[RISCV] Scalarize binop followed by extractelement to custom lowered instruction

[Jim]

Summary

isOperationLegalOrCustomOrPromote returns true only if VT is other or legal
and operation action is Legal, Custom or Promote.
Permit a vector binary operation can be converted to scalar binary operation which is custom lowered with illegal type.
One of cases is i32 isn't a legal type on RV64 and its ALU operations is set to custom lowering,
so vadd for element type i32 can be converted to addw.

[craig.topper]

llvm/lib/Target/RISCV/RISCVISelLowering.cpp

1864–1865

Can we use isOperationLegalOrCustomOrPromote?

[Jim]

Address @craig.topper's comment

[craig.topper]

llvm/lib/Target/RISCV/RISCVISelLowering.cpp

1865

Do we still need the || isOperationCustom(Opc, ScalarVT)?

[Jim]

llvm/lib/Target/RISCV/RISCVISelLowering.cpp

1865

isOperationLegalOrCustomOrPromote(Opc, ScalarVT) would return false for that i32 type (is not legal) with custom lowering operation on RV64 (ADDW, ADDIW, SUBW, ...).

bool isOperationLegalOrCustomOrPromote(unsigned Op, EVT VT,
                                         bool LegalOnly = false) const {
    if (LegalOnly)
      return isOperationLegal(Op, VT);
 
    return (VT == MVT::Other || isTypeLegal(VT)) &&
      (getOperationAction(Op, VT) == Legal ||
       getOperationAction(Op, VT) == Custom ||
       getOperationAction(Op, VT) == Promote);
  }

isOperationCustom(Opc, ScalarVT) is for ADDW, ADDIW, SUBW ... can be scalarized to.

[craig.topper]

It's not clear to me this should be restricted to i64 and i32 either. An i16 or i8 add for example doesn't require any extra code unless the result needs to be sign/zero extended.

[Jim]

In D156692#4547870, @craig.topper wrote:

It's not clear to me this should be restricted to i64 and i32 either. An i16 or i8 add for example doesn't require any extra code unless the result needs to be sign/zero extended.

It doesn't need to be restricted to i64 or i32 either. i32 type ALU operation on RV64 is one of cases here (Maybe is only case in all of tests we had now).
The change of this patch is if any type is not legal, but its operation action is set to custom. That we permit a vector binary operation can be converted to it. (one of cases here is vadd for element type i32 can be converted to addw).
Thanks for your feedback.

[craig.topper]

LGTM

[Jim]

Update comment.

llvm/lib/Target/RISCV/RISCVISelLowering.cpp

bool RISCVTargetLowering::shouldScalarizeBinop(SDValue VecOp) const {
 
   // If the vector op is not supported, try to convert to scalar.
   EVT VecVT = VecOp.getValueType();
   if (!isOperationLegalOrCustomOrPromote(Opc, VecVT))
     return true;
 
   // If the vector op is supported, but the scalar op is not, the transform may
   // not be worthwhile.
+  // Permit a vector binary operation can be converted to scalar binary
+  // operation which is custom lowered with illegal type.
   EVT ScalarVT = VecVT.getScalarType();
-  return isOperationLegalOrCustomOrPromote(Opc, ScalarVT);
+  return isOperationLegalOrCustomOrPromote(Opc, ScalarVT) ||
+         isOperationCustom(Opc, ScalarVT);
 }
 
 bool RISCVTargetLowering::isOffsetFoldingLegal(
     const GlobalAddressSDNode *GA) const {
   // In order to maximise the opportunity for common subexpression elimination,
   // keep a separate ADD node for the global address offset instead of folding
   // it in the global address node. Later peephole optimisations may choose to
   // fold it back in when profitable.

