[SEH] Ensure that empty __except blocks have their own BB

The 32-bit lowering assumed that WinEHPrepare had this invariant.
WinEHPrepare did it for C++, but not SEH. The result was that we would
insert calls to llvm.x86.seh.restoreframe in normal basic blocks, which
corrupted the frame pointer.

llvm-svn: 241699

3 files changed, 40 insertions, 3 deletions

diff --git a/llvm/lib/CodeGen/WinEHPrepare.cpp b/llvm/lib/CodeGen/WinEHPrepare.cpp
index 0f84ba0a723..62ef1d4ae57 100644
--- a/llvm/lib/CodeGen/WinEHPrepare.cpp
+++ b/llvm/lib/CodeGen/WinEHPrepare.cpp
@@ -533,9 +533,9 @@ void WinEHPrepare::findSEHEHReturnPoints(
     BasicBlock *NextBB;
     Constant *Selector;
     if (isSelectorDispatch(BB, CatchHandler, Selector, NextBB)) {
-      // Split the edge if there is a phi node. Returning from EH to a phi node
-      // is just as impossible as having a phi after an indirectbr.
-      if (isa<PHINode>(CatchHandler->begin())) {
+      // Split the edge if there are multiple predecessors. This creates a place
+      // where we can insert EH recovery code.
+      if (!CatchHandler->getSinglePredecessor()) {
         DEBUG(dbgs() << "splitting EH return edge from " << BB->getName()
                      << " to " << CatchHandler->getName() << '\n');
         BBI = CatchHandler = SplitCriticalEdge(
diff --git a/llvm/lib/Target/X86/X86WinEHState.cpp b/llvm/lib/Target/X86/X86WinEHState.cpp
index 0b88d7ab7e5..3a8bcaa4bb7 100644
--- a/llvm/lib/Target/X86/X86WinEHState.cpp
+++ b/llvm/lib/Target/X86/X86WinEHState.cpp
@@ -520,6 +520,11 @@ void WinEHStatePass::addSEHStateStores(Function &F, MachineModuleInfo &MMI) {
           for (auto &Handler : ActionList) {
             if (auto *CH = dyn_cast<CatchHandler>(Handler.get())) {
               auto *BA = cast<BlockAddress>(CH->getHandlerBlockOrFunc());
+#ifndef NDEBUG
+              for (BasicBlock *Pred : predecessors(BA->getBasicBlock()))
+                assert(Pred->isLandingPad() &&
+                       "WinEHPrepare failed to split block");
+#endif
               ExceptBlocks.insert(BA->getBasicBlock());
             }
           }
diff --git a/llvm/test/CodeGen/WinEH/seh-simple.ll b/llvm/test/CodeGen/WinEH/seh-simple.ll
index a2d13eeb190..060186484ae 100644
--- a/llvm/test/CodeGen/WinEH/seh-simple.ll
+++ b/llvm/test/CodeGen/WinEH/seh-simple.ll
@@ -107,6 +107,38 @@ eh.resume:
 ; CHECK-NEXT: %r = phi i32 [ 0, %entry ], [ 1, %lpad.return_crit_edge ]
 ; CHECK-NEXT: ret i32 %r
 
+define i32 @except_join() personality i32 (...)* @__C_specific_handler {
+entry:
+  invoke void @might_crash()
+          to label %return unwind label %lpad
+
+lpad:
+  %ehvals = landingpad { i8*, i32 }
+          catch i32 ()* @filt
+  %sel = extractvalue { i8*, i32 } %ehvals, 1
+  %filt_sel = tail call i32 @llvm.eh.typeid.for(i8* bitcast (i32 ()* @filt to i8*))
+  %matches = icmp eq i32 %sel, %filt_sel
+  br i1 %matches, label %return, label %eh.resume
+
+return:
+  ret i32 0
+
+eh.resume:
+  resume { i8*, i32 } %ehvals
+}
+
+; CHECK-LABEL: define i32 @except_join()
+; CHECK: landingpad { i8*, i32 }
+; CHECK-NEXT: catch i32 ()* @filt
+; CHECK-NEXT: call i8* (...) @llvm.eh.actions(i32 1, i8* bitcast (i32 ()* @filt to i8*), i32 -1, i8* blockaddress(@except_join, %lpad.return_crit_edge))
+; CHECK-NEXT: indirectbr {{.*}} [label %lpad.return_crit_edge]
+;
+; CHECK: lpad.return_crit_edge:
+; CHECK: br label %return
+;
+; CHECK: return:
+; CHECK-NEXT: ret i32 0
+
 define i32 @lpad_phi() personality i32 (...)* @__C_specific_handler {
 entry:
   invoke void @might_crash()