[RISCV] Support extract_vector_elt for fixed and scalable masked registers.

[craig.topper]

Summary

This uses a really simple approach of converting to an i8 vector
and extracting. This is probably not the best approach especially
if you know the index is constant.

Other ideas:
-Store to stack temporary using vse1, load as scalar and shift.
-Sort of bitcast the vector to a vector of i8, slide down the
appropriate 8 bit element, copy to scalar, shift down the
correct bit within the 8 bits we extracted. Not exactly sure
how to describe such a bitcast from i1 vector to i8 vector
within the type system for elements less than 8.

[frasercrmck]

Does this need to be limited to fixed-length vectors? We're currently unable to do this on scalable vectors too.

As you say, I suspect for vectors of (vscale x) 8/16/32/64/etc x i1 we 'd be better bitcasting to i8, extract an element and shift down any remaining bits. Not sure what's best for 2/4. Insert into a larger vector and do the same process? Same problem as for subvectors, really. A set of mask-vector slide instructions would be great.

[craig.topper]

-Support scalable vector.
-Add tests.

[frasercrmck]

LGTM

llvm/lib/Target/RISCV/RISCVISelLowering.cpp

if (Subtarget.hasStdExtV()) {
 
     for (MVT VT : BoolVecVTs) {
       setOperationAction(ISD::SPLAT_VECTOR, VT, Legal);
 
       // Mask VTs are custom-expanded into a series of standard nodes
       setOperationAction(ISD::TRUNCATE, VT, Custom);
       setOperationAction(ISD::INSERT_SUBVECTOR, VT, Custom);
       setOperationAction(ISD::EXTRACT_SUBVECTOR, VT, Custom);
+
+      setOperationAction(ISD::EXTRACT_VECTOR_ELT, VT, Custom);
     }
 
     for (MVT VT : IntVecVTs) {
       setOperationAction(ISD::SPLAT_VECTOR, VT, Legal);
       setOperationAction(ISD::SPLAT_VECTOR_PARTS, VT, Custom);
 
       setOperationAction(ISD::SMIN, VT, Legal);
       setOperationAction(ISD::SMAX, VT, Legal);
if (Subtarget.useRVVForFixedLengthVectors()) {
 
         // We use EXTRACT_SUBVECTOR as a "cast" from scalable to fixed.
         setOperationAction(ISD::INSERT_SUBVECTOR, VT, Custom);
         setOperationAction(ISD::EXTRACT_SUBVECTOR, VT, Custom);
 
         setOperationAction(ISD::BUILD_VECTOR, VT, Custom);
         setOperationAction(ISD::CONCAT_VECTORS, VT, Custom);
 
+        setOperationAction(ISD::EXTRACT_VECTOR_ELT, VT, Custom);
+
         setOperationAction(ISD::LOAD, VT, Custom);
         setOperationAction(ISD::STORE, VT, Custom);
 
         setOperationAction(ISD::SETCC, VT, Custom);
 
         setOperationAction(ISD::TRUNCATE, VT, Custom);
 
         // Operations below are different for between masks and other vectors.
         if (VT.getVectorElementType() == MVT::i1) {
           setOperationAction(ISD::AND, VT, Custom);
           setOperationAction(ISD::OR, VT, Custom);
           setOperationAction(ISD::XOR, VT, Custom);
           continue;
         }
 
         setOperationAction(ISD::VECTOR_SHUFFLE, VT, Custom);
         setOperationAction(ISD::INSERT_VECTOR_ELT, VT, Custom);
-        setOperationAction(ISD::EXTRACT_VECTOR_ELT, VT, Custom);
 
         setOperationAction(ISD::ADD, VT, Custom);
         setOperationAction(ISD::MUL, VT, Custom);
         setOperationAction(ISD::SUB, VT, Custom);
         setOperationAction(ISD::AND, VT, Custom);
         setOperationAction(ISD::OR, VT, Custom);
         setOperationAction(ISD::XOR, VT, Custom);
         setOperationAction(ISD::SDIV, VT, Custom);
SDValue RISCVTargetLowering::lowerEXTRACT_VECTOR_ELT(SDValue Op,
                                                      SelectionDAG &DAG) const {
   SDLoc DL(Op);
   SDValue Idx = Op.getOperand(1);
   SDValue Vec = Op.getOperand(0);
   EVT EltVT = Op.getValueType();
   MVT VecVT = Vec.getSimpleValueType();
   MVT XLenVT = Subtarget.getXLenVT();
 
