shader: support DS_READ_U16_D16_HI (#356)

Decode the high-half D16 LDS read and route it through the existing unsigned-short load lowering. Represent the destination as a high-half partial write so the low 16 bits of the VGPR remain intact. Add captured-instruction decode coverage and a Vulkan execution regression that verifies the preserved half.

Co-authored-by: SueryRD <the.ai.tester2@gmail.com>

tests/ShaderRecompilerComputeTests.cpp

@@ -12018,6 +12018,7 @@ CoverageClass ClassifyOpcode(ShaderOpcode opcode,
   case Opcode::DS_READ_I16:
   case Opcode::DS_READ_U16:
   case Opcode::DS_READ_U16_D16:
+  case Opcode::DS_READ_U16_D16_HI:
   case Opcode::DS_READ2_B32:
   case Opcode::DS_READ_B32:
   case Opcode::DS_READ_B64:
@@ -18038,6 +18039,33 @@ TestCase DsReadU16D16CapturedPreservesHighHalf() {
   return test;
 }
 
+TestCase DsReadU16D16HiCapturedPreservesLowHalf() {
+  using O = ShaderOpcode;
+
+  std::vector<u32> code;
+  AppendVMovU32(&code, 1, 0);
+  AppendVMovLiteral(&code, 2, 0x89abcdefu);
+  code.push_back(EncodeDs0(0x0d));
+  code.push_back(EncodeDs1(0, 2, 1)); // ds_write_b32 v2, v1
+
+  AppendVMovLiteral(&code, 5, 0x12345678u);
+  AppendVMovU32(&code, 6, 0);
+  code.push_back(0xda9c0000u);
+  code.push_back(0x05000006u); // captured ds_read_u16_d16_hi v5, v6
+
+  AppendStoreVgpr(&code, 5, 0);
+  AppendEnd(&code);
+
+  TestCase test{"DsReadU16D16HiCapturedPreservesLowHalf",
+                code,
+                std::vector<u32>(1, 0),
+                {0xcdef5678u},
+                {O::V_MOV_B32, O::DS_WRITE_B32, O::DS_READ_U16_D16_HI,
+                 O::BUFFER_STORE_DWORD, O::S_ENDPGM}};
+  test.decoded_counts = {{"DS_READ_U16_D16_HI", 1}};
+  return test;
+}
+
 TestCase DsReadWrite2Variants() {
   using O = ShaderOpcode;
 
@@ -20556,6 +20584,7 @@ std::vector<TestCase> MakeCases() {
   AddCase(FlatStoreVariants);
   AddCase(DsReadWriteVariants);
   AddCase(DsReadU16D16CapturedPreservesHighHalf);
+  AddCase(DsReadU16D16HiCapturedPreservesLowHalf);
   AddCase(DsAppendConsumeUsesEncodedLdsSelector);
   AddCase(DsAppendUsesEncodedGdsSelector);
   AddCase(DsGdsSubdwordAndAtomicWrites);

tests/shaderCfgTests.cpp

@@ -4099,6 +4099,15 @@ void TestNewShaderDecoderArchitecture() {
   Check(boot.opcode == Opcode::DS_SWIZZLE_B32 && boot.offset == 0xc480u,
         "DS decoder rejected a captured boot-shader instruction");
 
+  const uint32_t d16_hi_ds[] = {0xda9c0000u, 0x05000006u};
+  Instruction d16_hi;
+  Check(DecodeInstruction(d16_hi_ds, 0u, d16_hi, &error), error.c_str());
+  Check(d16_hi.opcode == Opcode::DS_READ_U16_D16_HI &&
+            d16_hi.src_count == 1u && d16_hi.data_bits == 16u &&
+            d16_hi.dst.reg == 5u && d16_hi.dst.sdwa_sel == 5u &&
+            d16_hi.dst.sdwa_dst_unused == 2u && d16_hi.src0.reg == 6u,
+        "DS decoder rejected the captured high-half D16 read");
+
   constexpr uint32_t packed_source_selectors[][2] = {
       {0xcc0e0000u, 0x0c0a0300u}, // Source 0: instruction bit 59.
       {0xcc0e0000u, 0x140a0300u}, // Source 1: instruction bit 60.