Make post-ra scheduling, anti-dep breaking, and register scavenger (conservatively) aware of predicated instructions. This enables ARM to move if-conversion before post-ra scheduler.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@106091 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/IfConversion.cpp b/lib/CodeGen/IfConversion.cpp
index 41734dd..710a9f1 100644
--- a/lib/CodeGen/IfConversion.cpp
+++ b/lib/CodeGen/IfConversion.cpp
@@ -20,6 +20,7 @@
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetLowering.h"
#include "llvm/Target/TargetMachine.h"
+#include "llvm/Target/TargetRegisterInfo.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
@@ -47,6 +48,8 @@
cl::init(false), cl::Hidden);
static cl::opt<bool> DisableDiamond("disable-ifcvt-diamond",
cl::init(false), cl::Hidden);
+static cl::opt<bool> IfCvtBranchFold("ifcvt-branch-fold",
+ cl::init(true), cl::Hidden);
STATISTIC(NumSimple, "Number of simple if-conversions performed");
STATISTIC(NumSimpleFalse, "Number of simple (F) if-conversions performed");
@@ -146,6 +149,7 @@
const TargetLowering *TLI;
const TargetInstrInfo *TII;
+ const TargetRegisterInfo *TRI;
bool MadeChange;
int FnNum;
public:
@@ -176,9 +180,11 @@
unsigned NumDups1, unsigned NumDups2);
void PredicateBlock(BBInfo &BBI,
MachineBasicBlock::iterator E,
- SmallVectorImpl<MachineOperand> &Cond);
+ SmallVectorImpl<MachineOperand> &Cond,
+ SmallSet<unsigned, 4> &Redefs);
void CopyAndPredicateBlock(BBInfo &ToBBI, BBInfo &FromBBI,
SmallVectorImpl<MachineOperand> &Cond,
+ SmallSet<unsigned, 4> &Redefs,
bool IgnoreBr = false);
void MergeBlocks(BBInfo &ToBBI, BBInfo &FromBBI);
@@ -226,6 +232,7 @@
bool IfConverter::runOnMachineFunction(MachineFunction &MF) {
TLI = MF.getTarget().getTargetLowering();
TII = MF.getTarget().getInstrInfo();
+ TRI = MF.getTarget().getRegisterInfo();
if (!TII) return false;
DEBUG(dbgs() << "\nIfcvt: function (" << ++FnNum << ") \'"
@@ -362,7 +369,7 @@
Roots.clear();
BBAnalysis.clear();
- if (MadeChange) {
+ if (MadeChange && !IfCvtBranchFold) {
BranchFolder BF(false);
BF.OptimizeFunction(MF, TII,
MF.getTarget().getRegisterInfo(),
@@ -823,12 +830,17 @@
/// that all the intervening blocks are empty (given BB can fall through to its
/// next block).
static bool canFallThroughTo(MachineBasicBlock *BB, MachineBasicBlock *ToBB) {
- MachineFunction::iterator I = BB;
+ MachineFunction::iterator PI = BB;
+ MachineFunction::iterator I = llvm::next(PI);
MachineFunction::iterator TI = ToBB;
MachineFunction::iterator E = BB->getParent()->end();
- while (++I != TI)
- if (I == E || !I->empty())
+ while (I != TI) {
+ // Check isSuccessor to avoid case where the next block is empty, but
+ // it's not a successor.
+ if (I == E || !I->empty() || !PI->isSuccessor(I))
return false;
+ PI = I++;
+ }
return true;
}
@@ -863,6 +875,66 @@
BBI.BB->CorrectExtraCFGEdges(TBB, FBB, !Cond.empty());
}
+/// InitPredRedefs / UpdatePredRedefs - Defs by predicated instructions are
+/// modeled as read + write (sort like two-address instructions). These
+/// routines track register liveness and add implicit uses to if-converted
+/// instructions to conform to the model.
