stop using associative comdats for SEH filter functions

Summary: We implement structured exception handling (SEH) by generating filter functions for functions that use exceptions. Currently, we use associative comdats to ensure that the filter functions are preserved if and only if the functions we generated them for are preserved. This can lead to problems when generating COFF objects - LLVM may decide to inline a function that uses SEH and remove its body, at which point we will end up with a comdat that COFF cannot represent. To avoid running into that situation, this change makes us not use associative comdats for SEH filter functions. We can still get the benefits we used the associative comdats for: we will always preserve filter functions we use, and dead stripping can eliminate the ones we don't use.

Reviewers: rnk, pcc, ruiu

Reviewed By: rnk

Differential Revision: https://reviews.llvm.org/D30117

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@295872 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/CodeGen/CGException.cpp b/lib/CodeGen/CGException.cpp
index f908bf2b3b0ac35d2eb6c95e28546c6b52fb97d2..8f999d175cbce41c336e99d4f1327e91e97fce27 100644 (file)
--- a/lib/CodeGen/CGException.cpp
+++ b/lib/CodeGen/CGException.cpp
@@ -1666,23 +1666,12 @@ void CodeGenFunction::startOutlinedSEHHelper(CodeGenFunction &ParentCGF,
 
   QualType RetTy = IsFilter ? getContext().LongTy : getContext().VoidTy;
 
-  llvm::Function *ParentFn = ParentCGF.CurFn;
   const CGFunctionInfo &FnInfo =
     CGM.getTypes().arrangeBuiltinFunctionDeclaration(RetTy, Args);
 
   llvm::FunctionType *FnTy = CGM.getTypes().GetFunctionType(FnInfo);
   llvm::Function *Fn = llvm::Function::Create(
       FnTy, llvm::GlobalValue::InternalLinkage, Name.str(), &CGM.getModule());
-  // The filter is either in the same comdat as the function, or it's internal.
-  if (llvm::Comdat *C = ParentFn->getComdat()) {
-    Fn->setComdat(C);
-  } else if (ParentFn->hasWeakLinkage() || ParentFn->hasLinkOnceLinkage()) {
-    llvm::Comdat *C = CGM.getModule().getOrInsertComdat(ParentFn->getName());
-    ParentFn->setComdat(C);
-    Fn->setComdat(C);
-  } else {
-    Fn->setLinkage(llvm::GlobalValue::InternalLinkage);
-  }
 
   IsOutlinedSEHHelper = true;
 

diff --git a/test/CodeGenCXX/exceptions-seh.cpp b/test/CodeGenCXX/exceptions-seh.cpp
index 7a11a1e50582f5c36c8ead2578d78156a0ebfcb5..4f7eacd6672087c90fc95a25f68458e2db01e17e 100644 (file)
--- a/test/CodeGenCXX/exceptions-seh.cpp
+++ b/test/CodeGenCXX/exceptions-seh.cpp
@@ -118,7 +118,7 @@ void use_inline() {
   use_seh_in_inline_func();
 }
 
-// CHECK-LABEL: define linkonce_odr void @use_seh_in_inline_func() #{{[0-9]+}} comdat
+// CHECK-LABEL: define linkonce_odr void @use_seh_in_inline_func() #{{[0-9]+}}
 // CHECK-SAME:  personality i8* bitcast (i32 (...)* @__C_specific_handler to i8*)
 // CHECK: invoke void @might_throw()
 //
@@ -134,12 +134,12 @@ void use_inline() {
 // CHECK: %[[fp:[^ ]*]] = call i8* @llvm.localaddress()
 // CHECK: call void @"\01?fin$0@0@use_seh_in_inline_func@@"(i8 1, i8* %[[fp]])
 
-// CHECK-LABEL: define internal i32 @"\01?filt$0@0@use_seh_in_inline_func@@"(i8* %exception_pointers, i8* %frame_pointer) #{{[0-9]+}} comdat($use_seh_in_inline_func)
+// CHECK-LABEL: define internal i32 @"\01?filt$0@0@use_seh_in_inline_func@@"(i8* %exception_pointers, i8* %frame_pointer) #{{[0-9]+}}
 // CHECK: icmp eq i32 %{{.*}}, 424242
 // CHECK: zext i1 %{{.*}} to i32
 // CHECK: ret i32
 
-// CHECK-LABEL: define internal void @"\01?fin$0@0@use_seh_in_inline_func@@"(i8 %abnormal_termination, i8* %frame_pointer) #{{[0-9]+}} comdat($use_seh_in_inline_func)
+// CHECK-LABEL: define internal void @"\01?fin$0@0@use_seh_in_inline_func@@"(i8 %abnormal_termination, i8* %frame_pointer) #{{[0-9]+}}
 // CHECK: store i32 1234, i32* @my_unique_global
 
 // CHECK: attributes #[[NOINLINE]] = { {{.*noinline.*}} }