http://bugzilla.opensuse.org/show_bug.cgi?id=1204267 http://bugzilla.opensuse.org/show_bug.cgi?id=1204267#c4 --- Comment #4 from Aaron Puchert <aaronpuchert@alice-dsl.net> --- In my understanding, "Cannot select" is always an LLVM bug, specifically in the backend. Early stages of the backend should "legalize" data types and instructions, sending to instruction selection only what the target supports. So I can have a look, but it would be appreciated if someone could extract the IR that Mesa sends to LLVM. Otherwise I'll have to reverse-engineer a reproducer. Nevertheless, some initial remarks: ARMISD::VCMPZ is a "Vector compare to zero." [1] It should correspond to "vcmpe" in assembly [2]. The first argument being a v4i32 is slightly suspicious. I would have expected a v4f32, but since they live in the same registers maybe the backend doesn't care. The second is a Constant:i32<2> = ARMCC::CondCodes::HS, corresponding to conditional execution only if the carry flag is set, if I understand this correctly. [3,4] Inside we have ARMISD::VLD1DUP, which is a "Vector load N-element structure to all lanes" (same file as [1], different line), and seems to correspond to "vld1.N" in assembly. [5] The Constant:i32<4> could be an alignment, but I'm not sure. [1] https://github.com/llvm/llvm-project/blob/llvmorg-15.0.2/llvm/lib/Target/ARM... [2] https://developer.arm.com/documentation/ddi0406/c/Application-Level-Architec... [3] https://developer.arm.com/documentation/ddi0406/c/Application-Level-Architec... [4] https://github.com/llvm/llvm-project/blob/llvmorg-15.0.2/llvm/lib/Target/ARM... [5] https://developer.arm.com/documentation/ddi0406/c/Application-Level-Architec... -- You are receiving this mail because: You are on the CC list for the bug.

http://bugzilla.opensuse.org/show_bug.cgi?id=1204267 http://bugzilla.opensuse.org/show_bug.cgi?id=1204267#c8 Aaron Puchert <aaronpuchert@alice-dsl.net> changed: What |Removed |Added ---------------------------------------------------------------------------- Assignee|gfx-bugs@suse.de |aaronpuchert@alice-dsl.net --- Comment #8 from Aaron Puchert <aaronpuchert@alice-dsl.net> --- Since I'm not sure what the precise target machine is, I've used flags similar to how we build LLVM itself (see the specfile): llc -march=arm --float-abi=hard -mattr=+armv7-a,+vfp3d16 This reproduces the crash, just with a slightly different message: LLVM ERROR: Cannot select: t933: v4i32 = ARMISD::VCMPZ t1307, Constant:i32<2> t1307: v4i32,ch = ARMISD::VLD1DUP<(load (s32) from %ir.584)> t0, t1429:1, Constant:i32<4> t1429: i32,i32,ch = load<(load (s32) from %ir."&context.constants_ptr[]5618", align 8), <post-inc>> t0, t2, Constant:i32<64> t2: i32,ch = CopyFromReg t0, Register:i32 %45 t1: i32 = Register %45 t212: i32 = Constant<64> t49: i32 = Constant<4> t28: i32 = Constant<2> What's different is the added IR names, but they're not immediately helpful: there is a "&context.constants_ptr[]56" in the source, maybe there was disambiguation. The crash is reproducible on the current main branch, so it's still not fixed. With bugpoint --run-llc <input-file> --tool-args <options as above> we can reduce it to this: define void @fs_variant_partial() { entry: %output = alloca <4 x float>, align 16 br label %loop_begin loop_begin: ; preds = %skip, %entry br i1 undef, label %skip, label %0 0: ; preds = %loop_begin %1 = icmp uge <4 x i32> zeroinitializer, undef %2 = sext <4 x i1> %1 to <4 x i32> %3 = load i32, i32* undef, align 4 %4 = insertelement <4 x i32> undef, i32 %3, i32 3 %5 = trunc <4 x i32> %2 to <4 x i1> %6 = select <4 x i1> %5, <4 x i32> zeroinitializer, <4 x i32> %4 %7 = insertvalue [4 x <4 x i32>] undef, <4 x i32> %6, 0 %8 = insertvalue [4 x <4 x i32>] %7, <4 x i32> undef, 1 %9 = insertvalue [4 x <4 x i32>] %8, <4 x i32> undef, 2 %10 = insertvalue [4 x <4 x i32>] %9, <4 x i32> undef, 3 %11 = extractvalue [4 x <4 x i32>] %10, 0 %12 = bitcast <4 x i32> %11 to <4 x float> %13 = fmul <4 x float> zeroinitializer, %12 %14 = fadd <4 x float> %13, zeroinitializer %15 = fadd <4 x float> %14, zeroinitializer %16 = bitcast <4 x float> %15 to <4 x i32> %17 = insertvalue [4 x <4 x i32>] undef, <4 x i32> %16, 0 %18 = insertvalue [4 x <4 x i32>] %17, <4 x i32> undef, 1 %19 = insertvalue [4 x <4 x i32>] %18, <4 x i32> undef, 2 %20 = insertvalue [4 x <4 x i32>] %19, <4 x i32> undef, 3 %21 = extractvalue [4 x <4 x i32>] %20, 0 %22 = bitcast <4 x i32> %21 to <4 x float> store <4 x float> %22, <4 x float>* %output, align 16 br label %skip skip: ; preds = %0, %loop_begin br label %loop_begin } Crash is slightly different now: LLVM ERROR: Cannot select: t48: v4i32 = ARMISD::VCMPZ undef:v4i32, Constant:i32<2> t3: v4i32 = undef t47: i32 = Constant<2> This obviously corresponds to the %1 = icmp uge <4 x i32> zeroinitializer, undef With that knowledge we can reduce further: define <4 x i32> @fs_variant_partial() { %1 = icmp uge <4 x i32> zeroinitializer, undef %2 = sext <4 x i1> %1 to <4 x i32> ret <4 x i32> %2 } or define <4 x i32> @fs_variant_partial(<4 x i32> %0) { %2 = icmp uge <4 x i32> zeroinitializer, %0 %3 = sext <4 x i1> %2 to <4 x i32> ret <4 x i32> %3 } I'll see if I can spot where we're missing something, but likely I'll just file a bug and let the ARM people figure it where this should be fixed. From the looks of it we're simply not able to lower "icmp uge <4 x i32> zeroinitializer, ...", and the nested instructions have nothing to do with it. -- You are receiving this mail because: You are on the CC list for the bug.

http://bugzilla.opensuse.org/show_bug.cgi?id=1204267 http://bugzilla.opensuse.org/show_bug.cgi?id=1204267#c10 --- Comment #10 from Aaron Puchert <aaronpuchert@alice-dsl.net> --- (In reply to Fabian Vogt from comment #9)

So the missing "instcombine" pass causes the "Cannot select" error and the pass is missing because Mesa passes an invalid list of passes to LLVMRunPasses and ignores the error.

Would it be possible to improve error handling here? At least some tracing would be nice. From your analysis it looks like this might affect more platforms and not just armv7, and we wouldn't have noticed anything were it not for the backend bug. -- You are receiving this mail because: You are on the CC list for the bug.

http://bugzilla.opensuse.org/show_bug.cgi?id=1204267 http://bugzilla.opensuse.org/show_bug.cgi?id=1204267#c13 --- Comment #13 from Aaron Puchert <aaronpuchert@alice-dsl.net> --- (In reply to OBSbugzilla Bot from comment #12)

This is an autogenerated message for OBS integration: This bug (1204267) was mentioned in https://build.opensuse.org/request/show/1031948 Factory / llvm15

This made it into snapshot 20221029 released today, and it fixes the compilation failure for the reproducer from attachment 862276. Factory:ARM hasn't released a new snapshot yet. Feel free to close once you're able to confirm that this fixes the original issue. -- You are receiving this mail because: You are on the CC list for the bug.