Revert "[DSE] Remove calls with known writes to dead memory"

This reverts commit a8a51fe55649f5e07f9f2973507dc20bc4e40765.

This breaks the strncpy-overflow.cpp test case.

1 files changed, 1 insertions, 38 deletions

diff --git a/llvm/lib/Analysis/MemoryLocation.cpp b/llvm/lib/Analysis/MemoryLocation.cpp
index 6365828..c74b625 100644
--- a/llvm/lib/Analysis/MemoryLocation.cpp
+++ b/llvm/lib/Analysis/MemoryLocation.cpp
@@ -147,44 +147,7 @@ MemoryLocation::getForDest(const CallBase *CB, const TargetLibraryInfo &TLI) {
     }
   }
 
-  if (!CB->onlyAccessesArgMemory())
-    return None;
-
-  if (CB->hasOperandBundles())
-    // TODO: remove implementation restriction
-    return None;
-
-  Value *UsedV = nullptr;
-  Optional<unsigned> UsedIdx;
-  for (unsigned i = 0; i < CB->arg_size(); i++) {
-    if (!CB->getArgOperand(i)->getType()->isPointerTy())
-      continue;
-    if (!CB->doesNotCapture(i))
-      // capture would allow the address to be read back in an untracked manner
-      return None;
-     if (CB->onlyReadsMemory(i))
-       continue;
-    if (!UsedV) {
-      // First potentially writing parameter
-      UsedV = CB->getArgOperand(i);
-      UsedIdx = i;
-      continue;
-    }
-    UsedIdx = None;
-    if (UsedV != CB->getArgOperand(i))
-      // Can't describe writing to two distinct locations.
-      // TODO: This results in an inprecision when two values derived from the
-      // same object are passed as arguments to the same function.
-      return None;
-  }
-  if (!UsedV)
-    // We don't currently have a way to represent a "does not write" result
-    // and thus have to be conservative and return unknown.
-    return None;
-
-  if (UsedIdx)
-    return getForArgument(CB, *UsedIdx, &TLI);
-  return MemoryLocation::getBeforeOrAfter(UsedV, CB->getAAMetadata());
+  return None;
 }
 
 MemoryLocation MemoryLocation::getForArgument(const CallBase *Call,