Iasm and obj lowering for advanced switch lowering.

src/IceAssembler.h

 //===- subzero/src/IceAssembler.h - Integrated assembler --------*- C++ -*-===//
 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 //
 // Modified by the Subzero authors.
 //
 //===----------------------------------------------------------------------===//
 //
 //                        The Subzero Code Generator
@@ skipping 11 matching lines @@
 //===----------------------------------------------------------------------===//
 
 #ifndef SUBZERO_SRC_ICEASSEMBLER_H
 #define SUBZERO_SRC_ICEASSEMBLER_H
 
 #include "IceDefs.h"
 #include "IceFixups.h"
 
 namespace Ice {
 
+/// A Label can be in one of three states:
+///  - Unused.
+///  - Linked, unplaced and tracking the position of branches to the label.
+///  - Bound, placed and tracking its position.
+class Label {
+  Label(const Label &) = delete;
+  Label &operator=(const Label &) = delete;
+
+public:
+  Label() = default;
+  ~Label() = default;
+
+  virtual void finalCheck() const {
+    // Assert if label is being destroyed with unresolved branches pending.
+    assert(!isLinked());
+  }
+
+  // TODO(jvoung): why are labels offset by this?
+  static const uint32_t kWordSize = sizeof(uint32_t);
+
+  /// Returns the position for bound labels (branches that come after this are
+  /// considered backward branches). Cannot be used for unused or linked labels.
+  intptr_t getPosition() const {
+    assert(isBound());
+    return -Position - kWordSize;
+  }
+
+  /// Returns the position of an earlier branch instruction that was linked to
+  /// this label (branches that use this are considered forward branches).  The
+  /// linked instructions form a linked list, of sorts, using the instruction's
+  /// displacement field for the location of the next instruction that is also
+  /// linked to this label.
+  intptr_t getLinkPosition() const {
+    assert(isLinked());
+    return Position - kWordSize;
+  }
+
+  bool isBound() const { return Position < 0; }
+  bool isLinked() const { return Position > 0; }
+  virtual bool isUnused() const { return Position == 0; }
+
+protected:
+  void bindTo(intptr_t position) {
+    assert(!isBound());
+    Position = -position - kWordSize;
+    assert(isBound());
+  }
+
+  void linkTo(intptr_t position) {
+    assert(!isBound());
+    Position = position + kWordSize;
+    assert(isLinked());
+  }
+
+  intptr_t Position = 0;
+};
+
 /// Assembler buffers are used to emit binary code. They grow on demand.
 class AssemblerBuffer {
   AssemblerBuffer(const AssemblerBuffer &) = delete;
   AssemblerBuffer &operator=(const AssemblerBuffer &) = delete;
 
 public:
   AssemblerBuffer(Assembler &);
   ~AssemblerBuffer();
 
   /// Basic support for emitting, loading, and storing.
@@ skipping 126 matching lines @@
     // second buffer should be aligned for NaCl.
     const size_t Alignment = 16;
     return reinterpret_cast<uintptr_t>(Allocator.Allocate(bytes, Alignment));
   }
 
   /// Allocate data of type T using the per-Assembler allocator.
   template <typename T> T *allocate() { return Allocator.Allocate<T>(); }
 
   /// Align the tail end of the function to the required target alignment.
   virtual void alignFunction() = 0;
+  /// Align the tail end of the basic block to the required target alignment.
+  virtual void alignCfgNode() = 0;

[jvoung (off chromium), 2015/07/29 21:31:16]

You might be able to make this non-virtual if it can be implemented by
padWithNop(X), where X is calculated from the Buffer.getPosition() vs
getBundleAlignLog2Bytes().

[ascull, 2015/07/29 22:43:04]

Done.

 
   /// Add nop padding of a particular width to the current bundle.
   virtual void padWithNop(intptr_t Padding) = 0;
 
   virtual SizeT getBundleAlignLog2Bytes() const = 0;
 
   virtual const char *getNonExecPadDirective() const = 0;
   virtual llvm::ArrayRef<uint8_t> getNonExecBundlePadding() const = 0;
 
+  /// Get the label for a CfgNode.
+  virtual Label *getOrCreateCfgNodeLabel(SizeT NodeNumber) = 0;
   /// Mark the current text location as the start of a CFG node
   /// (represented by NodeNumber).
   virtual void bindCfgNodeLabel(SizeT NodeNumber) = 0;
 
   virtual bool fixupIsPCRel(FixupKind Kind) const = 0;
 
   // Return a view of all the bytes of code for the current function.
   llvm::StringRef getBufferView() const;
 
   const FixupRefList &fixups() const { return Buffer.fixups(); }
@@ skipping 37 matching lines @@
 protected:
   // Buffer's constructor uses the Allocator, so it needs to appear after it.
   // TODO(jpp): dependencies on construction order are a nice way of shooting
   // yourself in the foot. Fix this.
   AssemblerBuffer Buffer;
 };
 
 } // end of namespace Ice
 
 #endif // SUBZERO_SRC_ICEASSEMBLER_H_