From fb8075d03f5c87bd57dcc9c5f2304f6b13c55aad Mon Sep 17 00:00:00 2001
From: Evan Cheng <evan.cheng@apple.com>
Date: Thu, 28 Feb 2008 00:43:03 +0000
Subject: Add a quick and dirty "loop aligner pass". x86 uses it to align its
 loops to 16-byte boundaries.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@47703 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/CodeGen/LoopAligner.cpp | 65 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 65 insertions(+)
 create mode 100644 lib/CodeGen/LoopAligner.cpp

(limited to 'lib/CodeGen/LoopAligner.cpp')

diff --git a/lib/CodeGen/LoopAligner.cpp b/lib/CodeGen/LoopAligner.cpp
new file mode 100644
index 0000000000..a40bb50565
--- /dev/null
+++ b/lib/CodeGen/LoopAligner.cpp
@@ -0,0 +1,65 @@
+//===-- LoopAligner.cpp - Loop aligner 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 pass that align loop headers to target specific
+// alignment boundary.
+//
+//===----------------------------------------------------------------------===//
+
+#define DEBUG_TYPE "loopalign"
+#include "llvm/CodeGen/MachineLoopInfo.h"
+#include "llvm/CodeGen/MachineFunctionPass.h"
+#include "llvm/CodeGen/Passes.h"
+#include "llvm/Target/TargetLowering.h"
+#include "llvm/Target/TargetMachine.h"
+#include "llvm/Support/Compiler.h"
+#include "llvm/Support/Debug.h"
+using namespace llvm;
+
+namespace {
+  class LoopAligner : public MachineFunctionPass {
+    const TargetLowering *TLI;
+
+  public:
+    static char ID;
+    LoopAligner() : MachineFunctionPass((intptr_t)&ID) {}
+
+    virtual bool runOnMachineFunction(MachineFunction &MF);
+    virtual const char *getPassName() const { return "Loop aligner"; }
+
+    virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+      AU.addRequired<MachineLoopInfo>();
+      AU.addPreserved<MachineLoopInfo>();
+      MachineFunctionPass::getAnalysisUsage(AU);
+    }
+  };
+
+  char LoopAligner::ID = 0;
+} // end anonymous namespace
+
+FunctionPass *llvm::createLoopAlignerPass() { return new LoopAligner(); }
+
+bool LoopAligner::runOnMachineFunction(MachineFunction &MF) {
+  const MachineLoopInfo *MLI = &getAnalysis<MachineLoopInfo>();
+
+  if (MLI->begin() == MLI->end())
+    return false;  // No loops.
+
+  unsigned Align = MF.getTarget().getTargetLowering()->getPrefLoopAlignment();
+  if (!Align)
+    return false;  // Don't care about loop alignment.
+
+  for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I) {
+    MachineBasicBlock *MBB = I;
+    if (MLI->isLoopHeader(MBB))
+      MBB->setAlignment(Align);
+  }
+
+  return true;
+}
-- 
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