From 6201fbc0edb2bca84d2b350ab16120da3c4c5bd6 Mon Sep 17 00:00:00 2001
From: Evgeny Leviant <eleviant@accesssoftek.com>
Date: Mon, 4 May 2026 18:47:42 +0200
Subject: [PATCH] [clang] Make signed integer overflow defined with -fms-kernel

---
 clang/lib/Frontend/CompilerInvocation.cpp     |  3 +-
 clang/test/CodeGen/MSKernel/signed-overflow.c | 28 +++++++++++++++++++
 2 files changed, 29 insertions(+), 2 deletions(-)
 create mode 100644 clang/test/CodeGen/MSKernel/signed-overflow.c

diff --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp
index db7c791059a3..57d380e717ed 100644
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -4075,8 +4075,7 @@ bool CompilerInvocation::ParseLangArgs(LangOptions &Opts, ArgList &Args,
     // Set the handler, if one is specified.
     Opts.OverflowHandler =
         std::string(Args.getLastArgValue(OPT_ftrapv_handler));
-  }
-  else if (Args.hasArg(OPT_fwrapv))
+  } else if (Args.hasArg(OPT_fwrapv) || Opts.Kernel)
     Opts.setSignedOverflowBehavior(LangOptions::SOB_Defined);
 
   Opts.MSCompatibilityVersion = 0;
diff --git a/clang/test/CodeGen/MSKernel/signed-overflow.c b/clang/test/CodeGen/MSKernel/signed-overflow.c
new file mode 100644
index 000000000000..0286eb95c505
--- /dev/null
+++ b/clang/test/CodeGen/MSKernel/signed-overflow.c
@@ -0,0 +1,28 @@
+// REQUIRES: x86-registered-target
+// RUN: %clang_cc1 -fms-kernel -triple x86_64-windows-msvc -O2 -emit-llvm %s -o - | FileCheck %s
+// CHECK:      define {{.*}} i32 @add2(i32 noundef %a, i32 noundef %b)
+// CHECK-NEXT: entry:
+// CHECK-NEXT:  %add = add i32 %b, %a
+// CHECK-NEXT:  ret i32 %add
+
+// CHECK:      define {{.*}} i32 @mul2(i32 noundef %a)
+// CHECK-NEXT: entry:
+// CHECK-NEXT:  %mul = shl i32 %a, 1
+// CHECK-NEXT:  ret i32 %mul
+
+// CHECK:      define {{.*}} ptr @add_ptr(ptr noundef {{.*}} %base, i64 noundef %off)
+// CHECK-NEXT: entry:
+// CHECK-NEXT:  %add.ptr = getelementptr i8, ptr %base, i64 %off
+// CHECK-NEXT:  ret ptr %add.ptr
+
+int add2(int a, int b) {
+  return a + b;
+}
+
+int mul2(int a) {
+  return a*=2;
+}
+
+char* add_ptr(char* base, long long off) {
+  return base + off;
+}