[PowerPC] Put PPCEarlyReturn into its own source file

PPCInstrInfo.cpp has ended up containing several small MI-level passes, and
this is making the file harder to read than necessary. Split out
PPCEarlyReturn into its own source file. NFC.

Now that PPCInstrInfo.cpp does not also contain pass implementations, I hope
that it will be slightly less unwieldy.

llvm-svn: 227775

3 files changed, 202 insertions, 165 deletions

diff --git a/llvm/lib/Target/PowerPC/CMakeLists.txt b/llvm/lib/Target/PowerPC/CMakeLists.txt
index 6bf5c5f..972cd52 100644
--- a/llvm/lib/Target/PowerPC/CMakeLists.txt
+++ b/llvm/lib/Target/PowerPC/CMakeLists.txt
@@ -20,6 +20,7 @@ add_llvm_target(PowerPCCodeGen
   PPCInstrInfo.cpp
   PPCISelDAGToDAG.cpp
   PPCISelLowering.cpp
+  PPCEarlyReturn.cpp
   PPCFastISel.cpp
   PPCFrameLowering.cpp
   PPCMCInstLower.cpp
diff --git a/llvm/lib/Target/PowerPC/PPCEarlyReturn.cpp b/llvm/lib/Target/PowerPC/PPCEarlyReturn.cpp
new file mode 100644
index 0000000..08673cc
--- /dev/null
+++ b/llvm/lib/Target/PowerPC/PPCEarlyReturn.cpp
@@ -0,0 +1,201 @@
+//===------------- PPCEarlyReturn.cpp - Form Early Returns ----------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// A pass that form early (predicated) returns. If-conversion handles some of
+// this, but this pass picks up some remaining cases.
+//
+//===----------------------------------------------------------------------===//
+
+#include "PPCInstrInfo.h"
+#include "MCTargetDesc/PPCPredicates.h"
+#include "PPC.h"
+#include "PPCInstrBuilder.h"
+#include "PPCMachineFunctionInfo.h"
+#include "PPCTargetMachine.h"
+#include "llvm/ADT/STLExtras.h"
+#include "llvm/ADT/Statistic.h"
+#include "llvm/CodeGen/MachineFrameInfo.h"
+#include "llvm/CodeGen/MachineFunctionPass.h"
+#include "llvm/CodeGen/MachineInstrBuilder.h"
+#include "llvm/CodeGen/MachineMemOperand.h"
+#include "llvm/CodeGen/MachineRegisterInfo.h"
+#include "llvm/MC/MCAsmInfo.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/ErrorHandling.h"
+#include "llvm/Support/TargetRegistry.h"
+#include "llvm/Support/raw_ostream.h"
+
+using namespace llvm;
+
+#define DEBUG_TYPE "ppc-early-ret"
+STATISTIC(NumBCLR, "Number of early conditional returns");
+STATISTIC(NumBLR,  "Number of early returns");
+
+namespace llvm {
+  void initializePPCEarlyReturnPass(PassRegistry&);
+}
+
+namespace {
+  // PPCEarlyReturn pass - For simple functions without epilogue code, move
+  // returns up, and create conditional returns, to avoid unnecessary
+  // branch-to-blr sequences.
+  struct PPCEarlyReturn : public MachineFunctionPass {
+    static char ID;
+    PPCEarlyReturn() : MachineFunctionPass(ID) {
+      initializePPCEarlyReturnPass(*PassRegistry::getPassRegistry());
+    }
+
+    const TargetInstrInfo *TII;
+
+protected:
+    bool processBlock(MachineBasicBlock &ReturnMBB) {
+      bool Changed = false;
+
+      MachineBasicBlock::iterator I = ReturnMBB.begin();
+      I = ReturnMBB.SkipPHIsAndLabels(I);
+
+      // The block must be essentially empty except for the blr.
