[BasicAA] Remove unneeded special case for malloc/calloc

This code pre-exists the generic handling for inaccessiblememonly.  If we remove it and update one test with inaccessiblememonly, nothing else changes.  Note that simply running O1 on that test would annotate malloc with the missing inaccessiblememonly.

llvm/lib/Analysis/BasicAliasAnalysis.cpp

@@ -994,20 +994,6 @@ ModRefInfo BasicAAResult::getModRefInfo(const CallBase *Call,
     }
   }
 
-  // If the call is malloc/calloc like, we can assume that it doesn't
-  // modify any IR visible value.  This is only valid because we assume these
-  // routines do not read values visible in the IR.  TODO: Consider special
-  // casing realloc and strdup routines which access only their arguments as
-  // well.  Or alternatively, replace all of this with inaccessiblememonly once
-  // that's implemented fully.
-  if (isMallocOrCallocLikeFn(Call, &TLI)) {
-    // Be conservative if the accessed pointer may alias the allocation -
-    // fallback to the generic handling below.
-    if (getBestAAResults().alias(MemoryLocation::getBeforeOrAfter(Call), Loc,
-                                 AAQI) == AliasResult::NoAlias)
-      return ModRefInfo::NoModRef;
-  }
-
   // Ideally, there should be no need to special case for memcpy/memove
   // intrinsics here since general machinery (based on memory attributes) should
   // already handle it just fine. Unfortunately, it doesn't due to deficiency in

llvm/test/Transforms/GVN/nonescaping-malloc.ll

@@ -35,7 +35,7 @@ entry:
 
 declare i64 @strlen(i8* nocapture) nounwind readonly
 
-declare noalias i8* @malloc(i64) nounwind
+declare noalias i8* @malloc(i64) nounwind inaccessiblememonly
 
 declare i32 @_ZN4llvm13StringMapImpl15LookupBucketForENS_9StringRefE(%"struct.llvm::StringMapImpl"*, i64, i64)