From 40a42a2ccaaa19a109667ed7abf224cc8733cd9c Mon Sep 17 00:00:00 2001
From: Jakob Stoklund Olesen <stoklund@2pi.dk>
Date: Fri, 4 Mar 2011 00:58:40 +0000
Subject: Precompute block frequencies, pow() isn't free.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@126975 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/CodeGen/RegAllocGreedy.cpp |  7 +++----
 lib/CodeGen/SpillPlacement.cpp | 16 +++++-----------
 lib/CodeGen/SpillPlacement.h   |  9 +++++++--
 3 files changed, 15 insertions(+), 17 deletions(-)

(limited to 'lib/CodeGen')

diff --git a/lib/CodeGen/RegAllocGreedy.cpp b/lib/CodeGen/RegAllocGreedy.cpp
index cbecc4b2d3..eada8f9910 100644
--- a/lib/CodeGen/RegAllocGreedy.cpp
+++ b/lib/CodeGen/RegAllocGreedy.cpp
@@ -602,7 +602,7 @@ float RAGreedy::calcInterferenceInfo(LiveInterval &VirtReg, unsigned PhysReg) {
     // The local cost of spill code in this block is the block frequency times
     // the number of spill instructions inserted.
     if (Inserts)
-      LocalCost += Inserts * SpillPlacer->getBlockFrequency(BI.MBB);
+      LocalCost += Inserts * SpillPlacer->getBlockFrequency(BC.Number);
   }
   DEBUG(dbgs() << "Local cost of " << PrintReg(PhysReg, TRI) << " = "
                << LocalCost << '\n');
@@ -625,8 +625,7 @@ float RAGreedy::calcGlobalSplitCost(const BitVector &LiveBundles) {
     Inserts += LiveBundles[Bundles->getBundle(BC.Number, 1)] !=
                  (BC.Exit == SpillPlacement::PrefReg);
     if (Inserts)
-      GlobalCost +=
-        Inserts * SpillPlacer->getBlockFrequency(SA->LiveBlocks[i].MBB);
+      GlobalCost += Inserts * SpillPlacer->getBlockFrequency(BC.Number);
   }
   DEBUG(dbgs() << "Global cost = " << GlobalCost << '\n');
   return GlobalCost;
@@ -1089,7 +1088,7 @@ unsigned RAGreedy::tryLocalSplit(LiveInterval &VirtReg, AllocationOrder &Order,
   unsigned BestAfter = 0;
   float BestDiff = 0;
 
-  const float blockFreq = SpillPlacer->getBlockFrequency(BI.MBB);
+  const float blockFreq = SpillPlacer->getBlockFrequency(BI.MBB->getNumber());
   SmallVector<float, 8> GapWeight;
 
   Order.rewind();
diff --git a/lib/CodeGen/SpillPlacement.cpp b/lib/CodeGen/SpillPlacement.cpp
index 9c0bf1629a..57951ed806 100644
--- a/lib/CodeGen/SpillPlacement.cpp
+++ b/lib/CodeGen/SpillPlacement.cpp
@@ -175,9 +175,12 @@ bool SpillPlacement::runOnMachineFunction(MachineFunction &mf) {
   nodes = new Node[bundles->getNumBundles()];
 
   // Compute total ingoing and outgoing block frequencies for all bundles.
+  BlockFrequency.resize(mf.getNumBlockIDs());
   for (MachineFunction::iterator I = mf.begin(), E = mf.end(); I != E; ++I) {
-    float Freq = getBlockFrequency(I);
+    float Freq = LiveIntervals::getSpillWeight(true, false,
+                                               loops->getLoopDepth(I));
     unsigned Num = I->getNumber();
+    BlockFrequency[Num] = Freq;
     nodes[bundles->getBundle(Num, 1)].Frequency[0] += Freq;
     nodes[bundles->getBundle(Num, 0)].Frequency[1] += Freq;
   }
@@ -206,8 +209,7 @@ void SpillPlacement::
 prepareNodes(const SmallVectorImpl<BlockConstraint> &LiveBlocks) {
   for (SmallVectorImpl<BlockConstraint>::const_iterator I = LiveBlocks.begin(),
        E = LiveBlocks.end(); I != E; ++I) {
-    MachineBasicBlock *MBB = MF->getBlockNumbered(I->Number);
-    float Freq = getBlockFrequency(MBB);
+    float Freq = getBlockFrequency(I->Number);
 
     // Is this a transparent block? Link ingoing and outgoing bundles.
     if (I->Entry == DontCare && I->Exit == DontCare) {
@@ -320,11 +322,3 @@ SpillPlacement::placeSpills(const SmallVectorImpl<BlockConstraint> &LiveBlocks,
     }
   return Perfect;
 }
-
-/// getBlockFrequency - Return our best estimate of the block frequency which is
-/// the expected number of block executions per function invocation.
-float SpillPlacement::getBlockFrequency(const MachineBasicBlock *MBB) {
-  // Use the unnormalized spill weight for real block frequencies.
-  return LiveIntervals::getSpillWeight(true, false, loops->getLoopDepth(MBB));
-}
-
diff --git a/lib/CodeGen/SpillPlacement.h b/lib/CodeGen/SpillPlacement.h
index ef2d516cdc..b0135cbc36 100644
--- a/lib/CodeGen/SpillPlacement.h
+++ b/lib/CodeGen/SpillPlacement.h
@@ -27,6 +27,7 @@
 #ifndef LLVM_CODEGEN_SPILLPLACEMENT_H
 #define LLVM_CODEGEN_SPILLPLACEMENT_H
 
+#include "llvm/ADT/SmallVector.h"
 #include "llvm/CodeGen/MachineFunctionPass.h"
 
 namespace llvm {
@@ -35,7 +36,6 @@ class BitVector;
 class EdgeBundles;
 class MachineBasicBlock;
 class MachineLoopInfo;
-template <typename> class SmallVectorImpl;
 
 class SpillPlacement  : public MachineFunctionPass {
   struct Node;
@@ -48,6 +48,9 @@ class SpillPlacement  : public MachineFunctionPass {
   // caller.
   BitVector *ActiveNodes;
 
+  // Block frequencies are computed once. Indexed by block number.
+  SmallVector<float, 4> BlockFrequency;
+
 public:
   static char ID; // Pass identification, replacement for typeid.
 
@@ -91,7 +94,9 @@ public:
 
   /// getBlockFrequency - Return the estimated block execution frequency per
   /// function invocation.
-  float getBlockFrequency(const MachineBasicBlock*);
+  float getBlockFrequency(unsigned Number) const {
+    return BlockFrequency[Number];
+  }
 
 private:
   virtual bool runOnMachineFunction(MachineFunction&);
-- 
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