[IR] Introduce a non-integral pointer type

Summary:
This change adds a `ni` specifier in the `datalayout` string to denote
pointers in some given address spaces as "non-integral", and adds some
typing rules around these special pointers.

Reviewers: majnemer, chandlerc, atrick, dberlin, eli.friedman, tstellarAMD, arsenm

Subscribers: arsenm, mcrosier, llvm-commits

Differential Revision: https://reviews.llvm.org/D22488

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@277085 91177308-0d34-0410-b5e6-96231b3b80d8

lib/IR/DataLayout.cpp

@@ -182,6 +182,7 @@ void DataLayout::reset(StringRef Desc) {
   BigEndian = false;
   StackNaturalAlign = 0;
   ManglingMode = MM_None;
+  NonIntegralAddressSpaces.clear();
 
   // Default alignments
   for (const LayoutAlignElem &E : DefaultAlignments) {
@@ -234,6 +235,19 @@ void DataLayout::parseSpecifier(StringRef Desc) {
     StringRef &Tok  = Split.first;  // Current token.
     StringRef &Rest = Split.second; // The rest of the string.
 
+    if (Tok == "ni") {
+      do {
+        Split = split(Rest, ':');
+        Rest = Split.second;
+        unsigned AS = getInt(Split.first);
+        if (AS == 0)
+          report_fatal_error("Address space 0 can never be non-integral");
+        NonIntegralAddressSpaces.push_back(AS);
+      } while (!Rest.empty());
+
+      continue;
+    }
+
     char Specifier = Tok.front();
     Tok = Tok.substr(1);