llvm/test/CodeGen/RISCV/rvv/extractelt-int-rv64.ll

 ; CHECK-NEXT:    ret
   %r = extractelement <vscale x 8 x i64> %v, i32 %idx
   ret i64 %r
 }
 
 define i32 @extractelt_add_nxv4i32_splat(<vscale x 4 x i32> %x) {
 ; CHECK-LABEL: extractelt_add_nxv4i32_splat:
 ; CHECK:       # %bb.0:
-; CHECK-NEXT:    vsetvli a0, zero, e32, m2, ta, ma
-; CHECK-NEXT:    vadd.vi v8, v8, 3
 ; CHECK-NEXT:    vsetivli zero, 1, e32, m2, ta, ma
 ; CHECK-NEXT:    vslidedown.vi v8, v8, 2
 ; CHECK-NEXT:    vmv.x.s a0, v8
+; CHECK-NEXT:    addiw a0, a0, 3
 ; CHECK-NEXT:    ret
   %head = insertelement <vscale x 4 x i32> poison, i32 3, i32 0
   %splat = shufflevector <vscale x 4 x i32> %head, <vscale x 4 x i32> poison, <vscale x 4 x i32> zeroinitializer
   %bo = add <vscale x 4 x i32> %x, %splat
   %ext = extractelement <vscale x 4 x i32> %bo, i32 2
   ret i32 %ext
 }
 
 define i32 @extractelt_sub_nxv4i32_splat(<vscale x 4 x i32> %x) {
 ; CHECK-LABEL: extractelt_sub_nxv4i32_splat:
 ; CHECK:       # %bb.0:
-; CHECK-NEXT:    vsetvli a0, zero, e32, m2, ta, ma
-; CHECK-NEXT:    vrsub.vi v8, v8, 3
 ; CHECK-NEXT:    vsetivli zero, 1, e32, m2, ta, ma
 ; CHECK-NEXT:    vslidedown.vi v8, v8, 1
 ; CHECK-NEXT:    vmv.x.s a0, v8
+; CHECK-NEXT:    li a1, 3
+; CHECK-NEXT:    subw a0, a1, a0
 ; CHECK-NEXT:    ret
   %head = insertelement <vscale x 4 x i32> poison, i32 3, i32 0
   %splat = shufflevector <vscale x 4 x i32> %head, <vscale x 4 x i32> poison, <vscale x 4 x i32> zeroinitializer
   %bo = sub <vscale x 4 x i32> %splat, %x
   %ext = extractelement <vscale x 4 x i32> %bo, i32 1
   ret i32 %ext
 }
 

llvm/test/CodeGen/RISCV/rvv/fixed-vectors-extract.ll

 ; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
 ; RUN: llc -mtriple=riscv32 -target-abi=ilp32d -mattr=+v,+zfh,+zvfh,+f,+d -riscv-v-vector-bits-min=128 -verify-machineinstrs < %s | FileCheck %s --check-prefixes=CHECK,RV32,RV32NOM
 ; RUN: llc -mtriple=riscv32 -target-abi=ilp32d -mattr=+v,+zfh,+zvfh,+f,+d,+m -riscv-v-vector-bits-min=128 -verify-machineinstrs < %s | FileCheck %s --check-prefixes=CHECK,RV32,RV32M
-; RUN: llc -mtriple=riscv64 -target-abi=lp64d -mattr=+v,+zfh,+zvfh,+f,+d -riscv-v-vector-bits-min=128 -verify-machineinstrs < %s | FileCheck %s --check-prefixes=CHECK,RV64
-; RUN: llc -mtriple=riscv64 -target-abi=lp64d -mattr=+v,+zfh,+zvfh,+f,+d,+m -riscv-v-vector-bits-min=128 -verify-machineinstrs < %s | FileCheck %s --check-prefixes=CHECK,RV64
+; RUN: llc -mtriple=riscv64 -target-abi=lp64d -mattr=+v,+zfh,+zvfh,+f,+d -riscv-v-vector-bits-min=128 -verify-machineinstrs < %s | FileCheck %s --check-prefixes=CHECK,RV64,RV64NOM
+; RUN: llc -mtriple=riscv64 -target-abi=lp64d -mattr=+v,+zfh,+zvfh,+f,+d,+m -riscv-v-vector-bits-min=128 -verify-machineinstrs < %s | FileCheck %s --check-prefixes=CHECK,RV64,RV64M
 
 define i8 @extractelt_v16i8(ptr %x) nounwind {
 ; CHECK-LABEL: extractelt_v16i8:
 ; CHECK:       # %bb.0:
 ; CHECK-NEXT:    vsetivli zero, 16, e8, m1, ta, ma
 ; CHECK-NEXT:    vle8.v v8, (a0)
 ; CHECK-NEXT:    vslidedown.vi v8, v8, 7
 ; CHECK-NEXT:    vmv.x.s a0, v8

