[SelectionDAG] PromoteIntRes_EXTRACT_SUBVECTOR for scalable vectors.

[sdesmalen]

Summary

This patch implements legalization of EXTRACT_SUBVECTOR for the case
where the result needs promoting, and the input type is either legal
or requires splitting.

The idea is that the operation is broken down into simpler steps,
by first extracting a smaller subvector until the input vector
becomes legal or requires promotion.

[CarolineConcatto]

Hey Sander,
That is a nice patch.

llvm/lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp

4738

It would not be best if NElts and IdxVal be the same type?
Both should be unsigned or uint64_t.

In the same topic, why getZExtValue the index?

4741

Should this be:

DAG.getConstant((IdxVal, dl, ...

Because:
(IdxVal / NElts) * NElts =. IdxVal?

[craig.topper]

llvm/lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp

4741

Unless this trying to align IdxVal to a multiple of NElts <= IdxVal. In which case it might be clearer as alignDown(IdxVal, NElts)

[sdesmalen]

Use alignDown instead of (IdxVal / NElts) * NElts.

[sdesmalen]

llvm/lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp

4738

That shouldn't really matter. IdxVal must be uint64_t because of the value returned by getZExtValue().
Any uses of NElts will be promoted to the widest type, which in case of IdxVal will be a 64-bit unsigned value type.

4741

Nice suggestion, thanks!

[CarolineConcatto]

Thank you Sander!

llvm/lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp

SDValue DAGTypeLegalizer::PromoteIntRes_EXTRACT_SUBVECTOR(SDNode *N) {
   SDValue BaseIdx = N->getOperand(1);
 
   // TODO: We may be able to use this for types other than scalable
   // vectors and fix those tests that expect BUILD_VECTOR to be used
   if (OutVT.isScalableVector()) {
     SDValue InOp0 = N->getOperand(0);
     EVT InVT = InOp0.getValueType();
 
+    // Try and extract from a smaller type so that it eventually falls
+    // into the promotion code below.
+    if (getTypeAction(InVT) == TargetLowering::TypeSplitVector ||
+        getTypeAction(InVT) == TargetLowering::TypeLegal) {
+      EVT NInVT = InVT.getHalfNumVectorElementsVT(*DAG.getContext());
+      unsigned NElts = NInVT.getVectorMinNumElements();
+      uint64_t IdxVal = cast<ConstantSDNode>(BaseIdx)->getZExtValue();
+
+      SDValue Step1 = DAG.getNode(ISD::EXTRACT_SUBVECTOR, dl, NInVT, InOp0,
+                                  DAG.getConstant((IdxVal / NElts) * NElts, dl,
+                                                  BaseIdx.getValueType()));
+      SDValue Step2 = DAG.getNode(
+          ISD::EXTRACT_SUBVECTOR, dl, OutVT, Step1,
+          DAG.getConstant(IdxVal % NElts, dl, BaseIdx.getValueType()));
+      return DAG.getNode(ISD::ANY_EXTEND, dl, NOutVT, Step2);
+    }
+
     // Promote operands and see if this is handled by target lowering,
     // Otherwise, use the BUILD_VECTOR approach below
     if (getTypeAction(InVT) == TargetLowering::TypePromoteInteger) {
       // Collect the (promoted) operands
       SDValue Ops[] = { GetPromotedInteger(InOp0), BaseIdx };
 
       EVT PromEltVT = Ops[0].getValueType().getVectorElementType();
       assert(PromEltVT.bitsLE(NOutVTElem) &&

llvm/test/CodeGen/AArch64/sve-extract-vector.ll

 ; CHECK-NEXT:    st1d { z0.d }, p0, [x8]
 ; CHECK-NEXT:    addvl sp, sp, #1
 ; CHECK-NEXT:    ldr x29, [sp], #16 // 8-byte Folded Reload
 ; CHECK-NEXT:    ret
   %retval = call <4 x i64> @llvm.experimental.vector.extract.v4i64.nxv2i64(<vscale x 2 x i64> %vec, i64 4)
   ret <4 x i64> %retval
 }
 
