while (!MBB->succ_empty())
MBB->removeSuccessor(MBB->succ_end()-1);
- // If there are any labels in the basic block, unregister them from
- // MachineModuleInfo.
- if (MMI && !MBB->empty()) {
- for (MachineBasicBlock::iterator I = MBB->begin(), E = MBB->end();
- I != E; ++I) {
- if (I->isLabel())
- // The label ID # is always operand #0, an immediate.
- MMI->InvalidateLabel(I->getOperand(0).getImm());
- }
- }
-
// Remove the block.
MF->erase(MBB);
}
SmallSet<unsigned, 4> ImpDefRegs;
MachineBasicBlock::iterator I = MBB->begin();
while (I != MBB->end()) {
- if (I->getOpcode() != TargetInstrInfo::IMPLICIT_DEF)
+ if (!I->isImplicitDef())
break;
unsigned Reg = I->getOperand(0).getReg();
ImpDefRegs.insert(Reg);
MadeChange |= MadeChangeThisIteration;
}
- // See if any jump tables have become mergable or dead as the code generator
+ // See if any jump tables have become dead as the code generator
// did its thing.
MachineJumpTableInfo *JTI = MF.getJumpTableInfo();
if (JTI == 0) {
return MadeChange;
}
- const std::vector<MachineJumpTableEntry> &JTs = JTI->getJumpTables();
- // Figure out how these jump tables should be merged.
- std::vector<unsigned> JTMapping;
- JTMapping.reserve(JTs.size());
-
- // We always keep the 0th jump table.
- JTMapping.push_back(0);
-
- // Scan the jump tables, seeing if there are any duplicates. Note that this
- // is N^2, which should be fixed someday.
- for (unsigned i = 1, e = JTs.size(); i != e; ++i) {
- if (JTs[i].MBBs.empty())
- JTMapping.push_back(i);
- else
- JTMapping.push_back(JTI->getJumpTableIndex(JTs[i].MBBs));
- }
-
- // If a jump table was merge with another one, walk the function rewriting
- // references to jump tables to reference the new JT ID's. Keep track of
- // whether we see a jump table idx, if not, we can delete the JT.
- BitVector JTIsLive(JTs.size());
+ // Walk the function to find jump tables that are live.
+ BitVector JTIsLive(JTI->getJumpTables().size());
for (MachineFunction::iterator BB = MF.begin(), E = MF.end();
BB != E; ++BB) {
for (MachineBasicBlock::iterator I = BB->begin(), E = BB->end();
for (unsigned op = 0, e = I->getNumOperands(); op != e; ++op) {
MachineOperand &Op = I->getOperand(op);
if (!Op.isJTI()) continue;
- unsigned NewIdx = JTMapping[Op.getIndex()];
- Op.setIndex(NewIdx);
// Remember that this JT is live.
- JTIsLive.set(NewIdx);
+ JTIsLive.set(Op.getIndex());
}
}
- // Finally, remove dead jump tables. This happens either because the
- // indirect jump was unreachable (and thus deleted) or because the jump
- // table was merged with some other one.
+ // Finally, remove dead jump tables. This happens when the
+ // indirect jump was unreachable (and thus deleted).
for (unsigned i = 0, e = JTIsLive.size(); i != e; ++i)
if (!JTIsLive.test(i)) {
JTI->RemoveJumpTable(i);
return 0; // Empty MBB.
--I;
+ // Skip debug info so it will not affect codegen.
+ while (I->isDebugValue()) {
+ if (I==MBB->begin())
+ return 0; // MBB empty except for debug info.
+ --I;
+ }
unsigned Hash = HashMachineInstr(I);
if (I == MBB->begin() || minCommonTailLength == 1)
return Hash; // Single instr MBB.
--I;
+ while (I->isDebugValue()) {
+ if (I==MBB->begin())
+ return Hash; // MBB with single non-debug instr.
