[PATCH] D117863: [ISEL] Move trivial step_vector folds to FoldConstantArithmetic.

[Sander de Smalen via Phabricator via llvm-commits]

sdesmalen created this revision.
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Given that step_vector is practically a constant, doing this early
helps with DAGCombine folds that happen before type legalization.

There is currently no way to test this happens earlier, although existing
tests for step_vector folds continue protect the folds happening at all.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D117863

Files:
  llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
  llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp


Index: llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
===================================================================
--- llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -5413,6 +5413,19 @@
     }
   }
 
+  // Fold (mul step_vector(C0), C1) to (step_vector(C0 * C1)).
+  //      (shl step_vector(C0), C1) -> (step_vector(C0 << C1))
+  if ((Opcode == ISD::MUL || Opcode == ISD::SHL) &&
+      Ops[0].getOpcode() == ISD::STEP_VECTOR) {
+    APInt RHSVal;
+    if (ISD::isConstantSplatVector(Ops[1].getNode(), RHSVal)) {
+      APInt NewStep = Opcode == ISD::MUL
+                          ? Ops[0].getConstantOperandAPInt(0) * RHSVal
+                          : Ops[0].getConstantOperandAPInt(0) << RHSVal;
+      return getStepVector(DL, VT, NewStep);
+    }
+  }
+
   auto IsScalarOrSameVectorSize = [NumElts](const SDValue &Op) {
     return !Op.getValueType().isVector() ||
            Op.getValueType().getVectorElementCount() == NumElts;
Index: llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
===================================================================
--- llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -3946,15 +3946,6 @@
       return DAG.getVScale(SDLoc(N), VT, C0 * C1);
     }
 
-  // Fold (mul step_vector(C0), C1) to (step_vector(C0 * C1)).
-  APInt MulVal;
-  if (N0.getOpcode() == ISD::STEP_VECTOR)
-    if (ISD::isConstantSplatVector(N1.getNode(), MulVal)) {
-      const APInt &C0 = N0.getConstantOperandAPInt(0);
-      APInt NewStep = C0 * MulVal;
-      return DAG.getStepVector(SDLoc(N), VT, NewStep);
-    }
-
   // Fold ((mul x, 0/undef) -> 0,
   //       (mul x, 1) -> x) -> x)
   // -> and(x, mask)
@@ -8666,17 +8657,6 @@
       return DAG.getVScale(SDLoc(N), VT, C0 << C1);
     }
 
-  // Fold (shl step_vector(C0), C1) to (step_vector(C0 << C1)).
-  APInt ShlVal;
-  if (N0.getOpcode() == ISD::STEP_VECTOR)
-    if (ISD::isConstantSplatVector(N1.getNode(), ShlVal)) {
-      const APInt &C0 = N0.getConstantOperandAPInt(0);
-      if (ShlVal.ult(C0.getBitWidth())) {
-        APInt NewStep = C0 << ShlVal;
-        return DAG.getStepVector(SDLoc(N), VT, NewStep);
-      }
-    }
-
   return SDValue();
 }
 


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