+;
+; Extracting illegal vector that needs promotion from a vector that needs widening.
+;
+
+define <vscale x 2 x i8> @extract_nxv2i8_nxv32i8_0(<vscale x 32 x i8> %vec) {
+; CHECK-LABEL: extract_nxv2i8_nxv32i8_0:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    uunpklo z0.h, z0.b
+; CHECK-NEXT:    uunpklo z0.s, z0.h
+; CHECK-NEXT:    uunpklo z0.d, z0.s
+; CHECK-NEXT:    ret
+  %res = call <vscale x 2 x i8> @llvm.experimental.vector.extract.nxv2i8.nxv32i8(<vscale x 32 x i8> %vec, i64 0)
+  ret <vscale x 2 x i8> %res
+}
+
+define <vscale x 2 x i8> @extract_nxv2i8_nxv32i8_2(<vscale x 32 x i8> %vec) {
+; CHECK-LABEL: extract_nxv2i8_nxv32i8_2:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    uunpklo z0.h, z0.b
+; CHECK-NEXT:    uunpklo z0.s, z0.h
+; CHECK-NEXT:    uunpkhi z0.d, z0.s
+; CHECK-NEXT:    ret
+  %res = call <vscale x 2 x i8> @llvm.experimental.vector.extract.nxv2i8.nxv32i8(<vscale x 32 x i8> %vec, i64 2)
+  ret <vscale x 2 x i8> %res
+}
+
+define <vscale x 2 x i8> @extract_nxv2i8_nxv32i8_4(<vscale x 32 x i8> %vec) {
+; CHECK-LABEL: extract_nxv2i8_nxv32i8_4:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    uunpklo z0.h, z0.b
+; CHECK-NEXT:    uunpkhi z0.s, z0.h
+; CHECK-NEXT:    uunpklo z0.d, z0.s
+; CHECK-NEXT:    ret
+  %res = call <vscale x 2 x i8> @llvm.experimental.vector.extract.nxv2i8.nxv32i8(<vscale x 32 x i8> %vec, i64 4)
+  ret <vscale x 2 x i8> %res
+}
+
+define <vscale x 2 x i8> @extract_nxv2i8_nxv32i8_6(<vscale x 32 x i8> %vec) {
+; CHECK-LABEL: extract_nxv2i8_nxv32i8_6:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    uunpklo z0.h, z0.b
+; CHECK-NEXT:    uunpkhi z0.s, z0.h
+; CHECK-NEXT:    uunpkhi z0.d, z0.s
+; CHECK-NEXT:    ret
+  %res = call <vscale x 2 x i8> @llvm.experimental.vector.extract.nxv2i8.nxv32i8(<vscale x 32 x i8> %vec, i64 6)
+  ret <vscale x 2 x i8> %res
+}
+
+define <vscale x 2 x i8> @extract_nxv2i8_nxv32i8_8(<vscale x 32 x i8> %vec) {
+; CHECK-LABEL: extract_nxv2i8_nxv32i8_8:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    uunpkhi z0.h, z0.b
+; CHECK-NEXT:    uunpklo z0.s, z0.h
+; CHECK-NEXT:    uunpklo z0.d, z0.s
+; CHECK-NEXT:    ret
+  %res = call <vscale x 2 x i8> @llvm.experimental.vector.extract.nxv2i8.nxv32i8(<vscale x 32 x i8> %vec, i64 8)
+  ret <vscale x 2 x i8> %res
+}
+
+define <vscale x 2 x i8> @extract_nxv2i8_nxv32i8_10(<vscale x 32 x i8> %vec) {
+; CHECK-LABEL: extract_nxv2i8_nxv32i8_10:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    uunpkhi z0.h, z0.b
+; CHECK-NEXT:    uunpklo z0.s, z0.h
+; CHECK-NEXT:    uunpkhi z0.d, z0.s
+; CHECK-NEXT:    ret
+  %res = call <vscale x 2 x i8> @llvm.experimental.vector.extract.nxv2i8.nxv32i8(<vscale x 32 x i8> %vec, i64 10)
