[Stackmap] Liveness Analysis Pass

This optional register liveness analysis pass can be enabled with either
-enable-stackmap-liveness, -enable-patchpoint-liveness, or both. The pass
traverses each basic block in a machine function. For each basic block the
instructions are processed in reversed order and if a patchpoint or stackmap
instruction is encountered the current live-out register set is encoded as a
register mask and attached to the instruction.

Later on during stackmap generation the live-out register mask is processed and
also emitted as part of the stackmap.

This information is optional and intended for optimization purposes only. This
will enable a client of the stackmap to reason about the registers it can use
and which registers need to be preserved.

Reviewed by Andy

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@197317 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/CodeGen/StackMapLivenessAnalysis.h

@@ -0,0 +1,65 @@
+//===--- StackMapLivenessAnalysis - StackMap Liveness Analysis --*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This pass calculates the liveness for each basic block in a function and
+// attaches the register live-out information to a stackmap or patchpoint
+// intrinsic if present.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CODEGEN_STACKMAP_LIVENESS_ANALYSIS_H
+#define LLVM_CODEGEN_STACKMAP_LIVENESS_ANALYSIS_H
+
+#include "llvm/CodeGen/LivePhysRegs.h"
+#include "llvm/CodeGen/MachineFunctionPass.h"
+
+
+namespace llvm {
+
+/// \brief This pass calculates the liveness information for each basic block in
+/// a function and attaches the register live-out information to a stackmap or
+/// patchpoint intrinsic if present.
+///
+/// This is an optional pass that has to be explicitly enabled via the
+/// -enable-stackmap-liveness and/or -enable-patchpoint-liveness flag. The pass
+/// skips functions that don't have any stackmap or patchpoint intrinsics. The
+/// information provided by this pass is optional and not required by the
+/// aformentioned intrinsics to function.
+class StackMapLiveness : public MachineFunctionPass {
+  MachineFunction *MF;
+  const TargetRegisterInfo *TRI;
+  LivePhysRegs LiveRegs;
+public:
+  static char ID;
+
+  /// \brief Default construct and initialize the pass.
+  StackMapLiveness();
+
+  /// \brief Tell the pass manager which passes we depend on and what
+  /// information we preserve.
+  virtual void getAnalysisUsage(AnalysisUsage &AU) const;
+
+  /// \brief Calculate the liveness information for the given machine function.
+  virtual bool runOnMachineFunction(MachineFunction &MF);
+
+private:
+  /// \brief Performs the actual liveness calculation for the function.
+  bool calculateLiveness();
+
+  /// \brief Add the current register live set to the instruction.
+  void addLiveOutSetToMI(MachineInstr &MI);
+
+  /// \brief Create a register mask and initialize it with the registers from
+  /// the register live set.
+  uint32_t *createRegisterMask() const;
+};
+
+} // llvm namespace
+
+#endif // LLVM_CODEGEN_STACKMAP_LIVENESS_ANALYSIS_H