MachineSink: Sort the successors before trying to find SuccToSinkTo.
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
diff --git a/lib/CodeGen/MachineSink.cpp b/lib/CodeGen/MachineSink.cpp
index 1ce546b..d02aa6f 100644
--- a/lib/CodeGen/MachineSink.cpp
+++ b/lib/CodeGen/MachineSink.cpp
@@ -99,6 +99,16 @@
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 @@
// 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,