From 69cb6e8f300d77e74bd2c7dfe15d12e10b38f512 Mon Sep 17 00:00:00 2001
From: Alexey Panteleev <alpanteleev@nvidia.com>
Date: Wed, 18 May 2022 10:57:37 -0700
Subject: Support for querying which parameters are used in emitted code
 (#2239)

See https://github.com/shader-slang/slang/issues/2213
---
 source/slang/slang-ir-metadata.cpp | 77 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 77 insertions(+)
 create mode 100644 source/slang/slang-ir-metadata.cpp

(limited to 'source/slang/slang-ir-metadata.cpp')

diff --git a/source/slang/slang-ir-metadata.cpp b/source/slang/slang-ir-metadata.cpp
new file mode 100644
index 000000000..cc5922e93
--- /dev/null
+++ b/source/slang/slang-ir-metadata.cpp
@@ -0,0 +1,77 @@
+// slang-ir-metadata.cpp
+#include "slang-ir-metadata.h"
+
+#include "slang-ir.h"
+#include "slang-ir-insts.h"
+
+namespace Slang
+{
+
+// This file currently implements a pass that collects information about the shader parameters that
+// are referenced in the IR. It's named 'metadata' in order to support other potential code
+// analysis scenarios in the future.
+
+
+// Inserts a single resource binding (which takes `count` slots, where 0 means unbounded) into the list of resource ranges.
+static void _insertBinding(List<ShaderBindingRange>& ranges, LayoutResourceKind kind, UInt spaceIndex, UInt registerIndex, UInt count)
+{
+    // Construct a new range from the provided resource.
+    ShaderBindingRange newRange;
+    newRange.category = kind;
+    newRange.spaceIndex = spaceIndex;
+    newRange.registerIndex = registerIndex;
+    newRange.registerCount = count;
+
+    // See if the new range is adjacent to any of the existing ranges, merge with that.
+    for (auto& range : ranges)
+    {
+        if (range.adjacentTo(newRange))
+        {
+            range.mergeWith(newRange);
+            return;
+        }
+    }
+
+    // No adjacent ranges found - create a new one.
+    ranges.add(newRange);
+}
+
+// Collects the metadata from the provided IR module, saves it in outMetadata.
+void collectMetadata(const IRModule* irModule, PostEmitMetadata& outMetadata)
+{
+    // Scan the instructions looking for global resource declarations
+    for (const auto& inst : irModule->getGlobalInsts())
+    {
+        auto param = as<IRGlobalParam>(inst);
+        if (!param) continue;
+        
+        auto layoutDecoration = param->findDecoration<IRLayoutDecoration>();
+        if (!layoutDecoration) continue;
+        
+        auto varLayout = as<IRVarLayout>(layoutDecoration->getLayout());
+        if (!varLayout) continue;
+        
+        for(auto sizeAttr : varLayout->getTypeLayout()->getSizeAttrs())
+        {
+            auto kind = sizeAttr->getResourceKind();
+
+            // Only track resource types that we can reliably track, such as textures.
+            // Do not track individual uniforms, for example.
+            if (!ShaderBindingRange::isUsageTracked(kind))
+                continue;
+
+            if (auto offsetAttr = varLayout->findOffsetAttr(kind))
+            {
+                // Get the binding information from this attribute and insert it into the list
+                auto spaceIndex = offsetAttr->getSpace();
+                auto registerIndex = offsetAttr->getOffset();
+                auto size = sizeAttr->getSize();
+                auto count = size.isFinite() ? size.getFiniteValue() : 0;
+                _insertBinding(outMetadata.usedBindings, kind, spaceIndex, registerIndex, count);
+            }
+        }
+    }
+}
+
+
+}
-- 
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