Allow PPC B and BLR to be if-converted into some predicated forms

This enables us to form predicated branches (which are the same conditional
branches we had before) and also a larger set of predicated returns (including
instructions like bdnzlr which is a conditional return and loop-counter
decrement all in one).

At the moment, if conversion does not capture all possible opportunities. A
simple example is provided in early-ret2.ll, where if conversion forms one
predicated return, and then the PPCEarlyReturn pass picks up the other one. So,
at least for now, we'll keep both mechanisms.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@179134 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/PowerPC/PPCInstr64Bit.td

@@ -83,8 +83,17 @@ let isBranch = 1, isTerminator = 1, hasCtrlDep = 1, PPC970_Unit = 7 in {
     def BDNZ8 : BForm_1<16, 16, 0, 0, (outs), (ins condbrtarget:$dst),
                         "bdnz $dst">;
   }
+
+  let isReturn = 1, Defs = [CTR8], Uses = [CTR8, LR8, RM] in {
+    def BDZLR8  : XLForm_2_ext<19, 16, 18, 0, 0, (outs), (ins),
+                              "bdzlr", BrB, []>;
+    def BDNZLR8 : XLForm_2_ext<19, 16, 16, 0, 0, (outs), (ins),
+                              "bdnzlr", BrB, []>;
+  }
 }
 
+
+
 let isCall = 1, PPC970_Unit = 7, Defs = [LR8] in {
   // Convenient aliases for call instructions
   let Uses = [RM] in {

lib/Target/PowerPC/PPCInstrInfo.cpp

@@ -876,6 +876,143 @@ bool PPCInstrInfo::FoldImmediate(MachineInstr *UseMI, MachineInstr *DefMI,
   return true;
 }
 
