From 2c1d7726f25b6b219a1518b411351b99d25c1a02 Mon Sep 17 00:00:00 2001
From: Bill Wendling <isanbard@gmail.com>
Date: Thu, 7 May 2009 01:33:38 +0000
Subject: [PATCH] Just turn aggressive stack coloring off at -O3.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@71140 91177308-0d34-0410-b5e6-96231b3b80d8
---
 include/llvm/CodeGen/Passes.h     |  2 +-
 lib/CodeGen/LLVMTargetMachine.cpp |  3 ++-
 lib/CodeGen/StackSlotColoring.cpp | 30 +++++++++++++++++++++---------
 3 files changed, 24 insertions(+), 11 deletions(-)

diff --git a/include/llvm/CodeGen/Passes.h b/include/llvm/CodeGen/Passes.h
index e9d26cf4c23..faf98319525 100644
--- a/include/llvm/CodeGen/Passes.h
+++ b/include/llvm/CodeGen/Passes.h
@@ -191,7 +191,7 @@ namespace llvm {
   FunctionPass *createMachineSinkingPass();
 
   /// createStackSlotColoringPass - This pass performs stack slot coloring.
-  FunctionPass *createStackSlotColoringPass();
+  FunctionPass *createStackSlotColoringPass(bool);
 
   /// createStackProtectorPass - This pass adds stack protectors to functions.
   FunctionPass *createStackProtectorPass(const TargetLowering *tli);
diff --git a/lib/CodeGen/LLVMTargetMachine.cpp b/lib/CodeGen/LLVMTargetMachine.cpp
index faaa41b68b6..b4a0bc2b7ae 100644
--- a/lib/CodeGen/LLVMTargetMachine.cpp
+++ b/lib/CodeGen/LLVMTargetMachine.cpp
@@ -193,7 +193,8 @@ bool LLVMTargetMachine::addCommonCodeGenPasses(PassManagerBase &PM,
 
   // Perform stack slot coloring.
   if (OptLevel != CodeGenOpt::None)
-    PM.add(createStackSlotColoringPass());
+    PM.add(createStackSlotColoringPass(false));
+           /*OptLevel >= CodeGenOpt::Aggressive*/
 
   if (PrintMachineCode)  // Print the register-allocated code
     PM.add(createMachineFunctionPrinterPass(cerr));
diff --git a/lib/CodeGen/StackSlotColoring.cpp b/lib/CodeGen/StackSlotColoring.cpp
index 0d9b85af8e7..18fe59f3b72 100644
--- a/lib/CodeGen/StackSlotColoring.cpp
+++ b/lib/CodeGen/StackSlotColoring.cpp
@@ -37,21 +37,22 @@ DisableSharing("no-stack-slot-sharing",
              cl::desc("Suppress slot sharing during stack coloring"));
 
 static cl::opt<bool>
-ColorWithRegs("color-ss-with-regs",
-             cl::init(false), cl::Hidden,
-             cl::desc("Color stack slots with free registers"));
+ColorWithRegsOpt("color-ss-with-regs",
+                 cl::init(false), cl::Hidden,
+                 cl::desc("Color stack slots with free registers"));
 
 
 static cl::opt<int> DCELimit("ssc-dce-limit", cl::init(-1), cl::Hidden);
 
 STATISTIC(NumEliminated, "Number of stack slots eliminated due to coloring");
 STATISTIC(NumRegRepl,    "Number of stack slot refs replaced with reg refs");
-STATISTIC(NumLoadElim,   "Number of load eliminated");
+STATISTIC(NumLoadElim,   "Number of loads eliminated");
 STATISTIC(NumStoreElim,  "Number of stores eliminated");
 STATISTIC(NumDead,       "Number of trivially dead stack accesses eliminated");
 
 namespace {
   class VISIBILITY_HIDDEN StackSlotColoring : public MachineFunctionPass {
+    bool ColorWithRegs;
     LiveStacks* LS;
     VirtRegMap* VRM;
     MachineFrameInfo *MFI;
@@ -89,7 +90,10 @@ namespace {
 
   public:
     static char ID; // Pass identification
-    StackSlotColoring() : MachineFunctionPass(&ID), NextColor(-1) {}
+    StackSlotColoring() :
+      MachineFunctionPass(&ID), ColorWithRegs(false), NextColor(-1) {}
+    StackSlotColoring(bool RegColor) :
+      MachineFunctionPass(&ID), ColorWithRegs(RegColor), NextColor(-1) {}
     
     virtual void getAnalysisUsage(AnalysisUsage &AU) const {
       AU.addRequired<LiveStacks>();
@@ -136,8 +140,8 @@ char StackSlotColoring::ID = 0;
 static RegisterPass<StackSlotColoring>
 X("stack-slot-coloring", "Stack Slot Coloring");
 
-FunctionPass *llvm::createStackSlotColoringPass() {
-  return new StackSlotColoring();
+FunctionPass *llvm::createStackSlotColoringPass(bool RegColor) {
+  return new StackSlotColoring(RegColor);
 }
 
 namespace {
@@ -231,7 +235,7 @@ bool
 StackSlotColoring::ColorSlotsWithFreeRegs(SmallVector<int, 16> &SlotMapping,
                                    SmallVector<SmallVector<int, 4>, 16> &RevMap,
                                    BitVector &SlotIsReg) {
-  if (!ColorWithRegs || !VRM->HasUnusedRegisters())
+  if (!(ColorWithRegs || ColorWithRegsOpt) || !VRM->HasUnusedRegisters())
     return false;
 
   bool Changed = false;
@@ -239,7 +243,9 @@ StackSlotColoring::ColorSlotsWithFreeRegs(SmallVector<int, 16> &SlotMapping,
   for (unsigned i = 0, e = SSIntervals.size(); i != e; ++i) {
     LiveInterval *li = SSIntervals[i];
     int SS = li->getStackSlotIndex();
-    if (!UsedColors[SS])
+    if (!UsedColors[SS] || li->weight < 20)
+      // If the weight is < 20, i.e. two references in a loop with depth 1,
+      // don't bother with it.
       continue;
 
     // These slots allow to share the same registers.
@@ -472,6 +478,9 @@ void StackSlotColoring::RewriteInstruction(MachineInstr *MI, int OldFI,
 bool StackSlotColoring::PropagateBackward(MachineBasicBlock::iterator MII,
                                           MachineBasicBlock *MBB,
                                           unsigned OldReg, unsigned NewReg) {
+  if (MII == MBB->begin())
+    return false;
+
   SmallVector<MachineOperand*, 4> Refs;
   while (--MII != MBB->begin()) {
     bool FoundDef = false;  // Not counting 2address def.
@@ -522,6 +531,9 @@ bool StackSlotColoring::PropagateBackward(MachineBasicBlock::iterator MII,
 bool StackSlotColoring::PropagateForward(MachineBasicBlock::iterator MII,
                                          MachineBasicBlock *MBB,
                                          unsigned OldReg, unsigned NewReg) {
+  if (MII == MBB->end())
+    return false;
+
   SmallVector<MachineOperand*, 4> Uses;
   while (++MII != MBB->end()) {
     bool FoundUse = false;