#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/BasicBlock.h"
#include "llvm/CodeGen/MachineFunction.h"
+#include "llvm/MC/MCAsmInfo.h"
+#include "llvm/MC/MCContext.h"
#include "llvm/Target/TargetRegisterInfo.h"
#include "llvm/Target/TargetData.h"
#include "llvm/Target/TargetInstrDesc.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetMachine.h"
+#include "llvm/Assembly/Writer.h"
+#include "llvm/ADT/SmallString.h"
+#include "llvm/ADT/SmallPtrSet.h"
+#include "llvm/Support/Debug.h"
#include "llvm/Support/LeakDetector.h"
#include "llvm/Support/raw_ostream.h"
-#include "llvm/Assembly/Writer.h"
#include <algorithm>
using namespace llvm;
LeakDetector::removeGarbageObject(this);
}
+/// getSymbol - Return the MCSymbol for this basic block.
+///
+MCSymbol *MachineBasicBlock::getSymbol() const {
+ const MachineFunction *MF = getParent();
+ MCContext &Ctx = MF->getContext();
+ const char *Prefix = Ctx.getAsmInfo().getPrivateGlobalPrefix();
+ return Ctx.GetOrCreateSymbol(Twine(Prefix) + "BB" +
+ Twine(MF->getFunctionNumber()) + "_" +
+ Twine(getNumber()));
+}
+
+
raw_ostream &llvm::operator<<(raw_ostream &OS, const MachineBasicBlock &MBB) {
MBB.print(OS);
return OS;
return I;
}
-/// isOnlyReachableViaFallthough - Return true if this basic block has
-/// exactly one predecessor and the control transfer mechanism between
-/// the predecessor and this block is a fall-through.
-bool MachineBasicBlock::isOnlyReachableByFallthrough() const {
- // If this is a landing pad, it isn't a fall through. If it has no preds,
- // then nothing falls through to it.
- if (isLandingPad() || pred_empty())
- return false;
-
- // If there isn't exactly one predecessor, it can't be a fall through.
- const_pred_iterator PI = pred_begin(), PI2 = PI;
- ++PI2;
- if (PI2 != pred_end())
- return false;
-
- // The predecessor has to be immediately before this block.
- const MachineBasicBlock *Pred = *PI;
-
- if (!Pred->isLayoutSuccessor(this))
- return false;
-
- // If the block is completely empty, then it definitely does fall through.
- if (Pred->empty())
- return true;
-
- // Otherwise, check the last instruction.
- const MachineInstr &LastInst = Pred->back();
- return !LastInst.getDesc().isBarrier();
-}
-
void MachineBasicBlock::dump() const {
- print(errs());
+ print(dbgs());
}
static inline void OutputReg(raw_ostream &os, unsigned RegNo,
os << " %reg" << RegNo;
}
+StringRef MachineBasicBlock::getName() const {
+ if (const BasicBlock *LBB = getBasicBlock())
+ return LBB->getName();
+ else
+ return "(null)";
+}
+
void MachineBasicBlock::print(raw_ostream &OS) const {
const MachineFunction *MF = getParent();
if (!MF) {
const TargetRegisterInfo *TRI = MF->getTarget().getRegisterInfo();
if (!livein_empty()) {
OS << " Live Ins:";
- for (const_livein_iterator I = livein_begin(),E = livein_end(); I != E; ++I)
+ for (livein_iterator I = livein_begin(),E = livein_end(); I != E; ++I)
OutputReg(OS, *I, TRI);
OS << '\n';
}
}
void MachineBasicBlock::removeLiveIn(unsigned Reg) {
- livein_iterator I = std::find(livein_begin(), livein_end(), Reg);
- assert(I != livein_end() && "Not a live in!");
+ std::vector<unsigned>::iterator I =
+ std::find(LiveIns.begin(), LiveIns.end(), Reg);
+ assert(I != LiveIns.end() && "Not a live in!");
LiveIns.erase(I);
}
bool MachineBasicBlock::isLiveIn(unsigned Reg) const {
- const_livein_iterator I = std::find(livein_begin(), livein_end(), Reg);
+ livein_iterator I = std::find(livein_begin(), livein_end(), Reg);
return I != livein_end();
}
// successors is its layout successor, rewrite it to a fallthrough
// conditional branch.
if (isLayoutSuccessor(TBB)) {
+ if (TII->ReverseBranchCondition(Cond))
+ return;
TII->RemoveBranch(*this);
- TII->ReverseBranchCondition(Cond);
TII->InsertBranch(*this, FBB, 0, Cond);
} else if (isLayoutSuccessor(FBB)) {
TII->RemoveBranch(*this);
} else {
// The block has a fallthrough conditional branch.
