From 7d9966a8ee730127d7cc43a9370f3950d3eba365 Mon Sep 17 00:00:00 2001
From: Nixitov <Nixitov@users.noreply.github.com>
Date: Sun, 11 Oct 2026 23:51:54 +0200
Subject: [PATCH] feat(libc): implement __divti3

Kart PS5 (PPSA99611) imports __divti3 and stops at start-up on main. The guest has no signed 128-bit division; add it alongside __udivti3, dividing the magnitudes and negating the quotient, and throwing on a zero divisor like the unsigned routine.
---
 core/libs/prx/libc/include/SonyCrt.hpp    | 13 ++++++++++++
 core/libs/prx/libc/src/RuntimeSupport.cpp |  4 ++++
 core/libs/tests/GuestCrt.cpp              | 24 +++++++++++++++++++++++
 3 files changed, 41 insertions(+)

diff --git a/core/libs/prx/libc/include/SonyCrt.hpp b/core/libs/prx/libc/include/SonyCrt.hpp
index 2016da156..cc544b21c 100644
--- a/core/libs/prx/libc/include/SonyCrt.hpp
+++ b/core/libs/prx/libc/include/SonyCrt.hpp
@@ -194,6 +194,19 @@ inline unsigned __int128 SonyUdivti3(unsigned __int128 dividend, unsigned __int1
     return quotient;
 }
 
+inline __int128 SonyDivti3(__int128 dividend, __int128 divisor) {
+    if (divisor == 0) throw std::runtime_error("__divti3: integer divide by zero");
+    const bool negative = (dividend < 0) != (divisor < 0);
+    const unsigned __int128 magnitudeDividend = dividend < 0
+        ? (unsigned __int128)0 - (unsigned __int128)dividend
+        : (unsigned __int128)dividend;
+    const unsigned __int128 magnitudeDivisor = divisor < 0
+        ? (unsigned __int128)0 - (unsigned __int128)divisor
+        : (unsigned __int128)divisor;
+    const unsigned __int128 magnitude = SonyUdivti3(magnitudeDividend, magnitudeDivisor);
+    return (__int128)(negative ? (unsigned __int128)0 - magnitude : magnitude);
+}
+
 }
 
 #endif
diff --git a/core/libs/prx/libc/src/RuntimeSupport.cpp b/core/libs/prx/libc/src/RuntimeSupport.cpp
index 69be0d848..6731cbb4c 100644
--- a/core/libs/prx/libc/src/RuntimeSupport.cpp
+++ b/core/libs/prx/libc/src/RuntimeSupport.cpp
@@ -181,6 +181,10 @@ void APS5_VABI _Unlocksyslock_nid_postfix() {
     g_sysLock.unlock();
 }
 
+__int128 APS5_VABI __divti3_nid_postfix(__int128 dividend, __int128 divisor) {
+    return SonyDivti3(dividend, divisor);
+}
+
 unsigned __int128 APS5_VABI __udivti3_nid_postfix(unsigned __int128 dividend, unsigned __int128 divisor) {
     return SonyUdivti3(dividend, divisor);
 }
diff --git a/core/libs/tests/GuestCrt.cpp b/core/libs/tests/GuestCrt.cpp
index 7bd72ca01..10257c096 100644
--- a/core/libs/tests/GuestCrt.cpp
+++ b/core/libs/tests/GuestCrt.cpp
@@ -31,6 +31,7 @@ std::size_t APS5_VABI mbstowcs_nid_postfix(std::uint16_t* dest, const char* src,
 char* APS5_VABI strtok_s_nid_postfix(char* str, const char* delim, char** context);
 int APS5_VABI __fpclassifyd_nid_postfix(double value);
 unsigned __int128 APS5_VABI __udivti3_nid_postfix(unsigned __int128 dividend, unsigned __int128 divisor);
+__int128 APS5_VABI __divti3_nid_postfix(__int128 dividend, __int128 divisor);
 SonyLconv* APS5_VABI localeconv_nid_postfix(void);
 int APS5_VABI sceAmprFpclassifyd(double value);
 }
@@ -84,6 +85,29 @@ int main() {
     }
     Require(trapped);
 
+    Require(__divti3_nid_postfix(100, 3) == 33);
+    Require(__divti3_nid_postfix(-100, 3) == -33);
+    Require(__divti3_nid_postfix(100, -3) == -33);
+    Require(__divti3_nid_postfix(-100, -3) == 33);
+    Require(SonyDivti3(0, 5) == 0);
+    const __int128 large = (__int128)1 << 100;
+    Require(SonyDivti3(large, 3) == large / 3);
+    Require(SonyDivti3(-large, 3) == -(large / 3));
+    Require(SonyDivti3(large, -3) == -(large / 3));
+    Require(SonyDivti3(-large, -3) == large / 3);
+    const __int128 minimum = (__int128)((unsigned __int128)1 << 127);
+    const __int128 maximum = (__int128)(((unsigned __int128)1 << 127) - 1);
+    Require(SonyDivti3(minimum, 1) == minimum);
+    Require(SonyDivti3(minimum, -1) == minimum);
+    Require(SonyDivti3(maximum, -1) == -maximum);
+    trapped = false;
+    try {
+        SonyDivti3(1, 0);
+    } catch (const std::exception&) {
+        trapped = true;
+    }
+    Require(trapped);
+
     void* previous = sceAmprSetConstraintHandlerS(reinterpret_cast<void*>(&CountingHandler));
     Require(previous != nullptr);
     Require(previous != reinterpret_cast<void*>(&CountingHandler));