gl_shader_decompiler: Implement TEXS component mask.

src/video_core/engines/shader_bytecode.h

@@ -270,8 +270,22 @@ union Instruction {
     } tex;
 
     union {
-        // TODO(bunnei): This is just a guess, needs to be verified
-        BitField<52, 1, u64> enable_g_component;
+        BitField<50, 3, u64> component_mask_selector;
+        BitField<28, 8, Register> gpr28;
+
+        bool HasTwoDestinations() const {
+            return gpr28.Value() != Register::ZeroIndex;
+        }
+
+        bool IsComponentEnabled(size_t component) const {
+            static constexpr std::array<size_t, 5> one_dest_mask{0x1, 0x2, 0x4, 0x8, 0x3};
+            static constexpr std::array<size_t, 5> two_dest_mask{0x7, 0xb, 0xd, 0xe, 0xf};
+            const auto& mask{HasTwoDestinations() ? two_dest_mask : one_dest_mask};
+
+            ASSERT(component_mask_selector < mask.size());
+
+            return ((1 << component) & mask[component_mask_selector]) != 0;
+        }
     } texs;
 
     BitField<61, 1, u64> is_b_imm;

src/video_core/renderer_opengl/gl_shader_decompiler.cpp

@@ -938,18 +938,21 @@ private:
                 // TEXS has two destination registers. RG goes into gpr0+0 and gpr0+1, and BA goes
                 // into gpr28+0 and gpr28+1
                 size_t offset{};
+
                 for (const auto& dest : {instr.gpr0.Value(), instr.gpr28.Value()}) {
                     for (unsigned elem = 0; elem < 2; ++elem) {
-                        if (dest + elem >= Register::ZeroIndex) {
-                            // Skip invalid register values
-                            break;
+                        if (!instr.texs.IsComponentEnabled(elem)) {
+                            // Skip disabled components
+                            continue;
                         }
                         regs.SetRegisterToFloat(dest, elem + offset, texture, 1, 4, false, elem);
-                        if (!instr.texs.enable_g_component) {
-                            // Skip the second component
-                            break;
-                        }
                     }
+
+                    if (!instr.texs.HasTwoDestinations()) {
+                        // Skip the second destination
+                        break;
+                    }
+
                     offset += 2;
                 }
                 --shader.scope;