+ --I;
+ }
// Hash in the second-to-last instruction.
Hash ^= HashMachineInstr(I) << 2;
return Hash;
unsigned TailLen = 0;
while (I1 != MBB1->begin() && I2 != MBB2->begin()) {
--I1; --I2;
+ // Skip debugging pseudos; necessary to avoid changing the code.
+ while (I1->isDebugValue()) {
+ if (I1==MBB1->begin()) {
+ while (I2->isDebugValue()) {
+ if (I2==MBB2->begin())
+ // I1==DBG at begin; I2==DBG at begin
+ return TailLen;
+ --I2;
+ }
+ ++I2;
+ // I1==DBG at begin; I2==non-DBG, or first of DBGs not at begin
+ return TailLen;
+ }
+ --I1;
+ }
+ // I1==first (untested) non-DBG preceding known match
+ while (I2->isDebugValue()) {
+ if (I2==MBB2->begin()) {
+ ++I1;
+ // I1==non-DBG, or first of DBGs not at begin; I2==DBG at begin
+ return TailLen;
+ }
+ --I2;
+ }
+ // I1, I2==first (untested) non-DBGs preceding known match
if (!I1->isIdenticalTo(I2) ||
// FIXME: This check is dubious. It's used to get around a problem where
// people incorrectly expect inline asm directives to remain in the same
// relative order. This is untenable because normal compiler
// optimizations (like this one) may reorder and/or merge these
// directives.
- I1->getOpcode() == TargetInstrInfo::INLINEASM) {
+ I1->isInlineAsm()) {
++I1; ++I2;
break;
}
++TailLen;
}
+ // Back past possible debugging pseudos at beginning of block. This matters
+ // when one block differs from the other only by whether debugging pseudos
+ // are present at the beginning. (This way, the various checks later for
+ // I1==MBB1->begin() work as expected.)
+ if (I1 == MBB1->begin() && I2 != MBB2->begin()) {
+ --I2;
+ while (I2->isDebugValue()) {
+ if (I2 == MBB2->begin()) {
+ return TailLen;
+ }
+ --I2;
+ }
+ ++I2;
+ }
+ if (I2 == MBB2->begin() && I1 != MBB1->begin()) {
+ --I1;
+ while (I1->isDebugValue()) {
+ if (I1 == MBB1->begin())
+ return TailLen;
+ --I1;
+ }
+ ++I1;
+ }
return TailLen;
}
MachineBasicBlock::iterator E) {
unsigned Time = 0;
for (; I != E; ++I) {
+ if (I->isDebugValue())
+ continue;
const TargetInstrDesc &TID = I->getDesc();
if (TID.isCall())
Time += 10;
SameTails[commonTailIndex].getTailStartPos();
MachineBasicBlock *MBB = SameTails[commonTailIndex].getBlock();
+ // If the common tail includes any debug info we will take it pretty
+ // randomly from one of the inputs. Might be better to remove it?
DEBUG(dbgs() << "\nSplitting BB#" << MBB->getNumber() << ", size "
<< maxCommonTailLength);
return MadeChange;
}
+// Blocks should be considered empty if they contain only debug info;
+// else the debug info would affect codegen.
+static bool IsEmptyBlock(MachineBasicBlock *MBB) {
+ if (MBB->empty())
+ return true;
+ for (MachineBasicBlock::iterator MBBI = MBB->begin(), MBBE = MBB->end();
+ MBBI!=MBBE; ++MBBI) {
+ if (!MBBI->isDebugValue())
+ return false;
+ }
+ return true;
+}
+
+// Blocks with only debug info and branches should be considered the same
+// as blocks with only branches.