+      if (I == ReturnMBB.end() ||
+          (I->getOpcode() != PPC::BLR && I->getOpcode() != PPC::BLR8) ||
+          I != ReturnMBB.getLastNonDebugInstr())
+        return Changed;
+
+      SmallVector<MachineBasicBlock*, 8> PredToRemove;
+      for (MachineBasicBlock::pred_iterator PI = ReturnMBB.pred_begin(),
+           PIE = ReturnMBB.pred_end(); PI != PIE; ++PI) {
+        bool OtherReference = false, BlockChanged = false;
+        for (MachineBasicBlock::iterator J = (*PI)->getLastNonDebugInstr();;) {
+          MachineInstrBuilder MIB;
+          if (J->getOpcode() == PPC::B) {
+            if (J->getOperand(0).getMBB() == &ReturnMBB) {
+              // This is an unconditional branch to the return. Replace the
+              // branch with a blr.
+              MIB =
+                BuildMI(**PI, J, J->getDebugLoc(), TII->get(I->getOpcode()));
+              MIB.copyImplicitOps(I);
+              MachineBasicBlock::iterator K = J--;
+              K->eraseFromParent();
+              BlockChanged = true;
+              ++NumBLR;
+              continue;
+            }
+          } else if (J->getOpcode() == PPC::BCC) {
+            if (J->getOperand(2).getMBB() == &ReturnMBB) {
+              // This is a conditional branch to the return. Replace the branch
+              // with a bclr.
+              MIB = BuildMI(**PI, J, J->getDebugLoc(), TII->get(PPC::BCCLR))
+                      .addImm(J->getOperand(0).getImm())
+                      .addReg(J->getOperand(1).getReg());
+              MIB.copyImplicitOps(I);
+              MachineBasicBlock::iterator K = J--;
+              K->eraseFromParent();
+              BlockChanged = true;
+              ++NumBCLR;
+              continue;
+            }
+          } else if (J->getOpcode() == PPC::BC || J->getOpcode() == PPC::BCn) {
+            if (J->getOperand(1).getMBB() == &ReturnMBB) {
+              // This is a conditional branch to the return. Replace the branch
+              // with a bclr.
+              MIB = BuildMI(**PI, J, J->getDebugLoc(),
+                            TII->get(J->getOpcode() == PPC::BC ?
+                                     PPC::BCLR : PPC::BCLRn))
+                      .addReg(J->getOperand(0).getReg());
+              MIB.copyImplicitOps(I);
+              MachineBasicBlock::iterator K = J--;
+              K->eraseFromParent();
+              BlockChanged = true;
+              ++NumBCLR;
+              continue;
+            }
+          } else if (J->isBranch()) {
+            if (J->isIndirectBranch()) {
+              if (ReturnMBB.hasAddressTaken())
+                OtherReference = true;
+            } else
+              for (unsigned i = 0; i < J->getNumOperands(); ++i)
+                if (J->getOperand(i).isMBB() &&
+                    J->getOperand(i).getMBB() == &ReturnMBB)
+                  OtherReference = true;
+          } else if (!J->isTerminator() && !J->isDebugValue())
+            break;
+
+          if (J == (*PI)->begin())
+            break;
+
+          --J;
+        }
+
+        if ((*PI)->canFallThrough() && (*PI)->isLayoutSuccessor(&ReturnMBB))
+          OtherReference = true;
+
+        // Predecessors are stored in a vector and can't be removed here.
+        if (!OtherReference && BlockChanged) {
+          PredToRemove.push_back(*PI);
+        }
+
+        if (BlockChanged)
+          Changed = true;
+      }
+
+      for (unsigned i = 0, ie = PredToRemove.size(); i != ie; ++i)
+        PredToRemove[i]->removeSuccessor(&ReturnMBB);
+
+      if (Changed && !ReturnMBB.hasAddressTaken()) {
+        // We now might be able to merge this blr-only block into its
+        // by-layout predecessor.
+        if (ReturnMBB.pred_size() == 1 &&
+            (*ReturnMBB.pred_begin())->isLayoutSuccessor(&ReturnMBB)) {
+          // Move the blr into the preceding block.
+          MachineBasicBlock &PrevMBB = **ReturnMBB.pred_begin();
+          PrevMBB.splice(PrevMBB.end(), &ReturnMBB, I);
+          PrevMBB.removeSuccessor(&ReturnMBB);
+        }
+
+        if (ReturnMBB.pred_empty())
+          ReturnMBB.eraseFromParent();
+      }
+
+      return Changed;
+    }
+
+public:
+    bool runOnMachineFunction(MachineFunction &MF) override {
+      TII = MF.getSubtarget().getInstrInfo();
+
+      bool Changed = false;
+
+      // If the function does not have at least two blocks, then there is
+      // nothing to do.
