[WinEH] Add an EH registration and state insertion pass for 32-bit x86

This pass is responsible for constructing the EH registration object
that gets linked into fs:00, which is all it does in this change. In the
future, it will also insert stores to update the EH state number.

I considered keeping this functionality in WinEHPrepare, but it's pretty
separable and X86 specific. It has conceptually very little to do with
the task of WinEHPrepare, which is currently outlining.  WinEHPrepare is
also in theory useful on ARM, but this logic is pretty x86 specific.

Reviewers: andrew.w.kaylor, majnemer

Differential Revision: http://reviews.llvm.org/D9422

llvm-svn: 236339

1 files changed, 6 insertions, 5 deletions

diff --git a/llvm/lib/CodeGen/WinEHPrepare.cpp b/llvm/lib/CodeGen/WinEHPrepare.cpp
index c1067c5d560..db91c02ee46 100644
--- a/llvm/lib/CodeGen/WinEHPrepare.cpp
+++ b/llvm/lib/CodeGen/WinEHPrepare.cpp
@@ -8,9 +8,11 @@
 //===----------------------------------------------------------------------===//
 //
 // This pass lowers LLVM IR exception handling into something closer to what the
-// backend wants. It snifs the personality function to see which kind of
-// preparation is necessary. If the personality function uses the Itanium LSDA,
-// this pass delegates to the DWARF EH preparation pass.
+// backend wants for functions using a personality function from a runtime
+// provided by MSVC. Functions with other personality functions are left alone
+// and may be prepared by other passes. In particular, all supported MSVC
+// personality functions require cleanup code to be outlined, and the C++
+// personality requires catch handler code to be outlined.
 //
 //===----------------------------------------------------------------------===//
 
@@ -31,7 +33,6 @@
 #include "llvm/IR/Module.h"
 #include "llvm/IR/PatternMatch.h"
 #include "llvm/Pass.h"
-#include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/raw_ostream.h"
 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
@@ -922,7 +923,7 @@ bool WinEHPrepare::prepareExceptionHandlers(
   if (SEHExceptionCodeSlot) {
     if (SEHExceptionCodeSlot->hasNUses(0))
       SEHExceptionCodeSlot->eraseFromParent();
-    else
+    else if (isAllocaPromotable(SEHExceptionCodeSlot))
       PromoteMemToReg(SEHExceptionCodeSlot, *DT);
   }