[WinEH] Don't use lifetime markers for MS catch parameters

We don't have a good place to put them. Our previous spot was causing us
to optimize loads from the exception object to undef, because it was
after the catchpad instruction that models the write to the catch
object.

llvm-svn: 249616

1 files changed, 7 insertions, 1 deletions

diff --git a/clang/lib/CodeGen/CGDecl.cpp b/clang/lib/CodeGen/CGDecl.cpp
index 07684f9..3cff635 100644
--- a/clang/lib/CodeGen/CGDecl.cpp
+++ b/clang/lib/CodeGen/CGDecl.cpp
@@ -974,9 +974,15 @@ CodeGenFunction::EmitAutoVarAlloca(const VarDecl &D) {
       address = CreateTempAlloca(allocaTy, allocaAlignment);
       address.getPointer()->setName(D.getName());
 
+      // Don't emit lifetime markers for MSVC catch parameters. The lifetime of
+      // the catch parameter starts in the catchpad instruction, and we can't
+      // insert code in those basic blocks.
+      bool IsMSCatchParam =
+          D.isExceptionVariable() && getTarget().getCXXABI().isMicrosoft();
+
       // Emit a lifetime intrinsic if meaningful.  There's no point
       // in doing this if we don't have a valid insertion point (?).
-      if (HaveInsertPoint()) {
+      if (HaveInsertPoint() && !IsMSCatchParam) {
         uint64_t size = CGM.getDataLayout().getTypeAllocSize(allocaTy);
         emission.SizeForLifetimeMarkers =
           EmitLifetimeStart(size, address.getPointer());