2 files changed, 129 insertions, 0 deletions
diff --git a/llvm/lib/CodeGen/GlobalISel/CMakeLists.txt b/llvm/lib/CodeGen/GlobalISel/CMakeLists.txt
index e3e81ae5c4b..960f51a842d 100644
--- a/llvm/lib/CodeGen/GlobalISel/CMakeLists.txt
+++ b/llvm/lib/CodeGen/GlobalISel/CMakeLists.txt
@@ -2,6 +2,7 @@
 set(GLOBAL_ISEL_FILES
       IRTranslator.cpp
       MachineIRBuilder.cpp
+      MachineLegalizer.cpp
       RegBankSelect.cpp
       RegisterBank.cpp
       RegisterBankInfo.cpp
diff --git a/llvm/lib/CodeGen/GlobalISel/MachineLegalizer.cpp b/llvm/lib/CodeGen/GlobalISel/MachineLegalizer.cpp
new file mode 100644
index 00000000000..edd5ccfd9cd
--- /dev/null
+++ b/llvm/lib/CodeGen/GlobalISel/MachineLegalizer.cpp
@@ -0,0 +1,128 @@
+//===---- lib/CodeGen/GlobalISel/MachineLegalizer.cpp - IRTranslator -------==//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// Implement an interface to specify and query how an illegal operation on a
+// given type should be expanded.
+//
+// Issues to be resolved:
+//   + Make it fast.
+//   + Support weird types like i3, <7 x i3>, ...
+//   + Operations with more than one type (ICMP, CMPXCHG, intrinsics, ...)
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/CodeGen/MachineInstr.h"
+#include "llvm/CodeGen/ValueTypes.h"
+#include "llvm/CodeGen/GlobalISel/MachineLegalizer.h"
+#include "llvm/IR/Type.h"
+#include "llvm/Target/TargetOpcodes.h"
+using namespace llvm;
+
+MachineLegalizer::MachineLegalizer() : TablesInitialized(false) {
+  DefaultActions[TargetOpcode::G_ADD] = NarrowScalar;
+}
+
+bool MachineLegalizer::legalizeInstr(MachineInstr &MI) const {
+  llvm_unreachable("Unimplemented functionality");
+}
+
+void MachineLegalizer::computeTables() {
+  for (auto &Op : Actions) {
+    LLT Ty = Op.first.second;
+    if (!Ty.isVector())
+      continue;
+
+    auto &Entry =
+        MaxLegalVectorElts[std::make_pair(Op.first.first, Ty.getElementType())];
+    Entry = std::max(Entry, Ty.getNumElements());
+  }
+
+  TablesInitialized = true;
+}
+
+// FIXME: inefficient implementation for now. Without ComputeValueVTs we're
+// probably going to need specialized lookup structures for various types before
+// we have any hope of doing well with something like <13 x i3>. Even the common
+// cases should do better than what we have now.
+std::pair<MachineLegalizer::LegalizeAction, LLT>
+MachineLegalizer::getAction(unsigned Opcode, LLT Ty) const {
+  assert(TablesInitialized && "backend forgot to call computeTables");
+  // These *have* to be implemented for now, they're the fundamental basis of
+  // how everything else is transformed.
+
+  auto ActionIt = Actions.find(std::make_pair(Opcode, Ty));
+  if (ActionIt != Actions.end())
+    return findLegalAction(Opcode, Ty, ActionIt->second);
+
+  if (!Ty.isVector()) {
+    auto DefaultAction = DefaultActions.find(Opcode);
+    if (DefaultAction != DefaultActions.end() && DefaultAction->second == Legal)
+      return std::make_pair(Legal, Ty);
+
+    assert(DefaultAction->second == NarrowScalar && "unexpected default");
+    return findLegalAction(Opcode, Ty, NarrowScalar);
+  }
+
+  LLT EltTy = Ty.getElementType();
+  int NumElts = Ty.getNumElements();
+
+  auto ScalarAction = ScalarInVectorActions.find(std::make_pair(Opcode, EltTy));
+  if (ScalarAction != ScalarInVectorActions.end() &&
+      ScalarAction->second != Legal)
+    return findLegalAction(Opcode, EltTy, ScalarAction->second);
+
+  // The element type is legal in principle, but the number of elements is
+  // wrong.
+  auto MaxLegalElts = MaxLegalVectorElts.lookup(std::make_pair(Opcode, EltTy));
+  if (MaxLegalElts > NumElts)
+    return findLegalAction(Opcode, Ty, MoreElements);
+
+  if (MaxLegalElts == 0) {
+    // Scalarize if there's no legal vector type, which is just a special case
+    // of FewerElements.
+    return std::make_pair(FewerElements, EltTy);
+  }
+
+  return findLegalAction(Opcode, Ty, FewerElements);
+}
+
+std::pair<MachineLegalizer::LegalizeAction, LLT>
+MachineLegalizer::getAction(MachineInstr &MI) const {
+  return getAction(MI.getOpcode(), MI.getType());
+}
+
+bool MachineLegalizer::isLegal(MachineInstr &MI) const {
+  return getAction(MI).first == Legal;
+}
+
+LLT MachineLegalizer::findLegalType(unsigned Opcode, LLT Ty,
+                                    LegalizeAction Action) const {
+  switch(Action) {
+  default:
+    llvm_unreachable("Cannot find legal type");
+  case Legal:
+    return Ty;
+  case NarrowScalar: {
+    return findLegalType(Opcode, Ty,
+                         [&](LLT Ty) -> LLT { return Ty.halfScalarSize(); });
+  }
+  case WidenScalar: {
+    return findLegalType(Opcode, Ty,
+                         [&](LLT Ty) -> LLT { return Ty.doubleScalarSize(); });
+  }
+  case FewerElements: {
+    return findLegalType(Opcode, Ty,
+                         [&](LLT Ty) -> LLT { return Ty.halfElements(); });
+  }
+  case MoreElements: {
+    return findLegalType(
+        Opcode, Ty, [&](LLT Ty) -> LLT { return Ty.doubleElements(); });
+  }
+  }
+}