 ; RV32-NEXT:    vsetivli zero, 1, e32, m1, ta, ma
 ; RV32-NEXT:    vslidedown.vi v8, v8, 2
 ; RV32-NEXT:    vmv.x.s a0, v8
 ; RV32-NEXT:    addi a0, a0, 13
 ; RV32-NEXT:    ret
 ;
 ; RV64-LABEL: extractelt_add_v4i32:
 ; RV64:       # %bb.0:
-; RV64-NEXT:    vsetivli zero, 4, e32, m1, ta, ma
-; RV64-NEXT:    vadd.vi v8, v8, 13
+; RV64-NEXT:    vsetivli zero, 1, e32, m1, ta, ma
 ; RV64-NEXT:    vslidedown.vi v8, v8, 2
 ; RV64-NEXT:    vmv.x.s a0, v8
+; RV64-NEXT:    addiw a0, a0, 13
 ; RV64-NEXT:    ret
   %bo = add <4 x i32> %x, <i32 11, i32 12, i32 13, i32 14>
   %ext = extractelement <4 x i32> %bo, i32 2
   ret i32 %ext
 }
 
 define i32 @extractelt_sub_v4i32(<4 x i32> %x) {
 ; RV32-LABEL: extractelt_sub_v4i32:
 ; RV32:       # %bb.0:
 ; RV32-NEXT:    vsetivli zero, 1, e32, m1, ta, ma
 ; RV32-NEXT:    vslidedown.vi v8, v8, 2
 ; RV32-NEXT:    vmv.x.s a0, v8
 ; RV32-NEXT:    li a1, 13
 ; RV32-NEXT:    sub a0, a1, a0
 ; RV32-NEXT:    ret
 ;
 ; RV64-LABEL: extractelt_sub_v4i32:
 ; RV64:       # %bb.0:
-; RV64-NEXT:    vsetivli zero, 4, e32, m1, ta, ma
-; RV64-NEXT:    vrsub.vi v8, v8, 13
+; RV64-NEXT:    vsetivli zero, 1, e32, m1, ta, ma
 ; RV64-NEXT:    vslidedown.vi v8, v8, 2
 ; RV64-NEXT:    vmv.x.s a0, v8
+; RV64-NEXT:    li a1, 13
+; RV64-NEXT:    subw a0, a1, a0
 ; RV64-NEXT:    ret
   %bo = sub <4 x i32> <i32 11, i32 12, i32 13, i32 14>, %x
   %ext = extractelement <4 x i32> %bo, i32 2
   ret i32 %ext
 }
 
 define i32 @extractelt_mul_v4i32(<4 x i32> %x) {
 ; RV32NOM-LABEL: extractelt_mul_v4i32:

 ; RV32M:       # %bb.0:
 ; RV32M-NEXT:    vsetivli zero, 1, e32, m1, ta, ma
 ; RV32M-NEXT:    vslidedown.vi v8, v8, 2
 ; RV32M-NEXT:    vmv.x.s a0, v8
 ; RV32M-NEXT:    li a1, 13
 ; RV32M-NEXT:    mul a0, a0, a1
 ; RV32M-NEXT:    ret
 ;
-; RV64-LABEL: extractelt_mul_v4i32:
-; RV64:       # %bb.0:
-; RV64-NEXT:    li a0, 13
-; RV64-NEXT:    vsetivli zero, 4, e32, m1, ta, ma
-; RV64-NEXT:    vmul.vx v8, v8, a0
-; RV64-NEXT:    vslidedown.vi v8, v8, 2
-; RV64-NEXT:    vmv.x.s a0, v8
-; RV64-NEXT:    ret
+; RV64NOM-LABEL: extractelt_mul_v4i32:
+; RV64NOM:       # %bb.0:
+; RV64NOM-NEXT:    li a0, 13
+; RV64NOM-NEXT:    vsetivli zero, 4, e32, m1, ta, ma
+; RV64NOM-NEXT:    vmul.vx v8, v8, a0
+; RV64NOM-NEXT:    vslidedown.vi v8, v8, 2
+; RV64NOM-NEXT:    vmv.x.s a0, v8
+; RV64NOM-NEXT:    ret
+;
+; RV64M-LABEL: extractelt_mul_v4i32:
+; RV64M:       # %bb.0:
+; RV64M-NEXT:    vsetivli zero, 1, e32, m1, ta, ma
+; RV64M-NEXT:    vslidedown.vi v8, v8, 2
+; RV64M-NEXT:    vmv.x.s a0, v8
+; RV64M-NEXT:    li a1, 13
+; RV64M-NEXT:    mulw a0, a0, a1
+; RV64M-NEXT:    ret
   %bo = mul <4 x i32> %x, <i32 11, i32 12, i32 13, i32 14>
   %ext = extractelement <4 x i32> %bo, i32 2
   ret i32 %ext
 }
 
