//
//===----------------------------------------------------------------------===//
//
-// This file implements the pass that optimize code placement and align loop
-// headers to target specific alignment boundary.
+// This file implements the pass that optimizes code placement and aligns loop
+// headers to target-specific alignment boundaries.
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "code-placement"
-#include "llvm/CodeGen/MachineLoopInfo.h"
-#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/Passes.h"
+#include "llvm/ADT/Statistic.h"
+#include "llvm/CodeGen/MachineFunctionPass.h"
+#include "llvm/CodeGen/MachineLoopInfo.h"
+#include "llvm/Support/Compiler.h"
+#include "llvm/Support/Debug.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetLowering.h"
#include "llvm/Target/TargetMachine.h"
-#include "llvm/Support/Compiler.h"
-#include "llvm/Support/Debug.h"
-#include "llvm/ADT/Statistic.h"
using namespace llvm;
STATISTIC(NumLoopsAligned, "Number of loops aligned");
public:
static char ID;
- CodePlacementOpt() : MachineFunctionPass(&ID) {}
+ CodePlacementOpt() : MachineFunctionPass(ID) {}
virtual bool runOnMachineFunction(MachineFunction &MF);
- virtual const char *getPassName() const {
- return "Code Placement Optimizater";
- }
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
AU.addRequired<MachineLoopInfo>();
MachineFunction::iterator InsertPt,
MachineFunction::iterator Begin,
MachineFunction::iterator End);
- void UpdateTerminator(MachineBasicBlock *MBB);
bool EliminateUnconditionalJumpsToTop(MachineFunction &MF,
MachineLoop *L);
bool MoveDiscontiguousLoopBlocks(MachineFunction &MF,
char CodePlacementOpt::ID = 0;
} // end anonymous namespace
-FunctionPass *llvm::createCodePlacementOptPass() {
- return new CodePlacementOpt();
-}
+char &llvm::CodePlacementOptID = CodePlacementOpt::ID;
+INITIALIZE_PASS(CodePlacementOpt, "code-placement",
+ "Code Placement Optimizer", false, false)
/// HasFallthrough - Test whether the given branch has a fallthrough, either as
/// a plain fallthrough or as a fallthrough case of a conditional branch.
// Conservatively ignore EH landing pads.
if (MBB->isLandingPad()) return false;
- // Ignore blocks which look like they might have EH-related control flow.
- // At the time of this writing, there are blocks which AnalyzeBranch
- // thinks end in single uncoditional branches, yet which have two CFG
- // successors. Code in this file is not prepared to reason about such things.
- if (!MBB->empty() && MBB->back().getOpcode() == TargetInstrInfo::EH_LABEL)
- return false;
-
// Aggressively handle return blocks and similar constructs.
if (MBB->succ_empty()) return true;
// Ask the target's AnalyzeBranch if it can handle this block.
MachineBasicBlock *TBB = 0, *FBB = 0;
SmallVector<MachineOperand, 4> Cond;
- // Make the the terminator is understood.
+ // Make sure the terminator is understood.
if (TII->AnalyzeBranch(*MBB, TBB, FBB, Cond))
return false;
+ // Ignore blocks which look like they might have EH-related control flow.
+ // AnalyzeBranch thinks it knows how to analyze such things, but it doesn't
+ // recognize the possibility of a control transfer through an unwind.
+ // Such blocks contain EH_LABEL instructions, however they may be in the
+ // middle of the block. Instead of searching for them, just check to see
+ // if the CFG disagrees with AnalyzeBranch.
+ if (1u + !Cond.empty() != MBB->succ_size())
+ return false;
// Make sure we have the option of reversing the condition.
if (!Cond.empty() && TII->ReverseBranchCondition(Cond))
return false;
MF.splice(InsertPt, Begin, End);
- UpdateTerminator(prior(Begin));
- UpdateTerminator(OldBeginPrior);
- UpdateTerminator(OldEndPrior);
-}
-
-/// UpdateTerminator - Update the terminator instructions in MBB to account
-/// for changes to the layout. If the block previously used a fallthrough,
-/// it may now need a branch, and if it previously used branching it may now
-/// be able to use a fallthrough.
-///
-void CodePlacementOpt::UpdateTerminator(MachineBasicBlock *MBB) {
- // A block with no successors has no concerns with fall-through edges.
- if (MBB->succ_empty()) return;
-
- MachineBasicBlock *TBB = 0, *FBB = 0;
- SmallVector<MachineOperand, 4> Cond;
- bool B = TII->AnalyzeBranch(*MBB, TBB, FBB, Cond);
- (void) B;
- assert(!B && "UpdateTerminators requires analyzable predecessors!");
- if (Cond.empty()) {
- if (TBB) {
- // The block has an unconditional branch. If its successor is now
- // its layout successor, delete the branch.
- if (MBB->isLayoutSuccessor(TBB))
- TII->RemoveBranch(*MBB);
- } else {
- // The block has an unconditional fallthrough. If its successor is not
- // its layout successor, insert a branch.
