From 9a1a9194653ef5aa15ef32120c26f39c22a5332f Mon Sep 17 00:00:00 2001
From: Reid Kleckner <reid@kleckner.net>
Date: Mon, 13 Jul 2015 20:41:46 +0000
Subject: [PATCH] [WinEH] Emit the LSDA even if no lpads remain but outlining
 occurred

The outlined funclets call intrinsics which reference labels from the
LSDA. This situation can easily arise in small functions with a single
cleanup at -O0, where Clang marks a definition as nounwind, and then
WinEHPrepare "discovers" that the landingpad is dead by accident and
deletes it.

We now need to ask the LLVM IR Function for it's personality directly,
rather than going through MachineModuleInfo.

Fixes PR23892.

llvm-svn: 242063
---
 llvm/lib/CodeGen/AsmPrinter/WinException.cpp | 20 +++++++++++-----
 llvm/test/CodeGen/X86/cppeh-nounwind.ll      | 35 ++++++++++++++++++++++++++++
 2 files changed, 49 insertions(+), 6 deletions(-)
 create mode 100644 llvm/test/CodeGen/X86/cppeh-nounwind.ll

diff --git a/llvm/lib/CodeGen/AsmPrinter/WinException.cpp b/llvm/lib/CodeGen/AsmPrinter/WinException.cpp
index 55f97e6..7ef2832 100644
--- a/llvm/lib/CodeGen/AsmPrinter/WinException.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/WinException.cpp
@@ -70,7 +70,9 @@ void WinException::beginFunction(const MachineFunction *MF) {
 
   const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering();
   unsigned PerEncoding = TLOF.getPersonalityEncoding();
-  const Function *Per = MMI->getPersonality();
+  const Function *Per = nullptr;
+  if (F->hasPersonalityFn())
+    Per = dyn_cast<Function>(F->getPersonalityFn()->stripPointerCasts());
 
   shouldEmitPersonality = hasLandingPads &&
     PerEncoding != dwarf::DW_EH_PE_omit && Per;
@@ -79,10 +81,12 @@ void WinException::beginFunction(const MachineFunction *MF) {
   shouldEmitLSDA = shouldEmitPersonality &&
     LSDAEncoding != dwarf::DW_EH_PE_omit;
 
-  // If we're not using CFI, we don't want the CFI or the personality. Emit the
-  // LSDA if this is the parent function.
+  // If we're not using CFI, we don't want the CFI or the personality. If
+  // WinEHPrepare outlined something, we should emit the LSDA.
   if (!Asm->MAI->usesWindowsCFI()) {
-    shouldEmitLSDA = (hasLandingPads && F == ParentF);
+    bool HasOutlinedChildren =
+        F->hasFnAttribute("wineh-parent") && F == ParentF;
+    shouldEmitLSDA = HasOutlinedChildren;
     shouldEmitPersonality = false;
     return;
   }
@@ -121,7 +125,10 @@ void WinException::endFunction(const MachineFunction *MF) {
   if (!shouldEmitPersonality && !shouldEmitMoves && !shouldEmitLSDA)
     return;
 
-  EHPersonality Per = MMI->getPersonalityType();
+  const Function *F = MF->getFunction();
+  EHPersonality Per = EHPersonality::Unknown;
+  if (F->hasPersonalityFn())
+    Per = classifyEHPersonality(F->getPersonalityFn());
 
   // Get rid of any dead landing pads if we're not using a Windows EH scheme. In
   // Windows EH schemes, the landing pad is not actually reachable. It only
@@ -582,7 +589,8 @@ void WinException::emitExceptHandlerTable(const MachineFunction *MF) {
   OS.EmitValueToAlignment(4);
   OS.EmitLabel(LSDALabel);
 
-  const Function *Per = MMI->getPersonality();
+  const Function *Per =
+      dyn_cast<Function>(F->getPersonalityFn()->stripPointerCasts());
   StringRef PerName = Per->getName();
   int BaseState = -1;
   if (PerName == "_except_handler4") {
diff --git a/llvm/test/CodeGen/X86/cppeh-nounwind.ll b/llvm/test/CodeGen/X86/cppeh-nounwind.ll
new file mode 100644
index 0000000..d9bc001
--- /dev/null
+++ b/llvm/test/CodeGen/X86/cppeh-nounwind.ll
@@ -0,0 +1,35 @@
+; RUN: llc -mtriple=i686-pc-windows-msvc < %s | FileCheck %s
+
+; Sometimes invokes of nounwind functions make it through to CodeGen, especially
+; at -O0, where Clang sometimes optimistically annotates functions as nounwind.
+; WinEHPrepare ends up outlining functions, and emitting references to LSDA
+; labels. Make sure we emit the LSDA in that case.
+
+declare i32 @__CxxFrameHandler3(...)
+declare void @nounwind_func() nounwind
+declare void @cleanup()
+
+define void @should_emit_tables() personality i32 (...)* @__CxxFrameHandler3 {
+entry:
+  invoke void @nounwind_func()
+      to label %done unwind label %lpad
+
+done:
+  ret void
+
+lpad:
+  %vals = landingpad { i8*, i32 }
+      cleanup
+  call void @cleanup()
+  resume { i8*, i32 } %vals
+}
+
+; CHECK: _should_emit_tables:
+; CHECK: calll _nounwind_func
+; CHECK: retl
+
+; CHECK: L__ehtable$should_emit_tables:
+
+; CHECK: ___ehhandler$should_emit_tables:
+; CHECK: movl $L__ehtable$should_emit_tables, %eax
+; CHECK: jmp ___CxxFrameHandler3 # TAILCALL
-- 
2.7.4