 define i32 @extractelt_sdiv_v4i32(<4 x i32> %x) {
 ; RV32NOM-LABEL: extractelt_sdiv_v4i32:
 ; RV32NOM:       # %bb.0:

 ; RV32M-NEXT:    lui a1, 322639
 ; RV32M-NEXT:    addi a1, a1, -945
 ; RV32M-NEXT:    mulh a0, a0, a1
 ; RV32M-NEXT:    srli a1, a0, 31
 ; RV32M-NEXT:    srai a0, a0, 2
 ; RV32M-NEXT:    add a0, a0, a1
 ; RV32M-NEXT:    ret
 ;
-; RV64-LABEL: extractelt_sdiv_v4i32:
-; RV64:       # %bb.0:
-; RV64-NEXT:    vsetivli zero, 4, e32, m1, ta, ma
-; RV64-NEXT:    vmv.v.i v9, -1
-; RV64-NEXT:    vmv.v.i v10, 0
-; RV64-NEXT:    vslideup.vi v10, v9, 3
-; RV64-NEXT:    lui a0, %hi(.LCPI38_0)
-; RV64-NEXT:    addi a0, a0, %lo(.LCPI38_0)
-; RV64-NEXT:    vle32.v v9, (a0)
-; RV64-NEXT:    lui a0, %hi(.LCPI38_1)
-; RV64-NEXT:    addi a0, a0, %lo(.LCPI38_1)
-; RV64-NEXT:    vle32.v v11, (a0)
-; RV64-NEXT:    vand.vv v10, v8, v10
-; RV64-NEXT:    vmulh.vv v8, v8, v9
-; RV64-NEXT:    vadd.vv v8, v8, v10
-; RV64-NEXT:    vsra.vv v8, v8, v11
-; RV64-NEXT:    vsrl.vi v9, v8, 31
-; RV64-NEXT:    vadd.vv v8, v8, v9
-; RV64-NEXT:    vslidedown.vi v8, v8, 2
-; RV64-NEXT:    vmv.x.s a0, v8
-; RV64-NEXT:    ret
+; RV64NOM-LABEL: extractelt_sdiv_v4i32:
+; RV64NOM:       # %bb.0:
+; RV64NOM-NEXT:    vsetivli zero, 4, e32, m1, ta, ma
+; RV64NOM-NEXT:    vmv.v.i v9, -1
+; RV64NOM-NEXT:    vmv.v.i v10, 0
+; RV64NOM-NEXT:    vslideup.vi v10, v9, 3
+; RV64NOM-NEXT:    lui a0, %hi(.LCPI38_0)
+; RV64NOM-NEXT:    addi a0, a0, %lo(.LCPI38_0)
+; RV64NOM-NEXT:    vle32.v v9, (a0)
+; RV64NOM-NEXT:    lui a0, %hi(.LCPI38_1)
+; RV64NOM-NEXT:    addi a0, a0, %lo(.LCPI38_1)
+; RV64NOM-NEXT:    vle32.v v11, (a0)
+; RV64NOM-NEXT:    vand.vv v10, v8, v10
+; RV64NOM-NEXT:    vmulh.vv v8, v8, v9
+; RV64NOM-NEXT:    vadd.vv v8, v8, v10
+; RV64NOM-NEXT:    vsra.vv v8, v8, v11
+; RV64NOM-NEXT:    vsrl.vi v9, v8, 31
+; RV64NOM-NEXT:    vadd.vv v8, v8, v9
+; RV64NOM-NEXT:    vslidedown.vi v8, v8, 2
+; RV64NOM-NEXT:    vmv.x.s a0, v8
+; RV64NOM-NEXT:    ret
+;
+; RV64M-LABEL: extractelt_sdiv_v4i32:
+; RV64M:       # %bb.0:
+; RV64M-NEXT:    vsetivli zero, 1, e32, m1, ta, ma
+; RV64M-NEXT:    vslidedown.vi v8, v8, 2
+; RV64M-NEXT:    vmv.x.s a0, v8
+; RV64M-NEXT:    lui a1, 322639
+; RV64M-NEXT:    addiw a1, a1, -945
+; RV64M-NEXT:    mul a0, a0, a1
+; RV64M-NEXT:    srli a1, a0, 63
+; RV64M-NEXT:    srai a0, a0, 34
+; RV64M-NEXT:    add a0, a0, a1
+; RV64M-NEXT:    ret
   %bo = sdiv <4 x i32> %x, <i32 11, i32 12, i32 13, i32 14>
   %ext = extractelement <4 x i32> %bo, i32 2
   ret i32 %ext
 }
 