+  if (VecVT.getVectorElementType() == MVT::i1) {
+    // FIXME: For now we just promote to an i8 vector and extract from that,
+    // but this is probably not optimal.
+    MVT WideVT = MVT::getVectorVT(MVT::i8, VecVT.getVectorElementCount());
+    Vec = DAG.getNode(ISD::ZERO_EXTEND, DL, WideVT, Vec);
+    return DAG.getNode(ISD::EXTRACT_VECTOR_ELT, DL, EltVT, Vec, Idx);
+  }
+
   // If this is a fixed vector, we need to convert it to a scalable vector.
   MVT ContainerVT = VecVT;
   if (VecVT.isFixedLengthVector()) {
     ContainerVT = getContainerForFixedLengthVector(VecVT);
     Vec = convertToScalableVector(ContainerVT, Vec, DAG, Subtarget);
   }
 
   // If the index is 0, the vector is already in the right position.

llvm/test/CodeGen/RISCV/rvv/extractelt-i1.ll

+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc -mtriple=riscv32 -mattr=+experimental-v -verify-machineinstrs < %s | FileCheck %s --check-prefixes=CHECK
+; RUN: llc -mtriple=riscv64 -mattr=+experimental-v -verify-machineinstrs < %s | FileCheck %s --check-prefixes=CHECK
+
+define i1 @extractelt_nxv1i1(<vscale x 1 x i8>* %x, i64 %idx) nounwind {
+; CHECK-LABEL: extractelt_nxv1i1:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    vsetvli a2, zero, e8,mf8,ta,mu
+; CHECK-NEXT:    vle8.v v25, (a0)
+; CHECK-NEXT:    vmseq.vi v0, v25, 0
+; CHECK-NEXT:    vmv.v.i v25, 0
+; CHECK-NEXT:    vmerge.vim v25, v25, 1, v0
+; CHECK-NEXT:    vsetivli a0, 1, e8,mf8,ta,mu
+; CHECK-NEXT:    vslidedown.vx v25, v25, a1
+; CHECK-NEXT:    vmv.x.s a0, v25
+; CHECK-NEXT:    ret
+  %a = load <vscale x 1 x i8>, <vscale x 1 x i8>* %x
+  %b = icmp eq <vscale x 1 x i8> %a, zeroinitializer
+  %c = extractelement <vscale x 1 x i1> %b, i64 %idx
+  ret i1 %c
+}
+
+define i1 @extractelt_nxv2i1(<vscale x 2 x i8>* %x, i64 %idx) nounwind {
+; CHECK-LABEL: extractelt_nxv2i1:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    vsetvli a2, zero, e8,mf4,ta,mu
+; CHECK-NEXT:    vle8.v v25, (a0)
+; CHECK-NEXT:    vmseq.vi v0, v25, 0
+; CHECK-NEXT:    vmv.v.i v25, 0
+; CHECK-NEXT:    vmerge.vim v25, v25, 1, v0
+; CHECK-NEXT:    vsetivli a0, 1, e8,mf4,ta,mu
+; CHECK-NEXT:    vslidedown.vx v25, v25, a1
+; CHECK-NEXT:    vmv.x.s a0, v25
+; CHECK-NEXT:    ret
+  %a = load <vscale x 2 x i8>, <vscale x 2 x i8>* %x
+  %b = icmp eq <vscale x 2 x i8> %a, zeroinitializer
+  %c = extractelement <vscale x 2 x i1> %b, i64 %idx
+  ret i1 %c
+}
+
+define i1 @extractelt_nxv4i1(<vscale x 4 x i8>* %x, i64 %idx) nounwind {
+; CHECK-LABEL: extractelt_nxv4i1:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    vsetvli a2, zero, e8,mf2,ta,mu
+; CHECK-NEXT:    vle8.v v25, (a0)
+; CHECK-NEXT:    vmseq.vi v0, v25, 0
+; CHECK-NEXT:    vmv.v.i v25, 0
+; CHECK-NEXT:    vmerge.vim v25, v25, 1, v0
+; CHECK-NEXT:    vsetivli a0, 1, e8,mf2,ta,mu
+; CHECK-NEXT:    vslidedown.vx v25, v25, a1
+; CHECK-NEXT:    vmv.x.s a0, v25
+; CHECK-NEXT:    ret
