Rename "loop aligner" pass to "code placement optimization" pass.

llvm-svn: 71150

1 files changed, 82 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/CodePlacementOpt.cpp b/llvm/lib/CodeGen/CodePlacementOpt.cpp
new file mode 100644
index 00000000000..54121afefda
--- /dev/null
+++ b/llvm/lib/CodeGen/CodePlacementOpt.cpp
@@ -0,0 +1,82 @@
+//===-- CodePlacementOpt.cpp - Code Placement 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 optimize code placement and align loop
+// headers to target specific alignment boundary.
+//
+//===----------------------------------------------------------------------===//
+
+#define DEBUG_TYPE "code-placement"
+#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 CodePlacementOpt : public MachineFunctionPass {
+  public:
+    static char ID;
+    CodePlacementOpt() : MachineFunctionPass(&ID) {}
+
+    virtual bool runOnMachineFunction(MachineFunction &MF);
+    virtual const char *getPassName() const {
+      return "Code Placement Optimizater";
+    }
+
+    virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+      AU.addRequired<MachineLoopInfo>();
+      AU.addPreserved<MachineLoopInfo>();
+      AU.addPreservedID(MachineDominatorsID);
+      MachineFunctionPass::getAnalysisUsage(AU);
+    }
+  };
+
+  char CodePlacementOpt::ID = 0;
+} // end anonymous namespace
+
+FunctionPass *llvm::createCodePlacementOptPass() {
+  return new CodePlacementOpt();
+}
+
+bool CodePlacementOpt::runOnMachineFunction(MachineFunction &MF) {
+  const MachineLoopInfo *MLI = &getAnalysis<MachineLoopInfo>();
+
+  if (MLI->empty())
+    return false;  // No loops.
+
+  const TargetLowering *TLI = MF.getTarget().getTargetLowering();
+  if (!TLI)
+    return false;
+
+  unsigned Align = TLI->getPrefLoopAlignment();
+  if (!Align)
+    return false;  // Don't care about loop alignment.
+
+  const Function *F = MF.getFunction();
+  if (F->hasFnAttr(Attribute::OptimizeForSize))
+    return false;
+
+  for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I) {
+    MachineBasicBlock *MBB = I;
+    if (MLI->isLoopHeader(MBB)) {
+      MachineBasicBlock *PredBB = prior(I);
+      if (MLI->getLoopFor(MBB) == MLI->getLoopFor(PredBB))
+        // If previously BB is in the same loop, don't align this BB. We want
+        // to prevent adding noop's inside a loop.
+        continue;
+      MBB->setAlignment(Align);
+    }
+  }
+
+  return true;
+}