+bool PPCInstrInfo::isPredicated(const MachineInstr *MI) const {
+  unsigned OpC = MI->getOpcode();
+  switch (OpC) {
+  default:
+    return false;
+  case PPC::BCC:
+  case PPC::BCLR:
+  case PPC::BDZLR:
+  case PPC::BDZLR8:
+  case PPC::BDNZLR:
+  case PPC::BDNZLR8:
+    return true;
+  }
+}
+
+bool PPCInstrInfo::isUnpredicatedTerminator(const MachineInstr *MI) const {
+  if (!MI->isTerminator())
+    return false;
+
+  // Conditional branch is a special case.
+  if (MI->isBranch() && !MI->isBarrier())
+    return true;
+
+  return !isPredicated(MI);
+}
+
+bool PPCInstrInfo::PredicateInstruction(
+                     MachineInstr *MI,
+                     const SmallVectorImpl<MachineOperand> &Pred) const {
+  unsigned OpC = MI->getOpcode();
+  if (OpC == PPC::BLR) {
+    if (Pred[1].getReg() == PPC::CTR8 || Pred[1].getReg() == PPC::CTR) {
+      bool isPPC64 = TM.getSubtargetImpl()->isPPC64();
+      MI->setDesc(get(Pred[0].getImm() ?
+                      (isPPC64 ? PPC::BDNZLR8 : PPC::BDNZLR) :
+                      (isPPC64 ? PPC::BDZLR8  : PPC::BDZLR)));
+    } else {
+      MI->setDesc(get(PPC::BCLR));
+      MachineInstrBuilder(*MI->getParent()->getParent(), MI)
+        .addImm(Pred[0].getImm())
+        .addReg(Pred[1].getReg());
+    }
+
+    return true;
+  } else if (OpC == PPC::B) {
+    if (Pred[1].getReg() == PPC::CTR8 || Pred[1].getReg() == PPC::CTR) {
+      bool isPPC64 = TM.getSubtargetImpl()->isPPC64();
+      MI->setDesc(get(Pred[0].getImm() ?
+                      (isPPC64 ? PPC::BDNZ8 : PPC::BDNZ) :
+                      (isPPC64 ? PPC::BDZ8  : PPC::BDZ)));
+    } else {
+      MachineBasicBlock *MBB = MI->getOperand(0).getMBB();
+      MI->RemoveOperand(0);
+
+      MI->setDesc(get(PPC::BCC));
+      MachineInstrBuilder(*MI->getParent()->getParent(), MI)
+        .addImm(Pred[0].getImm())
+        .addReg(Pred[1].getReg())
+        .addMBB(MBB);
+    }
+
+    return true;
+  }
+
+  return false;
+}
+
+bool PPCInstrInfo::SubsumesPredicate(
+                     const SmallVectorImpl<MachineOperand> &Pred1,
+                     const SmallVectorImpl<MachineOperand> &Pred2) const {
+  assert(Pred1.size() == 2 && "Invalid PPC first predicate");
+  assert(Pred2.size() == 2 && "Invalid PPC second predicate");
+
+  if (Pred1[1].getReg() == PPC::CTR8 || Pred1[1].getReg() == PPC::CTR)
+    return false;
+  if (Pred2[1].getReg() == PPC::CTR8 || Pred2[1].getReg() == PPC::CTR)
+    return false;
+
+  PPC::Predicate P1 = (PPC::Predicate) Pred1[0].getImm();
+  PPC::Predicate P2 = (PPC::Predicate) Pred2[0].getImm();
+
+  if (P1 == P2)
+    return true;
+
+  // Does P1 subsume P2, e.g. GE subsumes GT.
+  if (P1 == PPC::PRED_LE &&
+      (P2 == PPC::PRED_LT || P2 == PPC::PRED_EQ))
+    return true;
+  if (P1 == PPC::PRED_GE &&
+      (P2 == PPC::PRED_GT || P2 == PPC::PRED_EQ))
+    return true;
+
+  return false;
+}
+
+bool PPCInstrInfo::DefinesPredicate(MachineInstr *MI,
+                                    std::vector<MachineOperand> &Pred) const {
+  // Note: At the present time, the contents of Pred from this function is
+  // unused by IfConversion. This implementation follows ARM by pushing the
+  // CR-defining operand. Because the 'DZ' and 'DNZ' count as types of
+  // predicate, instructions defining CTR or CTR8 are also included as
+  // predicate-defining instructions.
+
+  const TargetRegisterClass *RCs[] =
+    { &PPC::CRRCRegClass, &PPC::CRBITRCRegClass,
+      &PPC::CTRRCRegClass, &PPC::CTRRC8RegClass };
+
+  bool Found = false;
+  for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
+    const MachineOperand &MO = MI->getOperand(i);
+    for (int c = 0; c < 2 && !Found; ++c) {
+      const TargetRegisterClass *RC = RCs[c];
+      for (TargetRegisterClass::iterator I = RC->begin(),
+           IE = RC->end(); I != IE; ++I) {
+        if ((MO.isRegMask() && MO.clobbersPhysReg(*I)) ||
+            (MO.isReg() && MO.isDef() && MO.getReg() == *I)) {
+          Pred.push_back(MO);
+          Found = true;
+        }
+      }
+    }
+  }
+
+  return Found;
+}
+
+bool PPCInstrInfo::isPredicable(MachineInstr *MI) const {
+  unsigned OpC = MI->getOpcode();
+  switch (OpC) {
+  default:
+    return false;
+  case PPC::B:
+  case PPC::BLR:
+    return true;
+  }
+}
+
 /// GetInstSize - Return the number of bytes of code the specified
 /// instruction may be.  This returns the maximum number of bytes.
 ///

lib/Target/PowerPC/PPCInstrInfo.h

@@ -160,6 +160,53 @@ public:
   virtual bool FoldImmediate(MachineInstr *UseMI, MachineInstr *DefMI,
                              unsigned Reg, MachineRegisterInfo *MRI) const;
 
+  // If conversion by predication (only supported by some branch instructions).
+  // All of the profitability checks always return true; it is always
+  // profitable to use the predicated branches.
+  virtual bool isProfitableToIfCvt(MachineBasicBlock &MBB,
+                                   unsigned NumCycles, unsigned ExtraPredCycles,
+                                   const BranchProbability &Probability) const {
+    return true;
+  }
+
+  virtual bool isProfitableToIfCvt(MachineBasicBlock &TMBB,
+                                   unsigned NumT, unsigned ExtraT,
+                                   MachineBasicBlock &FMBB,
+                                   unsigned NumF, unsigned ExtraF,
+                                   const BranchProbability &Probability) const {
+    return true;
+  }
+
+  virtual bool isProfitableToDupForIfCvt(MachineBasicBlock &MBB,
+                                         unsigned NumCycles,
+                                         const BranchProbability
+                                         &Probability) const {
+    return true;
+  }
+
+  virtual bool isProfitableToUnpredicate(MachineBasicBlock &TMBB,
+                                         MachineBasicBlock &FMBB) const {
+    return false;
+  }
+
+  // Predication support.
+  bool isPredicated(const MachineInstr *MI) const;
+
+  virtual bool isUnpredicatedTerminator(const MachineInstr *MI) const;
+
+  virtual
+  bool PredicateInstruction(MachineInstr *MI,
+                            const SmallVectorImpl<MachineOperand> &Pred) const;
+
+  virtual
+  bool SubsumesPredicate(const SmallVectorImpl<MachineOperand> &Pred1,
+                         const SmallVectorImpl<MachineOperand> &Pred2) const;
+
+  virtual bool DefinesPredicate(MachineInstr *MI,
+                                std::vector<MachineOperand> &Pred) const;
+
+  virtual bool isPredicable(MachineInstr *MI) const;
+
   /// GetInstSize - Return the number of bytes of code the specified
   /// instruction may be.  This returns the maximum number of bytes.
   ///