+  ret <vscale x 2 x i8> %res
+}
+
+define <vscale x 2 x i8> @extract_nxv2i8_nxv32i8_12(<vscale x 32 x i8> %vec) {
+; CHECK-LABEL: extract_nxv2i8_nxv32i8_12:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    uunpkhi z0.h, z0.b
+; CHECK-NEXT:    uunpkhi z0.s, z0.h
+; CHECK-NEXT:    uunpklo z0.d, z0.s
+; CHECK-NEXT:    ret
+  %res = call <vscale x 2 x i8> @llvm.experimental.vector.extract.nxv2i8.nxv32i8(<vscale x 32 x i8> %vec, i64 12)
+  ret <vscale x 2 x i8> %res
+}
+
+define <vscale x 2 x i8> @extract_nxv2i8_nxv32i8_14(<vscale x 32 x i8> %vec) {
+; CHECK-LABEL: extract_nxv2i8_nxv32i8_14:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    uunpkhi z0.h, z0.b
+; CHECK-NEXT:    uunpkhi z0.s, z0.h
+; CHECK-NEXT:    uunpkhi z0.d, z0.s
+; CHECK-NEXT:    ret
+  %res = call <vscale x 2 x i8> @llvm.experimental.vector.extract.nxv2i8.nxv32i8(<vscale x 32 x i8> %vec, i64 14)
+  ret <vscale x 2 x i8> %res
+}
+
+define <vscale x 2 x i8> @extract_nxv2i8_nxv32i8_16(<vscale x 32 x i8> %vec) {
+; CHECK-LABEL: extract_nxv2i8_nxv32i8_16:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    uunpklo z0.h, z1.b
+; CHECK-NEXT:    uunpklo z0.s, z0.h
+; CHECK-NEXT:    uunpklo z0.d, z0.s
+; CHECK-NEXT:    ret
+  %res = call <vscale x 2 x i8> @llvm.experimental.vector.extract.nxv2i8.nxv32i8(<vscale x 32 x i8> %vec, i64 16)
+  ret <vscale x 2 x i8> %res
+}
+
+define <vscale x 2 x i8> @extract_nxv2i8_nxv32i8_18(<vscale x 32 x i8> %vec) {
+; CHECK-LABEL: extract_nxv2i8_nxv32i8_18:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    uunpklo z0.h, z1.b
+; CHECK-NEXT:    uunpklo z0.s, z0.h
+; CHECK-NEXT:    uunpkhi z0.d, z0.s
+; CHECK-NEXT:    ret
+  %res = call <vscale x 2 x i8> @llvm.experimental.vector.extract.nxv2i8.nxv32i8(<vscale x 32 x i8> %vec, i64 18)
+  ret <vscale x 2 x i8> %res
+}
+
+define <vscale x 2 x i8> @extract_nxv2i8_nxv32i8_20(<vscale x 32 x i8> %vec) {
+; CHECK-LABEL: extract_nxv2i8_nxv32i8_20:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    uunpklo z0.h, z1.b
+; CHECK-NEXT:    uunpkhi z0.s, z0.h
+; CHECK-NEXT:    uunpklo z0.d, z0.s
+; CHECK-NEXT:    ret
+  %res = call <vscale x 2 x i8> @llvm.experimental.vector.extract.nxv2i8.nxv32i8(<vscale x 32 x i8> %vec, i64 20)
+  ret <vscale x 2 x i8> %res
+}
+
+define <vscale x 2 x i8> @extract_nxv2i8_nxv32i8_22(<vscale x 32 x i8> %vec) {
+; CHECK-LABEL: extract_nxv2i8_nxv32i8_22:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    uunpklo z0.h, z1.b
+; CHECK-NEXT:    uunpkhi z0.s, z0.h
+; CHECK-NEXT:    uunpkhi z0.d, z0.s
+; CHECK-NEXT:    ret
+  %res = call <vscale x 2 x i8> @llvm.experimental.vector.extract.nxv2i8.nxv32i8(<vscale x 32 x i8> %vec, i64 22)
