[Draft] Disassembly: Merge li a0 + syscall

src/core/disr3000a.cc

@@ -1,4 +1,4 @@
 /***************************************************************************
  *   Copyright (C) 2023 PCSX-Redux authors                                 *
  *                                                                         *
  *   This program is free software; you can redistribute it and/or modify  *
@@ -57,6 +57,19 @@
     "TagLo",    "TagHi",  "ErrorEPC", "*RES*",     // 1c
 };
 
+const char *PCSX::Disasm::getSyscallName(uint32_t index) {
+    switch (index) {
+        case 0:
+            return "NOP";
+        case 1:
+            return "EnterCriticalSection";
+        case 2:
+            return "ExitCriticalSection";
+        default:
+            return "DeliverEvent";
+    }
+}
+
 #undef declare
 #undef _Funct_
 #undef _Rd_
@@ -226,6 +239,7 @@
             }
         }
     }
+    virtual void SyscallName(const char *name) final { append(name); }
     virtual void reset() final {
         m_buf[0] = 0;
         m_len = 0;
@@ -281,8 +295,9 @@
 declare(disADDIU) {
     if (_Rs_ == 0) {
         // this is the common pseudo-instruction to load an immediate 16 bits value
-        dOpCode("li");
-        GPR(_Rt_);
+        if (disLI(_Rt_, _Im_, nextCode, skipNext, delaySlotNext)) {
+            return;
+        }
     } else {
         dOpCode("addiu");
         GPR(_Rt_);
@@ -299,8 +314,9 @@
 declare(disORI) {
     if (_Rs_ == 0) {
         // while rare, this can also be used to load an immediate 16-bits value
-        dOpCode("li");
-        GPR(_Rt_);
+        if (disLI(_Rt_, _Im_, nextCode, skipNext, delaySlotNext)) {
+            return;
+        }
     } else {
         dOpCode("ori");
         GPR(_Rt_);
@@ -680,6 +696,27 @@
     }
 }
 
+bool PCSX::Disasm::disLI(uint32_t reg, uint32_t imm, uint32_t nextCode, bool *skipNext, bool *delaySlotNext) {
+    // Merge syscalls, which usually have the pattern
+    // li $a0, syscallNumber
+    // syscall 0x0000
+    uint8_t nextIns = nextCode >> 26;
+    uint8_t nextSubfunc = nextCode & 0x3f;
+
+    if (skipNext && reg == 4 && nextIns == 0 && nextSubfunc == 0xC) {
+        dOpCode("syscall");
+        SyscallName(getSyscallName(imm));
+
+        *skipNext = true;
+        return true;
+    } else {
+        dOpCode("li");
+        GPR(reg);
+
+        return false;
+    }
+}
+
 /*********************************************************
  * Move from HI/LO to GPR                                 *
  * Format:  OP rd                                         *
@@ -969,7 +1006,7 @@
 }
 
 /*********************************************************
- * Unknow instruction (would generate an exception)       *
+ * Unknown instruction (would generate an exception)      *
  * Format:  ?                                             *
  *********************************************************/
 declare(disNULL) {

src/core/disr3000a.h

@@ -36,6 +36,7 @@ class Disasm {
     static const char *s_disRNameCP2D[];
     static const char *s_disRNameCP2C[];
     static const char *s_disRNameCP0[];
+    static const char *getSyscallName(uint32_t index);
 
 #define declare(n) \
     void n(uint32_t code, uint32_t nextCode, uint32_t pc, bool *skipNext = nullptr, bool *delaySlotNext = nullptr)
@@ -72,6 +73,7 @@ class Disasm {
     virtual void OfB(int16_t offset, uint8_t reg, int size) = 0;
     virtual void BranchDest(uint32_t offset) = 0;
     virtual void Offset(uint32_t offset, int size) = 0;
+    virtual void SyscallName(const char *) = 0;
 
   private:
     // Type definition of our functions
@@ -188,6 +190,9 @@ class Disasm {
     declare(disGPL);
     declare(disNCCT);
 #undef declare
+
+    // li has a slightly different signature, being a pseudoinstruction
+    bool disLI(uint32_t reg, uint32_t imm, uint32_t nextCode, bool *skipNext = nullptr, bool *delaySlotNext = nullptr);
 };
 
 }  // namespace PCSX

src/gui/widgets/assembly.cc

@@ -1,4 +1,4 @@
 /***************************************************************************
  *   Copyright (C) 2019 PCSX-Redux authors                                 *
  *                                                                         *
  *   This program is free software; you can redistribute it and/or modify  *
@@ -104,6 +104,7 @@
     virtual void OfB(int16_t offset, uint8_t reg, int size) final {}
     virtual void BranchDest(uint32_t offset) final {}
     virtual void Offset(uint32_t offset, int size) final {}
+    virtual void SyscallName(const char*) final {}
 };
 
 }  // namespace
@@ -310,6 +311,10 @@
     }
     ImGui::PopStyleVar();
 }
+void PCSX::Widgets::Assembly::SyscallName(const char* name) {
+    sameLine();
+    ImGui::TextUnformatted(name);
+}
 void PCSX::Widgets::Assembly::Sa(uint8_t value) {
     comma();
     sameLine();

src/gui/widgets/assembly.h

@@ -92,6 +92,7 @@ class Assembly : private Disasm {
     virtual void OfB(int16_t offset, uint8_t reg, int size) final;
     virtual void BranchDest(uint32_t value) final;
     virtual void Offset(uint32_t addr, int size) final;
+    virtual void SyscallName(const char*) final;
     bool m_gotArg = false;
     bool m_notch = false;
     bool m_notchAfterSkip[2] = {false, false};