[Windows SEH] Fix the frame-ptr of a nested-filter within a _finally

This change fixed a SEH bug (exposed by test58 & test61 in MSVC test xcpt4u.c);
when an Except-filter is located inside a finally, the frame-pointer generated today
via intrinsic @llvm.eh.recoverfp is the frame-pointer of the immediate
parent _finally, not the frame-ptr of outermost host function.

The fix is to retrieve the Establisher's frame-pointer that was previously saved in
parent's frame.
The prolog of a filter inside a _finally should be like code below:

%0 = call i8* @llvm.eh.recoverfp(i8* bitcast (@"?fin$0@0@main@@"), i8*%frame_pointer)
%1 = call i8* @llvm.localrecover(i8* bitcast (@"?fin$0@0@main@@"), i8*%0, i32 0)
%2 = bitcast i8* %1 to i8**
%3 = load i8*, i8** %2, align 8

Differential Revision: https://reviews.llvm.org/D77982

1 files changed, 3 insertions, 0 deletions

diff --git a/clang/lib/CodeGen/CodeGenFunction.h b/clang/lib/CodeGen/CodeGenFunction.h
index b1841d6..1fc2ed7 100644
--- a/clang/lib/CodeGen/CodeGenFunction.h
+++ b/clang/lib/CodeGen/CodeGenFunction.h
@@ -264,6 +264,9 @@ public:
   CodeGenModule &CGM;  // Per-module state.
   const TargetInfo &Target;
 
+  // For EH/SEH outlined funclets, this field points to parent's CGF
+  CodeGenFunction *ParentCGF = nullptr;
+
   typedef std::pair<llvm::Value *, llvm::Value *> ComplexPairTy;
   LoopInfoStack LoopStack;
   CGBuilderTy Builder;