CodeGen support for x86_64 SEH catch handlers in LLVM

This adds handling for ExceptionHandling::MSVC, used by the
x86_64-pc-windows-msvc triple. It assumes that filter functions have
already been outlined in either the frontend or the backend. Filter
functions are used in place of the landingpad catch clause type info
operands. In catch clause order, the first filter to return true will
catch the exception.

The C specific handler table expects the landing pad to be split into
one block per handler, but LLVM IR uses a single landing pad for all
possible unwind actions. This patch papers over the mismatch by
synthesizing single instruction BBs for every catch clause to fill in
the EH selector that the landing pad block expects.

Missing functionality:
- Accessing data in the parent frame from outlined filters
- Cleanups (from __finally) are unsupported, as they will require
  outlining and parent frame access
- Filter clauses are unsupported, as there's no clear analogue in SEH

In other words, this is the minimal set of changes needed to write IR to
catch arbitrary exceptions and resume normal execution.

Reviewers: majnemer

Differential Revision: http://reviews.llvm.org/D6300

llvm-svn: 225904

1 files changed, 8 insertions, 7 deletions

diff --git a/llvm/lib/CodeGen/AsmPrinter/EHStreamer.cpp b/llvm/lib/CodeGen/AsmPrinter/EHStreamer.cpp
index f112120c1ab..1bc86f6c222 100644
--- a/llvm/lib/CodeGen/AsmPrinter/EHStreamer.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/EHStreamer.cpp
@@ -121,7 +121,8 @@ computeActionsTable(const SmallVectorImpl<const LandingPadInfo*> &LandingPads,
       for (unsigned J = NumShared, M = TypeIds.size(); J != M; ++J) {
         int TypeID = TypeIds[J];
         assert(-1 - TypeID < (int)FilterOffsets.size() && "Unknown filter id!");
-        int ValueForTypeID = TypeID < 0 ? FilterOffsets[-1 - TypeID] : TypeID;
+        int ValueForTypeID =
+            isFilterEHSelector(TypeID) ? FilterOffsets[-1 - TypeID] : TypeID;
         unsigned SizeTypeID = getSLEB128Size(ValueForTypeID);
 
         int NextAction = SizeAction ? -(SizeAction + SizeTypeID) : 0;
@@ -269,14 +270,14 @@ computeCallSiteTable(SmallVectorImpl<CallSiteEntry> &CallSites,
         CallSiteEntry Site = {
           BeginLabel,
           LastLabel,
-          LandingPad->LandingPadLabel,
+          LandingPad,
           FirstActions[P.PadIndex]
         };
 
         // Try to merge with the previous call-site. SJLJ doesn't do this
         if (PreviousIsInvoke && !IsSJLJ) {
           CallSiteEntry &Prev = CallSites.back();
-          if (Site.PadLabel == Prev.PadLabel && Site.Action == Prev.Action) {
+          if (Site.LPad == Prev.LPad && Site.Action == Prev.Action) {
             // Extend the range of the previous entry.
             Prev.EndLabel = Site.EndLabel;
             continue;
@@ -576,15 +577,15 @@ void EHStreamer::emitExceptionTable() {
 
       // Offset of the landing pad, counted in 16-byte bundles relative to the
       // @LPStart address.
-      if (!S.PadLabel) {
+      if (!S.LPad) {
         if (VerboseAsm)
           Asm->OutStreamer.AddComment("    has no landing pad");
         Asm->OutStreamer.EmitIntValue(0, 4/*size*/);
       } else {
         if (VerboseAsm)
           Asm->OutStreamer.AddComment(Twine("    jumps to ") +
-                                      S.PadLabel->getName());
-        Asm->EmitLabelDifference(S.PadLabel, EHFuncBeginSym, 4);
+                                      S.LPad->LandingPadLabel->getName());
+        Asm->EmitLabelDifference(S.LPad->LandingPadLabel, EHFuncBeginSym, 4);
       }
 
       // Offset of the first associated action record, relative to the start of
@@ -681,7 +682,7 @@ void EHStreamer::emitTypeInfos(unsigned TTypeEncoding) {
     unsigned TypeID = *I;
     if (VerboseAsm) {
       --Entry;
-      if (TypeID != 0)
+      if (isFilterEHSelector(TypeID))
         Asm->OutStreamer.AddComment("FilterInfo " + Twine(Entry));
     }