[CodeGen] Force emission of personality directive if explicitly specified

Summary:
Before this change, personality directives were not emitted
if there was no invoke left in the function (of course until
recently this also meant that we couldn't know what
the personality actually was). This patch forces personality directives
to still be emitted, unless it is known to be a noop in the absence of
invokes, or the user explicitly specified `nounwind` (and not
`uwtable`) on the function.

Reviewers: majnemer, rnk

Subscribers: rnk, llvm-commits

Differential Revision: http://reviews.llvm.org/D10884

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@242185 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/llvm/Analysis/LibCallSemantics.h b/include/llvm/Analysis/LibCallSemantics.h
index 170e2a49a8ea59bc7825c231f9200a78cc993634..b4bef310e59099d7055da9fc8c8a0d321ae494d4 100644 (file)
--- a/include/llvm/Analysis/LibCallSemantics.h
+++ b/include/llvm/Analysis/LibCallSemantics.h
@@ -206,6 +206,18 @@ class InvokeInst;
     llvm_unreachable("invalid enum");
   }
 
+  /// \brief Return true if this personality may be safely removed if there
+  /// are no invoke instructions remaining in the current function.
+  inline bool isNoOpWithoutInvoke(EHPersonality Pers) {
+    switch (Pers) {
+    case EHPersonality::Unknown:
+      return false;
+    // All known personalities currently have this behavior
+    default: return true;
+    }
+    llvm_unreachable("invalid enum");
+  }
+
   bool canSimplifyInvokeNoUnwind(const Function *F);
 
 } // end namespace llvm

diff --git a/include/llvm/CodeGen/MachineModuleInfo.h b/include/llvm/CodeGen/MachineModuleInfo.h
index ccaa83a238a6231dc2c3bfc8ad29c8d5f26e7922..4cdfe2463c99505666f98e10bca71e112a460474 100644 (file)
--- a/include/llvm/CodeGen/MachineModuleInfo.h
+++ b/include/llvm/CodeGen/MachineModuleInfo.h
@@ -320,6 +320,7 @@ public:
   /// information.
   void addPersonality(MachineBasicBlock *LandingPad,
                       const Function *Personality);
+  void addPersonality(const Function *Personality);
 
   void addWinEHState(MachineBasicBlock *LandingPad, int State);
 

diff --git a/lib/CodeGen/AsmPrinter/ARMException.cpp b/lib/CodeGen/AsmPrinter/ARMException.cpp
index 4cb460a7bbfc911dbde968a0322f5842261cc32b..0bad7954b98091073b3f456861771cd91943e808 100644 (file)
--- a/lib/CodeGen/AsmPrinter/ARMException.cpp
+++ b/lib/CodeGen/AsmPrinter/ARMException.cpp
@@ -69,24 +69,32 @@ void ARMException::beginFunction(const MachineFunction *MF) {
 ///
 void ARMException::endFunction(const MachineFunction *MF) {
   ARMTargetStreamer &ATS = getTargetStreamer();
+  const Function *F = MF->getFunction();
+  const Function *Per = nullptr;
+  if (F->hasPersonalityFn())
+    Per = dyn_cast<Function>(F->getPersonalityFn()->stripPointerCasts());
+  assert(!MMI->getPersonality() || Per == MMI->getPersonality());
+  bool forceEmitPersonality =
+    F->hasPersonalityFn() && !isNoOpWithoutInvoke(classifyEHPersonality(Per)) &&
+    F->needsUnwindTableEntry();
+  bool shouldEmitPersonality = forceEmitPersonality ||
+    !MMI->getLandingPads().empty();
   if (!Asm->MF->getFunction()->needsUnwindTableEntry() &&
-      MMI->getLandingPads().empty())
+      !shouldEmitPersonality)
     ATS.emitCantUnwind();
-  else {
-    if (!MMI->getLandingPads().empty()) {
-      // Emit references to personality.
-      if (const Function *Personality = MMI->getPersonality()) {
-        MCSymbol *PerSym = Asm->getSymbol(Personality);
-        Asm->OutStreamer->EmitSymbolAttribute(PerSym, MCSA_Global);
-        ATS.emitPersonality(PerSym);
-      }
-
-      // Emit .handlerdata directive.
-      ATS.emitHandlerData();
-
-      // Emit actual exception table
-      emitExceptionTable();
+  else if (shouldEmitPersonality) {
+    // Emit references to personality.
+    if (Per) {
+      MCSymbol *PerSym = Asm->getSymbol(Per);
+      Asm->OutStreamer->EmitSymbolAttribute(PerSym, MCSA_Global);
+      ATS.emitPersonality(PerSym);
     }
+
+    // Emit .handlerdata directive.
+    ATS.emitHandlerData();
+
+    // Emit actual exception table
+    emitExceptionTable();
   }
 