+      if (MF.size() < 2)
+        return Changed;
+
+      for (MachineFunction::iterator I = MF.begin(); I != MF.end();) {
+        MachineBasicBlock &B = *I++;
+        if (processBlock(B))
+          Changed = true;
+      }
+
+      return Changed;
+    }
+
+    void getAnalysisUsage(AnalysisUsage &AU) const override {
+      MachineFunctionPass::getAnalysisUsage(AU);
+    }
+  };
+}
+
+INITIALIZE_PASS(PPCEarlyReturn, DEBUG_TYPE,
+                "PowerPC Early-Return Creation", false, false)
+
+char PPCEarlyReturn::ID = 0;
+FunctionPass*
+llvm::createPPCEarlyReturnPass() { return new PPCEarlyReturn(); }
+
diff --git a/llvm/lib/Target/PowerPC/PPCInstrInfo.cpp b/llvm/lib/Target/PowerPC/PPCInstrInfo.cpp
index e5b2cf1..51d68fd 100644
--- a/llvm/lib/Target/PowerPC/PPCInstrInfo.cpp
+++ b/llvm/lib/Target/PowerPC/PPCInstrInfo.cpp
@@ -1605,168 +1605,3 @@ unsigned PPCInstrInfo::GetInstSizeInBytes(const MachineInstr *MI) const {
   }
 }
 
-#undef DEBUG_TYPE
-#define DEBUG_TYPE "ppc-early-ret"
-STATISTIC(NumBCLR, "Number of early conditional returns");
-STATISTIC(NumBLR,  "Number of early returns");
-
-namespace llvm {
-  void initializePPCEarlyReturnPass(PassRegistry&);
-}
-
-namespace {
-  // PPCEarlyReturn pass - For simple functions without epilogue code, move
-  // returns up, and create conditional returns, to avoid unnecessary
-  // branch-to-blr sequences.
-  struct PPCEarlyReturn : public MachineFunctionPass {
-    static char ID;
-    PPCEarlyReturn() : MachineFunctionPass(ID) {
-      initializePPCEarlyReturnPass(*PassRegistry::getPassRegistry());
-    }
-
-    const TargetInstrInfo *TII;
-
-protected:
-    bool processBlock(MachineBasicBlock &ReturnMBB) {
-      bool Changed = false;
-
-      MachineBasicBlock::iterator I = ReturnMBB.begin();
-      I = ReturnMBB.SkipPHIsAndLabels(I);
-
-      // The block must be essentially empty except for the blr.
-      if (I == ReturnMBB.end() ||
-          (I->getOpcode() != PPC::BLR && I->getOpcode() != PPC::BLR8) ||
-          I != ReturnMBB.getLastNonDebugInstr())
-        return Changed;
-
-      SmallVector<MachineBasicBlock*, 8> PredToRemove;
-      for (MachineBasicBlock::pred_iterator PI = ReturnMBB.pred_begin(),
-           PIE = ReturnMBB.pred_end(); PI != PIE; ++PI) {
-        bool OtherReference = false, BlockChanged = false;
-        for (MachineBasicBlock::iterator J = (*PI)->getLastNonDebugInstr();;) {
-          MachineInstrBuilder MIB;
-          if (J->getOpcode() == PPC::B) {
-            if (J->getOperand(0).getMBB() == &ReturnMBB) {
-              // This is an unconditional branch to the return. Replace the
-              // branch with a blr.
-              MIB =
-                BuildMI(**PI, J, J->getDebugLoc(), TII->get(I->getOpcode()));
-              MIB.copyImplicitOps(I);
-              MachineBasicBlock::iterator K = J--;
-              K->eraseFromParent();
-              BlockChanged = true;
-              ++NumBLR;
-              continue;
-            }
-          } else if (J->getOpcode() == PPC::BCC) {
-            if (J->getOperand(2).getMBB() == &ReturnMBB) {
-              // This is a conditional branch to the return. Replace the branch
-              // with a bclr.
