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MachineSink: Sort the successors before trying to find SuccToSinkTo.

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One motivating example is to sink an instruction from a basic block which has
two successors: one outside the loop, the other inside the loop. We should try
to sink the instruction outside the loop.

rdar://11980766


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@161062 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Manman Ren
2012-07-31 18:10:39 +00:00
parent 8c574be2fe
commit 53b59d1d97
2 changed files with 69 additions and 2 deletions
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lib/CodeGen/MachineSink.cpp
+15 -2
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@@ -99,6 +99,16 @@ namespace {
bool PerformTrivialForwardCoalescing(MachineInstr *MI,
MachineBasicBlock *MBB);
};
// SuccessorSorter - Sort Successors according to their loop depth.
struct SuccessorSorter {
SuccessorSorter(MachineLoopInfo *LoopInfo) : LI(LoopInfo) {}
bool operator()(const MachineBasicBlock *LHS,
const MachineBasicBlock *RHS) const {
return LI->getLoopDepth(LHS) < LI->getLoopDepth(RHS);
}
MachineLoopInfo *LI;
};
} // end anonymous namespace
char MachineSinking::ID = 0;
@@ -526,8 +536,11 @@ MachineBasicBlock *MachineSinking::FindSuccToSinkTo(MachineInstr *MI,
// Otherwise, we should look at all the successors and decide which one
// we should sink to.
for (MachineBasicBlock::succ_iterator SI = MBB->succ_begin(),
E = MBB->succ_end(); SI != E; ++SI) {
// We give successors with smaller loop depth higher priority.
SmallVector<MachineBasicBlock*, 4> Succs(MBB->succ_begin(), MBB->succ_end());
std::sort(Succs.begin(), Succs.end(), SuccessorSorter(LI));
for (SmallVector<MachineBasicBlock*, 4>::iterator SI = Succs.begin(),
E = Succs.end(); SI != E; ++SI) {
MachineBasicBlock *SuccBlock = *SI;
bool LocalUse = false;
if (AllUsesDominatedByBlock(Reg, SuccBlock, MBB,