[WinEH] Prevent EH state numbering from skipping nested cleanup pads that never return

[andrew.w.kaylor]

Summary

This patch addresses a problem with EH state numbering for C++ EH and SEH where a nested cleanup pad that is post-dominated by an unreachable instruction will be skipped by the EH state numbering routines. This leads to an assertion failure later in the code generation process when we try to retrieve the EH state for that cleanup pad.

[majnemer]

LGTM

llvm/trunk/lib/CodeGen/WinEHPrepare.cpp

if (auto *CatchSwitch = dyn_cast<CatchSwitchInst>(FirstNonPHI)) {
     int TryHigh = CatchLow - 1;
     for (const auto *CatchPad : Handlers) {
       FuncInfo.FuncletBaseStateMap[CatchPad] = CatchLow;
       for (const User *U : CatchPad->users()) {
         const auto *UserI = cast<Instruction>(U);
         if (auto *InnerCatchSwitch = dyn_cast<CatchSwitchInst>(UserI))
           if (InnerCatchSwitch->getUnwindDest() == CatchSwitch->getUnwindDest())
             calculateCXXStateNumbers(FuncInfo, UserI, CatchLow);
-        if (auto *InnerCleanupPad = dyn_cast<CleanupPadInst>(UserI))
-          if (getCleanupRetUnwindDest(InnerCleanupPad) ==
-              CatchSwitch->getUnwindDest())
+        if (auto *InnerCleanupPad = dyn_cast<CleanupPadInst>(UserI)) {
+          BasicBlock *UnwindDest = getCleanupRetUnwindDest(InnerCleanupPad);
+          // If a nested cleanup pad reports a null unwind destination and the
+          // enclosing catch pad doesn't it must be post-dominated by an
+          // unreachable instruction.
+          if (!UnwindDest || UnwindDest == CatchSwitch->getUnwindDest())
             calculateCXXStateNumbers(FuncInfo, UserI, CatchLow);
         }
       }
+    }
     int CatchHigh = FuncInfo.getLastStateNumber();
     addTryBlockMapEntry(FuncInfo, TryLow, TryHigh, CatchHigh, Handlers);
     DEBUG(dbgs() << "TryLow[" << BB->getName() << "]: " << TryLow << '\n');
     DEBUG(dbgs() << "TryHigh[" << BB->getName() << "]: " << TryHigh << '\n');
     DEBUG(dbgs() << "CatchHigh[" << BB->getName() << "]: " << CatchHigh
                  << '\n');
   } else {
     auto *CleanupPad = cast<CleanupPadInst>(FirstNonPHI);
if (auto *CatchSwitch = dyn_cast<CatchSwitchInst>(FirstNonPHI)) {
 
     // Everything in the __except block unwinds to ParentState, just like code
     // outside the __try.
     for (const User *U : CatchPad->users()) {
       const auto *UserI = cast<Instruction>(U);
       if (auto *InnerCatchSwitch = dyn_cast<CatchSwitchInst>(UserI))
         if (InnerCatchSwitch->getUnwindDest() == CatchSwitch->getUnwindDest())
           calculateSEHStateNumbers(FuncInfo, UserI, ParentState);
-      if (auto *InnerCleanupPad = dyn_cast<CleanupPadInst>(UserI))
-        if (getCleanupRetUnwindDest(InnerCleanupPad) ==
-            CatchSwitch->getUnwindDest())
+      if (auto *InnerCleanupPad = dyn_cast<CleanupPadInst>(UserI)) {
+        BasicBlock *UnwindDest = getCleanupRetUnwindDest(InnerCleanupPad);
+        // If a nested cleanup pad reports a null unwind destination and the
+        // enclosing catch pad doesn't it must be post-dominated by an
+        // unreachable instruction.
+        if (!UnwindDest || UnwindDest == CatchSwitch->getUnwindDest())
           calculateSEHStateNumbers(FuncInfo, UserI, ParentState);
       }
+    }
   } else {
     auto *CleanupPad = cast<CleanupPadInst>(FirstNonPHI);
 
