[XRay] Lazily compute MachineLoopInfo instead of requiring it.
Summary:
Currently X-Ray Instrumentation pass has a dependency on MachineLoopInfo
(and thus on MachineDominatorTree as well) and we have to compute them
even if X-Ray is not used. This patch changes it to a lazy computation
to save compile time by avoiding these redundant computations.
Reviewers: dberris, kubamracek
Subscribers: llvm-commits, hiraditya
Differential Revision: https://reviews.llvm.org/D44666
llvm-svn: 327999
diff --git a/llvm/lib/CodeGen/XRayInstrumentation.cpp b/llvm/lib/CodeGen/XRayInstrumentation.cpp
index 3d83afc..32a7457 100644
--- a/llvm/lib/CodeGen/XRayInstrumentation.cpp
+++ b/llvm/lib/CodeGen/XRayInstrumentation.cpp
@@ -52,7 +52,6 @@
void getAnalysisUsage(AnalysisUsage &AU) const override {
AU.setPreservesCFG();
- AU.addRequired<MachineLoopInfo>();
AU.addPreserved<MachineLoopInfo>();
AU.addPreserved<MachineDominatorTree>();
MachineFunctionPass::getAnalysisUsage(AU);
@@ -160,11 +159,26 @@
for (const auto &MBB : MF)
MICount += MBB.size();
+ // Get MachineDominatorTree or compute it on the fly if it's unavailable
+ auto *MDT = getAnalysisIfAvailable<MachineDominatorTree>();
+ MachineDominatorTree ComputedMDT;
+ if (!MDT) {
+ ComputedMDT.getBase().recalculate(MF);
+ MDT = &ComputedMDT;
+ }
+
+ // Get MachineLoopInfo or compute it on the fly if it's unavailable
+ auto *MLI = getAnalysisIfAvailable<MachineLoopInfo>();
+ MachineLoopInfo ComputedMLI;
+ if (!MLI) {
+ ComputedMLI.getBase().analyze(MDT->getBase());
+ MLI = &ComputedMLI;
+ }
+
// Check if we have a loop.
// FIXME: Maybe make this smarter, and see whether the loops are dependent
// on inputs or side-effects?
- MachineLoopInfo &MLI = getAnalysis<MachineLoopInfo>();
- if (MLI.empty() && MICount < XRayThreshold)
+ if (MLI->empty() && MICount < XRayThreshold)
return false; // Function is too small and has no loops.
}