shadps4-emu · mikusp · Mar 31, 2026
diff --git a/src/shader_recompiler/frontend/decode.cpp b/src/shader_recompiler/frontend/decode.cpp
@@ -132,6 +132,7 @@ GcnInst GcnDecodeContext::decodeInstruction(GcnCodeSlice& code) {
     // Note: Literal constant decode must be performed after meta info updated.
     if (encodingLen == sizeof(u32)) {
         decodeLiteralConstant(encoding, code);
+        decodeSubDwordAddressing(encoding, code);
     }
 
     repairOperandType();
@@ -431,6 +432,78 @@ void GcnDecodeContext::decodeLiteralConstant(InstEncoding encoding, GcnCodeSlice
     }
 }
 
+void GcnDecodeContext::decodeSubDwordAddressing(InstEncoding encoding, GcnCodeSlice& code) {
+    // Find if the instruction contains SDWA (it's legal only as src0)
+    if (m_instruction.src[0].field == OperandField::Sdwa) {
+        ASSERT_MSG(Libraries::Kernel::sceKernelIsNeoMode(), "SDWA is not supported in Base mode");
+
+        m_instruction.src[0].code = code.readu32();
+        m_instruction.length += sizeof(u32);
+
+        if (encoding == InstEncoding::VOPC) {
+            SdwaVopc sdwa = *reinterpret_cast<SdwaVopc*>(&m_instruction.src[0].code);
+            m_instruction.src[0].field =
+                sdwa.s0 == 0 ? OperandField::VectorGPR : OperandField::ScalarGPR;
+            m_instruction.src[0].code = sdwa.src0;
+            m_instruction.src[0].sdwa_sel = SdwaSelector(sdwa.src0_sel);
+
+            m_instruction.src[0].input_modifier.neg = sdwa.src0_neg;
+            m_instruction.src[0].input_modifier.abs = sdwa.src0_abs;
+            m_instruction.src[0].input_modifier.sext = sdwa.src0_sext;
+
+            m_instruction.src[1].field =
+                sdwa.s1 == 0 ? OperandField::VectorGPR : OperandField::ScalarGPR;
+            m_instruction.src[1].sdwa_sel = SdwaSelector(sdwa.src1_sel);
+
+            m_instruction.src[1].input_modifier.neg = sdwa.src1_neg;
+            m_instruction.src[1].input_modifier.abs = sdwa.src1_abs;
+            m_instruction.src[1].input_modifier.sext = sdwa.src1_sext;
+
+            m_instruction.dst[0].sdwa_sel = SdwaSelector(sdwa.dst_sel);
+            m_instruction.dst[0].sdwa_dst = SdwaDstUnused(sdwa.dst_u);
+            m_instruction.dst[0].output_modifier.clamp = sdwa.clamp;
+
+            switch (sdwa.omod) {
+            case 0:
+                m_instruction.dst[0].output_modifier.multiplier = 0.f;
+                break;
+            case 1:
+                m_instruction.dst[0].output_modifier.multiplier = 2.0f;
+                break;
+            case 2:
+                m_instruction.dst[0].output_modifier.multiplier = 4.0f;
+                break;
+            case 3:
+                m_instruction.dst[0].output_modifier.multiplier = 0.5f;
+                break;
+            }
+        } else if (encoding == InstEncoding::VOP1 || encoding == InstEncoding::VOP2) {
+            SdwaVop12 sdwa = *reinterpret_cast<SdwaVop12*>(&m_instruction.src[0].code);
+            m_instruction.src[0].field =
+                sdwa.s0 == 0 ? OperandField::VectorGPR : OperandField::ScalarGPR;
+            m_instruction.src[0].code = sdwa.src0;
+            m_instruction.src[0].sdwa_sel = SdwaSelector(sdwa.src0_sel);
+
+            m_instruction.src[0].input_modifier.neg = sdwa.src0_neg;
+            m_instruction.src[0].input_modifier.abs = sdwa.src0_abs;
+            m_instruction.src[0].input_modifier.sext = sdwa.src0_sext;
+
+            m_instruction.src[1].field =
+                sdwa.s1 == 0 ? OperandField::VectorGPR : OperandField::ScalarGPR;
+            m_instruction.src[1].sdwa_sel = SdwaSelector(sdwa.src1_sel);
+
+            m_instruction.src[1].input_modifier.neg = sdwa.src1_neg;
+            m_instruction.src[1].input_modifier.abs = sdwa.src1_abs;
+            m_instruction.src[1].input_modifier.sext = sdwa.src1_sext;
+
+            m_instruction.dst[0].field = OperandField::ScalarGPR;
+            m_instruction.dst[0].code = sdwa.sdst;
+        } else {
+            UNREACHABLE_MSG("illegal instruction: SDWA used outside VOP1/VOP2/VOPC");
+        }
+    }
+}
+
 void GcnDecodeContext::decodeInstructionSOP1(u32 hexInstruction) {
     u32 ssrc0 = bit::extract(hexInstruction, 7, 0);
     u32 op = bit::extract(hexInstruction, 15, 8);

diff --git a/src/shader_recompiler/frontend/decode.h b/src/shader_recompiler/frontend/decode.h
@@ -70,6 +70,7 @@ class GcnDecodeContext {
     void decodeInstruction32(InstEncoding encoding, GcnCodeSlice& code);
     void decodeInstruction64(InstEncoding encoding, GcnCodeSlice& code);
     void decodeLiteralConstant(InstEncoding encoding, GcnCodeSlice& code);
+    void decodeSubDwordAddressing(InstEncoding encoding, GcnCodeSlice& code);
 