- TBB = *MBB->succ_begin();
- if (!MBB->isLayoutSuccessor(TBB))
- TII->InsertBranch(*MBB, TBB, 0, Cond);
- }
- } else {
- if (FBB) {
- // The block has a non-fallthrough conditional branch. If one of its
- // successors is its layout successor, rewrite it to a fallthrough
- // conditional branch.
- if (MBB->isLayoutSuccessor(TBB)) {
- TII->RemoveBranch(*MBB);
- TII->ReverseBranchCondition(Cond);
- TII->InsertBranch(*MBB, FBB, 0, Cond);
- } else if (MBB->isLayoutSuccessor(FBB)) {
- TII->RemoveBranch(*MBB);
- TII->InsertBranch(*MBB, TBB, 0, Cond);
- }
- } else {
- // The block has a fallthrough conditional branch.
- MachineBasicBlock *MBBA = *MBB->succ_begin();
- MachineBasicBlock *MBBB = *next(MBB->succ_begin());
- if (MBBA == TBB) std::swap(MBBB, MBBA);
- if (MBB->isLayoutSuccessor(TBB)) {
- TII->RemoveBranch(*MBB);
- TII->ReverseBranchCondition(Cond);
- TII->InsertBranch(*MBB, MBBA, 0, Cond);
- } else if (!MBB->isLayoutSuccessor(MBBA)) {
- TII->RemoveBranch(*MBB);
- TII->InsertBranch(*MBB, TBB, MBBA, Cond);
- }
- }
- }
+ prior(Begin)->updateTerminator();
+ OldBeginPrior->updateTerminator();
+ OldEndPrior->updateTerminator();
}
/// EliminateUnconditionalJumpsToTop - Move blocks which unconditionally jump
continue;
// Move the block.
+ DEBUG(dbgs() << "CGP: Moving blocks starting at BB#" << Pred->getNumber()
+ << " to top of loop.\n");
Changed = true;
// Move it and all the blocks that can reach it via fallthrough edges
// exclusively, to keep existing fallthrough edges intact.
MachineFunction::iterator Begin = Pred;
- MachineFunction::iterator End = next(Begin);
+ MachineFunction::iterator End = llvm::next(Begin);
while (Begin != MF.begin()) {
MachineFunction::iterator Prior = prior(Begin);
if (Prior == MF.begin())
// fallthrough edge.
if (!Prior->isSuccessor(End))
goto next_pred;
- // Otherwise we can stop scanning and procede to move the blocks.
+ // Otherwise we can stop scanning and proceed to move the blocks.
break;
}
// If we hit a switch or something complicated, don't move anything
!BotHasFallthrough &&
HasFallthrough(L->getBottomBlock())) {
++NumIntraElim;
- BotHasFallthrough = true;
}
return Changed;
// Determine a position to move orphaned loop blocks to. If TopMBB is not
// entered via fallthrough and BotMBB is exited via fallthrough, prepend them
- // to the top of the loop to avoid loosing that fallthrough. Otherwise append
+ // to the top of the loop to avoid losing that fallthrough. Otherwise append
// them to the bottom, even if it previously had a fallthrough, on the theory
// that it's worth an extra branch to keep the loop contiguous.
- MachineFunction::iterator InsertPt = next(MachineFunction::iterator(BotMBB));
+ MachineFunction::iterator InsertPt =
+ llvm::next(MachineFunction::iterator(BotMBB));
bool InsertAtTop = false;
if (TopMBB != MF.begin() &&
!HasFallthrough(prior(MachineFunction::iterator(TopMBB))) &&
// with the loop header.
SmallPtrSet<MachineBasicBlock *, 8> ContiguousBlocks;
for (MachineFunction::iterator I = TopMBB,
- E = next(MachineFunction::iterator(BotMBB)); I != E; ++I)
+ E = llvm::next(MachineFunction::iterator(BotMBB)); I != E; ++I)
ContiguousBlocks.insert(I);
// Find non-contigous blocks and fix them.
continue;
// Move the block.
+ DEBUG(dbgs() << "CGP: Moving blocks starting at BB#" << BB->getNumber()
+ << " to be contiguous with loop.\n");
Changed = true;
// Process this block and all loop blocks contiguous with it, to keep
// them in their relative order.
MachineFunction::iterator Begin = BB;
- MachineFunction::iterator End = next(MachineFunction::iterator(BB));
+ MachineFunction::iterator End = llvm::next(MachineFunction::iterator(BB));
for (; End != MF.end(); ++End) {
if (!L->contains(End)) break;
if (!HasAnalyzableTerminator(End)) break;
///
bool CodePlacementOpt::AlignLoops(MachineFunction &MF) {
const Function *F = MF.getFunction();
- if (F->hasFnAttr(Attribute::OptimizeForSize))
+ if (F->getFnAttributes().hasAttribute(Attributes::OptimizeForSize))
return false;
unsigned Align = TLI->getPrefLoopAlignment();
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