Avoid using the 'insertvalue' instruction here.

Fast ISel isn't able to handle 'insertvalue' and it causes a large slowdown
during -O0 compilation. We don't necessarily need to generate an aggregate of
the values here if they're just going to be extracted directly afterwards.
<rdar://problem/10530851>

llvm-svn: 146481

Author: isanbard

llvm/lib/CodeGen/SjLjEHPrepare.cpp

@@ -69,6 +69,8 @@ namespace {
 
   private:
     bool setupEntryBlockAndCallSites(Function &F);
+    void substituteLPadValues(LandingPadInst *LPI, Value *ExnVal,
+                              Value *SelVal, IRBuilder<> &Builder);
     Value *setupFunctionContext(Function &F, ArrayRef<LandingPadInst*> LPads);
     void lowerIncomingArguments(Function &F);
     void lowerAcrossUnwindEdges(Function &F, ArrayRef<InvokeInst*> Invokes);
@@ -138,6 +140,36 @@ static void MarkBlocksLiveIn(BasicBlock *BB,
     MarkBlocksLiveIn(*PI, LiveBBs);
 }
 
+/// substituteLPadValues - Substitute the values returned by the landingpad
+/// instruction with those returned by the personality function.
+void SjLjEHPass::substituteLPadValues(LandingPadInst *LPI, Value *ExnVal,
+                                      Value *SelVal, IRBuilder<> &Builder) {
+  SmallVector<Value*, 8> UseWorkList(LPI->use_begin(), LPI->use_end());
+  while (!UseWorkList.empty()) {
+    Value *Val = UseWorkList.pop_back_val();
+    ExtractValueInst *EVI = dyn_cast<ExtractValueInst>(Val);
+    if (!EVI) continue;
+    if (EVI->getNumIndices() != 1) continue;
+    if (*EVI->idx_begin() == 0)
+      EVI->replaceAllUsesWith(ExnVal);
+    else if (*EVI->idx_begin() == 1)
+      EVI->replaceAllUsesWith(SelVal);
+    if (EVI->getNumUses() == 0)
+      EVI->eraseFromParent();
+  }
+
+  if (LPI->getNumUses() == 0)  return;
+
+  // There are still some uses of LPI. Construct an aggregate with the exception
+  // values and replace the LPI with that aggregate.
+  Type *LPadType = LPI->getType();
+  Value *LPadVal = UndefValue::get(LPadType);
+  LPadVal = Builder.CreateInsertValue(LPadVal, ExnVal, 0, "lpad.val");
+  LPadVal = Builder.CreateInsertValue(LPadVal, SelVal, 1, "lpad.val");
+
+  LPI->replaceAllUsesWith(LPadVal);
+}
+
 /// setupFunctionContext - Allocate the function context on the stack and fill
 /// it with all of the data that we know at this point.
 Value *SjLjEHPass::
@@ -189,12 +221,7 @@ setupFunctionContext(Function &F, ArrayRef<LandingPadInst*> LPads) {
     ExnVal = Builder.CreateIntToPtr(ExnVal, Type::getInt8PtrTy(F.getContext()));
     Value *SelVal = Builder.CreateLoad(SelectorAddr, true, "exn_selector_val");
 
-    Type *LPadType = LPI->getType();
-    Value *LPadVal = UndefValue::get(LPadType);
-    LPadVal = Builder.CreateInsertValue(LPadVal, ExnVal, 0, "lpad.val");
-    LPadVal = Builder.CreateInsertValue(LPadVal, SelVal, 1, "lpad.val");
-
-    LPI->replaceAllUsesWith(LPadVal);
+    substituteLPadValues(LPI, ExnVal, SelVal, Builder);
   }
 
   // Personality function