[SEH] Deal with users of the old lpad for SEH catch-all blocks

The way we split SEH catch-all blocks can leave some dead EH values
behind at -O0. Try to remove them, and if we fail, replace them all with
undef.

Fixes a crash when removing the old unreachable landingpad which is
still used by extractvalue instructions in the catch-all block.

llvm-svn: 235061

1 files changed, 9 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/WinEHPrepare.cpp b/llvm/lib/CodeGen/WinEHPrepare.cpp
index afe26ff8224..4b0ce21111b 100644
--- a/llvm/lib/CodeGen/WinEHPrepare.cpp
+++ b/llvm/lib/CodeGen/WinEHPrepare.cpp
@@ -433,6 +433,10 @@ bool WinEHPrepare::prepareExceptionHandlers(
       Invoke->setUnwindDest(NewLPadBB);
     }
 
+    // If anyone is still using the old landingpad value, just give them undef
+    // instead. The eh pointer and selector values are not real.
+    LPad->replaceAllUsesWith(UndefValue::get(LPad->getType()));
+
     // Replace the mapping of any nested landing pad that previously mapped
     // to this landing pad with a referenced to the cloned version.
     for (auto &LPadPair : NestedLPtoOriginalLP) {
@@ -636,6 +640,11 @@ void WinEHPrepare::promoteLandingPadValues(LandingPadInst *LPad) {
     PromoteMemToReg(EHAllocas, *DT);
     EHAllocas.clear();
   }
+
+  // After promotion, some extracts may be trivially dead. Remove them.
+  SmallVector<Value *, 4> Users(LPad->user_begin(), LPad->user_end());
+  for (auto *U : Users)
+    RecursivelyDeleteTriviallyDeadInstructions(U);
 }
 
 void WinEHPrepare::completeNestedLandingPad(Function *ParentFn,