Merge origin/main into feature/iop-emulator

Preserve the branch's GS CLUT and texture cache implementation while integrating upstream thread initialization and syscall resume coverage. Build passes; 448/456 tests pass with the same eight failures reproduced on pre-merge HEAD (447/455).

ps2xRecomp/src/lib/control_flow_analyzer.cpp

@@ -135,6 +135,9 @@ namespace ps2recomp
 
         for (const auto &inst : instructions)
         {
+            // A guest-installed syscall handler runs as a separate invocation,
+            // so the scheduler resumes this thread at syscall+4 and needs an
+            // entry point there. +4, not +8: syscall has no delay slot.
             if (inst.opcode == OPCODE_SPECIAL && inst.function == SPECIAL_SYSCALL)
             {
                 queueResumeEntryTarget(inst.address + 4u);

ps2xRuntime/include/ps2_runtime.h

@@ -153,10 +153,10 @@ struct alignas(16) R5900Context
 
         // Reset COP0 registers
         cop0_random = 47; // Start at maximum value
-        // cop0_status = 0x400000; // BEV set, ERL clear, kernel mode
-        // 0x00400000 = BEV (Boot Exception Vectors).
-        // 0x00000000 = Normal mode (after BIOS handoff).
-        cop0_status = 0x00000000;
+        // Status as the EE kernel leaves it at handoff. IE (bit 0) and EIE
+        // (bit 16) are separate enables and guest code reads both; libkernel's
+        // StartThread refuses to run while IE is clear.
+        cop0_status = 0x00010001; // EIE | IE
         cop0_prid = 0x00002e20; // CPU ID for R5900
 
         in_delay_slot = false;

ps2xRuntime/src/lib/ps2_runtime.cpp

@@ -491,7 +491,9 @@ PS2Runtime::PS2Runtime()
     }
 #endif
 
-    std::memset(&m_cpuContext, 0, sizeof(m_cpuContext));
+    // Assign rather than memset: R5900Context's constructor zeroes itself and
+    // then applies the COP0 reset values, which a memset here would discard.
+    m_cpuContext = R5900Context{};
 
     // R0 is always zero in MIPS
     m_cpuContext.r[0] = _mm_set1_epi32(0);

ps2xTest/src/code_generator_tests.cpp

@@ -144,6 +144,17 @@ static Instruction makeJr(uint32_t address, uint8_t rs)
     return inst;
 }
 
+static Instruction makeSyscall(uint32_t address)
+{
+    Instruction inst{};
+    inst.address = address;
+    inst.opcode = OPCODE_SPECIAL;
+    inst.function = SPECIAL_SYSCALL;
+    inst.hasDelaySlot = false;
+    inst.raw = (OPCODE_SPECIAL << 26) | SPECIAL_SYSCALL;
+    return inst;
+}
+
 static void printGeneratedCode(const std::string& name, const std::string& code)
 {
 #ifdef PRINT_GENERATED_CODE
@@ -644,6 +655,35 @@ void register_code_generator_tests()
                   "unresolved JALR should not pretend it has a resolved local jump table");
     });
 
+    tc.Run("syscall marks the following instruction as a resume entry", [](TestCase &t) {
+        // Shape of a real SDK syscall wrapper:
+        //   addiu $v1, $zero, <num> ; syscall ; jr $ra ; <delay slot>
+        Function func;
+        func.name = "syscall_wrapper";
+        func.start = 0x4000;
+        func.end = 0x4010;
+        func.isRecompiled = true;
+        func.isStub = false;
+
+        std::vector<Instruction> instructions{
+            makeAddiu(0x4000, 3, 0, 0x83),
+            makeSyscall(0x4004),
+            makeJr(0x4008, 31),
+            makeNop(0x400C),
+        };
+
+        CodeGenerator gen({}, {});
+        CodeGenerator::AnalysisResult analysis = gen.collectInternalBranchTargets(func, instructions);
+
+        // +4, not +8: syscall has no delay slot.
+        t.IsTrue(analysis.resumeEntryPoints.contains(0x4008u),
+                 "syscall should mark the next instruction as resumable");
+        t.IsTrue(analysis.entryPoints.contains(0x4008u),
+                 "syscall resume pc should emit a label in the owner");
+        t.IsFalse(analysis.resumeEntryPoints.contains(0x400Cu),
+                  "syscall must not claim a delay slot it does not have");
+    });
+
     tc.Run("resume entry targets emit a top-level pc switch in the owner wrapper", [](TestCase &t) {
         Function func;
         func.name = "resume_owner";