[llvm] 1cd2a5a - [RISCV] Add isel support for bitcasts between fixed vector types.

[Craig Topper via llvm-commits]

Author: Craig Topper
Date: 2021-02-22T12:05:46-08:00
New Revision: 1cd2a5a7da3db812fe2844caefcd40f8a52eff5b

URL: https://github.com/llvm/llvm-project/commit/1cd2a5a7da3db812fe2844caefcd40f8a52eff5b
DIFF: https://github.com/llvm/llvm-project/commit/1cd2a5a7da3db812fe2844caefcd40f8a52eff5b.diff

LOG: [RISCV] Add isel support for bitcasts between fixed vector types.

This should fix the issue reported in D96972.

I don't have a good test case for this without those changes.

Differential Revision: https://reviews.llvm.org/D97082

Added: 
    

Modified: 
    llvm/lib/Target/RISCV/RISCVISelDAGToDAG.cpp
    llvm/lib/Target/RISCV/RISCVISelLowering.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Target/RISCV/RISCVISelDAGToDAG.cpp b/llvm/lib/Target/RISCV/RISCVISelDAGToDAG.cpp
index 42f65b182c7f..7ef40b9011a1 100644
--- a/llvm/lib/Target/RISCV/RISCVISelDAGToDAG.cpp
+++ b/llvm/lib/Target/RISCV/RISCVISelDAGToDAG.cpp
@@ -912,15 +912,18 @@ void RISCVDAGToDAGISel::Select(SDNode *Node) {
     }
     break;
   }
-  case ISD::BITCAST:
-    // Just drop bitcasts between scalable vectors.
-    if (VT.isScalableVector() &&
-        Node->getOperand(0).getSimpleValueType().isScalableVector()) {
+  case ISD::BITCAST: {
+    MVT SrcVT = Node->getOperand(0).getSimpleValueType();
+    // Just drop bitcasts between vectors if both are fixed or both are
+    // scalable.
+    if ((VT.isScalableVector() && SrcVT.isScalableVector()) ||
+        (VT.isFixedLengthVector() && SrcVT.isFixedLengthVector())) {
       ReplaceUses(SDValue(Node, 0), Node->getOperand(0));
       CurDAG->RemoveDeadNode(Node);
       return;
     }
     break;
+  }
   case ISD::INSERT_SUBVECTOR: {
     SDValue V = Node->getOperand(0);
     SDValue SubV = Node->getOperand(1);

diff  --git a/llvm/lib/Target/RISCV/RISCVISelLowering.cpp b/llvm/lib/Target/RISCV/RISCVISelLowering.cpp
index 06fc8e918a9a..de0f0bb41edd 100644
--- a/llvm/lib/Target/RISCV/RISCVISelLowering.cpp
+++ b/llvm/lib/Target/RISCV/RISCVISelLowering.cpp
@@ -571,6 +571,8 @@ RISCVTargetLowering::RISCVTargetLowering(const TargetMachine &TM,
         setOperationAction(ISD::ANY_EXTEND, VT, Custom);
         setOperationAction(ISD::SIGN_EXTEND, VT, Custom);
         setOperationAction(ISD::ZERO_EXTEND, VT, Custom);
+
+        setOperationAction(ISD::BITCAST, VT, Custom);
       }
 
       for (MVT VT : MVT::fp_fixedlen_vector_valuetypes()) {
@@ -602,6 +604,8 @@ RISCVTargetLowering::RISCVTargetLowering(const TargetMachine &TM,
           setCondCodeAction(CC, VT, Expand);
 
         setOperationAction(ISD::VSELECT, VT, Custom);
+
+        setOperationAction(ISD::BITCAST, VT, Custom);
       }
     }
   }
@@ -1099,11 +1103,18 @@ SDValue RISCVTargetLowering::LowerOperation(SDValue Op,
   case ISD::SRL_PARTS:
     return lowerShiftRightParts(Op, DAG, false);
   case ISD::BITCAST: {
+    SDValue Op0 = Op.getOperand(0);
+    // We can handle fixed length vector bitcasts with a simple replacement
+    // in isel.
+    if (Op.getValueType().isFixedLengthVector()) {
+      if (Op0.getValueType().isFixedLengthVector())
+        return Op;
+      return SDValue();
+    }
     assert(((Subtarget.is64Bit() && Subtarget.hasStdExtF()) ||
             Subtarget.hasStdExtZfh()) &&
            "Unexpected custom legalisation");
     SDLoc DL(Op);
-    SDValue Op0 = Op.getOperand(0);
     if (Op.getValueType() == MVT::f16 && Subtarget.hasStdExtZfh()) {
       if (Op0.getValueType() != MVT::i16)
         return SDValue();