From dccca4ab33be7977c1b640d793257203d121e7d0 Mon Sep 17 00:00:00 2001
From: Laszlo Agocs <laszlo.agocs@qt.io>
Date: Fri, 16 Sep 2022 14:52:34 +0200
Subject: [PATCH] rhi: QShader: Only hash the first shader

This is good enough for a hash value and brings a not
insignificant boost to cases when this is used heavily.

In qmlbench with delegates_shadereffect.qml this improves
the results in my runs 386->405.

Pick-to: 6.4
Change-Id: I3dbb9ffabf5986c5ff6b69928b3f073e944450ee
Reviewed-by: Andy Nichols <andy.nichols@qt.io>
---
 src/gui/rhi/qshader.cpp | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/src/gui/rhi/qshader.cpp b/src/gui/rhi/qshader.cpp
index 6802be36ef..769a5767b0 100644
--- a/src/gui/rhi/qshader.cpp
+++ b/src/gui/rhi/qshader.cpp
@@ -597,9 +597,10 @@ size_t qHash(const QShader &s, size_t seed) noexcept
 {
     QtPrivate::QHashCombine hash;
     seed = hash(seed, s.stage());
-    seed = qHashRange(s.d->shaders.keyValueBegin(),
-                      s.d->shaders.keyValueEnd(),
-                      seed);
+    if (!s.d->shaders.isEmpty()) {
+        seed = hash(seed, s.d->shaders.firstKey());
+        seed = hash(seed, s.d->shaders.first());
+    }
     return seed;
 }