//
//===----------------------------------------------------------------------===//
//
-// 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.
//
//===----------------------------------------------------------------------===//
public:
static char ID;
- CodePlacementOpt() : MachineFunctionPass(&ID) {}
+ CodePlacementOpt() : MachineFunctionPass(ID) {}
virtual bool runOnMachineFunction(MachineFunction &MF);
virtual const char *getPassName() const {
- return "Code Placement Optimizater";
+ return "Code Placement Optimizer";
}
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
// 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().isEHLabel())
- 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;
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
// 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 =
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