Fix more fallout from r158919, similar to PR13547.

This code used to only handle malloc-like calls, which do not read memory.
r158919 changed it to check isNoAliasFn(), which includes strdup-like and
realloc-like calls, but it was not checking for dependencies on the memory
read by those calls.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@163106 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 21 insertions, 2 deletions

diff --git a/lib/Analysis/MemoryDependenceAnalysis.cpp b/lib/Analysis/MemoryDependenceAnalysis.cpp
index 2accaef..804217a 100644
--- a/lib/Analysis/MemoryDependenceAnalysis.cpp
+++ b/lib/Analysis/MemoryDependenceAnalysis.cpp
@@ -479,12 +479,17 @@ getPointerDependencyFrom(const AliasAnalysis::Location &MemLoc, bool isLoad,
     // a subsequent bitcast of the malloc call result.  There can be stores to
     // the malloced memory between the malloc call and its bitcast uses, and we
     // need to continue scanning until the malloc call.
-    if (isa<AllocaInst>(Inst) || isNoAliasFn(Inst, AA->getTargetLibraryInfo())){
+    const TargetLibraryInfo *TLI = AA->getTargetLibraryInfo();
+    if (isa<AllocaInst>(Inst) || isNoAliasFn(Inst, TLI)) {
       const Value *AccessPtr = GetUnderlyingObject(MemLoc.Ptr, TD);
       
       if (AccessPtr == Inst || AA->isMustAlias(Inst, AccessPtr))
         return MemDepResult::getDef(Inst);
-      continue;
+      // If the allocation is not aliased and does not read memory (like
+      // strdup), it is safe to ignore.
+      if (isa<AllocaInst>(Inst) ||
+          isMallocLikeFn(Inst, TLI) || isCallocLikeFn(Inst, TLI))
+        continue;
     }
 
     // See if this instruction (e.g. a call or vaarg) mod/ref's the pointer.
diff --git a/test/Transforms/DeadStoreElimination/simple.ll b/test/Transforms/DeadStoreElimination/simple.ll
index 7a8cdd5..e0eb90a 100644
--- a/test/Transforms/DeadStoreElimination/simple.ll
+++ b/test/Transforms/DeadStoreElimination/simple.ll
@@ -310,3 +310,17 @@ define void @test24([2 x i32]* %a, i32 %b, i32 %c) nounwind {
   store i32 %c, i32* %4, align 4
   ret void
 }
+
+; Check another case like PR13547 where strdup is not like malloc.
+; CHECK: @test25
+; CHECK: load i8
+; CHECK: store i8 0
+; CHECK: store i8 %tmp
+define i8* @test25(i8* %p) nounwind {
+  %p.4 = getelementptr i8* %p, i64 4
+  %tmp = load i8* %p.4, align 1
+  store i8 0, i8* %p.4, align 1
+  %q = call i8* @strdup(i8* %p) nounwind optsize
+  store i8 %tmp, i8* %p.4, align 1
+  ret i8* %q
+}