[globalisel] Change LLT constructor string into an LLT subclass that knows how to generate it.

Summary:
This will allow future patches to inspect the details of the LLT. The implementation is now split between
the Support and CodeGen libraries to allow TableGen to use this class without introducing layering concerns.

Thanks to Ahmed Bougacha for finding a reasonable way to avoid the layering issue and providing the version of this patch without that problem.

Reviewers: t.p.northover, qcolombet, rovka, aditya_nandakumar, ab, javed.absar

Subscribers: arsenm, nhaehnle, mgorny, dberris, llvm-commits, kristof.beyls

Differential Revision: https://reviews.llvm.org/D30046

llvm-svn: 296474

2 files changed, 48 insertions, 0 deletions

diff --git a/llvm/lib/Support/CMakeLists.txt b/llvm/lib/Support/CMakeLists.txt
index 4f7f2166cd0..4011cde3266 100644
--- a/llvm/lib/Support/CMakeLists.txt
+++ b/llvm/lib/Support/CMakeLists.txt
@@ -68,6 +68,7 @@ add_llvm_library(LLVMSupport
   LineIterator.cpp
   Locale.cpp
   LockFileManager.cpp
+  LowLevelType.cpp
   ManagedStatic.cpp
   MathExtras.cpp
   MemoryBuffer.cpp
diff --git a/llvm/lib/Support/LowLevelType.cpp b/llvm/lib/Support/LowLevelType.cpp
new file mode 100644
index 00000000000..4290d69cd19
--- /dev/null
+++ b/llvm/lib/Support/LowLevelType.cpp
@@ -0,0 +1,47 @@
+//===-- llvm/Support/LowLevelType.cpp -------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+/// \file This file implements the more header-heavy bits of the LLT class to
+/// avoid polluting users' namespaces.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Support/LowLevelTypeImpl.h"
+#include "llvm/Support/raw_ostream.h"
+using namespace llvm;
+
+LLT::LLT(MVT VT) {
+  if (VT.isVector()) {
+    SizeInBits = VT.getVectorElementType().getSizeInBits();
+    ElementsOrAddrSpace = VT.getVectorNumElements();
+    Kind = ElementsOrAddrSpace == 1 ? Scalar : Vector;
+  } else if (VT.isValid()) {
+    // Aggregates are no different from real scalars as far as GlobalISel is
+    // concerned.
+    Kind = Scalar;
+    SizeInBits = VT.getSizeInBits();
+    ElementsOrAddrSpace = 1;
+    assert(SizeInBits != 0 && "invalid zero-sized type");
+  } else {
+    Kind = Invalid;
+    SizeInBits = ElementsOrAddrSpace = 0;
+  }
+}
+
+void LLT::print(raw_ostream &OS) const {
+  if (isVector())
+    OS << "<" << ElementsOrAddrSpace << " x s" << SizeInBits << ">";
+  else if (isPointer())
+    OS << "p" << getAddressSpace();
+  else if (isValid()) {
+    assert(isScalar() && "unexpected type");
+    OS << "s" << getScalarSizeInBits();
+  } else
+    llvm_unreachable("trying to print an invalid type");
+}