+  %a = load <vscale x 4 x i8>, <vscale x 4 x i8>* %x
+  %b = icmp eq <vscale x 4 x i8> %a, zeroinitializer
+  %c = extractelement <vscale x 4 x i1> %b, i64 %idx
+  ret i1 %c
+}
+
+define i1 @extractelt_nxv8i1(<vscale x 8 x i8>* %x, i64 %idx) nounwind {
+; CHECK-LABEL: extractelt_nxv8i1:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    vl1r.v v25, (a0)
+; CHECK-NEXT:    vsetvli a0, zero, e8,m1,ta,mu
+; CHECK-NEXT:    vmseq.vi v0, v25, 0
+; CHECK-NEXT:    vmv.v.i v25, 0
+; CHECK-NEXT:    vmerge.vim v25, v25, 1, v0
+; CHECK-NEXT:    vsetivli a0, 1, e8,m1,ta,mu
+; CHECK-NEXT:    vslidedown.vx v25, v25, a1
+; CHECK-NEXT:    vmv.x.s a0, v25
+; CHECK-NEXT:    ret
+  %a = load <vscale x 8 x i8>, <vscale x 8 x i8>* %x
+  %b = icmp eq <vscale x 8 x i8> %a, zeroinitializer
+  %c = extractelement <vscale x 8 x i1> %b, i64 %idx
+  ret i1 %c
+}
+
+define i1 @extractelt_nxv16i1(<vscale x 16 x i8>* %x, i64 %idx) nounwind {
+; CHECK-LABEL: extractelt_nxv16i1:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    vl2r.v v26, (a0)
+; CHECK-NEXT:    vsetvli a0, zero, e8,m2,ta,mu
+; CHECK-NEXT:    vmseq.vi v0, v26, 0
+; CHECK-NEXT:    vmv.v.i v26, 0
+; CHECK-NEXT:    vmerge.vim v26, v26, 1, v0
+; CHECK-NEXT:    vsetivli a0, 1, e8,m2,ta,mu
+; CHECK-NEXT:    vslidedown.vx v26, v26, a1
+; CHECK-NEXT:    vmv.x.s a0, v26
+; CHECK-NEXT:    ret
+  %a = load <vscale x 16 x i8>, <vscale x 16 x i8>* %x
+  %b = icmp eq <vscale x 16 x i8> %a, zeroinitializer
+  %c = extractelement <vscale x 16 x i1> %b, i64 %idx
+  ret i1 %c
+}
+
+define i1 @extractelt_nxv32i1(<vscale x 32 x i8>* %x, i64 %idx) nounwind {
+; CHECK-LABEL: extractelt_nxv32i1:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    vl4r.v v28, (a0)
+; CHECK-NEXT:    vsetvli a0, zero, e8,m4,ta,mu
+; CHECK-NEXT:    vmseq.vi v0, v28, 0
+; CHECK-NEXT:    vmv.v.i v28, 0
+; CHECK-NEXT:    vmerge.vim v28, v28, 1, v0
+; CHECK-NEXT:    vsetivli a0, 1, e8,m4,ta,mu
+; CHECK-NEXT:    vslidedown.vx v28, v28, a1
+; CHECK-NEXT:    vmv.x.s a0, v28
+; CHECK-NEXT:    ret
+  %a = load <vscale x 32 x i8>, <vscale x 32 x i8>* %x
+  %b = icmp eq <vscale x 32 x i8> %a, zeroinitializer
+  %c = extractelement <vscale x 32 x i1> %b, i64 %idx
+  ret i1 %c
+}
+
+define i1 @extractelt_nxv64i1(<vscale x 64 x i8>* %x, i64 %idx) nounwind {
+; CHECK-LABEL: extractelt_nxv64i1:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    vl8r.v v8, (a0)
+; CHECK-NEXT:    vsetvli a0, zero, e8,m8,ta,mu
+; CHECK-NEXT:    vmseq.vi v0, v8, 0
+; CHECK-NEXT:    vmv.v.i v8, 0
+; CHECK-NEXT:    vmerge.vim v8, v8, 1, v0
+; CHECK-NEXT:    vsetivli a0, 1, e8,m8,ta,mu
+; CHECK-NEXT:    vslidedown.vx v8, v8, a1
+; CHECK-NEXT:    vmv.x.s a0, v8
+; CHECK-NEXT:    ret
+  %a = load <vscale x 64 x i8>, <vscale x 64 x i8>* %x
+  %b = icmp eq <vscale x 64 x i8> %a, zeroinitializer
+  %c = extractelement <vscale x 64 x i1> %b, i64 %idx
+  ret i1 %c
+}

