shader_decode: Implement LDG and basic cbuf tracking

1 files changed, 76 insertions, 0 deletions

diff --git a/src/video_core/shader/track.cpp b/src/video_core/shader/track.cpp
new file mode 100644
index 000000000..d6d29ee9f
--- /dev/null
+++ b/src/video_core/shader/track.cpp
@@ -0,0 +1,76 @@
+// Copyright 2018 yuzu Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#include <algorithm>
+#include <utility>
+#include <variant>
+
+#include "video_core/shader/shader_ir.h"
+
+namespace VideoCommon::Shader {
+
+namespace {
+std::pair<Node, s64> FindOperation(const BasicBlock& code, s64 cursor,
+                                   OperationCode operation_code) {
+    for (; cursor >= 0; --cursor) {
+        const Node node = code[cursor];
+        if (const auto operation = std::get_if<OperationNode>(node)) {
+            if (operation->GetCode() == operation_code)
+                return {node, cursor};
+        }
+    }
+    return {};
+}
+} // namespace
+
+Node ShaderIR::TrackCbuf(Node tracked, const BasicBlock& code, s64 cursor) {
+    if (const auto cbuf = std::get_if<CbufNode>(tracked)) {
+        // Cbuf found, but it has to be immediate
+        return std::holds_alternative<ImmediateNode>(*cbuf->GetOffset()) ? tracked : nullptr;
+    }
+    if (const auto gpr = std::get_if<GprNode>(tracked)) {
+        if (gpr->GetIndex() == Tegra::Shader::Register::ZeroIndex) {
+            return nullptr;
+        }
+        // Reduce the cursor in one to avoid infinite loops when the instruction sets the same
+        // register that it uses as operand
+        const auto [source, new_cursor] = TrackRegister(gpr, code, cursor - 1);
+        if (!source) {
+            return nullptr;
+        }
+        return TrackCbuf(source, code, new_cursor);
+    }
+    if (const auto operation = std::get_if<OperationNode>(tracked)) {
+        for (std::size_t i = 0; i < operation->GetOperandsCount(); ++i) {
+            if (const auto found = TrackCbuf((*operation)[i], code, cursor)) {
+                // Cbuf found in operand
+                return found;
+            }
+        }
+        return nullptr;
+    }
+    return nullptr;
+}
+
+std::pair<Node, s64> ShaderIR::TrackRegister(const GprNode* tracked, const BasicBlock& code,
+                                             s64 cursor) {
+    for (; cursor >= 0; --cursor) {
+        const auto [found_node, new_cursor] = FindOperation(code, cursor, OperationCode::Assign);
+        if (!found_node) {
+            return {};
+        }
+        const auto operation = std::get_if<OperationNode>(found_node);
+        ASSERT(operation);
+
+        const auto& target = (*operation)[0];
+        if (const auto gpr_target = std::get_if<GprNode>(target)) {
+            if (gpr_target->GetIndex() == tracked->GetIndex()) {
+                return {(*operation)[1], new_cursor};
+            }
+        }
+    }
+    return {};
+}
+
+} // namespace VideoCommon::Shader