Generate .eh_frame contents for nounwind function with landingpads

[lliu0]

Summary

Nounwind function should have .eh_frame contents to catch exceptions thrown in the function itself. We should generate it if the function has landingpads even if it is declared with nounwind.

[lliu0]

Ping.

Could anyone help review this please?

Thanks,
Lei

include/llvm/CodeGen/AsmPrinter.h

   /// If the target supports dwarf debug info, this pointer is non-null.
   DwarfDebug *DD = nullptr;
 
-  /// If the current module uses dwarf CFI annotations strictly for debugging.
-  bool isCFIMoveForDebugging = false;
-
 protected:
   explicit AsmPrinter(TargetMachine &TM, std::unique_ptr<MCStreamer> Streamer);
 

 
   /// Returns false if needsCFIMoves() == CFI_M_EH for any function
   /// in the module.
-  bool needsOnlyDebugCFIMoves() const { return isCFIMoveForDebugging; }
+  bool needsOnlyDebugCFIMoves() const;
 
   bool needsSEHMoves();
 

lib/CodeGen/AsmPrinter/AsmPrinter.cpp

     }
   }
 
-  switch (MAI->getExceptionHandlingType()) {
-  case ExceptionHandling::SjLj:
-  case ExceptionHandling::DwarfCFI:
-  case ExceptionHandling::ARM:
-    isCFIMoveForDebugging = true;
-    if (MAI->getExceptionHandlingType() != ExceptionHandling::DwarfCFI)
-      break;
-    for (auto &F: M.getFunctionList()) {
-      // If the module contains any function with unwind data,
-      // .eh_frame has to be emitted.
-      // Ignore functions that won't get emitted.
-      if (!F.isDeclarationForLinker() && F.needsUnwindTableEntry()) {
-        isCFIMoveForDebugging = false;
-        break;
-      }
-    }
-    break;
-  default:
-    isCFIMoveForDebugging = false;
-    break;
-  }
-
   EHStreamer *ES = nullptr;
   switch (MAI->getExceptionHandlingType()) {
   case ExceptionHandling::None:

   return false;
 }
 
+bool AsmPrinter::needsOnlyDebugCFIMoves() const {
+  switch (MAI->getExceptionHandlingType()) {
+  case ExceptionHandling::SjLj:
+  case ExceptionHandling::DwarfCFI:
+  case ExceptionHandling::ARM:
+    if (MAI->getExceptionHandlingType() != ExceptionHandling::DwarfCFI)
+      return true;
+    for (auto &F: MMI->getModule()->getFunctionList()) {
+      // If the module contains any function with unwind data,
+      // .eh_frame has to be emitted.
+      // Ignore functions that won't get emitted.
+      MachineFunction *MF = MMI->getMachineFunction(F);
+      bool hasLandingPads = MF && !MF->getLandingPads().empty();
+      if (!F.isDeclarationForLinker() &&
+          (F.needsUnwindTableEntry() || hasLandingPads)) {
+        return false;
+      }
+    }
+    return true;
+  default:
+    return false;
+  }
+}
+
 static bool canBeHidden(const GlobalValue *GV, const MCAsmInfo &MAI) {
   if (!MAI.hasWeakDefCanBeHiddenDirective())
     return false;

 
 AsmPrinter::CFIMoveType AsmPrinter::needsCFIMoves() const {
   if (MAI->getExceptionHandlingType() == ExceptionHandling::DwarfCFI &&
-      MF->getFunction().needsUnwindTableEntry())
+      (MF->getFunction().needsUnwindTableEntry() ||
+      !MF->getLandingPads().empty()))
     return CFI_M_EH;
 
   if (MMI->hasDebugInfo())