MachineBasicBlock *MBBA = *succ_begin();
- MachineBasicBlock *MBBB = *next(succ_begin());
+ MachineBasicBlock *MBBB = *llvm::next(succ_begin());
if (MBBA == TBB) std::swap(MBBB, MBBA);
if (isLayoutSuccessor(TBB)) {
+ if (TII->ReverseBranchCondition(Cond)) {
+ // We can't reverse the condition, add an unconditional branch.
+ Cond.clear();
+ TII->InsertBranch(*this, MBBA, 0, Cond);
+ return;
+ }
TII->RemoveBranch(*this);
- TII->ReverseBranchCondition(Cond);
TII->InsertBranch(*this, MBBA, 0, Cond);
} else if (!isLayoutSuccessor(MBBA)) {
TII->RemoveBranch(*this);
bool MachineBasicBlock::isLayoutSuccessor(const MachineBasicBlock *MBB) const {
MachineFunction::const_iterator I(this);
- return next(I) == MachineFunction::const_iterator(MBB);
+ return llvm::next(I) == MachineFunction::const_iterator(MBB);
+}
+
+bool MachineBasicBlock::canFallThrough() {
+ MachineFunction::iterator Fallthrough = this;
+ ++Fallthrough;
+ // If FallthroughBlock is off the end of the function, it can't fall through.
+ if (Fallthrough == getParent()->end())
+ return false;
+
+ // If FallthroughBlock isn't a successor, no fallthrough is possible.
+ if (!isSuccessor(Fallthrough))
+ return false;
+
+ // Analyze the branches, if any, at the end of the block.
+ MachineBasicBlock *TBB = 0, *FBB = 0;
+ SmallVector<MachineOperand, 4> Cond;
+ const TargetInstrInfo *TII = getParent()->getTarget().getInstrInfo();
+ if (TII->AnalyzeBranch(*this, TBB, FBB, Cond)) {
+ // If we couldn't analyze the branch, examine the last instruction.
+ // If the block doesn't end in a known control barrier, assume fallthrough
+ // is possible. The isPredicable check is needed because this code can be
+ // called during IfConversion, where an instruction which is normally a
+ // Barrier is predicated and thus no longer an actual control barrier. This
+ // is over-conservative though, because if an instruction isn't actually
+ // predicated we could still treat it like a barrier.
+ return empty() || !back().getDesc().isBarrier() ||
+ back().getDesc().isPredicable();
+ }
+
+ // If there is no branch, control always falls through.
+ if (TBB == 0) return true;
+
+ // If there is some explicit branch to the fallthrough block, it can obviously
+ // reach, even though the branch should get folded to fall through implicitly.
+ if (MachineFunction::iterator(TBB) == Fallthrough ||
+ MachineFunction::iterator(FBB) == Fallthrough)
+ return true;
+
+ // If it's an unconditional branch to some block not the fall through, it
+ // doesn't fall through.
+ if (Cond.empty()) return false;
+
+ // Otherwise, if it is conditional and has no explicit false block, it falls
+ // through.
+ return FBB == 0;
}
/// removeFromParent - This method unlinks 'this' from the containing function,
/// CorrectExtraCFGEdges - Various pieces of code can cause excess edges in the
/// CFG to be inserted. If we have proven that MBB can only branch to DestA and
-/// DestB, remove any other MBB successors from the CFG. DestA and DestB can
-/// be null.
+/// DestB, remove any other MBB successors from the CFG. DestA and DestB can be
+/// null.
+///
/// Besides DestA and DestB, retain other edges leading to LandingPads
/// (currently there can be only one; we don't check or require that here).
/// Note it is possible that DestA and/or DestB are LandingPads.
bool MachineBasicBlock::CorrectExtraCFGEdges(MachineBasicBlock *DestA,
MachineBasicBlock *DestB,
bool isCond) {
- bool MadeChange = false;
- bool AddedFallThrough = false;
-
- MachineFunction::iterator FallThru = next(MachineFunction::iterator(this));
-
- // If this block ends with a conditional branch that falls through to its
- // successor, set DestB as the successor.
