Make changes to rev 84292 as requested by Chris Lattner.

Most changes are cleanup, but there is 1 correctness fix:
I fixed InstCombine so that the icmp is removed only if the malloc call is removed (which requires explicit removal because the Worklist won't DCE any calls since they can have side-effects).


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@84772 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 20 insertions, 2 deletions

diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp
index 46fac19..1088684 100644
--- a/lib/Transforms/Scalar/InstructionCombining.cpp
+++ b/lib/Transforms/Scalar/InstructionCombining.cpp
@@ -6359,10 +6359,28 @@ Instruction *InstCombiner::visitICmpInst(ICmpInst &I) {
         // can assume it is successful and remove the malloc.
         if (isMalloc(LHSI) && LHSI->hasOneUse() &&
             isa<ConstantPointerNull>(RHSC)) {
-          Worklist.Add(LHSI);
-          return ReplaceInstUsesWith(I,
+          // Need to explicitly erase malloc call here, instead of adding it to
+          // Worklist, because it won't get DCE'd from the Worklist since
+          // isInstructionTriviallyDead() returns false for function calls.
+          // It is OK to replace LHSI/MallocCall with Undef because the 
+          // instruction that uses it will be erased via Worklist.
+          if (extractMallocCall(LHSI)) {
+            LHSI->replaceAllUsesWith(UndefValue::get(LHSI->getType()));
+            EraseInstFromFunction(*LHSI);
+            return ReplaceInstUsesWith(I,
                                      ConstantInt::get(Type::getInt1Ty(*Context),
                                                       !I.isTrueWhenEqual()));
+          }
+          if (CallInst* MallocCall = extractMallocCallFromBitCast(LHSI))
+            if (MallocCall->hasOneUse()) {
+              MallocCall->replaceAllUsesWith(
+                                        UndefValue::get(MallocCall->getType()));
+              EraseInstFromFunction(*MallocCall);
+              Worklist.Add(LHSI); // The malloc's bitcast use.
+              return ReplaceInstUsesWith(I,
+                                     ConstantInt::get(Type::getInt1Ty(*Context),
+                                                      !I.isTrueWhenEqual()));
+            }
         }
         break;
       }