     // 32 bits encodings
     void decodeInstructionSOP1(uint32_t hexInstruction);

diff --git a/src/shader_recompiler/frontend/instruction.h b/src/shader_recompiler/frontend/instruction.h
@@ -28,6 +28,7 @@ struct InputModifiers {
     bool neg = false;
     bool neg_hi = false;
     bool abs = false;
+    bool sext = false;
 };
 
 /// These are applied before storing an operand register.
@@ -41,13 +42,33 @@ struct OperandSelection {
     bool op_sel_hi = false;
 };
 
+enum class SdwaSelector : u32 {
+    Byte0 = 0,
+    Byte1 = 1,
+    Byte2 = 2,
+    Byte3 = 3,
+    Word0 = 4,
+    Word1 = 5,
+    Dword = 6,
+    Invalid = 7,
+};
+
+enum class SdwaDstUnused : u32 {
+    Pad = 0,
+    Sext = 1,
+    Preserve = 2,
+    Invalid = 3,
+};
+
 struct InstOperand {
     OperandField field = OperandField::Undefined;
     ScalarType type = ScalarType::Undefined;
     InputModifiers input_modifier = {};
     OutputModifiers output_modifier = {};
     // only valid for packed 16bit operations
     OperandSelection op_sel = {};
+    SdwaDstUnused sdwa_dst = SdwaDstUnused::Invalid;
+    SdwaSelector sdwa_sel = SdwaSelector::Invalid;
     u32 code = 0xFFFFFFFF;
 };
 
@@ -219,6 +240,51 @@ union InstControl {
     InstControlEXP exp;
 };
 
+struct SdwaVopc {
+    u32 src0 : 8;
+    u32 dst_sel : 3;
+    u32 dst_u : 2;
+    u32 clamp : 1;
+    u32 omod : 2;
+    u32 src0_sel : 3;
+    u32 src0_sext : 1;
+    u32 src0_neg : 1;
+    u32 src0_abs : 1;
+    u32 : 1;
+    u32 s0 : 1;
+
+    u32 src1_sel : 3;
+    u32 src1_sext : 1;
+    u32 src1_neg : 1;
+    u32 src1_abs : 1;
+    u32 : 1;
+    u32 s1 : 1;
+};
+
+struct SdwaVop12 {
+    u32 src0 : 8;
+    u32 sdst : 7;
+    u32 sd : 1;
+    u32 src0_sel : 3;
+    u32 src0_sext : 1;
+    u32 src0_neg : 1;
+    u32 src0_abs : 1;
+    u32 : 1;
+    u32 s0 : 1;
+
+    u32 src1_sel : 3;
+    u32 src1_sext : 1;
+    u32 src1_neg : 1;
+    u32 src1_abs : 1;
+    u32 : 1;
+    u32 s1 : 1;
+};
+
+union Sdwa {
+    SdwaVopc vopc;
+    SdwaVop12 vop12;
+};
+
 struct GcnInst {
     Opcode opcode;
     InstEncoding encoding;

diff --git a/src/shader_recompiler/frontend/opcodes.h b/src/shader_recompiler/frontend/opcodes.h
@@ -2448,6 +2448,9 @@ enum class OperandField : u32 {
     ConstFloatNeg_2_0,
     ConstFloatPos_4_0,
     ConstFloatNeg_4_0,
+    Inv2Pi,
+    Sdwa,
+    Dpp,
     VccZ = 251,
     ExecZ = 252,
     Scc = 253,

diff --git a/src/shader_recompiler/frontend/translate/translate.cpp b/src/shader_recompiler/frontend/translate/translate.cpp
@@ -4,6 +4,7 @@
 #include "common/io_file.h"
 #include "common/path_util.h"
 #include "core/emulator_settings.h"
+#include "core/libraries/kernel/process.h"
 #include "shader_recompiler/frontend/decode.h"
 #include "shader_recompiler/frontend/fetch_shader.h"
 #include "shader_recompiler/frontend/translate/translate.h"
@@ -15,6 +16,7 @@
 #include "shader_recompiler/runtime_info.h"
 #include "video_core/amdgpu/resource.h"
 
+#include <numbers>
 #define MAGIC_ENUM_RANGE_MIN 0
 #define MAGIC_ENUM_RANGE_MAX 1515
 #include <magic_enum/magic_enum.hpp>
@@ -339,8 +341,22 @@ T Translator::GetSrc(const InstOperand& operand) {
             value = ir.BitCast<IR::U32>(ir.GetScc());
         }
         break;
-    default:
-        UNREACHABLE();
+    default: {
+        if (Libraries::Kernel::sceKernelIsNeoMode()) {
+            switch (operand.field) {
+            case OperandField::Inv2Pi:
+                value = get_imm(static_cast<float>(1.0f / (2.0f * std::numbers::pi)));
+                break;
+            case OperandField::Sdwa:
+                UNREACHABLE_MSG("unhandled SDWA");
+            case OperandField::Dpp:
+                UNREACHABLE_MSG("unhandled DPP");
+            default:
+                break;
+            }
+        }
+        UNREACHABLE_MSG("unexpected operand: {}", std::to_underlying(operand.field));
+    }
     }
 
     if constexpr (is_float) {