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
diff --git a/lib/CodeGen/LoopAligner.cpp b/lib/CodeGen/LoopAligner.cpp
new file mode 100644
index 0000000..a40bb50
--- /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;
+}