commit cd151d2f95eabae61b3cf8e675717d5674afbe85
author Chris Lattner <sabre@nondot.org> Fri Jan 21 05:29:50 2011 +0000
committer Chris Lattner <sabre@nondot.org> Fri Jan 21 05:29:50 2011 +0000
tree 6b0ba1ff831463880ba598adabe81c57217b56b6
parent 084fe6243a4e69ef8d032303fcad116fa6695386

fix PR9013, an infinite loop in instcombine.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@123968 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Transforms/InstCombine/InstructionCombining.cpp

diff --git a/lib/Transforms/InstCombine/InstructionCombining.cpp b/lib/Transforms/InstCombine/InstructionCombining.cpp
index 06fbaad..2d5773a 100644
--- a/lib/Transforms/InstCombine/InstructionCombining.cpp
+++ b/lib/Transforms/InstCombine/InstructionCombining.cpp
@@ -538,9 +538,11 @@
   if (!PN->hasOneUse()) {
     // Walk the use list for the instruction, comparing them to I.
     for (Value::use_iterator UI = PN->use_begin(), E = PN->use_end();
-         UI != E; ++UI)
-      if (!I.isIdenticalTo(cast<Instruction>(*UI))) 
+         UI != E; ++UI) {
+      Instruction *User = cast<Instruction>(*UI);
+      if (User != &I && !I.isIdenticalTo(User))
         return 0;
+    }
     // Otherwise, we can replace *all* users with the new PHI we form.
   }
   
@@ -565,6 +567,12 @@
     if (InvokeInst *II = dyn_cast<InvokeInst>(InVal))
       if (II->getParent() == NonConstBB)
         return 0;
+    
+    // If the incoming non-constant value is in I's block, we will remove one
+    // instruction, but insert another equivalent one, leading to infinite
+    // instcombine.
+    if (NonConstBB == I.getParent())
+      return 0;
   }
   
   // If there is exactly one non-constant value, we can insert a copy of the