[SEH] Push reloads of the SEH code past phi nodes

This in turn would sometimes introduce new cleanupblocks that didn't
previously exist. The uses were being introduced by SSA value demotion.
We actually want to *promote* uses of EH pointers and selectors, so I
added some spcecial casing to avoid demoting such instructions.  This is
getting overly complicated, but hopefully we'll come along and delete it
in the new representation.

llvm-svn: 241950

1 files changed, 28 insertions, 6 deletions

diff --git a/llvm/lib/CodeGen/WinEHPrepare.cpp b/llvm/lib/CodeGen/WinEHPrepare.cpp
index 62ef1d4ae57..0d26ed333ca 100644
--- a/llvm/lib/CodeGen/WinEHPrepare.cpp
+++ b/llvm/lib/CodeGen/WinEHPrepare.cpp
@@ -616,6 +616,26 @@ void WinEHPrepare::demoteValuesLiveAcrossHandlers(
   // identifyEHBlocks() should have been called before this function.
   assert(!NormalBlocks.empty());
 
+  // Try to avoid demoting EH pointer and selector values. They get in the way
+  // of our pattern matching.
+  SmallPtrSet<Instruction *, 10> EHVals;
+  for (BasicBlock &BB : F) {
+    LandingPadInst *LP = BB.getLandingPadInst();
+    if (!LP)
+      continue;
+    EHVals.insert(LP);
+    for (User *U : LP->users()) {
+      auto *EI = dyn_cast<ExtractValueInst>(U);
+      if (!EI)
+        continue;
+      EHVals.insert(EI);
+      for (User *U2 : EI->users()) {
+        if (auto *PN = dyn_cast<PHINode>(U2))
+          EHVals.insert(PN);
+      }
+    }
+  }
+
   SetVector<Argument *> ArgsToDemote;
   SetVector<Instruction *> InstrsToDemote;
   for (BasicBlock &BB : F) {
@@ -641,7 +661,11 @@ void WinEHPrepare::demoteValuesLiveAcrossHandlers(
           continue;
         }
 
+        // Don't demote EH values.
         auto *OpI = cast<Instruction>(Op);
+        if (EHVals.count(OpI))
+          continue;
+
         BasicBlock *OpBB = OpI->getParent();
         // If a value is produced and consumed in the same BB, we don't need to
         // demote it.
@@ -822,7 +846,8 @@ bool WinEHPrepare::prepareExceptionHandlers(
     LPad->replaceAllUsesWith(UndefValue::get(LPad->getType()));
 
     // Rewrite uses of the exception pointer to loads of an alloca.
-    for (Instruction *E : SEHCodeUses) {
+    while (!SEHCodeUses.empty()) {
+      Instruction *E = SEHCodeUses.pop_back_val();
       SmallVector<Use *, 4> Uses;
       for (Use &U : E->uses())
         Uses.push_back(&U);
@@ -830,13 +855,10 @@ bool WinEHPrepare::prepareExceptionHandlers(
         auto *I = cast<Instruction>(U->getUser());
         if (isa<ResumeInst>(I))
           continue;
-        LoadInst *LI;
         if (auto *Phi = dyn_cast<PHINode>(I))
-          LI = new LoadInst(SEHExceptionCodeSlot, "sehcode", false,
-                            Phi->getIncomingBlock(*U)->getTerminator());
+          SEHCodeUses.push_back(Phi);
         else
-          LI = new LoadInst(SEHExceptionCodeSlot, "sehcode", false, I);
-        U->set(LI);
+          U->set(new LoadInst(SEHExceptionCodeSlot, "sehcode", false, I));
       }
       E->replaceAllUsesWith(UndefValue::get(E->getType()));
       E->eraseFromParent();