[llvm] r299267 - [InstCombine] When adding an Instruction and its Users to the worklist at the same time, make sure we put the Users in first. Then put in the instruction.

[Craig Topper via llvm-commits]

Author: ctopper
Date: Fri Mar 31 16:35:30 2017
New Revision: 299267

URL: http://llvm.org/viewvc/llvm-project?rev=299267&view=rev
Log:
[InstCombine] When adding an Instruction and its Users to the worklist at the same time, make sure we put the Users in first. Then put in the instruction.

This way we ensure we immediately revisit the instruction and do any additional optimizations before visiting the users. Otherwise we might visit the users, then the instruction, then users again, then instruction again.


Modified:
    llvm/trunk/lib/Transforms/InstCombine/InstructionCombining.cpp

Modified: llvm/trunk/lib/Transforms/InstCombine/InstructionCombining.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstructionCombining.cpp?rev=299267&r1=299266&r2=299267&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstructionCombining.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstructionCombining.cpp Fri Mar 31 16:35:30 2017
@@ -2935,8 +2935,8 @@ bool InstCombiner::run() {
         Result->takeName(I);
 
         // Push the new instruction and any users onto the worklist.
-        Worklist.Add(Result);
         Worklist.AddUsersToWorkList(*Result);
+        Worklist.Add(Result);
 
         // Insert the new instruction into the basic block...
         BasicBlock *InstParent = I->getParent();
@@ -2959,8 +2959,8 @@ bool InstCombiner::run() {
         if (isInstructionTriviallyDead(I, &TLI)) {
           eraseInstFromFunction(*I);
         } else {
-          Worklist.Add(I);
           Worklist.AddUsersToWorkList(*I);
+          Worklist.Add(I);
         }
       }
       MadeIRChange = true;