, uint32_t b) {
-		return ((a << 5) + a) ^ b;
+		uint32_t hash = ((a << 5) + a) ^ b;
+		if (fudge)
+			hash = fudge ^ mkhash_xorshift(hash);
+		return hash;
 	}
 	public:
 	void hash32(uint32_t i) {
diff --git a/kernel/scopeinfo.h b/kernel/scopeinfo.h
index 5d2e6d4b1..fa550dab6 100644
--- a/kernel/scopeinfo.h
+++ b/kernel/scopeinfo.h
@@ -169,8 +169,11 @@ public:
 			return !(*this == other);
 		}
 
-		int hash() const {
-			return mkhash(scope_name.hash(), hash_ptr_ops::hash(target));
+		Hasher hash_acc(Hasher h) const
+		{
+			h.acc(scope_name);
+			h.acc(target);
+			return h;
 		}
 
 		bool valid() const {
diff --git a/kernel/yosys.cc b/kernel/yosys.cc
index bdd7303aa..7cf60f068 100644
--- a/kernel/yosys.cc
+++ b/kernel/yosys.cc
@@ -93,6 +93,7 @@ std::set<std::string> yosys_input_files, yosys_output_files;
 bool memhasher_active = false;
 uint32_t memhasher_rng = 123456;
 std::vector<void*> memhasher_store;
+uint32_t Hasher::fudge = 0;
 
 std::string yosys_share_dirname;
 std::string yosys_abc_executable;