   if (Asm->MAI->getExceptionHandlingType() == ExceptionHandling::ARM)

diff --git a/lib/CodeGen/AsmPrinter/DwarfCFIException.cpp b/lib/CodeGen/AsmPrinter/DwarfCFIException.cpp
index 0bc873e326beae47693d4897e5b817019b3a130a..2c212c7ecee1e7efffff709d9d1bb1c750fac088 100644 (file)
--- a/lib/CodeGen/AsmPrinter/DwarfCFIException.cpp
+++ b/lib/CodeGen/AsmPrinter/DwarfCFIException.cpp
@@ -89,6 +89,7 @@ void DwarfCFIException::endModule() {
 
 void DwarfCFIException::beginFunction(const MachineFunction *MF) {
   shouldEmitMoves = shouldEmitPersonality = shouldEmitLSDA = false;
+  const Function *F = MF->getFunction();
 
   // If any landing pads survive, we need an EH table.
   bool hasLandingPads = !MMI->getLandingPads().empty();
@@ -104,10 +105,24 @@ void DwarfCFIException::beginFunction(const MachineFunction *MF) {
 
   const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering();
   unsigned PerEncoding = TLOF.getPersonalityEncoding();
-  const Function *Per = MMI->getPersonality();
-
-  shouldEmitPersonality = hasLandingPads &&
-    PerEncoding != dwarf::DW_EH_PE_omit && Per;
+  const Function *Per = nullptr;
+  if (F->hasPersonalityFn())
+    Per = dyn_cast<Function>(F->getPersonalityFn()->stripPointerCasts());
+  assert(!MMI->getPersonality() || Per == MMI->getPersonality());
+
+  // Emit a personality function even when there are no landing pads
+  bool forceEmitPersonality =
+      // ...if a personality function is explicitly specified
+      F->hasPersonalityFn() &&
+      // ... and it's not known to be a noop in the absence of invokes
+      !isNoOpWithoutInvoke(classifyEHPersonality(Per)) &&
+      // ... and we're not explicitly asked not to emit it
+      F->needsUnwindTableEntry();
+
+  shouldEmitPersonality =
+      (forceEmitPersonality ||
+       (hasLandingPads && PerEncoding != dwarf::DW_EH_PE_omit)) &&
+      Per;
 
   unsigned LSDAEncoding = TLOF.getLSDAEncoding();
   shouldEmitLSDA = shouldEmitPersonality &&
@@ -123,6 +138,11 @@ void DwarfCFIException::beginFunction(const MachineFunction *MF) {
   if (!shouldEmitPersonality)
     return;
 
