From: Chris Lattner <sabre@nondot.org>
Date: Sat, 4 Mar 2006 23:33:26 +0000 (+0000)
Subject: fold (mul (add x, c1), c2) -> (add (mul x, c2), c1*c2)
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=a1deca3cd62963c1f5a7c48e7e5e67fec9beadaa;p=oota-llvm.git

fold (mul (add x, c1), c2) -> (add (mul x, c2), c1*c2)
fold (shl (add x, c1), c2) -> (add (shl x, c2), c1<<c2)

This allows us to compile CodeGen/PowerPC/addi-reassoc.ll into:

_test1:
        slwi r2, r4, 4
        add r2, r2, r3
        lwz r3, 36(r2)
        blr
_test2:
        mulli r2, r4, 5
        add r2, r2, r3
        lbz r2, 11(r2)
        extsb r3, r2
        blr

instead of:

_test1:
        addi r2, r4, 2
        slwi r2, r2, 4
        add r2, r3, r2
        lwz r3, 4(r2)
        blr
_test2:
        addi r2, r4, 2
        mulli r2, r2, 5
        add r2, r3, r2
        lbz r2, 1(r2)
        extsb r3, r2
        blr


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@26535 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 280c7081f15..0cf6801831f 100644
--- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -802,7 +802,13 @@ SDOperand DAGCombiner::visitMUL(SDNode *N) {
       return DAG.getNode(ISD::SHL, VT, Mul, Sh.getOperand(1));
     }
   }
-      
+  // fold (mul (add x, c1), c2) -> (add (mul x, c2), c1*c2)
+  if (N1C && N0.getOpcode() == ISD::ADD && N0.Val->hasOneUse() && 
+      isa<ConstantSDNode>(N0.getOperand(1))) {
+    return DAG.getNode(ISD::ADD, VT, 
+                       DAG.getNode(ISD::MUL, VT, N0.getOperand(0), N1),
+                       DAG.getNode(ISD::MUL, VT, N0.getOperand(1), N1));
+  }
   
   // reassociate mul
   SDOperand RMUL = ReassociateOps(ISD::MUL, N0, N1);
@@ -1446,6 +1452,13 @@ SDOperand DAGCombiner::visitSHL(SDNode *N) {
   if (N1C && N0.getOpcode() == ISD::SRA && N1 == N0.getOperand(1))
     return DAG.getNode(ISD::AND, VT, N0.getOperand(0),
                        DAG.getConstant(~0ULL << N1C->getValue(), VT));
+  // fold (shl (add x, c1), c2) -> (add (shl x, c2), c1<<c2)
+  if (N1C && N0.getOpcode() == ISD::ADD && N0.Val->hasOneUse() && 
+      isa<ConstantSDNode>(N0.getOperand(1))) {
+    return DAG.getNode(ISD::ADD, VT, 
+                       DAG.getNode(ISD::SHL, VT, N0.getOperand(0), N1),
+                       DAG.getNode(ISD::SHL, VT, N0.getOperand(1), N1));
+  }
   return SDOperand();
 }