+  ret <vscale x 2 x i8> %res
+}
+
+define <vscale x 2 x i8> @extract_nxv2i8_nxv32i8_24(<vscale x 32 x i8> %vec) {
+; CHECK-LABEL: extract_nxv2i8_nxv32i8_24:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    uunpkhi z0.h, z1.b
+; CHECK-NEXT:    uunpklo z0.s, z0.h
+; CHECK-NEXT:    uunpklo z0.d, z0.s
+; CHECK-NEXT:    ret
+  %res = call <vscale x 2 x i8> @llvm.experimental.vector.extract.nxv2i8.nxv32i8(<vscale x 32 x i8> %vec, i64 24)
+  ret <vscale x 2 x i8> %res
+}
+
+define <vscale x 2 x i8> @extract_nxv2i8_nxv32i8_26(<vscale x 32 x i8> %vec) {
+; CHECK-LABEL: extract_nxv2i8_nxv32i8_26:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    uunpkhi z0.h, z1.b
+; CHECK-NEXT:    uunpklo z0.s, z0.h
+; CHECK-NEXT:    uunpkhi z0.d, z0.s
+; CHECK-NEXT:    ret
+  %res = call <vscale x 2 x i8> @llvm.experimental.vector.extract.nxv2i8.nxv32i8(<vscale x 32 x i8> %vec, i64 26)
+  ret <vscale x 2 x i8> %res
+}
+
+define <vscale x 2 x i8> @extract_nxv2i8_nxv32i8_28(<vscale x 32 x i8> %vec) {
+; CHECK-LABEL: extract_nxv2i8_nxv32i8_28:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    uunpkhi z0.h, z1.b
+; CHECK-NEXT:    uunpkhi z0.s, z0.h
+; CHECK-NEXT:    uunpklo z0.d, z0.s
+; CHECK-NEXT:    ret
+  %res = call <vscale x 2 x i8> @llvm.experimental.vector.extract.nxv2i8.nxv32i8(<vscale x 32 x i8> %vec, i64 28)
+  ret <vscale x 2 x i8> %res
+}
+
+define <vscale x 2 x i8> @extract_nxv2i8_nxv32i8_30(<vscale x 32 x i8> %vec) {
+; CHECK-LABEL: extract_nxv2i8_nxv32i8_30:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    uunpkhi z0.h, z1.b
+; CHECK-NEXT:    uunpkhi z0.s, z0.h
+; CHECK-NEXT:    uunpkhi z0.d, z0.s
+; CHECK-NEXT:    ret
+  %res = call <vscale x 2 x i8> @llvm.experimental.vector.extract.nxv2i8.nxv32i8(<vscale x 32 x i8> %vec, i64 30)
+  ret <vscale x 2 x i8> %res
+}
+
 attributes #0 = { vscale_range(2,2) }
 
 declare <2 x i64> @llvm.experimental.vector.extract.v2i64.nxv2i64(<vscale x 2 x i64>, i64)
 declare <4 x i32> @llvm.experimental.vector.extract.v4i32.nxv4i32(<vscale x 4 x i32>, i64)
 declare <8 x i16> @llvm.experimental.vector.extract.v8i16.nxv8i16(<vscale x 8 x i16>, i64)
 declare <16 x i8> @llvm.experimental.vector.extract.v16i8.nxv16i8(<vscale x 16 x i8>, i64)
 
 declare <4 x i64> @llvm.experimental.vector.extract.v4i64.nxv2i64(<vscale x 2 x i64>, i64)
 
 declare <vscale x 1 x i32> @llvm.experimental.vector.extract.nxv1i32.nxv4i32(<vscale x 4 x i32>, i64)
 declare <vscale x 1 x i16> @llvm.experimental.vector.extract.nxv1i16.nxv6i16(<vscale x 6 x i16>, i64)
+
+declare <vscale x 2 x i8> @llvm.experimental.vector.extract.nxv2i8.nxv32i8(<vscale x 32 x i8> , i64)
+
+