+static void InitPredRedefs(MachineBasicBlock *BB, SmallSet<unsigned,4> &Redefs,
+ const TargetRegisterInfo *TRI) {
+ for (MachineBasicBlock::livein_iterator I = BB->livein_begin(),
+ E = BB->livein_end(); I != E; ++I) {
+ unsigned Reg = *I;
+ Redefs.insert(Reg);
+ for (const unsigned *Subreg = TRI->getSubRegisters(Reg);
+ *Subreg; ++Subreg)
+ Redefs.insert(*Subreg);
+ }
+}
+
+static void UpdatePredRedefs(MachineInstr *MI, SmallSet<unsigned,4> &Redefs,
+ const TargetRegisterInfo *TRI,
+ bool AddImpUse = false) {
+ SmallVector<unsigned, 4> Defs;
+ for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
+ const MachineOperand &MO = MI->getOperand(i);
+ if (!MO.isReg())
+ continue;
+ unsigned Reg = MO.getReg();
+ if (!Reg)
+ continue;
+ if (MO.isDef())
+ Defs.push_back(Reg);
+ else if (MO.isKill()) {
+ Redefs.erase(Reg);
+ for (const unsigned *SR = TRI->getSubRegisters(Reg); *SR; ++SR)
+ Redefs.erase(*SR);
+ }
+ }
+ for (unsigned i = 0, e = Defs.size(); i != e; ++i) {
+ unsigned Reg = Defs[i];
+ if (Redefs.count(Reg)) {
+ if (AddImpUse)
+ // Treat predicated update as read + write.
+ MI->addOperand(MachineOperand::CreateReg(Reg, false/*IsDef*/,
+ true/*IsImp*/,false/*IsKill*/));
+ } else {
+ Redefs.insert(Reg);
+ for (const unsigned *SR = TRI->getSubRegisters(Reg); *SR; ++SR)
+ Redefs.insert(*SR);
+ }
+ }
+}
+
+static void UpdatePredRedefs(MachineBasicBlock::iterator I,
+ MachineBasicBlock::iterator E,
+ SmallSet<unsigned,4> &Redefs,
+ const TargetRegisterInfo *TRI) {
+ while (I != E) {
+ UpdatePredRedefs(I, Redefs, TRI);
+ ++I;
+ }
+}
+
/// IfConvertSimple - If convert a simple (split, no rejoin) sub-CFG.
///
bool IfConverter::IfConvertSimple(BBInfo &BBI, IfcvtKind Kind) {
@@ -887,13 +959,19 @@
if (TII->ReverseBranchCondition(Cond))
assert(false && "Unable to reverse branch condition!");
+ // Initialize liveins to the first BB. These are potentiall re-defined by
+ // predicated instructions.
+ SmallSet<unsigned, 4> Redefs;
+ InitPredRedefs(CvtBBI->BB, Redefs, TRI);
+ InitPredRedefs(NextBBI->BB, Redefs, TRI);
+
if (CvtBBI->BB->pred_size() > 1) {
BBI.NonPredSize -= TII->RemoveBranch(*BBI.BB);
// Copy instructions in the true block, predicate them, and add them to
// the entry block.
- CopyAndPredicateBlock(BBI, *CvtBBI, Cond);
+ CopyAndPredicateBlock(BBI, *CvtBBI, Cond, Redefs);
} else {
- PredicateBlock(*CvtBBI, CvtBBI->BB->end(), Cond);
+ PredicateBlock(*CvtBBI, CvtBBI->BB->end(), Cond, Redefs);
// Merge converted block into entry block.
BBI.NonPredSize -= TII->RemoveBranch(*BBI.BB);
@@ -971,17 +1049,23 @@
}
}
+ // Initialize liveins to the first BB. These are potentiall re-defined by
+ // predicated instructions.
+ SmallSet<unsigned, 4> Redefs;
+ InitPredRedefs(CvtBBI->BB, Redefs, TRI);
+ InitPredRedefs(NextBBI->BB, Redefs, TRI);
+
bool HasEarlyExit = CvtBBI->FalseBB != NULL;
bool DupBB = CvtBBI->BB->pred_size() > 1;
if (DupBB) {
BBI.NonPredSize -= TII->RemoveBranch(*BBI.BB);
// Copy instructions in the true block, predicate them, and add them to
// the entry block.
- CopyAndPredicateBlock(BBI, *CvtBBI, Cond, true);
+ CopyAndPredicateBlock(BBI, *CvtBBI, Cond, Redefs, true);
} else {
// Predicate the 'true' block after removing its branch.
