Enable the new LoopInfo algorithm by default.
The primary advantage is that loop optimizations will be applied in a
stable order. This helps debugging and unit test creation. It is also
a better overall implementation without pathologically bad performance
on deep functions.
On large functions (llvm-stress --size=200000 | opt -loops)
Before: 0.1263s
After: 0.0225s
On deep functions (after tweaking llvm-stress, thanks Nadav):
Before: 0.2281s
After: 0.0227s
See r158790 for more comments.
The loop tree is now consistently generated in forward order, but loop
passes are applied in reverse order over the program. If we have a
loop optimization that prefers forward order, that can easily be
achieved by adding a different type of LoopPassManager.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@159183 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/MachineLoopInfo.cpp b/lib/CodeGen/MachineLoopInfo.cpp
index b7298e4..9f3829e 100644
--- a/lib/CodeGen/MachineLoopInfo.cpp
+++ b/lib/CodeGen/MachineLoopInfo.cpp
@@ -18,7 +18,6 @@
#include "llvm/CodeGen/MachineDominators.h"
#include "llvm/CodeGen/Passes.h"
#include "llvm/Analysis/LoopInfoImpl.h"
-#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
using namespace llvm;
@@ -26,10 +25,6 @@
template class llvm::LoopBase<MachineBasicBlock, MachineLoop>;
template class llvm::LoopInfoBase<MachineBasicBlock, MachineLoop>;
-static cl::opt<bool>
-StableLoopInfo("stable-machine-loops", cl::Hidden, cl::init(false),
- cl::desc("Compute a stable loop tree."));
-
char MachineLoopInfo::ID = 0;
INITIALIZE_PASS_BEGIN(MachineLoopInfo, "machine-loops",
"Machine Natural Loop Construction", true, true)
@@ -41,10 +36,7 @@
bool MachineLoopInfo::runOnMachineFunction(MachineFunction &) {
releaseMemory();
- if (StableLoopInfo)
- LI.Analyze(getAnalysis<MachineDominatorTree>().getBase());
- else
- LI.Calculate(getAnalysis<MachineDominatorTree>().getBase()); // Update
+ LI.Analyze(getAnalysis<MachineDominatorTree>().getBase());
return false;
}