From 09e8ca8a582bb67ef290d77d9b9441716dd6ba2e Mon Sep 17 00:00:00 2001
From: Evan Cheng <evan.cheng@apple.com>
Date: Mon, 20 Oct 2008 21:44:59 +0000
Subject: [PATCH] Add skeleton for the pre-register allocation live interval
 splitting pass.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@57847 91177308-0d34-0410-b5e6-96231b3b80d8
---
 include/llvm/CodeGen/Passes.h     |  2 +
 lib/CodeGen/PreAllocSplitting.cpp | 81 +++++++++++++++++++++++++++++++
 2 files changed, 83 insertions(+)
 create mode 100644 lib/CodeGen/PreAllocSplitting.cpp

diff --git a/include/llvm/CodeGen/Passes.h b/include/llvm/CodeGen/Passes.h
index e07f7de12ac..6357f0635bf 100644
--- a/include/llvm/CodeGen/Passes.h
+++ b/include/llvm/CodeGen/Passes.h
@@ -61,6 +61,8 @@ namespace llvm {
   ///  This pass is still in development
   extern const PassInfo *const StrongPHIEliminationID;
 
+  extern const PassInfo *const PreAllocSplittingID;
+
   /// SimpleRegisterCoalescing pass.  Aggressively coalesces every register
   /// copy it can.
   ///
diff --git a/lib/CodeGen/PreAllocSplitting.cpp b/lib/CodeGen/PreAllocSplitting.cpp
new file mode 100644
index 00000000000..7b4ec8efbcf
--- /dev/null
+++ b/lib/CodeGen/PreAllocSplitting.cpp
@@ -0,0 +1,81 @@
+//===-- PreAllocSplitting.cpp - Pre-allocation Interval Spltting Pass. ----===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements the machine instruction level pre-register allocation
+// live interval splitting pass. It finds live interval barriers, i.e.
+// instructions which will kill all physical registers in certain register
+// classes, and split all live intervals which cross the barrier.
+//
+//===----------------------------------------------------------------------===//
+
+#define DEBUG_TYPE "pre-alloc-split"
+#include "llvm/CodeGen/LiveIntervalAnalysis.h"
+#include "llvm/CodeGen/MachineFunctionPass.h"
+#include "llvm/CodeGen/MachineLoopInfo.h"
+#include "llvm/CodeGen/MachineRegisterInfo.h"
+#include "llvm/CodeGen/Passes.h"
+#include "llvm/CodeGen/RegisterCoalescer.h"
+#include "llvm/Target/TargetMachine.h"
+#include "llvm/Target/TargetOptions.h"
+#include "llvm/Target/TargetRegisterInfo.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/ADT/PostOrderIterator.h"
+#include "llvm/ADT/SmallPtrSet.h"
+using namespace llvm;
+
+namespace {
+  class VISIBILITY_HIDDEN PreAllocSplitting : public MachineFunctionPass {
+    // ProcessedBarriers - Register live interval barriers that have already
+    // been processed.
+    SmallPtrSet<MachineInstr*, 16> ProcessedBarriers;
+
+    // ActiveBarriers - Register live interval barriers that are currently
+    // being processed.
+    SmallSet<unsigned, 16> ActiveBarriers;
+  public:
+    static char ID;
+    PreAllocSplitting() : MachineFunctionPass(&ID) {}
+
+    virtual bool runOnMachineFunction(MachineFunction &MF);
+
+    virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+      AU.addRequired<LiveIntervals>();
+      AU.addPreserved<LiveIntervals>();
+      AU.addPreserved<MachineLoopInfo>();
+      AU.addPreserved<RegisterCoalescer>();
+      if (StrongPHIElim)
+        AU.addPreservedID(StrongPHIEliminationID);
+      else
+        AU.addPreservedID(PHIEliminationID);
+      AU.addPreservedID(TwoAddressInstructionPassID);
+      MachineFunctionPass::getAnalysisUsage(AU);
+    }
+    
+    virtual void releaseMemory() {
+      ProcessedBarriers.clear();
+      ActiveBarriers.clear();
+    }
+
+    virtual const char *getPassName() const {
+      return "Pre-Register Allocaton Live Interval Splitting";
+    }
+  };
+} // end anonymous namespace
+
+char PreAllocSplitting::ID = 0;
+
+static RegisterPass<PreAllocSplitting>
+X("pre-alloc-splitting", "Pre-Register Allocation Live Interval Splitting");
+
+const PassInfo *const llvm::PreAllocSplittingID = &X;
+
+bool PreAllocSplitting::runOnMachineFunction(MachineFunction &MF) {
+  return false;
+}