[PATCH] D20984: add control flags to LICM

[Sebastian Pop via llvm-commits]

sebpop created this revision.
sebpop added reviewers: dberlin, majnemer.
sebpop added a subscriber: llvm-commits.
sebpop set the repository for this revision to rL LLVM.

This patch adds -licm-max-hoist and -licm-max-sink to debug the LICM pass.

Repository:
  rL LLVM

http://reviews.llvm.org/D20984

Files:
  llvm/lib/Transforms/Scalar/LICM.cpp

Index: llvm/lib/Transforms/Scalar/LICM.cpp
===================================================================
--- llvm/lib/Transforms/Scalar/LICM.cpp
+++ llvm/lib/Transforms/Scalar/LICM.cpp
@@ -77,6 +77,16 @@
 static cl::opt<bool>
     DisablePromotion("disable-licm-promotion", cl::Hidden,
                      cl::desc("Disable memory promotion in LICM pass"));
+static cl::opt<int>
+    LICMMaxHoist("licm-max-hoist", cl::Hidden, cl::init(-1),
+                 cl::desc("Max number of instructions to hoist "
+                          "(default unlimited = -1)"));
+static cl::opt<int>
+    LICMMaxSink("licm-max-sink", cl::Hidden, cl::init(-1),
+                cl::desc("Max number of instructions to sink "
+                         "(default unlimited = -1)"));
+static int HoistCtr = 0;
+static int SinkCtr = 0;
 
 static bool inSubLoop(BasicBlock *BB, Loop *CurLoop, LoopInfo *LI);
 static bool isNotUsedInLoop(const Instruction &I, const Loop *CurLoop,
@@ -628,14 +638,18 @@
 static bool sink(Instruction &I, const LoopInfo *LI, const DominatorTree *DT,
                  const Loop *CurLoop, AliasSetTracker *CurAST,
                  const LICMSafetyInfo *SafetyInfo) {
+  if (LICMMaxSink != -1) {
+    if (SinkCtr >= LICMMaxSink)
+      return false;
+    ++SinkCtr;
+  }
+
   DEBUG(dbgs() << "LICM sinking instruction: " << I << "\n");
-  bool Changed = false;
   if (isa<LoadInst>(I))
     ++NumMovedLoads;
   else if (isa<CallInst>(I))
     ++NumMovedCalls;
   ++NumSunk;
-  Changed = true;
 
 #ifndef NDEBUG
   SmallVector<BasicBlock *, 32> ExitBlocks;
@@ -688,14 +702,20 @@
 
   CurAST->deleteValue(&I);
   I.eraseFromParent();
-  return Changed;
+  return true;
 }
 
-/// When an instruction is found to only use loop invariant operands that
-/// is safe to hoist, this instruction is called to do the dirty work.
+/// When an instruction is found to only use loop invariant operands that is
+/// safe to hoist, this function is called to do the dirty work.
 ///
 static bool hoist(Instruction &I, const DominatorTree *DT, const Loop *CurLoop,
                   const LICMSafetyInfo *SafetyInfo) {
+  if (LICMMaxHoist != -1) {
+    if (HoistCtr >= LICMMaxHoist)
+      return false;
+    ++HoistCtr;
+  }
+
   auto *Preheader = CurLoop->getLoopPreheader();
   DEBUG(dbgs() << "LICM hoisting to " << Preheader->getName() << ": " << I
                << "\n");


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