[AArch64] Avoid NEON fixed-point SCVTF in Streaming-SVE mode.

NEON fixed-point SCVTF instruction is not available in Streaming-SVE
mode. There is no equivalent SVE instruction, so we simply expand to a
regular FDIV operation.

Author: sdesmalen-arm

llvm/lib/Target/AArch64/AArch64ISelLowering.cpp

@@ -17912,7 +17912,7 @@ static SDValue performFpToIntCombine(SDNode *N, SelectionDAG &DAG,
 static SDValue performFDivCombine(SDNode *N, SelectionDAG &DAG,
                                   TargetLowering::DAGCombinerInfo &DCI,
                                   const AArch64Subtarget *Subtarget) {
-  if (!Subtarget->hasNEON())
+  if (!Subtarget->isNeonAvailable())
     return SDValue();
 
   SDValue Op = N->getOperand(0);

llvm/test/CodeGen/AArch64/sve-streaming-mode-fixed-length-fp-arith.ll

@@ -219,7 +219,12 @@ define <2 x float> @fdiv_v2f32(<2 x float> %op1, <2 x float> %op2) {
 define <2 x float> @fdiv_v232_pow2(<2 x i32> %in) {
 ; CHECK-LABEL: fdiv_v232_pow2:
 ; CHECK:       // %bb.0: // %entry
-; CHECK-NEXT:    scvtf v0.2s, v0.2s, #4
+; CHECK-NEXT:    ptrue p0.s, vl2
+; CHECK-NEXT:    // kill: def $d0 killed $d0 def $z0
+; CHECK-NEXT:    fmov z1.s, #16.00000000
+; CHECK-NEXT:    scvtf z0.s, p0/m, z0.s
+; CHECK-NEXT:    fdiv z0.s, p0/m, z0.s, z1.s
+; CHECK-NEXT:    // kill: def $d0 killed $d0 killed $z0
 ; CHECK-NEXT:    ret
 entry:
   %vcvt.i = sitofp <2 x i32> %in to <2 x float>