llvm/test/CodeGen/RISCV/rvv/fixed-vectors-extract-i1.ll

+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc -mtriple=riscv32 -target-abi=ilp32d -mattr=+experimental-v,+experimental-zfh,+f,+d -verify-machineinstrs -riscv-v-vector-bits-min=128 -verify-machineinstrs < %s | FileCheck %s --check-prefixes=CHECK,RV32
+; RUN: llc -mtriple=riscv64 -target-abi=lp64d -mattr=+experimental-v,+experimental-zfh,+f,+d -verify-machineinstrs -riscv-v-vector-bits-min=128 -verify-machineinstrs < %s | FileCheck %s --check-prefixes=CHECK,RV64
+
+define i1 @extractelt_v1i1(<1 x i8>* %x, i64 %idx) nounwind {
+; CHECK-LABEL: extractelt_v1i1:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    vsetivli a2, 1, e8,m1,ta,mu
+; CHECK-NEXT:    vle8.v v25, (a0)
+; CHECK-NEXT:    vmseq.vi v0, v25, 0
+; CHECK-NEXT:    vmv.v.i v25, 0
+; CHECK-NEXT:    vmerge.vim v25, v25, 1, v0
+; CHECK-NEXT:    vslidedown.vx v25, v25, a1
+; CHECK-NEXT:    vmv.x.s a0, v25
+; CHECK-NEXT:    ret
+  %a = load <1 x i8>, <1 x i8>* %x
+  %b = icmp eq <1 x i8> %a, zeroinitializer
+  %c = extractelement <1 x i1> %b, i64 %idx
+  ret i1 %c
+}
+
+define i1 @extractelt_v2i1(<2 x i8>* %x, i64 %idx) nounwind {
+; CHECK-LABEL: extractelt_v2i1:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    vsetivli a2, 2, e8,m1,ta,mu
+; CHECK-NEXT:    vle8.v v25, (a0)
+; CHECK-NEXT:    vmseq.vi v0, v25, 0
+; CHECK-NEXT:    vmv.v.i v25, 0
+; CHECK-NEXT:    vmerge.vim v25, v25, 1, v0
+; CHECK-NEXT:    vsetivli a0, 1, e8,m1,ta,mu
+; CHECK-NEXT:    vslidedown.vx v25, v25, a1
+; CHECK-NEXT:    vmv.x.s a0, v25
+; CHECK-NEXT:    ret
+  %a = load <2 x i8>, <2 x i8>* %x
+  %b = icmp eq <2 x i8> %a, zeroinitializer
+  %c = extractelement <2 x i1> %b, i64 %idx
+  ret i1 %c
+}
+
+define i1 @extractelt_v4i1(<4 x i8>* %x, i64 %idx) nounwind {
+; CHECK-LABEL: extractelt_v4i1:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    vsetivli a2, 4, e8,m1,ta,mu
+; CHECK-NEXT:    vle8.v v25, (a0)
+; CHECK-NEXT:    vmseq.vi v0, v25, 0
+; CHECK-NEXT:    vmv.v.i v25, 0
+; CHECK-NEXT:    vmerge.vim v25, v25, 1, v0
+; CHECK-NEXT:    vsetivli a0, 1, e8,m1,ta,mu
+; CHECK-NEXT:    vslidedown.vx v25, v25, a1
+; CHECK-NEXT:    vmv.x.s a0, v25
+; CHECK-NEXT:    ret
+  %a = load <4 x i8>, <4 x i8>* %x
+  %b = icmp eq <4 x i8> %a, zeroinitializer
+  %c = extractelement <4 x i1> %b, i64 %idx
+  ret i1 %c
+}
+
+define i1 @extractelt_v8i1(<8 x i8>* %x, i64 %idx) nounwind {
+; CHECK-LABEL: extractelt_v8i1:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    vsetivli a2, 8, e8,m1,ta,mu
+; CHECK-NEXT:    vle8.v v25, (a0)
+; CHECK-NEXT:    vmseq.vi v0, v25, 0
+; CHECK-NEXT:    vmv.v.i v25, 0
+; CHECK-NEXT:    vmerge.vim v25, v25, 1, v0
