[SVE][CodeGen] Fix bug with store of unpacked FP scalable vectors

Fixed an incorrect pattern in lib/Target/AArch64/AArch64SVEInstrInfo.td
for storing out <vscale x 2 x f32> unpacked scalable vectors. Added
a couple of tests to

  test/CodeGen/AArch64/sve-st1-addressing-mode-reg-imm.ll

Differential Revision: https://reviews.llvm.org/D85441

Author: david-arm

llvm/lib/Target/AArch64/AArch64SVEInstrInfo.td

@@ -1790,7 +1790,7 @@ multiclass sve_prefetch<SDPatternOperator prefetch, ValueType PredTy, Instructio
   defm : unpred_store<         store, nxv4f16, ST1H_S_IMM, PTRUE_S>;
   defm : unpred_store<         store, nxv2f16, ST1H_D_IMM, PTRUE_D>;
   defm : unpred_store<         store, nxv4f32,   ST1W_IMM, PTRUE_S>;
-  defm : unpred_store<         store, nxv4f32, ST1W_D_IMM, PTRUE_D>;
+  defm : unpred_store<         store, nxv2f32, ST1W_D_IMM, PTRUE_D>;
   defm : unpred_store<         store, nxv2f64,   ST1D_IMM, PTRUE_D>;
 
   multiclass unpred_load<PatFrag Load, ValueType Ty, Instruction RegImmInst,

llvm/test/CodeGen/AArch64/sve-st1-addressing-mode-reg-imm.ll

@@ -104,3 +104,32 @@ define void @st1d_inbound(<vscale x 2 x i64> %data, <vscale x 2 x i64>* %a) {
   store <vscale x 2 x i64> %data, <vscale x 2 x i64>* %base
   ret void
 }
+
+
+; Splat stores of unpacked FP scalable vectors
+
+define void @store_nxv2f32(<vscale x 2 x float>* %out) {
+; CHECK-LABEL: store_nxv2f32:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    fmov z0.s, #1.00000000
+; CHECK-NEXT:    ptrue p0.d
+; CHECK-NEXT:    st1w { z0.d }, p0, [x0]
+; CHECK-NEXT:    ret
+  %ins = insertelement <vscale x 2 x float> undef, float 1.0, i32 0
+  %splat = shufflevector <vscale x 2 x float> %ins, <vscale x 2 x float> undef, <vscale x 2 x i32> zeroinitializer
+  store <vscale x 2 x float> %splat, <vscale x 2 x float>* %out
+  ret void
+}
+
+define void @store_nxv4f16(<vscale x 4 x half>* %out) {
+; CHECK-LABEL: store_nxv4f16:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    fmov z0.h, #1.00000000
+; CHECK-NEXT:    ptrue p0.s
+; CHECK-NEXT:    st1h { z0.s }, p0, [x0]
+; CHECK-NEXT:    ret
+  %ins = insertelement <vscale x 4 x half> undef, half 1.0, i32 0
+  %splat = shufflevector <vscale x 4 x half> %ins, <vscale x 4 x half> undef, <vscale x 4 x i32> zeroinitializer
+  store <vscale x 4 x half> %splat, <vscale x 4 x half>* %out
+  ret void
+}