[llvm] r242063 - [WinEH] Emit the LSDA even if no lpads remain but outlining occurred

[Reid Kleckner]

Author: rnk
Date: Mon Jul 13 15:41:46 2015
New Revision: 242063

URL: http://llvm.org/viewvc/llvm-project?rev=242063&view=rev
Log:
[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.

Added:
    llvm/trunk/test/CodeGen/X86/cppeh-nounwind.ll
Modified:
    llvm/trunk/lib/CodeGen/AsmPrinter/WinException.cpp

Modified: llvm/trunk/lib/CodeGen/AsmPrinter/WinException.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/AsmPrinter/WinException.cpp?rev=242063&r1=242062&r2=242063&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/AsmPrinter/WinException.cpp (original)
+++ llvm/trunk/lib/CodeGen/AsmPrinter/WinException.cpp Mon Jul 13 15:41:46 2015
@@ -70,7 +70,9 @@ void WinException::beginFunction(const M
 
   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 M
   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 Mac
   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::emitExceptHandlerTabl
   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") {

Added: llvm/trunk/test/CodeGen/X86/cppeh-nounwind.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/cppeh-nounwind.ll?rev=242063&view=auto
==============================================================================
--- llvm/trunk/test/CodeGen/X86/cppeh-nounwind.ll (added)
+++ llvm/trunk/test/CodeGen/X86/cppeh-nounwind.ll Mon Jul 13 15:41:46 2015
@@ -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