+  // If we are forced to emit this personality, make sure to record
+  // it because it might not appear in any landingpad
+  if (forceEmitPersonality)
+    MMI->addPersonality(Per);
+
   const MCSymbol *Sym =
       TLOF.getCFIPersonalitySymbol(Per, *Asm->Mang, Asm->TM, MMI);
   Asm->OutStreamer->EmitCFIPersonality(Sym, PerEncoding);

diff --git a/lib/CodeGen/AsmPrinter/EHStreamer.cpp b/lib/CodeGen/AsmPrinter/EHStreamer.cpp
index 1be3fd74d602c298fd23b31fe73cefbd2e3c4b9a..49ef8d3ddc8fda96557fc3a021cabbcbf6ef1c72 100644 (file)
--- a/lib/CodeGen/AsmPrinter/EHStreamer.cpp
+++ b/lib/CodeGen/AsmPrinter/EHStreamer.cpp
@@ -309,7 +309,7 @@ computeCallSiteTable(SmallVectorImpl<CallSiteEntry> &CallSites,
   // If some instruction between the previous try-range and the end of the
   // function may throw, create a call-site entry with no landing pad for the
   // region following the try-range.
-  if (SawPotentiallyThrowing && !IsSJLJ) {
+  if (SawPotentiallyThrowing && !IsSJLJ && LastLabel != nullptr) {
     CallSiteEntry Site = { LastLabel, nullptr, nullptr, 0 };
     CallSites.push_back(Site);
   }

diff --git a/lib/CodeGen/AsmPrinter/WinException.cpp b/lib/CodeGen/AsmPrinter/WinException.cpp
index 7ef2832d41a3e498b1ac22a24357d7d962e95976..71c77815e281df0ba06ea702cc37be3f10b40bcf 100644 (file)
--- a/lib/CodeGen/AsmPrinter/WinException.cpp
+++ b/lib/CodeGen/AsmPrinter/WinException.cpp
@@ -74,8 +74,12 @@ void WinException::beginFunction(const MachineFunction *MF) {
   if (F->hasPersonalityFn())
     Per = dyn_cast<Function>(F->getPersonalityFn()->stripPointerCasts());
 
-  shouldEmitPersonality = hasLandingPads &&
-    PerEncoding != dwarf::DW_EH_PE_omit && Per;
+  bool forceEmitPersonality =
+    F->hasPersonalityFn() && !isNoOpWithoutInvoke(classifyEHPersonality(Per)) &&
+    F->needsUnwindTableEntry();
+
+  shouldEmitPersonality = forceEmitPersonality || (hasLandingPads &&
+    PerEncoding != dwarf::DW_EH_PE_omit && Per);
 
   unsigned LSDAEncoding = TLOF.getLSDAEncoding();
   shouldEmitLSDA = shouldEmitPersonality &&

diff --git a/lib/CodeGen/MachineModuleInfo.cpp b/lib/CodeGen/MachineModuleInfo.cpp
index 42d0603ab96b43235798fd09d1960b5105f8679d..6a206249d8347251d4119ed594280747a6e3890c 100644 (file)
--- a/lib/CodeGen/MachineModuleInfo.cpp
+++ b/lib/CodeGen/MachineModuleInfo.cpp
@@ -320,7 +320,10 @@ void MachineModuleInfo::addPersonality(MachineBasicBlock *LandingPad,
                                        const Function *Personality) {
   LandingPadInfo &LP = getOrCreateLandingPadInfo(LandingPad);
   LP.Personality = Personality;
+  addPersonality(Personality);
+}
 
+void MachineModuleInfo::addPersonality(const Function *Personality) {
   for (unsigned i = 0; i < Personalities.size(); ++i)
     if (Personalities[i] == Personality)
       return;

diff --git a/test/CodeGen/X86/eh-nolandingpads.ll b/test/CodeGen/X86/eh-nolandingpads.ll
new file mode 100644 (file)
index 0000000..9629522
--- /dev/null
+++ b/test/CodeGen/X86/eh-nolandingpads.ll
@@ -0,0 +1,12 @@
+; RUN: llc < %s -mtriple=x86_64-pc-linux | FileCheck %s
+; Test that we emit functions with explicitly specified personality,
+; even if no landing pads are left.
+
+declare i32 @__my_personality_v0(...)
+declare void @might_throw()
+
+define i32 @foo() personality i32 (...)* @__my_personality_v0 {
+; CHECK: .cfi_personality 3, __my_personality_v0
+    call void @might_throw()
+    ret i32 0
+}