From 30c1ff234d30567fc20d6c41d8fd9c3aacbbf9ca Mon Sep 17 00:00:00 2001
From: Jim Grosbach <grosbach@apple.com>
Date: Wed, 5 Oct 2011 20:05:00 +0000
Subject: [PATCH] Update InstCombine worklist after instruction transform is
 complete.

When updating the worklist for InstCombine, the Add/AddUsersToWorklist
functions may access the instruction(s) being added, for debug output for
example. If the instructions aren't yet added to the basic block, this
can result in a crash. Finish the instruction transformation before
adjusting the worklist instead.

rdar://10238555


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@141203 91177308-0d34-0410-b5e6-96231b3b80d8
---
 .../InstCombine/InstructionCombining.cpp        | 17 +++++++++--------
 .../InstCombine/2010-11-01-lshr-mask.ll         |  4 ++--
 2 files changed, 11 insertions(+), 10 deletions(-)

diff --git a/lib/Transforms/InstCombine/InstructionCombining.cpp b/lib/Transforms/InstCombine/InstructionCombining.cpp
index cee27ff5913..a302a46290e 100644
--- a/lib/Transforms/InstCombine/InstructionCombining.cpp
+++ b/lib/Transforms/InstCombine/InstructionCombining.cpp
@@ -2009,21 +2009,18 @@ bool InstCombiner::DoOneIteration(Function &F, unsigned Iteration) {
       ++NumCombined;
       // Should we replace the old instruction with a new one?
       if (Result != I) {
-        DEBUG(errs() << "IC: Old = " << *I << '\n'
-                     << "    New = " << *Result << '\n');
-
         if (!I->getDebugLoc().isUnknown())
           Result->setDebugLoc(I->getDebugLoc());
         // Everything uses the new instruction now.
         I->replaceAllUsesWith(Result);
 
-        // Push the new instruction and any users onto the worklist.
-        Worklist.Add(Result);
-        Worklist.AddUsersToWorkList(*Result);
-
-        // Move the name to the new instruction first.
+        // Move the name to the new instruction.
         Result->takeName(I);
 
+        DEBUG(errs() << "IC: Old = " << *I << '\n'
+                     << "    New = " << *Result << '\n');
+
+
         // Insert the new instruction into the basic block...
         BasicBlock *InstParent = I->getParent();
         BasicBlock::iterator InsertPos = I;
@@ -2035,6 +2032,10 @@ bool InstCombiner::DoOneIteration(Function &F, unsigned Iteration) {
         InstParent->getInstList().insert(InsertPos, Result);
 
         EraseInstFromFunction(*I);
+
+        // Push the new instruction and any users onto the worklist.
+        Worklist.Add(Result);
+        Worklist.AddUsersToWorkList(*Result);
       } else {
 #ifndef NDEBUG
         DEBUG(errs() << "IC: Mod = " << OrigI << '\n'
diff --git a/test/Transforms/InstCombine/2010-11-01-lshr-mask.ll b/test/Transforms/InstCombine/2010-11-01-lshr-mask.ll
index 441d5f9b0b6..a2590b4eb85 100644
--- a/test/Transforms/InstCombine/2010-11-01-lshr-mask.ll
+++ b/test/Transforms/InstCombine/2010-11-01-lshr-mask.ll
@@ -5,8 +5,8 @@
 define i32 @main(i32 %argc) nounwind ssp {
 entry:
   %tmp3151 = trunc i32 %argc to i8
-; CHECK: %tmp3162 = shl i8 %tmp3151, 5
-; CHECK: and i8 %tmp3162, 64
+; CHECK: %0 = shl i8 %tmp3151, 5
+; CHECK: and i8 %0, 64
 ; CHECK-NOT: shl
 ; CHECK-NOT: shr
   %tmp3161 = or i8 %tmp3151, -17