From e5fe8434110c1299527a0d03bf450e1b6d08ca57 Mon Sep 17 00:00:00 2001
From: Noel Grandin <noel.grandin@collabora.co.uk>
Date: Thu, 1 Jun 2023 14:35:24 +0200
Subject: use a SIMD friendly hashcode for ScPatternAttr

which shaves 5% off load time of a large sheet with lots of formats.

We are calculating a hash over a decent sized array of pointers, so
unroll the loop and reduce data-dependencies to give the compiler (and
the CPU) a chance to do work in parallel

Change-Id: I3d58fcf547c9280437295b9c9ec10aff16419afc
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/152443
Tested-by: Jenkins
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>
---
 sc/source/core/data/patattr.cxx | 23 ++++++++++++++++++++---
 1 file changed, 20 insertions(+), 3 deletions(-)

(limited to 'sc/source')

diff --git a/sc/source/core/data/patattr.cxx b/sc/source/core/data/patattr.cxx
index 532831f90a78..d2be666aa349 100644
--- a/sc/source/core/data/patattr.cxx
+++ b/sc/source/core/data/patattr.cxx
@@ -52,6 +52,7 @@
 #include <tools/fract.hxx>
 #include <tools/UnitConversion.hxx>
 #include <osl/diagnose.h>
+#include <sal/log.hxx>
 
 #include <attrib.hxx>
 #include <patattr.hxx>
@@ -64,7 +65,6 @@
 #include <validat.hxx>
 #include <scmod.hxx>
 #include <fillinfo.hxx>
-#include <boost/functional/hash.hpp>
 #include <comphelper/lok.hxx>
 #include <tabvwsh.hxx>
 
@@ -1432,8 +1432,25 @@ void ScPatternAttr::CalcHashCode() const
         mxHashCode = 0; // invalid
         return;
     }
-    mxHashCode = 1; // Set up seed so that an empty pattern does not have an (invalid) hash of 0.
-    boost::hash_range(*mxHashCode, rSet.GetItems_Impl(), rSet.GetItems_Impl() + compareSize);
+    // This is an unrolled hash function so the compiler/CPU can execute it in parallel,
+    // because we hit this hard when loading documents with lots of styles.
+    // Set up seed so that an empty pattern does not have an (invalid) hash of 0.
+    sal_Int32 h1 = 1;
+    sal_Int32 h2 = 1;
+    sal_Int32 h3 = 1;
+    sal_Int32 h4 = 1;
+    for (auto it = rSet.GetItems_Impl(), end = rSet.GetItems_Impl() + (compareSize / 4 * 4); it != end; )
+    {
+        h1 = 31 * h1 + reinterpret_cast<size_t>(*it);
+        ++it;
+        h2 = 31 * h2 + reinterpret_cast<size_t>(*it);
+        ++it;
+        h3 = 31 * h3 + reinterpret_cast<size_t>(*it);
+        ++it;
+        h4 = 31 * h4 + reinterpret_cast<size_t>(*it);
+        ++it;
+    }
+    mxHashCode = h1 + h2 + h3 + h4;
 }
 
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cgit