[AArch64][GlobalISel] Cannot legalize G_ICMP for i192

[nitinjohnraj]

The following code snippet crashes the legalizer, since G_ICMP cannot be legalized for s192. The legalizer first widens s192 to s256, after which it fails to legalize the code. Other instructions (like G_ADD) do get legalized for s192.

[nraj@host llvm-project]$ cat test.mir
---
name:            cmp_sgt_i192
body:             |
  bb.0.entry:
    ; CHECK-LABEL: name: cmp_sgt_i64
    ; CHECK: %xhi:_(s64) = COPY $x10
    ; CHECK-NEXT: %xlo:_(s64) = COPY $x11
    ; CHECK-NEXT: %yhi:_(s64) = COPY $x12
    ; CHECK-NEXT: %ylo:_(s64) = COPY $x13
    ; CHECK-NEXT: [[ICMP:%[0-9]+]]:_(s64) = G_ICMP intpred(sgt), %xlo(s64), %ylo
    ; CHECK-NEXT: [[ICMP1:%[0-9]+]]:_(s64) = G_ICMP intpred(eq), %xlo(s64), %ylo
    ; CHECK-NEXT: [[ICMP2:%[0-9]+]]:_(s64) = G_ICMP intpred(ugt), %xhi(s64), %yhi
    ; CHECK-NEXT: [[C:%[0-9]+]]:_(s64) = G_CONSTANT i64 1
    ; CHECK-NEXT: [[AND:%[0-9]+]]:_(s64) = G_AND [[ICMP1]], [[C]]
    ; CHECK-NEXT: [[SELECT:%[0-9]+]]:_(s64) = G_SELECT [[AND]](s64), [[ICMP2]], [[ICMP]]
    ; CHECK-NEXT: $x10 = COPY [[SELECT]](s64)
    ; CHECK-NEXT: PseudoRET implicit $x10
    %x:_(s192) = G_IMPLICIT_DEF
    %y:_(s192) = G_IMPLICIT_DEF
    %z:_(s1) = G_ICMP intpred(sgt), %x, %y
    %z0:_(s64) = G_ANYEXT %z
    $x0 = COPY %z0(s64)
    RET_ReallyLR implicit $x0

...
[nraj@sw06 llvm-project]$ /scratch/nraj/gisel/build/x64_riscv_release/bin/llc -mtriple=aarch64 -run-pass=legalizer test.mir -o - --debug
... (Some lines skipped)
=== New Iteration ===
Legalizing: %z:_(s1) = G_ICMP intpred(sgt), %x:_(s192), %y:_
Applying legalizer ruleset to: 132, Tys={s1, s192, }, Opcode=132, MMOs={}
.. no match
.. match
.. .. WidenScalar, 1, s256
.. Widen scalar
.. .. Changing MI: %z:_(s1) = G_ICMP intpred(sgt), %x:_(s192), %y:_
CSEInfo::Recording new MI G_SEXT
CSEInfo::Recording new MI G_SEXT
.. .. Changed MI: %z:_(s1) = G_ICMP intpred(sgt), %4:_(s256), %5:_
.. .. New MI: %4:_(s256) = G_SEXT %x:_(s192)
.. .. New MI: %5:_(s256) = G_SEXT %y:_(s192)
.. No debug info was present
Legalizing: %z:_(s1) = G_ICMP intpred(sgt), %4:_(s256), %5:_
Applying legalizer ruleset to: 132, Tys={s1, s256, }, Opcode=132, MMOs={}
.. no match
.. no match
.. no match
.. match
.. .. NarrowScalar, 1, s64
.. Narrow scalar
LLVM ERROR: unable to legalize instruction: %z:_(s1) = G_ICMP intpred(sgt), %4:_(s256), %5:_ (in function: cmp_sgt_i192)
PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace.
Stack dump:
0.      Program arguments: /scratch/nraj/gisel/build/x64_riscv_release/bin/llc -mtriple=aarch64 -run-pass=legalizer test.mir -o - --debug
1.      Running pass 'Function Pass Manager' on module 'test.mir'.
2.      Running pass 'Legalizer' on function '@cmp_sgt_i192'
 #0 0x0000000001a881a7 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/scratch/nraj/gisel/build/x64_riscv_release/bin/llc+0x1a881a7)
 #1 0x0000000001a85ece llvm::sys::RunSignalHandlers() (/scratch/nraj/gisel/build/x64_riscv_release/bin/llc+0x1a85ece)
 #2 0x0000000001a889bf SignalHandler(int) Signals.cpp:0:0
 #3 0x00007fda7b5b1cf0 __restore_rt (/lib64/libpthread.so.0+0x12cf0)
 #4 0x00007fda7a025aff raise (/lib64/libc.so.6+0x4eaff)
 #5 0x00007fda79ff8ea5 abort (/lib64/libc.so.6+0x21ea5)
 #6 0x0000000001a05e63 llvm::report_fatal_error(llvm::Twine const&, bool) (/scratch/nraj/gisel/build/x64_riscv_release/bin/llc+0x1a05e63)
 #7 0x0000000001ce2e94 (/scratch/nraj/gisel/build/x64_riscv_release/bin/llc+0x1ce2e94)
 #8 0x0000000001ce3222 llvm::reportGISelFailure(llvm::MachineFunction&, llvm::TargetPassConfig const&, llvm::MachineOptimizationRemarkEmitter&, char const*, llvm::StringRef, llvm::MachineInstr const&) (/scratch/nraj/gisel/build/x64_riscv_release/bin/llc
+0x1ce3222)
 #9 0x0000000001c7eb9f llvm::Legalizer::runOnMachineFunction(llvm::MachineFunction&) (/scratch/nraj/gisel/build/x64_riscv_release/bin/llc+0x1c7eb9f)
#10 0x0000000000ee6e5c llvm::MachineFunctionPass::runOnFunction(llvm::Function&) (/scratch/nraj/gisel/build/x64_riscv_release/bin/llc+0xee6e5c)
#11 0x00000000013f62b3 llvm::FPPassManager::runOnFunction(llvm::Function&) (/scratch/nraj/gisel/build/x64_riscv_release/bin/llc+0x13f62b3)
#12 0x00000000013fdf31 llvm::FPPassManager::runOnModule(llvm::Module&) (/scratch/nraj/gisel/build/x64_riscv_release/bin/llc+0x13fdf31)
#13 0x00000000013f6ab6 llvm::legacy::PassManagerImpl::run(llvm::Module&) (/scratch/nraj/gisel/build/x64_riscv_release/bin/llc+0x13f6ab6)
#14 0x00000000006a7a78 compileModule(char**, llvm::LLVMContext&) llc.cpp:0:0
#15 0x00000000006a554d main (/scratch/nraj/gisel/build/x64_riscv_release/bin/llc+0x6a554d)
#16 0x00007fda7a011d85 __libc_start_main (/lib64/libc.so.6+0x3ad85)
#17 0x00000000006a1eee _start (/scratch/nraj/gisel/build/x64_riscv_release/bin/llc+0x6a1eee)
Aborted

[llvmbot]

@llvm/issue-subscribers-backend-aarch64

[nitinjohnraj]

The failure occurs due to an existing TODO in LegalizerHelper.