Codegen regression caused by r207337

[Richard Barton]

Hi Craig

Your refactoring change to the AArch64 backend at r207337 seems to have
caused an internal fault in the instruction selector.

> clang -c -O2 ~/scratch/besttry.c -target aarch64
fatal error: error in backend: Cannot select: 0x43e83d0: v2i64 = mulhs
0x43f1320, 0x43f0340
      [ORD=5] [ID=51]
  0x43f1320: v2i64 = add 0x43f1110, 0x43f0448 [ORD=4] [ID=47]
    0x43f1110: v2i64 = AArch64ISD::NEON_VDUP 0x43e7b90 [ORD=3] [ID=35]
      0x43e7b90: i64,ch = CopyFromReg 0x4390e90, 0x43e7560 [ORD=2] [ID=27]
        0x43e7560: i64 = Register %vreg0 [ID=1]
    0x43f0448: v2i64,ch = load 0x4390e90, 0x43f1f10,
0x43eb8e8<LD16[ConstantPool]> [ORD=4] [ID=41]
      0x43f1f10: i64 = AArch64ISD::WrapperSmall 0x43f3d90, 0x43e81c0,
0x43ecd60 [ID=34]
        0x43f3d90: i64 = TargetConstantPool<<2 x i64> <i64 6, i64 7>> 0
[ID=26]
        0x43e81c0: i64 = TargetConstantPool<<2 x i64> <i64 6, i64 7>> 0
[TF=11] [ID=25]
        0x43ecd60: i32 = Constant<16> [ID=18]
      0x43eb8e8: i64 = undef [ID=6]
  0x43f0340: v2i64 = AArch64ISD::NEON_VDUP 0x43e7c98 [ID=28]
    0x43e7c98: i64 = Constant<1166592510590327375> [ID=14]
In function: main
clang-3.5: error: clang frontend command failed with exit code 70 (use -v to
see invocation)

Below is a reduced example (also attached) that produces the fault:

int errs = 0;
int main()
{
#define SIZE 254L
#define SIZE2 253L
    unsigned char buf[SIZE];
    int i;
    for (i = 0; i < SIZE; ++i)
        buf[i] = i % SIZE2;
    if (!(buf[i] == i % SIZE2))
        ++errs; 
}

I can remove the fault by reducing the optimisation level or by playing with
the values of SIZE and SIZE2 (the fault only occurs when SIZE > SIZE2)

Thanks
Rich


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