From c3a8ea76f180fbaf2d58d0454e7adc2bb1f30009 Mon Sep 17 00:00:00 2001
From: Subv <subv2112@gmail.com>
Date: Fri, 20 Apr 2018 09:16:55 -0500
Subject: ShaderGen: Implemented predicated instruction execution.

Each predicated instruction will be wrapped in an `if (predicate) { instruction_body; }` in the GLSL, where `predicate` is one of the predicate boolean variables previously set by fsetp.
---
 .../renderer_opengl/gl_shader_decompiler.cpp       | 35 ++++++++++++++++++++++
 1 file changed, 35 insertions(+)

(limited to 'src/video_core/renderer_opengl/gl_shader_decompiler.cpp')

diff --git a/src/video_core/renderer_opengl/gl_shader_decompiler.cpp b/src/video_core/renderer_opengl/gl_shader_decompiler.cpp
index 2e0203a68..7aaee9464 100644
--- a/src/video_core/renderer_opengl/gl_shader_decompiler.cpp
+++ b/src/video_core/renderer_opengl/gl_shader_decompiler.cpp
@@ -293,6 +293,25 @@ private:
         declr_predicates.insert(std::move(variable));
     }
 
+    /*
+     * Returns the condition to use in the 'if' for a predicated instruction.
+     * @param instr Instruction to generate the if condition for.
+     * @returns string containing the predicate condition.
+     */
+    std::string GetPredicateCondition(Instruction instr) const {
+        using Tegra::Shader::Pred;
+        ASSERT(instr.pred.pred_index != static_cast<u64>(Pred::UnusedIndex));
+
+        std::string variable =
+            'p' + std::to_string(static_cast<u64>(instr.pred.pred_index.Value()));
+
+        if (instr.negate_pred) {
+            return "!(" + variable + ')';
+        }
+
+        return variable;
+    }
+
     /*
      * Returns whether the instruction at the specified offset is a 'sched' instruction.
      * Sched instructions always appear before a sequence of 3 instructions.
@@ -320,6 +339,16 @@ private:
 
         shader.AddLine("// " + std::to_string(offset) + ": " + OpCode::GetInfo(instr.opcode).name);
 
+        using Tegra::Shader::Pred;
+        ASSERT_MSG(instr.pred.full_pred != Pred::NeverExecute,
+                   "NeverExecute predicate not implemented");
+
+        if (instr.pred.pred_index != static_cast<u64>(Pred::UnusedIndex)) {
+            shader.AddLine("if (" + GetPredicateCondition(instr) + ')');
+            shader.AddLine('{');
+            ++shader.scope;
+        }
+
         switch (OpCode::GetInfo(instr.opcode).type) {
         case OpCode::Type::Arithmetic: {
             std::string dest = GetRegister(instr.gpr0);
@@ -559,6 +588,12 @@ private:
         }
         }
 
+        // Close the predicate condition scope.
+        if (instr.pred != Pred::UnusedIndex) {
+            --shader.scope;
+            shader.AddLine('}');
+        }
+
         return offset + 1;
     }
 
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