[SVE][IR] Scalable Vector size queries and IR instruction support

* Adds a TypeSize struct to represent the known minimum size of a type
  along with a flag to indicate that the runtime size is a integer multiple
  of that size
* Converts existing size query functions from Type.h and DataLayout.h to
  return a TypeSize result
* Adds convenience methods (including a transparent conversion operator
  to uint64_t) so that most existing code 'just works' as if the return
  values were still scalars.
* Uses the new size queries along with ElementCount to ensure that all
  supported instructions used with scalable vectors can be constructed
  in IR.

Reviewers: hfinkel, lattner, rkruppe, greened, rovka, rengolin, sdesmalen

Reviewed By: rovka, sdesmalen

Differential Revision: https://reviews.llvm.org/D53137

llvm-svn: 374042

llvm/lib/IR/DataLayout.cpp

@@ -29,6 +29,7 @@
 #include "llvm/Support/Casting.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/MathExtras.h"
+#include "llvm/Support/TypeSize.h"
 #include <algorithm>
 #include <cassert>
 #include <cstdint>
@@ -745,7 +746,10 @@ Align DataLayout::getAlignment(Type *Ty, bool abi_or_pref) const {
     llvm_unreachable("Bad type for getAlignment!!!");
   }
 
-  return getAlignmentInfo(AlignType, getTypeSizeInBits(Ty), abi_or_pref, Ty);
+  // If we're dealing with a scalable vector, we just need the known minimum
+  // size for determining alignment. If not, we'll get the exact size.
+  return getAlignmentInfo(AlignType, getTypeSizeInBits(Ty).getKnownMinSize(),
+                          abi_or_pref, Ty);
 }
 
 unsigned DataLayout::getABITypeAlignment(Type *Ty) const {