From: Craig Topper <craig.topper@gmail.com>
Date: Fri, 31 Mar 2017 21:35:30 +0000 (+0000)
Subject: [InstCombine] When adding an Instruction and its Users to the worklist at the same... 
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=a71015bc01315c54dd880599582e2d671fba1622;p=llvm

[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.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@299267 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Transforms/InstCombine/InstructionCombining.cpp b/lib/Transforms/InstCombine/InstructionCombining.cpp
index 5b5c99aca00..94e7a7f2ade 100644
--- a/lib/Transforms/InstCombine/InstructionCombining.cpp
+++ b/lib/Transforms/InstCombine/InstructionCombining.cpp
@@ -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;