+static bool IsBranchOnlyBlock(MachineBasicBlock *MBB) {
+ MachineBasicBlock::iterator MBBI, MBBE;
+ for (MBBI = MBB->begin(), MBBE = MBB->end(); MBBI!=MBBE; ++MBBI) {
+ if (!MBBI->isDebugValue())
+ break;
+ }
+ return (MBBI->getDesc().isBranch());
+}
/// IsBetterFallthrough - Return true if it would be clearly better to
/// fall-through to MBB1 than to fall through into MBB2. This has to return
// MBB1 doesn't, we prefer to fall through into MBB1. This allows us to
// optimize branches that branch to either a return block or an assert block
// into a fallthrough to the return.
- if (MBB1->empty() || MBB2->empty()) return false;
+ if (IsEmptyBlock(MBB1) || IsEmptyBlock(MBB2)) return false;
// If there is a clear successor ordering we make sure that one block
// will fall through to the next
if (MBB1->isSuccessor(MBB2)) return true;
if (MBB2->isSuccessor(MBB1)) return false;
- MachineInstr *MBB1I = --MBB1->end();
- MachineInstr *MBB2I = --MBB2->end();
+ // Neither block consists entirely of debug info (per IsEmptyBlock check),
+ // so we needn't test for falling off the beginning here.
+ MachineBasicBlock::iterator MBB1I = --MBB1->end();
+ while (MBB1I->isDebugValue())
+ --MBB1I;
+ MachineBasicBlock::iterator MBB2I = --MBB2->end();
+ while (MBB2I->isDebugValue())
+ --MBB2I;
return MBB2I->getDesc().isCall() && !MBB1I->getDesc().isCall();
}
// explicitly. Landing pads should not do this since the landing-pad table
// points to this block. Blocks with their addresses taken shouldn't be
// optimized away.
- if (MBB->empty() && !MBB->isLandingPad() && !MBB->hasAddressTaken()) {
+ if (IsEmptyBlock(MBB) && !MBB->isLandingPad() && !MBB->hasAddressTaken()) {
// Dead block? Leave for cleanup later.
if (MBB->pred_empty()) return MadeChange;
!IsBetterFallthrough(PriorTBB, MBB))
DoTransform = false;
- // We don't want to do this transformation if we have control flow like:
- // br cond BB2
- // BB1:
- // ..
- // jmp BBX
- // BB2:
- // ..
- // ret
- //
- // In this case, we could actually be moving the return block *into* a
- // loop!
- if (DoTransform && !MBB->succ_empty() &&
- (!PriorTBB->canFallThrough() || PriorTBB->empty()))
- DoTransform = false;
-
-
if (DoTransform) {
// Reverse the branch so we will fall through on the previous true cond.
SmallVector<MachineOperand, 4> NewPriorCond(PriorCond);
// If this branch is the only thing in its block, see if we can forward
// other blocks across it.
if (CurTBB && CurCond.empty() && CurFBB == 0 &&
- MBB->begin()->getDesc().isBranch() && CurTBB != MBB &&
+ IsBranchOnlyBlock(MBB) && CurTBB != MBB &&
!MBB->hasAddressTaken()) {
// This block may contain just an unconditional branch. Because there can
// be 'non-branch terminators' in the block, try removing the branch and
// then seeing if the block is empty.
TII->RemoveBranch(*MBB);
-
+ // If the only things remaining in the block are debug info, remove these
+ // as well, so this will behave the same as an empty block in non-debug
+ // mode.
+ if (!MBB->empty()) {
+ bool NonDebugInfoFound = false;
+ for (MachineBasicBlock::iterator I = MBB->begin(), E = MBB->end();
+ I != E; ++I) {
+ if (!I->isDebugValue()) {
+ NonDebugInfoFound = true;
+ break;
+ }
+ }
+ if (!NonDebugInfoFound)
+ // Make the block empty, losing the debug info (we could probably
+ // improve this in some cases.)
+ MBB->erase(MBB->begin(), MBB->end());
+ }
// If this block is just an unconditional branch to CurTBB, we can
// usually completely eliminate the block. The only case we cannot
// completely eliminate the block is when the block before this one
projects / oota-llvm.git / blobdiff