Use uniform mechanism for OOM errors handling

This is a recommit of r333390, which was reverted in r333395, because it
caused cyclic dependency when building shared library `LLVMDemangle.so`.
In this commit `ItaniumDemangler.cpp` was not changed.

The original commit message is below.

In r325551 many calls of malloc/calloc/realloc were replaces with calls of
their safe counterparts defined in the namespace llvm. There functions
generate crash if memory cannot be allocated, such behavior facilitates
handling of out of memory errors on Windows.

If the result of *alloc function were checked for success, the function was
not replaced with the safe variant. In these cases the calling function made
the error handling, like:

    T *NewElts = static_cast<T*>(malloc(NewCapacity*sizeof(T)));
    if (NewElts == nullptr)
      report_bad_alloc_error("Allocation of SmallVector element failed.");

Actually knowledge about the function where OOM occurred is useless. Moreover
having a single entry point for OOM handling is convenient for investigation
of memory problems. This change removes custom OOM errors handling and
replaces them with calls to functions `llvm::safe_*alloc`.

Declarations of `safe_*alloc` are moved to a separate include file, to avoid
cyclic dependency in SmallVector.h

Differential Revision: https://reviews.llvm.org/D47440


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@333506 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Support/StringMap.cpp

@@ -59,10 +59,8 @@ void StringMapImpl::init(unsigned InitSize) {
   NumTombstones = 0;
 
   TheTable = static_cast<StringMapEntryBase **>(
-      std::calloc(NewNumBuckets+1,
+      safe_calloc(NewNumBuckets+1,
                   sizeof(StringMapEntryBase **) + sizeof(unsigned)));
-  if (TheTable == nullptr)
-    report_bad_alloc_error("Allocation of StringMap table failed.");
 
   // Set the member only if TheTable was successfully allocated
   NumBuckets = NewNumBuckets;
@@ -220,9 +218,7 @@ unsigned StringMapImpl::RehashTable(unsigned BucketNo) {
   // Allocate one extra bucket which will always be non-empty.  This allows the
   // iterators to stop at end.
   auto NewTableArray = static_cast<StringMapEntryBase **>(
-      std::calloc(NewSize+1, sizeof(StringMapEntryBase *) + sizeof(unsigned)));
-  if (NewTableArray == nullptr)
-    report_bad_alloc_error("Allocation of StringMap hash table failed.");
+      safe_calloc(NewSize+1, sizeof(StringMapEntryBase *) + sizeof(unsigned)));
 
   unsigned *NewHashArray = (unsigned *)(NewTableArray + NewSize + 1);
   NewTableArray[NewSize] = (StringMapEntryBase*)2;