CvtBBI->NonPredSize -= TII->RemoveBranch(*CvtBBI->BB);
- PredicateBlock(*CvtBBI, CvtBBI->BB->end(), Cond);
+ PredicateBlock(*CvtBBI, CvtBBI->BB->end(), Cond, Redefs);
// Now merge the entry of the triangle with the true block.
BBI.NonPredSize -= TII->RemoveBranch(*BBI.BB);
@@ -1085,6 +1169,11 @@
// Remove the conditional branch from entry to the blocks.
BBI.NonPredSize -= TII->RemoveBranch(*BBI.BB);
+ // Initialize liveins to the first BB. These are potentiall re-defined by
+ // predicated instructions.
+ SmallSet<unsigned, 4> Redefs;
+ InitPredRedefs(BBI1->BB, Redefs, TRI);
+
// Remove the duplicated instructions at the beginnings of both paths.
MachineBasicBlock::iterator DI1 = BBI1->BB->begin();
MachineBasicBlock::iterator DI2 = BBI2->BB->begin();
@@ -1102,6 +1191,8 @@
++DI2;
--NumDups1;
}
+
+ UpdatePredRedefs(BBI1->BB->begin(), DI1, Redefs, TRI);
BBI.BB->splice(BBI.BB->end(), BBI1->BB, BBI1->BB->begin(), DI1);
BBI2->BB->erase(BBI2->BB->begin(), DI2);
@@ -1118,7 +1209,7 @@
++i;
}
BBI1->BB->erase(DI1, BBI1->BB->end());
- PredicateBlock(*BBI1, BBI1->BB->end(), *Cond1);
+ PredicateBlock(*BBI1, BBI1->BB->end(), *Cond1, Redefs);
// Predicate the 'false' block.
BBI2->NonPredSize -= TII->RemoveBranch(*BBI2->BB);
@@ -1132,7 +1223,7 @@
if (!DI2->isDebugValue())
--NumDups2;
}
- PredicateBlock(*BBI2, DI2, *Cond2);
+ PredicateBlock(*BBI2, DI2, *Cond2, Redefs);
// Merge the true block into the entry of the diamond.
MergeBlocks(BBI, *BBI1);
@@ -1168,7 +1259,8 @@
/// specified end with the specified condition.
void IfConverter::PredicateBlock(BBInfo &BBI,
MachineBasicBlock::iterator E,
- SmallVectorImpl<MachineOperand> &Cond) {
+ SmallVectorImpl<MachineOperand> &Cond,
+ SmallSet<unsigned, 4> &Redefs) {
for (MachineBasicBlock::iterator I = BBI.BB->begin(); I != E; ++I) {
if (I->isDebugValue() || TII->isPredicated(I))
continue;
@@ -1178,6 +1270,10 @@
#endif
llvm_unreachable(0);
}
+
+ // If the predicated instruction now re-defines a register as the result of
+ // if-conversion, add an implicit kill.
+ UpdatePredRedefs(I, Redefs, TRI, true);
}
std::copy(Cond.begin(), Cond.end(), std::back_inserter(BBI.Predicate));
@@ -1192,6 +1288,7 @@
/// the destination block. Skip end of block branches if IgnoreBr is true.
void IfConverter::CopyAndPredicateBlock(BBInfo &ToBBI, BBInfo &FromBBI,
SmallVectorImpl<MachineOperand> &Cond,
+ SmallSet<unsigned, 4> &Redefs,
bool IgnoreBr) {
MachineFunction &MF = *ToBBI.BB->getParent();
@@ -1207,13 +1304,18 @@
ToBBI.BB->insert(ToBBI.BB->end(), MI);
ToBBI.NonPredSize++;
- if (!isPredicated && !MI->isDebugValue())
+ if (!isPredicated && !MI->isDebugValue()) {
if (!TII->PredicateInstruction(MI, Cond)) {
#ifndef NDEBUG
dbgs() << "Unable to predicate " << *I << "!\n";
#endif
llvm_unreachable(0);
}
+ }
+
+ // If the predicated instruction now re-defines a register as the result of
+ // if-conversion, add an implicit kill.
+ UpdatePredRedefs(MI, Redefs, TRI, true);
}
std::vector<MachineBasicBlock *> Succs(FromBBI.BB->succ_begin(),