lib/Target/PowerPC/PPCInstrInfo.td

@@ -518,6 +518,13 @@ let isBranch = 1, isTerminator = 1, hasCtrlDep = 1, PPC970_Unit = 7 in {
     let isReturn = 1, Uses = [LR, RM] in
     def BCLR : XLForm_2_br<19, 16, 0, (outs), (ins pred:$cond),
                            "b${cond:cc}lr ${cond:reg}", BrB, []>;
+
+    let isReturn = 1, Defs = [CTR], Uses = [CTR, LR, RM] in {
+      def BDZLR  : XLForm_2_ext<19, 16, 18, 0, 0, (outs), (ins),
+                             "bdzlr", BrB, []>;
+      def BDNZLR : XLForm_2_ext<19, 16, 16, 0, 0, (outs), (ins),
+                             "bdnzlr", BrB, []>;
+    }
   }
 
   let Defs = [CTR], Uses = [CTR] in {

lib/Target/PowerPC/PPCTargetMachine.cpp

@@ -93,6 +93,7 @@ public:
   virtual bool addPreRegAlloc();
   virtual bool addILPOpts();
   virtual bool addInstSelector();
+  virtual bool addPreSched2();
   virtual bool addPreEmitPass();
 };
 } // namespace
@@ -123,6 +124,13 @@ bool PPCPassConfig::addInstSelector() {
   return false;
 }
 
+bool PPCPassConfig::addPreSched2() {
+  if (getOptLevel() != CodeGenOpt::None)
+    addPass(&IfConverterID);
+
+  return true;
+}
+
 bool PPCPassConfig::addPreEmitPass() {
   if (getOptLevel() != CodeGenOpt::None)
     addPass(createPPCEarlyReturnPass());

