[X86] Change multiply by 26 to use two multiplies by 5 and an add instead of multiply by 3 and 9 and a subtract.

Same number of operations, but ending in an add is friendlier due to it being commutable.

llvm-svn: 337869

1 files changed, 7 insertions, 7 deletions

diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index 12f6d409a60..352e8170007 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -33698,10 +33698,10 @@ static SDValue combineMulSpecial(uint64_t MulAmt, SDNode *N, SelectionDAG &DAG,
     return Result;
   };
 
-  auto combineMulMulAddOrSub = [&](bool isAdd) {
+  auto combineMulMulAddOrSub = [&](int Mul1, int Mul2, bool isAdd) {
     SDValue Result = DAG.getNode(X86ISD::MUL_IMM, DL, VT, N->getOperand(0),
-                                 DAG.getConstant(9, DL, VT));
-    Result = DAG.getNode(ISD::MUL, DL, VT, Result, DAG.getConstant(3, DL, VT));
+                                 DAG.getConstant(Mul1, DL, VT));
+    Result = DAG.getNode(ISD::MUL, DL, VT, Result, DAG.getConstant(Mul2, DL, VT));
     Result = DAG.getNode(isAdd ? ISD::ADD : ISD::SUB, DL, VT, Result,
                          N->getOperand(0));
     return Result;
@@ -33730,15 +33730,15 @@ static SDValue combineMulSpecial(uint64_t MulAmt, SDNode *N, SelectionDAG &DAG,
     // mul x, 23 => sub ((shl (mul x, 3), 3), x)
     return combineMulShlAddOrSub(3, 3, /*isAdd*/ false);
   case 26:
-    // mul x, 26 => sub ((mul (mul x, 9), 3), x)
-    return combineMulMulAddOrSub(/*isAdd*/ false);
+    // mul x, 26 => add ((mul (mul x, 5), 5), x)
+    return combineMulMulAddOrSub(5, 5, /*isAdd*/ true);
   case 28:
     // mul x, 28 => add ((mul (mul x, 9), 3), x)
-    return combineMulMulAddOrSub(/*isAdd*/ true);
+    return combineMulMulAddOrSub(9, 3, /*isAdd*/ true);
   case 29:
     // mul x, 29 => add (add ((mul (mul x, 9), 3), x), x)
     return DAG.getNode(ISD::ADD, DL, VT, N->getOperand(0),
-                       combineMulMulAddOrSub(/*isAdd*/ true));
+                       combineMulMulAddOrSub(9, 3, /*isAdd*/ true));
   }
   return SDValue();
 }