From 0dc619d6155b0f6533ff35d13cf5f00add4b1939 Mon Sep 17 00:00:00 2001
From: Jaklyy <102590697+Jaklyy@users.noreply.github.com>
Date: Mon, 5 Aug 2024 11:41:25 -0400
Subject: [PATCH] Revert "Improve accuracy of prefetch aborts"

This reverts commit 587958e6781cf4d44cd9c611f2589e7d3fc36e5d.
---
 src/ARM.cpp  | 38 ++++++++++++++++++++------------------
 src/CP15.cpp | 29 +++++++++++++++--------------
 2 files changed, 35 insertions(+), 32 deletions(-)

diff --git a/src/ARM.cpp b/src/ARM.cpp
index ae55514a..6ac387b2 100644
--- a/src/ARM.cpp
+++ b/src/ARM.cpp
@@ -343,6 +343,12 @@ void ARMv5::JumpTo(u32 addr, bool restorecpsr)
         CPSR &= ~0x20;
     }
 
+    if (!(PU_Map[addr>>12] & 0x04))
+    {
+        PrefetchAbort();
+        return;
+    }
+
     NDS.MonitorARM9Jump(addr);
 }
 
@@ -569,6 +575,15 @@ void ARMv5::PrefetchAbort()
     CPSR |= 0x97;
     UpdateMode(oldcpsr, CPSR);
 
+    // this shouldn't happen, but if it does, we're stuck in some nasty endless loop
+    // so better take care of it
+    if (!(PU_Map[ExceptionBase>>12] & 0x04))
+    {
+        Log(LogLevel::Error, "!!!!! EXCEPTION REGION NOT EXECUTABLE. THIS IS VERY BAD!!\n");
+        NDS.Stop(Platform::StopReason::BadExceptionRegion);
+        return;
+    }
+
     R_ABT[2] = oldcpsr;
     R[14] = R[15] + (oldcpsr & 0x20 ? 2 : 0);
     JumpTo(ExceptionBase + 0x0C);
@@ -670,18 +685,10 @@ void ARMv5::Execute()
                 NextInstr[0] = NextInstr[1];
                 if (R[15] & 0x2) { NextInstr[1] >>= 16; CodeCycles = 0; }
                 else             NextInstr[1] = CodeRead32(R[15], false);
-                
-                // handle aborted instructions
-                if (!(PU_Map[(R[15]-4)>>12] & 0x04)) [[unlikely]]
-                {
-                    PrefetchAbort();
-                }
+
                 // actually execute
-                else [[likely]]
-                {
-                    u32 icode = (CurInstr >> 6) & 0x3FF;
-                    ARMInterpreter::THUMBInstrTable[icode](this);
-                }
+                u32 icode = (CurInstr >> 6) & 0x3FF;
+                ARMInterpreter::THUMBInstrTable[icode](this);
             }
             else
             {
@@ -693,14 +700,9 @@ void ARMv5::Execute()
                 CurInstr = NextInstr[0];
                 NextInstr[0] = NextInstr[1];
                 NextInstr[1] = CodeRead32(R[15], false);
-                
-                // handle aborted instructions
-                if (!(PU_Map[(R[15]-8)>>12] & 0x04)) [[unlikely]] // todo: check for bkpt instruction?
-                {
-                    PrefetchAbort();
-                }
+
                 // actually execute
-                else if (CheckCondition(CurInstr >> 28)) [[likely]]
+                if (CheckCondition(CurInstr >> 28))
                 {
                     u32 icode = ((CurInstr >> 4) & 0xF) | ((CurInstr >> 16) & 0xFF0);
                     ARMInterpreter::ARMInstrTable[icode](this);
diff --git a/src/CP15.cpp b/src/CP15.cpp
index 6fcaff93..bf1d2edc 100644
--- a/src/CP15.cpp
+++ b/src/CP15.cpp
@@ -773,13 +773,14 @@ u32 ARMv5::CP15Read(u32 id) const
 
 u32 ARMv5::CodeRead32(u32 addr, bool branch)
 {
-    // prefetch abort
-    // the actual exception is not raised until the aborted instruction is executed
-    if (!(PU_Map[addr>>12] & 0x04)) [[unlikely]]
+    /*if (branch || (!(addr & 0xFFF)))
     {
-        CodeCycles = 1;
-        return 0;
-    }
+        if (!(PU_Map[addr>>12] & 0x04))
+        {
+            PrefetchAbort();
+            return 0;
+        }
+    }*/
 
     if (addr < ITCMSize)
     {
@@ -806,7 +807,7 @@ u32 ARMv5::CodeRead32(u32 addr, bool branch)
 
 bool ARMv5::DataRead8(u32 addr, u32* val)
 {
-    if (!(PU_Map[addr>>12] & 0x01)) [[unlikely]]
+    if (!(PU_Map[addr>>12] & 0x01))
     {
         DataAbort();
         return false;
@@ -832,7 +833,7 @@ bool ARMv5::DataRead8(u32 addr, u32* val)
 
 bool ARMv5::DataRead16(u32 addr, u32* val)
 {
-    if (!(PU_Map[addr>>12] & 0x01)) [[unlikely]]
+    if (!(PU_Map[addr>>12] & 0x01))
     {
         DataAbort();
         return false;
@@ -860,7 +861,7 @@ bool ARMv5::DataRead16(u32 addr, u32* val)
 
 bool ARMv5::DataRead32(u32 addr, u32* val)
 {
-    if (!(PU_Map[addr>>12] & 0x01)) [[unlikely]]
+    if (!(PU_Map[addr>>12] & 0x01))
     {
         DataAbort();
         return false;
@@ -888,7 +889,7 @@ bool ARMv5::DataRead32(u32 addr, u32* val)
 
 bool ARMv5::DataRead32S(u32 addr, u32* val)
 {
-    if (!(PU_Map[addr>>12] & 0x01)) [[unlikely]]
+    if (!(PU_Map[addr>>12] & 0x01))
     {
         DataAbort();
         return false;
@@ -916,7 +917,7 @@ bool ARMv5::DataRead32S(u32 addr, u32* val)
 
 bool ARMv5::DataWrite8(u32 addr, u8 val)
 {
-    if (!(PU_Map[addr>>12] & 0x02)) [[unlikely]]
+    if (!(PU_Map[addr>>12] & 0x02))
     {
         DataAbort();
         return false;
@@ -943,7 +944,7 @@ bool ARMv5::DataWrite8(u32 addr, u8 val)
 
 bool ARMv5::DataWrite16(u32 addr, u16 val)
 {
-    if (!(PU_Map[addr>>12] & 0x02)) [[unlikely]]
+    if (!(PU_Map[addr>>12] & 0x02))
     {
         DataAbort();
         return false;
@@ -972,7 +973,7 @@ bool ARMv5::DataWrite16(u32 addr, u16 val)
 
 bool ARMv5::DataWrite32(u32 addr, u32 val)
 {
-    if (!(PU_Map[addr>>12] & 0x02)) [[unlikely]]
+    if (!(PU_Map[addr>>12] & 0x02))
     {
         DataAbort();
         return false;
@@ -1001,7 +1002,7 @@ bool ARMv5::DataWrite32(u32 addr, u32 val)
 
 bool ARMv5::DataWrite32S(u32 addr, u32 val, bool dataabort)
 {
-    if (!(PU_Map[addr>>12] & 0x02)) [[unlikely]]
+    if (!(PU_Map[addr>>12] & 0x02))
     {
         if (!dataabort) DataAbort();
         return false;