[llvm] [LLT] mark the CFI jumptable naked on Windows (PR #170371)

[Mircea Trofin via llvm-commits]

https://github.com/mtrofin created https://github.com/llvm/llvm-project/pull/170371

None

>From 4dc36ce5e7d2e30de3d4fd28228a91468840fb05 Mon Sep 17 00:00:00 2001
From: Mircea Trofin <mtrofin at google.com>
Date: Tue, 2 Dec 2025 13:48:10 -0800
Subject: [PATCH] [LLT] mark the CFI jumptable naked on Windows

---
 llvm/lib/Transforms/IPO/LowerTypeTests.cpp      | 7 +------
 llvm/test/Transforms/LowerTypeTests/function.ll | 2 +-
 2 files changed, 2 insertions(+), 7 deletions(-)

diff --git a/llvm/lib/Transforms/IPO/LowerTypeTests.cpp b/llvm/lib/Transforms/IPO/LowerTypeTests.cpp
index fa35eef2c00f5..f7aeda95e41b3 100644
--- a/llvm/lib/Transforms/IPO/LowerTypeTests.cpp
+++ b/llvm/lib/Transforms/IPO/LowerTypeTests.cpp
@@ -1554,12 +1554,7 @@ void LowerTypeTestsModule::createJumpTable(
 
   // Align the whole table by entry size.
   F->setAlignment(Align(getJumpTableEntrySize(JumpTableArch)));
-  // Skip prologue.
-  // Disabled on win32 due to https://llvm.org/bugs/show_bug.cgi?id=28641#c3.
-  // Luckily, this function does not get any prologue even without the
-  // attribute.
-  if (OS != Triple::Win32)
-    F->addFnAttr(Attribute::Naked);
+  F->addFnAttr(Attribute::Naked);
   if (JumpTableArch == Triple::arm)
     F->addFnAttr("target-features", "-thumb-mode");
   if (JumpTableArch == Triple::thumb) {
diff --git a/llvm/test/Transforms/LowerTypeTests/function.ll b/llvm/test/Transforms/LowerTypeTests/function.ll
index ab3cfb6acccf8..e654da656362f 100644
--- a/llvm/test/Transforms/LowerTypeTests/function.ll
+++ b/llvm/test/Transforms/LowerTypeTests/function.ll
@@ -115,7 +115,7 @@ define i1 @foo(ptr %p) {
 ; NATIVE-SAME: "s"(ptr @g.cfi)
 
 ; X86-LINUX: attributes #[[ATTR]] = { naked nocf_check noinline }
-; X86-WIN32: attributes #[[ATTR]] = { nocf_check noinline }
+; X86-WIN32: attributes #[[ATTR]] = { naked nocf_check noinline }
 ; ARM: attributes #[[ATTR]] = { naked noinline
 ; THUMB: attributes #[[ATTR]] = { naked noinline "target-cpu"="cortex-a8" "target-features"="+thumb-mode" }
 ; THUMBV6M: attributes #[[ATTR]] = { naked noinline "target-features"="+thumb-mode" }