-              MIB = BuildMI(**PI, J, J->getDebugLoc(), TII->get(PPC::BCCLR))
-                      .addImm(J->getOperand(0).getImm())
-                      .addReg(J->getOperand(1).getReg());
-              MIB.copyImplicitOps(I);
-              MachineBasicBlock::iterator K = J--;
-              K->eraseFromParent();
-              BlockChanged = true;
-              ++NumBCLR;
-              continue;
-            }
-          } else if (J->getOpcode() == PPC::BC || J->getOpcode() == PPC::BCn) {
-            if (J->getOperand(1).getMBB() == &ReturnMBB) {
-              // This is a conditional branch to the return. Replace the branch
-              // with a bclr.
-              MIB = BuildMI(**PI, J, J->getDebugLoc(),
-                            TII->get(J->getOpcode() == PPC::BC ?
-                                     PPC::BCLR : PPC::BCLRn))
-                      .addReg(J->getOperand(0).getReg());
-              MIB.copyImplicitOps(I);
-              MachineBasicBlock::iterator K = J--;
-              K->eraseFromParent();
-              BlockChanged = true;
-              ++NumBCLR;
-              continue;
-            }
-          } else if (J->isBranch()) {
-            if (J->isIndirectBranch()) {
-              if (ReturnMBB.hasAddressTaken())
-                OtherReference = true;
-            } else
-              for (unsigned i = 0; i < J->getNumOperands(); ++i)
-                if (J->getOperand(i).isMBB() &&
-                    J->getOperand(i).getMBB() == &ReturnMBB)
-                  OtherReference = true;
-          } else if (!J->isTerminator() && !J->isDebugValue())
-            break;
-
-          if (J == (*PI)->begin())
-            break;
-
-          --J;
-        }
-
-        if ((*PI)->canFallThrough() && (*PI)->isLayoutSuccessor(&ReturnMBB))
-          OtherReference = true;
-
-        // Predecessors are stored in a vector and can't be removed here.
-        if (!OtherReference && BlockChanged) {
-          PredToRemove.push_back(*PI);
-        }
-
-        if (BlockChanged)
-          Changed = true;
-      }
-
-      for (unsigned i = 0, ie = PredToRemove.size(); i != ie; ++i)
-        PredToRemove[i]->removeSuccessor(&ReturnMBB);
-
-      if (Changed && !ReturnMBB.hasAddressTaken()) {
-        // We now might be able to merge this blr-only block into its
-        // by-layout predecessor.
-        if (ReturnMBB.pred_size() == 1 &&
-            (*ReturnMBB.pred_begin())->isLayoutSuccessor(&ReturnMBB)) {
-          // Move the blr into the preceding block.
-          MachineBasicBlock &PrevMBB = **ReturnMBB.pred_begin();
-          PrevMBB.splice(PrevMBB.end(), &ReturnMBB, I);
-          PrevMBB.removeSuccessor(&ReturnMBB);
-        }
-
-        if (ReturnMBB.pred_empty())
-          ReturnMBB.eraseFromParent();
-      }
-
-      return Changed;
-    }
-
-public:
-    bool runOnMachineFunction(MachineFunction &MF) override {
-      TII = MF.getSubtarget().getInstrInfo();
-
-      bool Changed = false;
-
-      // If the function does not have at least two blocks, then there is
-      // nothing to do.
-      if (MF.size() < 2)
-        return Changed;
-
-      for (MachineFunction::iterator I = MF.begin(); I != MF.end();) {
-        MachineBasicBlock &B = *I++;
-        if (processBlock(B))
-          Changed = true;
-      }
-
-      return Changed;
-    }
-
-    void getAnalysisUsage(AnalysisUsage &AU) const override {
-      MachineFunctionPass::getAnalysisUsage(AU);
-    }
-  };
-}
-
-INITIALIZE_PASS(PPCEarlyReturn, DEBUG_TYPE,
-                "PowerPC Early-Return Creation", false, false)
-
-char PPCEarlyReturn::ID = 0;
-FunctionPass*
-llvm::createPPCEarlyReturnPass() { return new PPCEarlyReturn(); }