+; CHECK-NEXT:    vsetivli a0, 1, e8,m1,ta,mu
+; CHECK-NEXT:    vslidedown.vx v25, v25, a1
+; CHECK-NEXT:    vmv.x.s a0, v25
+; CHECK-NEXT:    ret
+  %a = load <8 x i8>, <8 x i8>* %x
+  %b = icmp eq <8 x i8> %a, zeroinitializer
+  %c = extractelement <8 x i1> %b, i64 %idx
+  ret i1 %c
+}
+
+define i1 @extractelt_v16i1(<16 x i8>* %x, i64 %idx) nounwind {
+; CHECK-LABEL: extractelt_v16i1:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    vsetivli a2, 16, e8,m1,ta,mu
+; CHECK-NEXT:    vle8.v v25, (a0)
+; CHECK-NEXT:    vmseq.vi v0, v25, 0
+; CHECK-NEXT:    vmv.v.i v25, 0
+; CHECK-NEXT:    vmerge.vim v25, v25, 1, v0
+; CHECK-NEXT:    vsetivli a0, 1, e8,m1,ta,mu
+; CHECK-NEXT:    vslidedown.vx v25, v25, a1
+; CHECK-NEXT:    vmv.x.s a0, v25
+; CHECK-NEXT:    ret
+  %a = load <16 x i8>, <16 x i8>* %x
+  %b = icmp eq <16 x i8> %a, zeroinitializer
+  %c = extractelement <16 x i1> %b, i64 %idx
+  ret i1 %c
+}
+
+define i1 @extractelt_v32i1(<32 x i8>* %x, i64 %idx) nounwind {
+; CHECK-LABEL: extractelt_v32i1:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    addi a2, zero, 32
+; CHECK-NEXT:    vsetvli a2, a2, e8,m2,ta,mu
+; CHECK-NEXT:    vle8.v v26, (a0)
+; CHECK-NEXT:    vmseq.vi v0, v26, 0
+; CHECK-NEXT:    vmv.v.i v26, 0
+; CHECK-NEXT:    vmerge.vim v26, v26, 1, v0
+; CHECK-NEXT:    vsetivli a0, 1, e8,m2,ta,mu
+; CHECK-NEXT:    vslidedown.vx v26, v26, a1
+; CHECK-NEXT:    vmv.x.s a0, v26
+; CHECK-NEXT:    ret
+  %a = load <32 x i8>, <32 x i8>* %x
+  %b = icmp eq <32 x i8> %a, zeroinitializer
+  %c = extractelement <32 x i1> %b, i64 %idx
+  ret i1 %c
+}
+
+define i1 @extractelt_v64i1(<64 x i8>* %x, i64 %idx) nounwind {
+; CHECK-LABEL: extractelt_v64i1:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    addi a2, zero, 64
+; CHECK-NEXT:    vsetvli a2, a2, e8,m4,ta,mu
+; CHECK-NEXT:    vle8.v v28, (a0)
+; CHECK-NEXT:    vmseq.vi v0, v28, 0
+; CHECK-NEXT:    vmv.v.i v28, 0
+; CHECK-NEXT:    vmerge.vim v28, v28, 1, v0
+; CHECK-NEXT:    vsetivli a0, 1, e8,m4,ta,mu
+; CHECK-NEXT:    vslidedown.vx v28, v28, a1
+; CHECK-NEXT:    vmv.x.s a0, v28
+; CHECK-NEXT:    ret
+  %a = load <64 x i8>, <64 x i8>* %x
+  %b = icmp eq <64 x i8> %a, zeroinitializer
+  %c = extractelement <64 x i1> %b, i64 %idx
+  ret i1 %c
+}
+
+define i1 @extractelt_v128i1(<128 x i8>* %x, i64 %idx) nounwind {
+; CHECK-LABEL: extractelt_v128i1:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    addi a2, zero, 128
+; CHECK-NEXT:    vsetvli a2, a2, e8,m8,ta,mu
+; CHECK-NEXT:    vle8.v v8, (a0)
+; CHECK-NEXT:    vmseq.vi v0, v8, 0
+; CHECK-NEXT:    vmv.v.i v8, 0
+; CHECK-NEXT:    vmerge.vim v8, v8, 1, v0
+; CHECK-NEXT:    vsetivli a0, 1, e8,m8,ta,mu
