[llvm] b4ad450 - [TargetLowering] expandCTPOP don't create an used constant mask for i8 ctpop. NFC

[Craig Topper via llvm-commits]

Author: Craig Topper
Date: 2022-05-14T20:35:38-07:00
New Revision: b4ad450953f0d7fd85f29d467297ed266c3d33be

URL: https://github.com/llvm/llvm-project/commit/b4ad450953f0d7fd85f29d467297ed266c3d33be
DIFF: https://github.com/llvm/llvm-project/commit/b4ad450953f0d7fd85f29d467297ed266c3d33be.diff

LOG: [TargetLowering] expandCTPOP don't create an used constant mask for i8 ctpop. NFC

Use early out for the i8 case.

I'm looking at avoiding MUL on targets that use libcalls for MUL.
So doing a little pre-refactoring.

Added: 
    

Modified: 
    llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp

Removed: 
    


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diff  --git a/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp b/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
index 67e25b34743b..4eeec85bbd97 100644
--- a/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
@@ -7693,8 +7693,6 @@ SDValue TargetLowering::expandCTPOP(SDNode *Node, SelectionDAG &DAG) const {
       DAG.getConstant(APInt::getSplat(Len, APInt(8, 0x33)), dl, VT);
   SDValue Mask0F =
       DAG.getConstant(APInt::getSplat(Len, APInt(8, 0x0F)), dl, VT);
-  SDValue Mask01 =
-      DAG.getConstant(APInt::getSplat(Len, APInt(8, 0x01)), dl, VT);
 
   // v = v - ((v >> 1) & 0x55555555...)
   Op = DAG.getNode(ISD::SUB, dl, VT, Op,
@@ -7714,13 +7712,16 @@ SDValue TargetLowering::expandCTPOP(SDNode *Node, SelectionDAG &DAG) const {
                                DAG.getNode(ISD::SRL, dl, VT, Op,
                                            DAG.getConstant(4, dl, ShVT))),
                    Mask0F);
-  // v = (v * 0x01010101...) >> (Len - 8)
-  if (Len > 8)
-    Op =
-        DAG.getNode(ISD::SRL, dl, VT, DAG.getNode(ISD::MUL, dl, VT, Op, Mask01),
-                    DAG.getConstant(Len - 8, dl, ShVT));
 
-  return Op;
+  if (Len <= 8)
+    return Op;
+
+  // v = (v * 0x01010101...) >> (Len - 8)
+  SDValue Mask01 =
+      DAG.getConstant(APInt::getSplat(Len, APInt(8, 0x01)), dl, VT);
+  return DAG.getNode(ISD::SRL, dl, VT,
+                     DAG.getNode(ISD::MUL, dl, VT, Op, Mask01),
+                     DAG.getConstant(Len - 8, dl, ShVT));
 }
 
 SDValue TargetLowering::expandCTLZ(SDNode *Node, SelectionDAG &DAG) const {