[Vulkan] Shader memory export (#145)

src/xenia/gpu/spirv_builder.h

@@ -10,7 +10,10 @@
 #ifndef XENIA_GPU_SPIRV_BUILDER_H_
 #define XENIA_GPU_SPIRV_BUILDER_H_
 
+#include <memory>
 #include <optional>
+#include <utility>
+#include <vector>
 
 #include "third_party/glslang/SPIRV/SpvBuilder.h"
 #include "xenia/base/assert.h"
@@ -99,6 +102,50 @@ class SpirvBuilder : public spv::Builder {
     Branch currentBranch = Branch::kThen;
 #endif
   };
+
+  // Simpler and more flexible (such as multiple cases pointing to the same
+  // block) compared to makeSwitch.
+  class SwitchBuilder {
+   public:
+    SwitchBuilder(spv::Id selector, unsigned int selection_control,
+                  SpirvBuilder& builder);
+    ~SwitchBuilder() { assert_true(current_branch_ == Branch::kMerge); }
+
+    void makeBeginDefault();
+    void makeBeginCase(unsigned int literal);
+    void addCurrentCaseLiteral(unsigned int literal);
+    void makeEndSwitch();
+
+    // If there's no default block that branches to the merge block, the phi
+    // parent is the header block - this simplifies case-only usage.
+    spv::Id getDefaultPhiParent() const { return default_phi_parent_; }
+
+   private:
+    enum class Branch {
+      kSelection,
+      kDefault,
+      kCase,
+      kMerge,
+    };
+
+    void endSegment();
+
+    SpirvBuilder& builder_;
+    spv::Id selector_;
+    unsigned int selection_control_;
+
+    spv::Function& function_;
+
+    spv::Block* header_block_;
+    spv::Block* merge_block_;
+    spv::Block* default_block_ = nullptr;
+
+    std::vector<std::pair<unsigned int, spv::Id>> cases_;
+
+    spv::Id default_phi_parent_;
+
+    Branch current_branch_ = Branch::kSelection;
+  };
 };
 
 }  // namespace gpu