     // It's possible for a cleanup to be visited twice: it might have multiple
     // cleanupret instructions.
     if (FuncInfo.EHPadStateMap.count(CleanupPad))
       return;
 

llvm/trunk/test/CodeGen/WinEH/wineh-noret-cleanup.ll

+; RUN: sed -e s/.Cxx:// %s | llc -mtriple=x86_64-pc-windows-msvc | FileCheck %s --check-prefix=CXX
+; RUN: sed -e s/.Seh:// %s | llc -mtriple=x86_64-pc-windows-msvc | FileCheck %s --check-prefix=SEH
+
+declare i32 @__CxxFrameHandler3(...)
+declare i32 @__C_specific_handler(...)
+declare void @dummy_filter()
+
+declare void @f(i32)
+
+;Cxx: define void @test() personality i32 (...)* @__CxxFrameHandler3 {
+;Seh: define void @test() personality i32 (...)* @__C_specific_handler {
+entry:
+  invoke void @f(i32 1)
+          to label %invoke.cont unwind label %catch.dispatch
+
+catch.dispatch:
+  %cs1 = catchswitch within none [label %catch.body] unwind label %catch.dispatch.2
+
+catch.body:
+;Cxx: %catch = catchpad within %cs1 [i8* null, i32 u0x40, i8* null]
+;Seh: %catch = catchpad within %cs1 [void ()* @dummy_filter]
+  invoke void @f(i32 2) [ "funclet"(token %catch) ]
+          to label %unreachable unwind label %terminate
+
+terminate:
+  %cleanup = cleanuppad within %catch []
+  call void @f(i32 3) [ "funclet"(token %cleanup) ]
+  unreachable
+
+unreachable:
+  unreachable
+
+invoke.cont:
+  ret void
+
+catch.dispatch.2:
+  %cs2 = catchswitch within none [label %catch.body.2] unwind to caller
+
+catch.body.2:
+;Cxx: %catch2 = catchpad within %cs2 [i8* null, i32 u0x40, i8* null]
+;Seh: %catch2 = catchpad within %cs2 [void ()* @dummy_filter]
+  unreachable
+}
+
+; CXX-LABEL: test:
+; CXX-LABEL: $ip2state$test:
+; CXX-NEXT:   .long   .Lfunc_begin0@IMGREL
+; CXX-NEXT:   .long   -1
+; CXX-NEXT:   .long   .Ltmp0@IMGREL+1
+; CXX-NEXT:   .long   1
+; CXX-NEXT:   .long   .Ltmp1@IMGREL+1
+; CXX-NEXT:   .long   -1
+; CXX-NEXT:   .long   "?catch$3@?0?test@4HA"@IMGREL
+; CXX-NEXT:   .long   2
+; CXX-NEXT:   .long   .Ltmp2@IMGREL+1
+; CXX-NEXT:   .long   3
+; CXX-NEXT:   .long   .Ltmp3@IMGREL+1
+; CXX-NEXT:   .long   2
+; CXX-NEXT:   .long   "?catch$5@?0?test@4HA"@IMGREL
+; CXX-NEXT:   .long   4
+
+; SEH-LABEL: test:
+; SEH-LABEL: .Llsda_begin0:
+; SEH-NEXT:    .long   .Ltmp0@IMGREL+1
+; SEH-NEXT:    .long   .Ltmp1@IMGREL+1
+; SEH-NEXT:    .long   dummy_filter@IMGREL
+; SEH-NEXT:    .long   .LBB0_3@IMGREL
+; SEH-NEXT:    .long   .Ltmp0@IMGREL+1
+; SEH-NEXT:    .long   .Ltmp1@IMGREL+1
+; SEH-NEXT:    .long   dummy_filter@IMGREL
+; SEH-NEXT:    .long   .LBB0_5@IMGREL
+; SEH-NEXT:    .long   .Ltmp2@IMGREL+1
+; SEH-NEXT:    .long   .Ltmp3@IMGREL+1
+; SEH-NEXT:    .long   "?dtor$2@?0?test@4HA"@IMGREL
+; SEH-NEXT:    .long   0
+; SEH-NEXT:    .long   .Ltmp2@IMGREL+1
+; SEH-NEXT:    .long   .Ltmp3@IMGREL+1
+; SEH-NEXT:    .long   dummy_filter@IMGREL
+; SEH-NEXT:    .long   .LBB0_5@IMGREL
+; SEH-NEXT:  .Llsda_end0: