Simplify LoopStrengthReduce::DeleteTriviallyDeadInstructions by

making it use RecursivelyDeleteTriviallyDeadInstructions to do
the heavy lifting.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60195 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 20 insertions, 21 deletions

diff --git a/lib/Transforms/Scalar/LoopStrengthReduce.cpp b/lib/Transforms/Scalar/LoopStrengthReduce.cpp
index c2f3209f05..5fad309b0d 100644
--- a/lib/Transforms/Scalar/LoopStrengthReduce.cpp
+++ b/lib/Transforms/Scalar/LoopStrengthReduce.cpp
@@ -240,31 +240,30 @@ Value *LoopStrengthReduce::getCastedVersionOf(Instruction::CastOps opcode,
 /// their operands subsequently dead.
 void LoopStrengthReduce::
 DeleteTriviallyDeadInstructions(SetVector<Instruction*> &Insts) {
+  SmallVector<Instruction*, 16> DeadInsts;
+  
   while (!Insts.empty()) {
     Instruction *I = Insts.back();
     Insts.pop_back();
+    
+    // If I is dead, delete it and all the things that it recursively uses
+    // that become dead.
+    RecursivelyDeleteTriviallyDeadInstructions(I, &DeadInsts);
+    
+    if (DeadInsts.empty()) continue;
+    Changed = true;
 
-    if (PHINode *PN = dyn_cast<PHINode>(I)) {
-      // If all incoming values to the Phi are the same, we can replace the Phi
-      // with that value.
-      if (Value *PNV = PN->hasConstantValue()) {
-        if (Instruction *U = dyn_cast<Instruction>(PNV))
-          Insts.insert(U);
-        SE->deleteValueFromRecords(PN);
-        PN->replaceAllUsesWith(PNV);
-        PN->eraseFromParent();
-        Changed = true;
-        continue;
-      }
-    }
-
-    if (isInstructionTriviallyDead(I)) {
-      for (User::op_iterator i = I->op_begin(), e = I->op_end(); i != e; ++i)
-        if (Instruction *U = dyn_cast<Instruction>(*i))
-          Insts.insert(U);
-      SE->deleteValueFromRecords(I);
-      I->eraseFromParent();
-      Changed = true;
+    while (!DeadInsts.empty()) {
+      Instruction *DeadInst = DeadInsts.back();
+      DeadInsts.pop_back();
+      
+      // Make sure ScalarEvolutions knows this instruction is gone.
+      SE->deleteValueFromRecords(DeadInst);
+      
+      // Make sure that this instruction is removed from DeadInsts if it was
+      // recursively removed.
+      if (DeadInst != I)
+        Insts.remove(DeadInst);
     }
   }
 }