[HLSL] [DirectX] Unsupported intrinsic `llvm.fshl.i64` for DXIL lowering

[Icohedron]

https://godbolt.org/z/f6r7ThrcG

For the following shader, Clang emits the llvm.fshl.i64 intrinsic which is not supported for DXIL lowering.

struct Pair {
    int32_t a;
    int32_t b;
};
RWStructuredBuffer<Pair> src;
RWStructuredBuffer<Pair> dest;
Pair Swap(Pair p) {
    Pair result;
    result.a = p.b;
    result.b = p.a;
    return result;
}
[numthreads(1, 1, 1)]
void CSMain(uint3 Tid : SV_GroupThreadID) {
    dest[Tid.x] = Swap(src[Tid.x]);
}

edit: This can also be generated with a rotation left function in HLSL demonstrated here: https://godbolt.org/z/a44Pnohn4

define void @CSMain() local_unnamed_addr #1 {
entry:
  %0 = tail call target("dx.RawBuffer", %struct.Pair, 1, 0) @llvm.dx.resource.handlefromimplicitbinding.tdx.RawBuffer_s_struct.Pairs_1_0t(i32 0, i32 0, i32 1, i32 0, ptr nonnull @.str)
  %1 = tail call target("dx.RawBuffer", %struct.Pair, 1, 0) @llvm.dx.resource.handlefromimplicitbinding.tdx.RawBuffer_s_struct.Pairs_1_0t(i32 2, i32 0, i32 1, i32 0, ptr nonnull @.str.2)
  %2 = tail call i32 @llvm.dx.thread.id.in.group(i32 0)
  %3 = tail call noundef nonnull align 1 dereferenceable(8) ptr @llvm.dx.resource.getpointer.p0.tdx.RawBuffer_s_struct.Pairs_1_0t(target("dx.RawBuffer", %struct.Pair, 1, 0) %0, i32 %2)
  %4 = load i64, ptr %3, align 1
  %5 = tail call noundef nonnull align 1 dereferenceable(8) ptr @llvm.dx.resource.getpointer.p0.tdx.RawBuffer_s_struct.Pairs_1_0t(target("dx.RawBuffer", %struct.Pair, 1, 0) %1, i32 %2)
  %ref.tmp.i.sroa.0.0.insert.insert = tail call i64 @llvm.fshl.i64(i64 %4, i64 %4, i64 32)
  store i64 %ref.tmp.i.sroa.0.0.insert.insert, ptr %5, align 1
  ret void
}

[Icohedron]

First see if the solution to #165753 would resolve this, as this intrinsic only applies to the i64 type which shouldn't be kept around in the DXIL because the HLSL does not use i64.

[inbelic]

First see if the solution to #165753 would resolve this, as this intrinsic only applies to the i64 type which shouldn't be kept around in the DXIL because the HLSL does not use i64.

edit:

Locally fixing the other issue also resolves this as expected. I will make sure to link the pr for the other issue as resolving this as well.

Blocking on the resolution of above issue.

This issue can also be reproduced directly by defining a rotate left function: https://godbolt.org/z/a44Pnohn4.

This means the above issue will not solve this issue generally.