From 84cf3e8c84b785363fd89464ae9bb22fd3cf007e Mon Sep 17 00:00:00 2001
From: lizzie <lizzie@eden-emu.dev>
Date: Sat, 8 Nov 2025 00:42:10 +0100
Subject: [PATCH] [nce] remove software prefetching instances (#2857)

May be a complete hit or miss on performance with NCE
Signed-off-by: lizzie <lizzie@eden-emu.dev>

Reviewed-on: https://git.eden-emu.dev/eden-emu/eden/pulls/2857
Reviewed-by: crueter <crueter@eden-emu.dev>
Reviewed-by: Caio Oliveira <caiooliveirafarias0@gmail.com>
Co-authored-by: lizzie <lizzie@eden-emu.dev>
Co-committed-by: lizzie <lizzie@eden-emu.dev>
---
 src/core/arm/nce/arm_nce.cpp             | 22 ----------------
 src/core/arm/nce/interpreter_visitor.cpp | 32 ------------------------
 2 files changed, 54 deletions(-)

diff --git a/src/core/arm/nce/arm_nce.cpp b/src/core/arm/nce/arm_nce.cpp
index 0e0d72fc8a..f0b61f8042 100644
--- a/src/core/arm/nce/arm_nce.cpp
+++ b/src/core/arm/nce/arm_nce.cpp
@@ -388,14 +388,6 @@ void ArmNce::SignalInterrupt(Kernel::KThread* thread) {
 const std::size_t CACHE_PAGE_SIZE = 4096;
 
 void ArmNce::ClearInstructionCache() {
-#if defined(__GNUC__) || defined(__clang__)
-    void* start = (void*)((uintptr_t)__builtin_return_address(0) & ~(CACHE_PAGE_SIZE - 1));
-    void* end =
-        (void*)((uintptr_t)start + CACHE_PAGE_SIZE * 2); // Clear two pages for better coverage
-    // Prefetch next likely pages
-    __builtin_prefetch((void*)((uintptr_t)end), 1, 3);
-    __builtin___clear_cache(static_cast<char*>(start), static_cast<char*>(end));
-#endif
 #ifdef __aarch64__
     // Ensure all previous memory operations complete
     asm volatile("dmb ish" ::: "memory");
@@ -405,20 +397,6 @@ void ArmNce::ClearInstructionCache() {
 }
 
 void ArmNce::InvalidateCacheRange(u64 addr, std::size_t size) {
-    #if defined(__GNUC__) || defined(__clang__)
-        // Align the start address to cache line boundary for better performance
-        const size_t CACHE_LINE_SIZE = 64;
-        addr &= ~(CACHE_LINE_SIZE - 1);
-
-        // Round up size to nearest cache line
-        size = (size + CACHE_LINE_SIZE - 1) & ~(CACHE_LINE_SIZE - 1);
-
-        // Prefetch the range to be invalidated
-        for (size_t offset = 0; offset < size; offset += CACHE_LINE_SIZE) {
-            __builtin_prefetch((void*)(addr + offset), 1, 3);
-        }
-    #endif
-
     this->ClearInstructionCache();
 }
 
diff --git a/src/core/arm/nce/interpreter_visitor.cpp b/src/core/arm/nce/interpreter_visitor.cpp
index aa796ed929..78b78f8067 100644
--- a/src/core/arm/nce/interpreter_visitor.cpp
+++ b/src/core/arm/nce/interpreter_visitor.cpp
@@ -181,14 +181,6 @@ bool InterpreterVisitor::Ordered(size_t size, bool L, bool o0, Reg Rn, Reg Rt) {
     const size_t dbytes = datasize / 8;
 
     u64 address = (Rn == Reg::SP) ? this->GetSp() : this->GetReg(Rn);
-
-    // Conservative prefetch for atomic ops
-    if (memop == MemOp::Load) {
-        __builtin_prefetch(reinterpret_cast<const void*>(address), 0, 1);
-    } else {
-        __builtin_prefetch(reinterpret_cast<const void*>(address), 1, 1);
-    }
-
     switch (memop) {
     case MemOp::Store: {
         std::atomic_thread_fence(std::memory_order_seq_cst);
@@ -435,21 +427,6 @@ bool InterpreterVisitor::RegisterImmediate(bool wback, bool postindex, size_t sc
     if (!postindex)
         address += offset;
 
-    // Optimized prefetch for loads
-    if (memop == MemOp::Load) {
-        const size_t access_size = datasize / 8;
-        const bool is_aligned = (address % access_size) == 0;
-
-        if (is_aligned) {
-            __builtin_prefetch(reinterpret_cast<const void*>(address), 0, 3);
-            if (access_size >= 8 && access_size <= 32) {
-                __builtin_prefetch(reinterpret_cast<const void*>(address + PREFETCH_STRIDE), 0, 3);
-            }
-        } else {
-            __builtin_prefetch(reinterpret_cast<const void*>(address), 0, 1);
-        }
-    }
-
     switch (memop) {
     case MemOp::Store: {
         u64 data = this->GetReg(Rt);
@@ -516,15 +493,6 @@ bool InterpreterVisitor::SIMDImmediate(bool wback, bool postindex, size_t scale,
     if (!postindex)
         address += offset;
 
-    // Aggressive prefetch for SIMD
-    if (memop == MemOp::Load) {
-        __builtin_prefetch(reinterpret_cast<const void*>(address), 0, 3);
-        __builtin_prefetch(reinterpret_cast<const void*>(address + CACHE_LINE_SIZE), 0, 3);
-        if (datasize >= SIMD_PREFETCH_THRESHOLD) {
-            __builtin_prefetch(reinterpret_cast<const void*>(address + PREFETCH_STRIDE), 0, 3);
-        }
-    }
-
     switch (memop) {
     case MemOp::Store: {
         u128 data = VectorGetElement(this->GetVec(Vt), datasize);