[RISCV] Support isel of scalable vector bitcasts

These should be NOPs so we can just replace with the input. This
matches what SVE does with isel patterns for all permutations.
Custom isel saves us from having to list all permurations for
all LMULs.

Reviewed By: frasercrmck

Differential Revision: https://reviews.llvm.org/D96921

diff --git a/llvm/lib/Target/RISCV/RISCVISelDAGToDAG.cpp b/llvm/lib/Target/RISCV/RISCVISelDAGToDAG.cpp
index fba8da6..85bfc94 100644 (file)
--- a/llvm/lib/Target/RISCV/RISCVISelDAGToDAG.cpp
+++ b/llvm/lib/Target/RISCV/RISCVISelDAGToDAG.cpp
@@ -745,6 +745,15 @@ void RISCVDAGToDAGISel::Select(SDNode *Node) {
     }
     break;
   }
+  case ISD::BITCAST:
+    // Just drop bitcasts between scalable vectors.
+    if (VT.isScalableVector() &&
+        Node->getOperand(0).getSimpleValueType().isScalableVector()) {
+      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/test/CodeGen/RISCV/rvv/fixed-vectors-int-splat-rv32.ll b/llvm/test/CodeGen/RISCV/rvv/fixed-vectors-int-splat-rv32.ll
index 730f070..1755162 100644 (file)
--- a/llvm/test/CodeGen/RISCV/rvv/fixed-vectors-int-splat-rv32.ll
+++ b/llvm/test/CodeGen/RISCV/rvv/fixed-vectors-int-splat-rv32.ll
@@ -435,3 +435,43 @@ define void @splat_allones_v4i64(<4 x i64>* %x) {
   store <4 x i64> %b, <4 x i64>* %x
   ret void
 }
+
+; This requires a bitcast on RV32 due to type legalization rewriting the
+; build_vector to v8i32.
+; FIXME: We should prevent this and use the implicit sign extension of vmv.v.x
+; with SEW=64 on RV32.
+define void @splat_allones_with_use_v4i64(<4 x i64>* %x) {
+; LMULMAX2-LABEL: splat_allones_with_use_v4i64:
+; LMULMAX2:       # %bb.0:
+; LMULMAX2-NEXT:    addi a1, zero, 4
+; LMULMAX2-NEXT:    vsetvli a2, a1, e64,m2,ta,mu
+; LMULMAX2-NEXT:    vle64.v v26, (a0)
+; LMULMAX2-NEXT:    addi a2, zero, 8
+; LMULMAX2-NEXT:    vsetvli a2, a2, e32,m2,ta,mu
+; LMULMAX2-NEXT:    vmv.v.i v28, -1
+; LMULMAX2-NEXT:    vsetvli a1, a1, e64,m2,ta,mu
+; LMULMAX2-NEXT:    vadd.vv v26, v26, v28
+; LMULMAX2-NEXT:    vse64.v v26, (a0)
+; LMULMAX2-NEXT:    ret
+;
+; LMULMAX1-LABEL: splat_allones_with_use_v4i64:
+; LMULMAX1:       # %bb.0:
+; LMULMAX1-NEXT:    addi a1, zero, 2
+; LMULMAX1-NEXT:    vsetvli a2, a1, e64,m1,ta,mu
+; LMULMAX1-NEXT:    vle64.v v25, (a0)
+; LMULMAX1-NEXT:    addi a2, a0, 16
+; LMULMAX1-NEXT:    vle64.v v26, (a2)
+; LMULMAX1-NEXT:    addi a3, zero, 4
+; LMULMAX1-NEXT:    vsetvli a3, a3, e32,m1,ta,mu
+; LMULMAX1-NEXT:    vmv.v.i v27, -1
+; LMULMAX1-NEXT:    vsetvli a1, a1, e64,m1,ta,mu
+; LMULMAX1-NEXT:    vadd.vv v26, v26, v27
+; LMULMAX1-NEXT:    vadd.vv v25, v25, v27
+; LMULMAX1-NEXT:    vse64.v v25, (a0)
+; LMULMAX1-NEXT:    vse64.v v26, (a2)
+; LMULMAX1-NEXT:    ret
+  %a = load <4 x i64>, <4 x i64>* %x
+  %b = add <4 x i64> %a, <i64 -1, i64 -1, i64 -1, i64 -1>
+  store <4 x i64> %b, <4 x i64>* %x
+  ret void
+}