Fix ARM EHABI when function has landingpad and nounwind.

If the function has the landingpad instruction, then the
handlerdata should be emitted even if the function has
nouwnind attribute.  Otherwise, following code will not
work:

    void test1() noexcept {
      try {
        throw_exception();
      } catch (...) {
        log_unexpected_exception();
      }
    }

Since the cantunwind was incorrectly emitted and the
LSDA is not available.

llvm-svn: 208791

2 files changed, 68 insertions, 8 deletions

diff --git a/llvm/lib/CodeGen/AsmPrinter/ARMException.cpp b/llvm/lib/CodeGen/AsmPrinter/ARMException.cpp
index 97b288f1947..1cb0159d10f 100644
--- a/llvm/lib/CodeGen/AsmPrinter/ARMException.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/ARMException.cpp
@@ -59,9 +59,8 @@ void ARMException::endModule() {
 void ARMException::beginFunction(const MachineFunction *MF) {
   if (Asm->MAI->getExceptionHandlingType() == ExceptionHandling::ARM)
     getTargetStreamer().emitFnStart();
-  if (Asm->MF->getFunction()->needsUnwindTableEntry())
-    Asm->OutStreamer.EmitLabel(Asm->GetTempSymbol("eh_func_begin",
-                                                  Asm->getFunctionNumber()));
+  Asm->OutStreamer.EmitLabel(Asm->GetTempSymbol("eh_func_begin",
+                                                Asm->getFunctionNumber()));
   // See if we need call frame info.
   AsmPrinter::CFIMoveType MoveType = Asm->needsCFIMoves();
   assert(MoveType != AsmPrinter::CFI_M_EH &&
@@ -78,16 +77,16 @@ void ARMException::endFunction(const MachineFunction *) {
   if (shouldEmitCFI)
     Asm->OutStreamer.EmitCFIEndProc();
 
+  // Map all labels and get rid of any dead landing pads.
+  MMI->TidyLandingPads();
+
   ARMTargetStreamer &ATS = getTargetStreamer();
-  if (!Asm->MF->getFunction()->needsUnwindTableEntry())
+  if (!Asm->MF->getFunction()->needsUnwindTableEntry() &&
+      MMI->getLandingPads().empty())
     ATS.emitCantUnwind();
   else {
     Asm->OutStreamer.EmitLabel(Asm->GetTempSymbol("eh_func_end",
                                                   Asm->getFunctionNumber()));
-
-    // Map all labels and get rid of any dead landing pads.
-    MMI->TidyLandingPads();
-
     if (!MMI->getLandingPads().empty()) {
       // Emit references to personality.
       if (const Function * Personality =
diff --git a/llvm/test/CodeGen/ARM/ehabi-handlerdata-nounwind.ll b/llvm/test/CodeGen/ARM/ehabi-handlerdata-nounwind.ll
new file mode 100644
index 00000000000..42ca9888abb
--- /dev/null
+++ b/llvm/test/CodeGen/ARM/ehabi-handlerdata-nounwind.ll
@@ -0,0 +1,61 @@
+; Test for handlerdata when the function has landingpad and nounwind.
+
+; This test case checks whether the handlerdata is generated for the function
+; with landingpad instruction, even if the function has "nounwind" atttribute.
+;
+; For example, although the following function never throws any exception,
+; however, it is still required to generate LSDA, otherwise, we can't catch
+; the exception properly.
+;
+; void test1() noexcept {
+;   try {
+;     throw_exception();
+;   } catch (...) {
+;   }
+; }
+
+; RUN: llc -mtriple arm-unknown-linux-gnueabi -filetype=asm -o - %s \
+; RUN:   | FileCheck %s
+
+declare void @throw_exception()
+
+declare i32 @__gxx_personality_v0(...)
+
+declare i8* @__cxa_begin_catch(i8*)
+
+declare void @__cxa_end_catch()
+
+define void @test1() nounwind {
+entry:
+  invoke void @throw_exception() to label %try.cont unwind label %lpad
+
+lpad:
+  %0 = landingpad { i8*, i32 } personality i8* bitcast (i32 (...)* @__gxx_personality_v0 to i8*)
+          catch i8* null
+  %1 = extractvalue { i8*, i32 } %0, 0
+  %2 = tail call i8* @__cxa_begin_catch(i8* %1)
+  tail call void @__cxa_end_catch()
+  br label %try.cont
+
+try.cont:
+  ret void
+}
+
+; CHECK:   .globl test1
+; CHECK:   .align 2
+; CHECK:   .type test1,%function
+; CHECK-LABEL: test1:
+; CHECK:   .fnstart
+
+; CHECK-NOT: .cantunwind
+
+; CHECK:   .personality __gxx_personality_v0
+; CHECK:   .handlerdata
+; CHECK:   .align 2
+; CHECK-LABEL: GCC_except_table0:
+; CHECK-LABEL: .Lexception0:
+; CHECK:   .byte 255                     @ @LPStart Encoding = omit
+; CHECK:   .byte 0                       @ @TType Encoding = absptr
+; CHECK:   .asciz
+; CHECK:   .byte 3                       @ Call site Encoding = udata4
+; CHECK:   .fnend