[llvm-commits] CVS: llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp

[Chris Lattner]

Changes in directory llvm/lib/CodeGen/SelectionDAG:

DAGCombiner.cpp updated: 1.28 -> 1.29
---
Log message:

Implement trivial DSE.  If two stores are neighbors and store to the same
location, replace them with a new store of the last value.  This occurs
in the same neighborhood in 197.parser, speeding it up about 1.5%



---
Diffs of the changes:  (+29 -0)

 DAGCombiner.cpp |   29 +++++++++++++++++++++++++++++
 1 files changed, 29 insertions(+)


Index: llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
diff -u llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp:1.28 llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp:1.29
--- llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp:1.28	Mon Oct 10 17:04:48 2005
+++ llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp	Mon Oct 10 17:31:19 2005
@@ -77,6 +77,7 @@
     }
     
     SDOperand CombineTo(SDNode *N, const std::vector<SDOperand> &To) {
+      ++NodesCombined;
       DEBUG(std::cerr << "\nReplacing "; N->dump();
             std::cerr << "\nWith: "; To[0].Val->dump();
             std::cerr << " and " << To.size()-1 << " other values\n");
@@ -99,6 +100,12 @@
       DAG.DeleteNode(N);
       return SDOperand(N, 0);
     }
+
+    SDOperand CombineTo(SDNode *N, SDOperand Res) {
+      std::vector<SDOperand> To;
+      To.push_back(Res);
+      return CombineTo(N, To);
+    }
     
     SDOperand CombineTo(SDNode *N, SDOperand Res0, SDOperand Res1) {
       std::vector<SDOperand> To;
@@ -165,6 +172,7 @@
     SDOperand visitBRTWOWAY_CC(SDNode *N);
 
     SDOperand visitLOAD(SDNode *N);
+    SDOperand visitSTORE(SDNode *N);
 
     SDOperand SimplifySelect(SDOperand N0, SDOperand N1, SDOperand N2);
     SDOperand SimplifySelectCC(SDOperand N0, SDOperand N1, SDOperand N2, 
@@ -439,6 +447,7 @@
   case ISD::BR_CC:              return visitBR_CC(N);
   case ISD::BRTWOWAY_CC:        return visitBRTWOWAY_CC(N);
   case ISD::LOAD:               return visitLOAD(N);
+  case ISD::STORE:              return visitSTORE(N);
   }
   return SDOperand();
 }
@@ -1567,6 +1576,26 @@
   return SDOperand();
 }
 
+SDOperand DAGCombiner::visitSTORE(SDNode *N) {
+  SDOperand Chain    = N->getOperand(0);
+  SDOperand Value    = N->getOperand(1);
+  SDOperand Ptr      = N->getOperand(2);
+  SDOperand SrcValue = N->getOperand(3);
+ 
+  // If this is a store that kills a previous store, remove the previous store.
+  if (Chain.getOpcode() == ISD::STORE && Chain.getOperand(2) == Ptr) {
+    // Create a new store of Value that replaces both stores.
+    SDNode *PrevStore = Chain.Val;
+    SDOperand NewStore = DAG.getNode(ISD::STORE, MVT::Other,
+                                     PrevStore->getOperand(0), Value, Ptr,
+                                     SrcValue);
+    CombineTo(PrevStore, NewStore);  // Nuke the previous store.
+    return NewStore;  // Replace this store with NewStore.
+  }
+  
+  return SDOperand();
+}
+
 SDOperand DAGCombiner::SimplifySelect(SDOperand N0, SDOperand N1, SDOperand N2){
   assert(N0.getOpcode() ==ISD::SETCC && "First argument must be a SetCC node!");