There is an impedance matching problem between LLVM and

gcc exception handling: if an exception unwinds through
an invoke, then execution must branch to the invoke's
unwind target.  We previously tried to enforce this by
appending a cleanup action to every selector, however
this does not always work correctly due to an optimization
in the C++ unwinding runtime: if only cleanups would be
run while unwinding an exception, then the program just
terminates without actually executing the cleanups, as
invoke semantics would require.  I was hoping this
wouldn't be a problem, but in fact it turns out to be the
cause of all the remaining failures in the LLVM testsuite
(these also fail with -enable-correct-eh-support, so turning
on -enable-eh didn't make things worse!).  Instead we need
to append a full-blown catch-all to the end of each
selector.  The correct way of doing this depends on the
personality function, i.e. it is language dependent, so
can only be done by gcc.  Thus this patch which generalizes
the eh.selector intrinsic so that it can handle all possible
kinds of action table entries (before it didn't accomodate
cleanups): now 0 indicates a cleanup, and filters have to be
specified using the number of type infos plus one rather than
the number of type infos.  Related gcc patches will cause
Ada to pass a cleanup (0) to force the selector to always
fire, while C++ will use a C++ catch-all (null).


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@41484 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 19 insertions, 6 deletions

diff --git a/lib/CodeGen/MachineModuleInfo.cpp b/lib/CodeGen/MachineModuleInfo.cpp
index 77fb643b65..62224fdca8 100644
--- a/lib/CodeGen/MachineModuleInfo.cpp
+++ b/lib/CodeGen/MachineModuleInfo.cpp
@@ -1726,6 +1726,13 @@ void MachineModuleInfo::addFilterTypeInfo(MachineBasicBlock *LandingPad,
   LP.TypeIds.push_back(getFilterIDFor(IdsInFilter));
 }
 
+/// addCleanup - Add a cleanup action for a landing pad.
+///
+void MachineModuleInfo::addCleanup(MachineBasicBlock *LandingPad) {
+  LandingPadInfo &LP = getOrCreateLandingPadInfo(LandingPad);
+  LP.TypeIds.push_back(0);
+}
+
 /// TidyLandingPads - Remap landing pad labels and remove any deleted landing
 /// pads.
 void MachineModuleInfo::TidyLandingPads() {
diff --git a/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp b/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
index 7439e617d3..12024ff603 100644
--- a/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
@@ -2519,7 +2519,7 @@ static void addCatchInfo(CallInst &I, MachineModuleInfo *MMI,
   for (unsigned i = N - 1; i > 2; --i) {
     if (ConstantInt *CI = dyn_cast<ConstantInt>(I.getOperand(i))) {
       unsigned FilterLength = CI->getZExtValue();
-      unsigned FirstCatch = i + FilterLength + 1;
+      unsigned FirstCatch = i + FilterLength + !FilterLength;
       assert (FirstCatch <= N && "Invalid filter length");
 
       if (FirstCatch < N) {
@@ -2530,11 +2530,17 @@ static void addCatchInfo(CallInst &I, MachineModuleInfo *MMI,
         TyInfo.clear();
       }
 
-      TyInfo.reserve(FilterLength);
-      for (unsigned j = i + 1; j < FirstCatch; ++j)
-        TyInfo.push_back(ExtractTypeInfo(I.getOperand(j)));
-      MMI->addFilterTypeInfo(MBB, TyInfo);
-      TyInfo.clear();
+      if (!FilterLength) {
+        // Cleanup.
+        MMI->addCleanup(MBB);
+      } else {
+        // Filter.
+        TyInfo.reserve(FilterLength - 1);
+        for (unsigned j = i + 1; j < FirstCatch; ++j)
+          TyInfo.push_back(ExtractTypeInfo(I.getOperand(j)));
+        MMI->addFilterTypeInfo(MBB, TyInfo);
+        TyInfo.clear();
+      }
 
       N = i;
     }