From 223942a420cf5b9e888524186134cc652be8a921 Mon Sep 17 00:00:00 2001
From: Dan Gohman <gohman@apple.com>
Date: Sat, 3 Jan 2009 18:01:46 +0000
Subject: [PATCH] Remove the code from the scheduler that commuted two-address
 instructions to avoid copies, because TwoAddressInstructionPass also does
 this optimization.  The scheduler's version didn't account for live-out
 values, which resulted in spurious commutes and missed opportunities.

Now, TwoAddressInstructionPass handles all the opportunities,
instead of just those that the scheduler missed. The result is
usually the same, though there are occasional trivial differences
resulting from the avoidance of spurious commutes.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@61611 91177308-0d34-0410-b5e6-96231b3b80d8
---
 include/llvm/CodeGen/ScheduleDAGSDNodes.h     |  3 --
 .../SelectionDAG/ScheduleDAGRRList.cpp        | 54 -------------------
 .../SelectionDAG/ScheduleDAGSDNodesEmit.cpp   | 17 ------
 3 files changed, 74 deletions(-)

diff --git a/include/llvm/CodeGen/ScheduleDAGSDNodes.h b/include/llvm/CodeGen/ScheduleDAGSDNodes.h
index b9c6428fba7..2c3f0974c0d 100644
--- a/include/llvm/CodeGen/ScheduleDAGSDNodes.h
+++ b/include/llvm/CodeGen/ScheduleDAGSDNodes.h
@@ -17,7 +17,6 @@
 
 #include "llvm/CodeGen/ScheduleDAG.h"
 #include "llvm/CodeGen/SelectionDAG.h"
-#include "llvm/ADT/SmallSet.h"
 
 namespace llvm {
   /// HazardRecognizer - This determines whether or not an instruction can be
@@ -75,8 +74,6 @@ namespace llvm {
   ///
   class ScheduleDAGSDNodes : public ScheduleDAG {
   public:
-    SmallSet<SDNode*, 16> CommuteSet;     // Nodes that should be commuted.
-
     ScheduleDAGSDNodes(SelectionDAG *dag, MachineBasicBlock *bb,
                        const TargetMachine &tm);
 
diff --git a/lib/CodeGen/SelectionDAG/ScheduleDAGRRList.cpp b/lib/CodeGen/SelectionDAG/ScheduleDAGRRList.cpp
index aededf44440..e72c22c4727 100644
--- a/lib/CodeGen/SelectionDAG/ScheduleDAGRRList.cpp
+++ b/lib/CodeGen/SelectionDAG/ScheduleDAGRRList.cpp
@@ -186,60 +186,6 @@ void ScheduleDAGRRList::Schedule() {
     ListScheduleTopDown();
   
   AvailableQueue->releaseState();
-
-  CommuteNodesToReducePressure();
-}
-
-/// CommuteNodesToReducePressure - If a node is two-address and commutable, and
-/// it is not the last use of its first operand, add it to the CommuteSet if
-/// possible. It will be commuted when it is translated to a MI.
-void ScheduleDAGRRList::CommuteNodesToReducePressure() {
-  SmallPtrSet<SUnit*, 4> OperandSeen;
-  for (unsigned i = Sequence.size(); i != 0; ) {
-    --i;
-    SUnit *SU = Sequence[i];
-    if (!SU || !SU->getNode()) continue;
-    if (SU->isCommutable) {
-      unsigned Opc = SU->getNode()->getMachineOpcode();
-      const TargetInstrDesc &TID = TII->get(Opc);
-      unsigned NumRes = TID.getNumDefs();
-      unsigned NumOps = TID.getNumOperands() - NumRes;
-      for (unsigned j = 0; j != NumOps; ++j) {
-        if (TID.getOperandConstraint(j+NumRes, TOI::TIED_TO) == -1)
-          continue;
-
-        SDNode *OpN = SU->getNode()->getOperand(j).getNode();
-        SUnit *OpSU = isPassiveNode(OpN) ? NULL : &SUnits[OpN->getNodeId()];
-        if (OpSU && OperandSeen.count(OpSU) == 1) {
-          // Ok, so SU is not the last use of OpSU, but SU is two-address so
-          // it will clobber OpSU. Try to commute SU if no other source operands
-          // are live below.
-          bool DoCommute = true;
-          for (unsigned k = 0; k < NumOps; ++k) {
-            if (k != j) {
-              OpN = SU->getNode()->getOperand(k).getNode();
-              OpSU = isPassiveNode(OpN) ? NULL : &SUnits[OpN->getNodeId()];
-              if (OpSU && OperandSeen.count(OpSU) == 1) {
-                DoCommute = false;
-                break;
-              }
-            }
-          }
-          if (DoCommute)
-            CommuteSet.insert(SU->getNode());
-        }
-
-        // Only look at the first use&def node for now.
-        break;
-      }
-    }
-
-    for (SUnit::pred_iterator I = SU->Preds.begin(), E = SU->Preds.end();
-         I != E; ++I) {
-      if (!I->isCtrl())
-        OperandSeen.insert(I->getSUnit()->OrigNode);
-    }
-  }
 }
 
 //===----------------------------------------------------------------------===//
diff --git a/lib/CodeGen/SelectionDAG/ScheduleDAGSDNodesEmit.cpp b/lib/CodeGen/SelectionDAG/ScheduleDAGSDNodesEmit.cpp
index dc9313bb0c1..4019ec1303f 100644
--- a/lib/CodeGen/SelectionDAG/ScheduleDAGSDNodesEmit.cpp
+++ b/lib/CodeGen/SelectionDAG/ScheduleDAGSDNodesEmit.cpp
@@ -28,8 +28,6 @@
 #include "llvm/Support/MathExtras.h"
 using namespace llvm;
 
-STATISTIC(NumCommutes,   "Number of instructions commuted");
-
 /// getInstrOperandRegClass - Return register class of the operand of an
 /// instruction of the specified TargetInstrDesc.
 static const TargetRegisterClass*
@@ -500,21 +498,6 @@ void ScheduleDAGSDNodes::EmitNode(SDNode *Node, bool IsClone,
     for (unsigned i = NodeOperands; i != MemOperandsEnd; ++i)
       AddMemOperand(MI, cast<MemOperandSDNode>(Node->getOperand(i))->MO);
 
-    // Commute node if it has been determined to be profitable.
-    if (CommuteSet.count(Node)) {
-      MachineInstr *NewMI = TII->commuteInstruction(MI);
-      if (NewMI == 0)
-        DOUT << "Sched: COMMUTING FAILED!\n";
-      else {
-        DOUT << "Sched: COMMUTED TO: " << *NewMI;
-        if (MI != NewMI) {
-          MF->DeleteMachineInstr(MI);
-          MI = NewMI;
-        }
-        ++NumCommutes;
-      }
-    }
-
     if (II.usesCustomDAGSchedInsertionHook())
       // Insert this instruction into the basic block using a target
       // specific inserter which may returns a new basic block.
-- 
2.34.1