--- /dev/null
+//===------------- 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(); }
+
}
}
-#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(); }
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