 define i32 @extractelt_udiv_v4i32(<4 x i32> %x) {
 ; RV32NOM-LABEL: extractelt_udiv_v4i32:
 ; RV32NOM:       # %bb.0:

 ; RV32M-NEXT:    vslidedown.vi v8, v8, 2
 ; RV32M-NEXT:    vmv.x.s a0, v8
 ; RV32M-NEXT:    lui a1, 322639
 ; RV32M-NEXT:    addi a1, a1, -945
 ; RV32M-NEXT:    mulhu a0, a0, a1
 ; RV32M-NEXT:    srli a0, a0, 2
 ; RV32M-NEXT:    ret
 ;
-; RV64-LABEL: extractelt_udiv_v4i32:
-; RV64:       # %bb.0:
-; RV64-NEXT:    vsetivli zero, 4, e32, m1, ta, ma
-; RV64-NEXT:    vsrl.vi v8, v8, 0
-; RV64-NEXT:    lui a0, 322639
-; RV64-NEXT:    addiw a0, a0, -945
-; RV64-NEXT:    vmulhu.vx v8, v8, a0
-; RV64-NEXT:    vsrl.vi v8, v8, 2
-; RV64-NEXT:    vslidedown.vi v8, v8, 2
-; RV64-NEXT:    vmv.x.s a0, v8
-; RV64-NEXT:    ret
+; RV64NOM-LABEL: extractelt_udiv_v4i32:
+; RV64NOM:       # %bb.0:
+; RV64NOM-NEXT:    vsetivli zero, 4, e32, m1, ta, ma
+; RV64NOM-NEXT:    vsrl.vi v8, v8, 0
+; RV64NOM-NEXT:    lui a0, 322639
+; RV64NOM-NEXT:    addiw a0, a0, -945
+; RV64NOM-NEXT:    vmulhu.vx v8, v8, a0
+; RV64NOM-NEXT:    vslidedown.vi v8, v8, 2
+; RV64NOM-NEXT:    vmv.x.s a0, v8
+; RV64NOM-NEXT:    slli a0, a0, 33
+; RV64NOM-NEXT:    srli a0, a0, 35
+; RV64NOM-NEXT:    ret
+;
+; RV64M-LABEL: extractelt_udiv_v4i32:
+; RV64M:       # %bb.0:
+; RV64M-NEXT:    vsetivli zero, 1, e32, m1, ta, ma
+; RV64M-NEXT:    vslidedown.vi v8, v8, 2
+; RV64M-NEXT:    vmv.x.s a0, v8
+; RV64M-NEXT:    slli a0, a0, 32
+; RV64M-NEXT:    lui a1, 322639
+; RV64M-NEXT:    addiw a1, a1, -945
+; RV64M-NEXT:    slli a1, a1, 32
+; RV64M-NEXT:    mulhu a0, a0, a1
+; RV64M-NEXT:    srli a0, a0, 34
+; RV64M-NEXT:    ret
   %bo = udiv <4 x i32> %x, <i32 11, i32 12, i32 13, i32 14>
   %ext = extractelement <4 x i32> %bo, i32 2
   ret i32 %ext
 }
 
 define float @extractelt_fadd_v4f32(<4 x float> %x) {
 ; CHECK-LABEL: extractelt_fadd_v4f32:
 ; CHECK:       # %bb.0: