`LLVM ERROR: Cannot select: t391: v16f32 = fp_extend t442` where ` t442: v16bf16`

[joker-eph]

LLVM ERROR: Cannot select: t391: v16f32 = fp_extend t442
  t442: v16bf16,ch = load<(load (s256) from %stack.1 + 32)> t438, t624, undef:i64
    t624: i64 = or FrameIndex:i64<1>, Constant:i64<32>
      t437: i64 = FrameIndex<1>
      t440: i64 = Constant<32>
    t15: i64 = undef
In function: dump_vec

Here is the input to SelectionDag from a debug log:

[LowerAMXTYpe][combineAMXcast] IR dump after optimizeAMXCastFromPhi:
define void @dump_vec(ptr %0) {
  %2 = call { ptr, ptr, i64, [1 x i64], [1 x i64] } @sparseValuesBF16(ptr %0)
  %3 = extractvalue { ptr, ptr, i64, [1 x i64], [1 x i64] } %2, 3, 0
  %4 = trunc i64 %3 to i32
  %5 = insertelement <32 x i32> undef, i32 %4, i32 0
  %6 = shufflevector <32 x i32> %5, <32 x i32> undef, <32 x i32> zeroinitializer
  %7 = icmp sgt <32 x i32> %6, <i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7, i32 8, i32 9, i32 10, i32 11, i32 12, i32 13, i32 14, i32 15, i32 16, i32 17, i32 18, i32 19, i32 20, i32 21, i32 22, i32 23, i32 24, i32 25, i32 26, i32 27, i32 28, i32 29, i32 30, i32 31>
  %8 = extractvalue { ptr, ptr, i64, [1 x i64], [1 x i64] } %2, 1
  %9 = getelementptr bfloat, ptr %8, i64 0
  %10 = call <32 x bfloat> @llvm.masked.load.v32bf16.p0(ptr %9, i32 2, <32 x i1> %7, <32 x bfloat> <bfloat 0xRBF80, bfloat 0xRBF80, bfloat 0xRBF80, bfloat 0xRBF80, bfloat 0xRBF80, bfloat 0xRBF80, bfloat 0xRBF80, bfloat 0xRBF80, bfloat 0xRBF80, bfloat 0xRBF80, bfloat 0xRBF80, bfloat 0xRBF80, bfloat 0xRBF80, bfloat 0xRBF80, bfloat 0xRBF80, bfloat 0xRBF80, bfloat 0xRBF80, bfloat 0xRBF80, bfloat 0xRBF80, bfloat 0xRBF80, bfloat 0xRBF80, bfloat 0xRBF80, bfloat 0xRBF80, bfloat 0xRBF80, bfloat 0xRBF80, bfloat 0xRBF80, bfloat 0xRBF80, bfloat 0xRBF80, bfloat 0xRBF80, bfloat 0xRBF80, bfloat 0xRBF80, bfloat 0xRBF80>)
  %11 = fpext <32 x bfloat> %10 to <32 x float>
  call void @printOpen()
  %12 = extractelement <32 x float> %11, i64 0
  call void @printF32(float %12)
  call void @printComma()
  %13 = extractelement <32 x float> %11, i64 1
  call void @printF32(float %13)
  call void @printComma()
  %14 = extractelement <32 x float> %11, i64 2
  call void @printF32(float %14)
  call void @printComma()
  %15 = extractelement <32 x float> %11, i64 3
  call void @printF32(float %15)
  call void @printComma()
  %16 = extractelement <32 x float> %11, i64 4
  call void @printF32(float %16)
  call void @printComma()
  %17 = extractelement <32 x float> %11, i64 5
  call void @printF32(float %17)
  call void @printComma()
  %18 = extractelement <32 x float> %11, i64 6
  call void @printF32(float %18)
  call void @printComma()
  %19 = extractelement <32 x float> %11, i64 7
  call void @printF32(float %19)
  call void @printComma()
  %20 = extractelement <32 x float> %11, i64 8
  call void @printF32(float %20)
  call void @printComma()
  %21 = extractelement <32 x float> %11, i64 9
  call void @printF32(float %21)
  call void @printComma()
  %22 = extractelement <32 x float> %11, i64 10
  call void @printF32(float %22)
  call void @printComma()
  %23 = extractelement <32 x float> %11, i64 11
  call void @printF32(float %23)
  call void @printComma()
  %24 = extractelement <32 x float> %11, i64 12
  call void @printF32(float %24)
  call void @printComma()
  %25 = extractelement <32 x float> %11, i64 13
  call void @printF32(float %25)
  call void @printComma()
  %26 = extractelement <32 x float> %11, i64 14
  call void @printF32(float %26)
  call void @printComma()
  %27 = extractelement <32 x float> %11, i64 15
  call void @printF32(float %27)
  call void @printComma()
  %28 = extractelement <32 x float> %11, i64 16
  call void @printF32(float %28)
  call void @printComma()
  %29 = extractelement <32 x float> %11, i64 17
  call void @printF32(float %29)
  call void @printComma()
  %30 = extractelement <32 x float> %11, i64 18
  call void @printF32(float %30)
  call void @printComma()
  %31 = extractelement <32 x float> %11, i64 19
  call void @printF32(float %31)
  call void @printComma()
  %32 = extractelement <32 x float> %11, i64 20
  call void @printF32(float %32)
  call void @printComma()
  %33 = extractelement <32 x float> %11, i64 21
  call void @printF32(float %33)
  call void @printComma()
  %34 = extractelement <32 x float> %11, i64 22
  call void @printF32(float %34)
  call void @printComma()
  %35 = extractelement <32 x float> %11, i64 23
  call void @printF32(float %35)
  call void @printComma()
  %36 = extractelement <32 x float> %11, i64 24
  call void @printF32(float %36)
  call void @printComma()
  %37 = extractelement <32 x float> %11, i64 25
  call void @printF32(float %37)
  call void @printComma()
  %38 = extractelement <32 x float> %11, i64 26
  call void @printF32(float %38)
  call void @printComma()
  %39 = extractelement <32 x float> %11, i64 27
  call void @printF32(float %39)
  call void @printComma()
  %40 = extractelement <32 x float> %11, i64 28
  call void @printF32(float %40)
  call void @printComma()
  %41 = extractelement <32 x float> %11, i64 29
  call void @printF32(float %41)
  call void @printComma()
  %42 = extractelement <32 x float> %11, i64 30
  call void @printF32(float %42)
  call void @printComma()
  %43 = extractelement <32 x float> %11, i64 31
  call void @printF32(float %43)
  call void @printClose()
  call void @printNewline()
  ret void
}

Reproduce with the attached test running

bin/llc /tmp/test.ll  -mtriple=x86_64-unknown-linux-gnu   -mcpu="znver4"

test.ll.txt

[joker-eph]

Ping on this @phoebewang ? I think it'd be nice to fix it quickly and back port in 17.0.0

[phoebewang]

Sorry, busy on other tasks. Will try to solve it ASAP.

[tru]

What's the status on this issue? We are getting close to 17.x final, so it would be nice to know if we are still waiting for a issue fixed here.

[phoebewang]

I just root caused it but was stalled due to family issues. I'll back to it this week and hope solve it by EOW. I see the final date is Sep 5th. So think should be good to catch up with.

[phoebewang]

Candidate patch: https://reviews.llvm.org/D158950

[llvmbot]

@llvm/issue-subscribers-backend-x86

[joker-eph]

This fixes the crash, but somehow the test is providing incorrect result now:

llvm-project/mlir/test/Integration/Dialect/SparseTensor/CPU/dense_output_bf16.mlir:106:12: error: CHECK: expected string not found in input
 // CHECK: ( 1, 11, 0, 2, 13, 0, 0, 0, 0, 0, 14, 3, 0, 0, 0, 0, 15, 4, 16, 0, 5, 6, 0, 0, 0, 0, 0, 0, 7, 8, 0, 9 )
           ^
<stdin>:1:1: note: scanning from here
( 5.83155e-39, 5.98653e-39, 0, 5.87747e-39, 5.99801e-39, 0, 0, 0, 0, 0, 6.00375e-39, 5.90043e-39, 0, 0, 0, 0, 6.00949e-39, 5.92339e-39, 6.01522e-39, 0, 5.93487e-39, 5.94635e-39, 0, 0, 0, 0, 0, 0, 5.95783e-39, 5.96931e-39, 0, 5.97505e-39 )
^

Input file: <stdin>
Check file: llvm-project/mlir/test/Integration/Dialect/SparseTensor/CPU/dense_output_bf16.mlir

The result looks pretty far from what we expect

[joker-eph]

CC: @RKSimon since you reviewed here: https://reviews.llvm.org/D158950

[phoebewang]

I'll look at the new problem

[phoebewang]

@joker-eph could you help to have a quick check about changing 8 to 16 in the code below:

    In = DAG.getNode(ISD::ZERO_EXTEND, DL, NVT, In);
    In = DAG.getNode(ISD::SHL, DL, NVT, In, DAG.getConstant(8, DL, NVT));
    return DAG.getBitcast(VT, In);

I don't have a target with AVX512BF16 to verify it.

[phoebewang]

Checked changing to 16 solve the problem.

[tru]

Should this be backported.

[phoebewang]

Should this be backported.

This has been backported through #65032

[joker-eph]

It's fine it seems you cherry-picked the final commit @tru

[tru]

Ah it was a separate issue. Ok - thanks for confirming!