[PATCH] D127982: [X86][FP16] Enable vector support for FP16 emulation

[Alexander Kornienko via Phabricator via llvm-commits]

alexfh added subscribers: joanahalili, alexfh.
alexfh added a comment.

Hi @pengfei, this patch is causing clang to crash with a "fatal error: error in backend" when compiling some code with `-mno-avx2`. A (mostly automatically) reduced test case (thanks @joanahalili for preparing it) is below. I imagine it may already be a not perfectly valid C++, but the original code was a quite hairy template beast to be a good example. I hope, this helps fixing the issue soon.

  $ cat input.cc
  typedef long __m128i __attribute__((__vector_size__(16)));
  struct half {
    short x;
  };
  __m128i pset1(half from) {
    short __w7, __w6, __w5, __w4, __w3, __w2;
    return (__attribute__((__vector_size__(8 * sizeof(short)))) short){
            from.x, from.x, __w2, __w3, __w4, __w5, __w6, __w7};
  }
  __attribute__((__vector_size__(8 * sizeof(float)))) float pmul___trans_tmp_8;
  void g(int *);
  struct S {
    S() { g(&n); }
    virtual void c() {
      pmul___trans_tmp_8 = __builtin_ia32_vcvtph2ps256(pset1(m_value));
    }
    half m_value;
    int n;
  };
  void f() { S(); }
  $ ./clang-good -std=gnu++17 -O3 --target=x86_64--linux-gnu  -m64 -march=haswell -maes -mprefer-vector-width=128 -mno-avx2 -c input.cc
  $ ./clang-good --version
  clang version trunk (e97b2d413849d3dbc8b49740ce5a07ed0382309c)
  Target: x86_64-unknown-linux-gnu
  Thread model: posix
  InstalledDir: ...
  $ ./clang -std=gnu++17 -O3 --target=x86_64--linux-gnu  -m64 -march=haswell -maes -mprefer-vector-width=128 -c input.cc
  $ ./clang -std=gnu++17 -O3 --target=x86_64--linux-gnu  -m64 -march=haswell -maes -mprefer-vector-width=128 -mno-avx2 -c input.cc
  fatal error: error in backend: Cannot select: 0x55233f9ad270: v8f16,ch = X86ISD::VBROADCAST_LOAD<(dereferenceable load (s16) from %ir.0 + 8, align 8)> 0x55233f922068, 0x55233f9ad4e0
    0x55233f9ad4e0: i64 = add 0x55233f9ad750, Constant:i64<8>
      0x55233f9ad750: i64,ch = CopyFromReg 0x55233f922068, Register:i64 %0
        0x55233f9ad478: i64 = Register %0
      0x55233f9ad680: i64 = Constant<8>
  In function: _ZN1S1cEv
  clang: error: clang frontend command failed with exit code 70 (use -v to see invocation)
  clang version trunk (f18794816270244f9942e9217b96e23a94a7f32c)
  Target: x86_64-unknown-linux-gnu
  Thread model: posix
  InstalledDir: ...
  clang: note: diagnostic msg:
  ********************
  
  PLEASE ATTACH THE FOLLOWING FILES TO THE BUG REPORT:
  Preprocessed source(s) and associated run script(s) are located at:
  clang: note: diagnostic msg: /tmp/input-188997.cpp
  clang: note: diagnostic msg: /tmp/input-188997.sh
  clang: note: diagnostic msg:
  
  ********************




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