test/CodeGen/PowerPC/bdzlr.ll

@@ -0,0 +1,63 @@
+; RUN: llc < %s -mtriple=powerpc64-unknown-linux-gnu -mcpu=pwr7 | FileCheck %s
+target datalayout = "E-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-f128:128:128-v128:128:128-n32:64"
+target triple = "powerpc64-unknown-linux-gnu"
+
+%struct.lua_TValue.17.692 = type { %union.Value.16.691, i32 }
+%union.Value.16.691 = type { %union.GCObject.15.690* }
+%union.GCObject.15.690 = type { %struct.lua_State.14.689 }
+%struct.lua_State.14.689 = type { %union.GCObject.15.690*, i8, i8, i8, %struct.lua_TValue.17.692*, %struct.lua_TValue.17.692*, %struct.global_State.10.685*, %struct.CallInfo.11.686*, i32*, %struct.lua_TValue.17.692*, %struct.lua_TValue.17.692*, %struct.CallInfo.11.686*, %struct.CallInfo.11.686*, i32, i32, i16, i16, i8, i8, i32, i32, void (%struct.lua_State.14.689*, %struct.lua_Debug.12.687*)*, %struct.lua_TValue.17.692, %struct.lua_TValue.17.692, %union.GCObject.15.690*, %union.GCObject.15.690*, %struct.lua_longjmp.13.688*, i64 }
+%struct.global_State.10.685 = type { %struct.stringtable.0.675, i8* (i8*, i8*, i64, i64)*, i8*, i8, i8, i32, %union.GCObject.15.690*, %union.GCObject.15.690**, %union.GCObject.15.690*, %union.GCObject.15.690*, %union.GCObject.15.690*, %union.GCObject.15.690*, %struct.Mbuffer.1.676, i64, i64, i64, i64, i32, i32, i32 (%struct.lua_State.14.689*)*, %struct.lua_TValue.17.692, %struct.lua_State.14.689*, %struct.UpVal.3.678, [9 x %struct.Table.7.682*], [17 x %union.TString.9.684*] }
+%struct.stringtable.0.675 = type { %union.GCObject.15.690**, i32, i32 }
+%struct.Mbuffer.1.676 = type { i8*, i64, i64 }
+%struct.UpVal.3.678 = type { %union.GCObject.15.690*, i8, i8, %struct.lua_TValue.17.692*, %union.anon.2.677 }
+%union.anon.2.677 = type { %struct.lua_TValue.17.692 }
+%struct.Table.7.682 = type { %union.GCObject.15.690*, i8, i8, i8, i8, %struct.Table.7.682*, %struct.lua_TValue.17.692*, %struct.Node.6.681*, %struct.Node.6.681*, %union.GCObject.15.690*, i32 }
+%struct.Node.6.681 = type { %struct.lua_TValue.17.692, %union.TKey.5.680 }
+%union.TKey.5.680 = type { %struct.anon.0.4.679 }
+%struct.anon.0.4.679 = type { %union.Value.16.691, i32, %struct.Node.6.681* }
+%union.TString.9.684 = type { %struct.anon.1.8.683 }
+%struct.anon.1.8.683 = type { %union.GCObject.15.690*, i8, i8, i8, i32, i64 }
+%struct.CallInfo.11.686 = type { %struct.lua_TValue.17.692*, %struct.lua_TValue.17.692*, %struct.lua_TValue.17.692*, i32*, i32, i32 }
+%struct.lua_Debug.12.687 = type { i32, i8*, i8*, i8*, i8*, i32, i32, i32, i32, [60 x i8], i32 }
+%struct.lua_longjmp.13.688 = type opaque
+
+define void @lua_xmove(i32 signext %n) #0 {
+entry:
+  br i1 undef, label %for.end, label %if.end
+
+if.end:                                           ; preds = %entry
+  br i1 undef, label %for.body.lr.ph, label %for.end
+
+for.body.lr.ph:                                   ; preds = %if.end
+  br label %for.body
+
+for.body:                                         ; preds = %for.body.for.body_crit_edge, %for.body.lr.ph
+  %0 = phi %struct.lua_TValue.17.692* [ undef, %for.body.lr.ph ], [ %.pre, %for.body.for.body_crit_edge ]
+  %indvars.iv = phi i64 [ 0, %for.body.lr.ph ], [ %indvars.iv.next, %for.body.for.body_crit_edge ]
+  %tt = getelementptr inbounds %struct.lua_TValue.17.692* %0, i64 %indvars.iv, i32 1
+  %1 = load i32* %tt, align 4, !tbaa !0
+  store i32 %1, i32* undef, align 4, !tbaa !0
+  %indvars.iv.next = add i64 %indvars.iv, 1
+  %lftr.wideiv = trunc i64 %indvars.iv.next to i32
+  %exitcond = icmp eq i32 %lftr.wideiv, %n
+  br i1 %exitcond, label %for.end, label %for.body.for.body_crit_edge
+
+for.body.for.body_crit_edge:                      ; preds = %for.body
+  %.pre = load %struct.lua_TValue.17.692** undef, align 8, !tbaa !3
+  br label %for.body
+
+for.end:                                          ; preds = %for.body, %if.end, %entry
+  ret void
+
+; CHECK: @lua_xmove
+; CHECK: bnelr
+; CHECK: bnelr
+; CHECK: bdzlr
+}
+
+attributes #0 = { nounwind }
+
+!0 = metadata !{metadata !"int", metadata !1}
+!1 = metadata !{metadata !"omnipotent char", metadata !2}
+!2 = metadata !{metadata !"Simple C/C++ TBAA"}
+!3 = metadata !{metadata !"any pointer", metadata !1}

test/CodeGen/PowerPC/early-ret2.ll

@@ -0,0 +1,26 @@
+; RUN: llc < %s -mtriple=powerpc64-unknown-linux-gnu -mcpu=pwr7 | FileCheck %s
+target datalayout = "E-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-f128:128:128-v128:128:128-n32:64"
+target triple = "powerpc64-unknown-linux-gnu"
+
+define void @_Z8example3iPiS_() #0 {
+entry:
+  br i1 undef, label %while.end, label %while.body.lr.ph
+
+while.body.lr.ph:                                 ; preds = %entry
+  br i1 undef, label %while.end, label %while.body
+
+while.body:                                       ; preds = %while.body, %while.body.lr.ph
+  br i1 false, label %while.end, label %while.body, !llvm.vectorizer.already_vectorized !0
+
+while.end:                                        ; preds = %while.body, %while.body.lr.ph, %entry
+  ret void
+
+; CHECK: @_Z8example3iPiS_
+; CHECK: bnelr
+; CHECK: bnelr
+}
+
+attributes #0 = { noinline nounwind }
+
+!0 = metadata !{}
+