[SPIR-V] Instruction predication

src/xenia/gpu/spirv_shader_translator.cc

@@ -827,6 +827,51 @@ void SpirvShaderTranslator::UpdateExecConditionals(
   builder_->setBuildPoint(&inner_block);
 }
 
+void SpirvShaderTranslator::UpdateInstructionPredication(bool predicated,
+                                                         bool condition) {
+  if (!predicated) {
+    CloseInstructionPredication();
+    return;
+  }
+
+  if (cf_instruction_predicate_merge_) {
+    if (cf_instruction_predicate_condition_ == condition) {
+      // Already in the needed instruction-level conditional.
+      return;
+    }
+    CloseInstructionPredication();
+  }
+
+  // If the instruction predicate condition is the same as the exec predicate
+  // condition, no need to open a check. However, if there was a `setp` prior
+  // to this instruction, the predicate value now may be different than it was
+  // in the beginning of the exec.
+  if (!cf_exec_predicate_written_ && cf_exec_conditional_merge_ &&
+      cf_exec_bool_constant_or_predicate_ == kCfExecBoolConstantPredicate &&
+      cf_exec_condition_ == condition) {
+    return;
+  }
+
+  cf_instruction_predicate_condition_ = condition;
+  EnsureBuildPointAvailable();
+  spv::Id predicate_id =
+      builder_->createLoad(var_main_predicate_, spv::NoPrecision);
+  spv::Block& predicated_block = builder_->makeNewBlock();
+  cf_instruction_predicate_merge_ = &builder_->makeNewBlock();
+  {
+    std::unique_ptr<spv::Instruction> selection_merge_op =
+        std::make_unique<spv::Instruction>(spv::OpSelectionMerge);
+    selection_merge_op->addIdOperand(cf_instruction_predicate_merge_->getId());
+    selection_merge_op->addImmediateOperand(spv::SelectionControlMaskNone);
+    builder_->getBuildPoint()->addInstruction(std::move(selection_merge_op));
+  }
+  builder_->createConditionalBranch(
+      predicate_id,
+      condition ? &predicated_block : cf_instruction_predicate_merge_,
+      condition ? cf_instruction_predicate_merge_ : &predicated_block);
+  builder_->setBuildPoint(&predicated_block);
+}
+
 void SpirvShaderTranslator::CloseInstructionPredication() {
   if (!cf_instruction_predicate_merge_) {
     return;

src/xenia/gpu/spirv_shader_translator.h

@@ -66,6 +66,8 @@ class SpirvShaderTranslator : public ShaderTranslator {
       const ParsedLoopEndInstruction& instr) override;
   void ProcessJumpInstruction(const ParsedJumpInstruction& instr) override;
 
+  void ProcessAluInstruction(const ParsedAluInstruction& instr) override;
+
  private:
   // TODO(Triang3l): Depth-only pixel shader.
   bool IsSpirvVertexOrTessEvalShader() const { return is_vertex_shader(); }
@@ -96,6 +98,9 @@ class SpirvShaderTranslator : public ShaderTranslator {
   // needed (for example, in jumps).
   void UpdateExecConditionals(ParsedExecInstruction::Type type,
                               uint32_t bool_constant_index, bool condition);
+  // Opens or reopens the predicate check conditional for the instruction.
+  // Should be called before processing a non-control-flow instruction.
+  void UpdateInstructionPredication(bool predicated, bool condition);
   // Closes the instruction-level predicate conditional if it's open, useful if
   // a control flow instruction needs to do some code which needs to respect the
   // current exec conditional, but can't itself be predicated.

src/xenia/gpu/spirv_shader_translator_alu.cc

@@ -0,0 +1,28 @@
+/**
+ ******************************************************************************
+ * Xenia : Xbox 360 Emulator Research Project                                 *
+ ******************************************************************************
+ * Copyright 2020 Ben Vanik. All rights reserved.                             *
+ * Released under the BSD license - see LICENSE in the root for more details. *
+ ******************************************************************************
+ */
+
+#include "xenia/gpu/spirv_shader_translator.h"
+
+namespace xe {
+namespace gpu {
+
+void SpirvShaderTranslator::ProcessAluInstruction(
+    const ParsedAluInstruction& instr) {
+  if (instr.IsNop()) {
+    // Don't even disassemble or update predication.
+    return;
+  }
+
+  UpdateInstructionPredication(instr.is_predicated, instr.predicate_condition);
+
+  // TODO(Triang3l): Translate the ALU instruction.
+}
+
+}  // namespace gpu
+}  // namespace xe