From f01af29f01f17c15b95136f5608748b098d1faa3 Mon Sep 17 00:00:00 2001
From: Tom Stellard <thomas.stellard@amd.com>
Date: Sat, 9 May 2015 00:56:07 +0000
Subject: MachineCSE: Add a target query for the LookAheadLimit heurisitic

This is used to determine whether or not to CSE physical register
defs.

Differential Revision: http://reviews.llvm.org/D9472

llvm-svn: 236923
---
 llvm/lib/CodeGen/MachineCSE.cpp    | 5 +++--
 llvm/lib/Target/R600/SIInstrInfo.h | 2 ++
 2 files changed, 5 insertions(+), 2 deletions(-)

(limited to 'llvm/lib')

diff --git a/llvm/lib/CodeGen/MachineCSE.cpp b/llvm/lib/CodeGen/MachineCSE.cpp
index f72d72a2e87..87aaaa0834c 100644
--- a/llvm/lib/CodeGen/MachineCSE.cpp
+++ b/llvm/lib/CodeGen/MachineCSE.cpp
@@ -48,7 +48,7 @@ namespace {
     MachineRegisterInfo *MRI;
   public:
     static char ID; // Pass identification
-    MachineCSE() : MachineFunctionPass(ID), LookAheadLimit(5), CurrVN(0) {
+    MachineCSE() : MachineFunctionPass(ID), LookAheadLimit(0), CurrVN(0) {
       initializeMachineCSEPass(*PassRegistry::getPassRegistry());
     }
 
@@ -69,7 +69,7 @@ namespace {
     }
 
   private:
-    const unsigned LookAheadLimit;
+    unsigned LookAheadLimit;
     typedef RecyclingAllocator<BumpPtrAllocator,
         ScopedHashTableVal<MachineInstr*, unsigned> > AllocatorTy;
     typedef ScopedHashTable<MachineInstr*, unsigned,
@@ -716,5 +716,6 @@ bool MachineCSE::runOnMachineFunction(MachineFunction &MF) {
   MRI = &MF.getRegInfo();
   AA = &getAnalysis<AliasAnalysis>();
   DT = &getAnalysis<MachineDominatorTree>();
+  LookAheadLimit = TII->getMachineCSELookAheadLimit();
   return PerformCSE(DT->getRootNode());
 }
diff --git a/llvm/lib/Target/R600/SIInstrInfo.h b/llvm/lib/Target/R600/SIInstrInfo.h
index 7e049dca7b1..f952c0f0853 100644
--- a/llvm/lib/Target/R600/SIInstrInfo.h
+++ b/llvm/lib/Target/R600/SIInstrInfo.h
@@ -142,6 +142,8 @@ public:
   bool FoldImmediate(MachineInstr *UseMI, MachineInstr *DefMI,
                      unsigned Reg, MachineRegisterInfo *MRI) const final;
 
+  unsigned getMachineCSELookAheadLimit() const override { return 500; }
+
   bool isSALU(uint16_t Opcode) const {
     return get(Opcode).TSFlags & SIInstrFlags::SALU;
   }
-- 
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