+; CHECK-NEXT:    vslidedown.vx v8, v8, a1
+; CHECK-NEXT:    vmv.x.s a0, v8
+; CHECK-NEXT:    ret
+  %a = load <128 x i8>, <128 x i8>* %x
+  %b = icmp eq <128 x i8> %a, zeroinitializer
+  %c = extractelement <128 x i1> %b, i64 %idx
+  ret i1 %c
+}
+
+define i1 @extractelt_v256i1(<256 x i8>* %x, i64 %idx) nounwind {
+; RV32-LABEL: extractelt_v256i1:
+; RV32:       # %bb.0:
+; RV32-NEXT:    addi sp, sp, -384
+; RV32-NEXT:    sw ra, 380(sp) # 4-byte Folded Spill
+; RV32-NEXT:    sw s0, 376(sp) # 4-byte Folded Spill
+; RV32-NEXT:    addi s0, sp, 384
+; RV32-NEXT:    andi sp, sp, -128
+; RV32-NEXT:    andi a1, a1, 255
+; RV32-NEXT:    addi a2, a0, 128
+; RV32-NEXT:    addi a3, zero, 128
+; RV32-NEXT:    vsetvli a3, a3, e8,m8,ta,mu
+; RV32-NEXT:    vle8.v v8, (a0)
+; RV32-NEXT:    vle8.v v16, (a2)
+; RV32-NEXT:    mv a0, sp
+; RV32-NEXT:    add a0, a0, a1
+; RV32-NEXT:    vmseq.vi v25, v8, 0
+; RV32-NEXT:    vmseq.vi v0, v16, 0
+; RV32-NEXT:    vmv.v.i v8, 0
+; RV32-NEXT:    vmerge.vim v16, v8, 1, v0
+; RV32-NEXT:    addi a1, sp, 128
+; RV32-NEXT:    vse8.v v16, (a1)
+; RV32-NEXT:    vmv1r.v v0, v25
+; RV32-NEXT:    vmerge.vim v8, v8, 1, v0
+; RV32-NEXT:    vse8.v v8, (sp)
+; RV32-NEXT:    lb a0, 0(a0)
+; RV32-NEXT:    addi sp, s0, -384
+; RV32-NEXT:    lw s0, 376(sp) # 4-byte Folded Reload
+; RV32-NEXT:    lw ra, 380(sp) # 4-byte Folded Reload
+; RV32-NEXT:    addi sp, sp, 384
+; RV32-NEXT:    ret
+;
+; RV64-LABEL: extractelt_v256i1:
+; RV64:       # %bb.0:
+; RV64-NEXT:    addi sp, sp, -384
+; RV64-NEXT:    sd ra, 376(sp) # 8-byte Folded Spill
+; RV64-NEXT:    sd s0, 368(sp) # 8-byte Folded Spill
+; RV64-NEXT:    addi s0, sp, 384
+; RV64-NEXT:    andi sp, sp, -128
+; RV64-NEXT:    andi a1, a1, 255
+; RV64-NEXT:    addi a2, a0, 128
+; RV64-NEXT:    addi a3, zero, 128
+; RV64-NEXT:    vsetvli a3, a3, e8,m8,ta,mu
+; RV64-NEXT:    vle8.v v8, (a0)
+; RV64-NEXT:    vle8.v v16, (a2)
+; RV64-NEXT:    mv a0, sp
+; RV64-NEXT:    add a0, a0, a1
+; RV64-NEXT:    vmseq.vi v25, v8, 0
+; RV64-NEXT:    vmseq.vi v0, v16, 0
+; RV64-NEXT:    vmv.v.i v8, 0
+; RV64-NEXT:    vmerge.vim v16, v8, 1, v0
+; RV64-NEXT:    addi a1, sp, 128
+; RV64-NEXT:    vse8.v v16, (a1)
+; RV64-NEXT:    vmv1r.v v0, v25
+; RV64-NEXT:    vmerge.vim v8, v8, 1, v0
+; RV64-NEXT:    vse8.v v8, (sp)
+; RV64-NEXT:    lb a0, 0(a0)
+; RV64-NEXT:    addi sp, s0, -384
+; RV64-NEXT:    ld s0, 368(sp) # 8-byte Folded Reload
+; RV64-NEXT:    ld ra, 376(sp) # 8-byte Folded Reload
+; RV64-NEXT:    addi sp, sp, 384
+; RV64-NEXT:    ret
+  %a = load <256 x i8>, <256 x i8>* %x
+  %b = icmp eq <256 x i8> %a, zeroinitializer
+  %c = extractelement <256 x i1> %b, i64 %idx
+  ret i1 %c
+}