- if (isCond) {
- if (DestB == 0 && FallThru != getParent()->end()) {
+ // The values of DestA and DestB frequently come from a call to the
+ // 'TargetInstrInfo::AnalyzeBranch' method. We take our meaning of the initial
+ // values from there.
+ //
+ // 1. If both DestA and DestB are null, then the block ends with no branches
+ // (it falls through to its successor).
+ // 2. If DestA is set, DestB is null, and isCond is false, then the block ends
+ // with only an unconditional branch.
+ // 3. If DestA is set, DestB is null, and isCond is true, then the block ends
+ // with a conditional branch that falls through to a successor (DestB).
+ // 4. If DestA and DestB is set and isCond is true, then the block ends with a
+ // conditional branch followed by an unconditional branch. DestA is the
+ // 'true' destination and DestB is the 'false' destination.
+
+ bool Changed = false;
+
+ MachineFunction::iterator FallThru =
+ llvm::next(MachineFunction::iterator(this));
+
+ if (DestA == 0 && DestB == 0) {
+ // Block falls through to successor.
+ DestA = FallThru;
+ DestB = FallThru;
+ } else if (DestA != 0 && DestB == 0) {
+ if (isCond)
+ // Block ends in conditional jump that falls through to successor.
DestB = FallThru;
- AddedFallThrough = true;
- }
} else {
- // If this is an unconditional branch with no explicit dest, it must just be
- // a fallthrough into DestB.
- if (DestA == 0 && FallThru != getParent()->end()) {
- DestA = FallThru;
- AddedFallThrough = true;
- }
+ assert(DestA && DestB && isCond &&
+ "CFG in a bad state. Cannot correct CFG edges");
}
-
+
+ // Remove superfluous edges. I.e., those which aren't destinations of this
+ // basic block, duplicate edges, or landing pads.
+ SmallPtrSet<const MachineBasicBlock*, 8> SeenMBBs;
MachineBasicBlock::succ_iterator SI = succ_begin();
- MachineBasicBlock *OrigDestA = DestA, *OrigDestB = DestB;
while (SI != succ_end()) {
- if (*SI == DestA) {
- DestA = 0;
- ++SI;
- } else if (*SI == DestB) {
- DestB = 0;
- ++SI;
- } else if ((*SI)->isLandingPad() &&
- *SI!=OrigDestA && *SI!=OrigDestB) {
- ++SI;
- } else {
- // Otherwise, this is a superfluous edge, remove it.
+ const MachineBasicBlock *MBB = *SI;
+ if (!SeenMBBs.insert(MBB) ||
+ (MBB != DestA && MBB != DestB && !MBB->isLandingPad())) {
+ // This is a superfluous edge, remove it.
SI = removeSuccessor(SI);
- MadeChange = true;
+ Changed = true;
+ } else {
+ ++SI;
}
}
- if (!AddedFallThrough) {
- assert(DestA == 0 && DestB == 0 &&
- "MachineCFG is missing edges!");
- } else if (isCond) {
- assert(DestA == 0 && "MachineCFG is missing edges!");
+
+ return Changed;
+}
+
+/// findDebugLoc - find the next valid DebugLoc starting at MBBI, skipping
+/// any DBG_VALUE instructions. Return UnknownLoc if there is none.
+DebugLoc
+MachineBasicBlock::findDebugLoc(MachineBasicBlock::iterator &MBBI) {
+ DebugLoc DL;
+ MachineBasicBlock::iterator E = end();
+ if (MBBI != E) {
+ // Skip debug declarations, we don't want a DebugLoc from them.
+ MachineBasicBlock::iterator MBBI2 = MBBI;
+ while (MBBI2 != E && MBBI2->isDebugValue())
+ MBBI2++;
+ if (MBBI2 != E)
+ DL = MBBI2->getDebugLoc();
}
- return MadeChange;
+ return DL;
}
+
+void llvm::WriteAsOperand(raw_ostream &OS, const MachineBasicBlock *MBB,
+ bool t) {
+ OS << "BB#" << MBB->getNumber();
+}
+
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