Add pass to fold a load feeding an extract.
We have already disabled common uniform elimination because it created
sequences of loads an entire uniform object, then we extract just a
single element. This caused problems in some drivers, and is just
generally slow because it loads more memory than needed.
However, there are other way to get into this situation, so I've added
a pass that looks specifically for this pattern and removes it when only
a portion of the load is used.
Fixes #1547.
diff --git a/include/spirv-tools/optimizer.hpp b/include/spirv-tools/optimizer.hpp
index 9c26965..5630e36 100644
--- a/include/spirv-tools/optimizer.hpp
+++ b/include/spirv-tools/optimizer.hpp
@@ -578,6 +578,12 @@
// a pass of ADCE will be able to remove.
Optimizer::PassToken CreateVectorDCEPass();
+// Create a pass to reduce the size of loads.
+// This pass looks for loads of structures where only a few of its members are
+// used. It replaces the loads feeding an OpExtract with an OpAccessChain and
+// a load of the specific elements.
+Optimizer::PassToken CreateReduceLoadSizePass();
+
} // namespace spvtools
#endif // SPIRV_TOOLS_OPTIMIZER_HPP_