test/CodeGen/X86/eh_frame_nounwind.ll

+; RUN: llc -mtriple=i386 < %s -filetype=obj | llvm-dwarfdump -eh-frame - | FileCheck %s
+
+; Test that .eh_frame contents are generated for nounwind functions
+; with landingpads.
+
+; CHECK: .eh_frame contents:
+; CHECK: {{.*}}CIE{{.*}}
+; CHECK: {{.*}}FDE{{.*}}
+
+target datalayout = "e-m:e-p:32:32-f64:32:64-f80:32-n8:16:32-S128"
+target triple = "i386"
+
+$__clang_call_terminate = comdat any
+
+@_ZTIi = external constant i8*
+
+; Function Attrs: noinline nounwind optnone
+define dso_local i32 @_Z3foov() #0 personality i8* bitcast (i32 (...)* @__gxx_personality_v0 to i8*) {
+entry:
+  %retval = alloca i32, align 4
+  %exn.slot = alloca i8*
+  %ehselector.slot = alloca i32
+  %x = alloca i32, align 4
+  %exception = call i8* @__cxa_allocate_exception(i32 4) #3
+  %0 = bitcast i8* %exception to i32*
+  store i32 1, i32* %0, align 16
+  invoke void @__cxa_throw(i8* %exception, i8* bitcast (i8** @_ZTIi to i8*), i8* null) #4
+          to label %unreachable unwind label %lpad
+
+lpad:                                             ; preds = %entry
+  %1 = landingpad { i8*, i32 }
+          catch i8* bitcast (i8** @_ZTIi to i8*)
+          catch i8* null
+  %2 = extractvalue { i8*, i32 } %1, 0
+  store i8* %2, i8** %exn.slot, align 4
+  %3 = extractvalue { i8*, i32 } %1, 1
+  store i32 %3, i32* %ehselector.slot, align 4
+  br label %catch.dispatch
+
+catch.dispatch:                                   ; preds = %lpad
+  %sel = load i32, i32* %ehselector.slot, align 4
+  %4 = call i32 @llvm.eh.typeid.for(i8* bitcast (i8** @_ZTIi to i8*)) #3
+  %matches = icmp eq i32 %sel, %4
+  br i1 %matches, label %catch, label %terminate.handler
+
+catch:                                            ; preds = %catch.dispatch
+  %exn = load i8*, i8** %exn.slot, align 4
+  %5 = call i8* @__cxa_begin_catch(i8* %exn) #3
+  %6 = bitcast i8* %5 to i32*
+  %7 = load i32, i32* %6, align 4
+  store i32 %7, i32* %x, align 4
+  store i32 0, i32* %retval, align 4
+  call void @__cxa_end_catch() #3
+  br label %return
+
+try.cont:                                         ; No predecessors!
+  store i32 1, i32* %retval, align 4
+  br label %return
+
+return:                                           ; preds = %try.cont, %catch
+  %8 = load i32, i32* %retval, align 4
+  ret i32 %8
+
+terminate.handler:                                ; preds = %catch.dispatch
+  %exn1 = load i8*, i8** %exn.slot, align 4
+  call void @__clang_call_terminate(i8* %exn1) #5
+  unreachable
+
+unreachable:                                      ; preds = %entry
+  unreachable
+}
+
+declare i8* @__cxa_allocate_exception(i32)
+
+declare void @__cxa_throw(i8*, i8*, i8*)
+
+declare i32 @__gxx_personality_v0(...)
+
+; Function Attrs: nounwind readnone
+declare i32 @llvm.eh.typeid.for(i8*) #1
+
+; Function Attrs: noinline noreturn nounwind
+define linkonce_odr hidden void @__clang_call_terminate(i8*) #2 comdat {
+  %2 = call i8* @__cxa_begin_catch(i8* %0) #3
+  call void @_ZSt9terminatev() #5
+  unreachable
+}
+
+declare i8* @__cxa_begin_catch(i8*)
+
+declare void @_ZSt9terminatev()
+
+declare void @__cxa_end_catch()
+
+attributes #0 = { noinline nounwind optnone "correctly-rounded-divide-sqrt-fp-math"="false" "disable-tail-calls"="false" "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false" "no-jump-tables"="false" "no-nans-fp-math"="false" "no-signed-zeros-fp-math"="false" "no-trapping-math"="false" "stack-protector-buffer-size"="8" "target-cpu"="pentium4" "target-features"="+fxsr,+mmx,+sse,+sse2,+x87" "unsafe-fp-math"="false" "use-soft-float"="false" }
+attributes #1 = { nounwind readnone }
+attributes #2 = { noinline noreturn nounwind }
+attributes #3 = { nounwind }
+attributes #4 = { noreturn }
+attributes #5 = { noreturn nounwind }
+
+!llvm.module.flags = !{!0, !1}
+!llvm.ident = !{!2}
+
+!0 = !{i32 1, !"NumRegisterParameters", i32 0}
+!1 = !{i32 1, !"wchar_size", i32 4}
+!2 = !{!"clang version 7.0.0 (https://github.com/llvm-mirror/clang.git 43eac1f9d7d2c985831b485d9ccc807416d1cf29) (https://github.com/llvm-mirror/llvm.git eac9f2c06322ac1db665f3bc432b2b4fdcc81eed)"}