[AArch64] Compare BFI and ORR with left-shifted operand for OR instruction selection.

Before this patch:
- For `r = or op0, op1`, `tryBitfieldInsertOpFromOr` combines it to BFI when
  1) one of the two operands is bit-field-positioning or bit-field-extraction op; and
  2) bits from the two operands don't overlap

After this patch:
- Right before OR is combined to BFI, evaluates if ORR with left-shifted operand is better.

A motivating example (https://godbolt.org/z/rnMrzs5vn, which is added as a test case in `test_orr_not_bfi` in `CodeGen/AArch64/bitfield-insert.ll`)

For IR:
```
define i64 @test_orr_not_bfxil(i64 %0) {
  %2 = and i64 %0, 127
  %3 = lshr i64 %0, 1
  %4 = and i64 %3, 16256
  %5 = or i64 %4, %2
  ret i64 %5
}
```

Before:
```
   lsr     x8, x0, #1
   and     x8, x8, #0x3f80
   bfxil   x8, x0, #0, #7
```

After:
```
   ubfx x8, x0, #8, #7
   and x9, x0, #0x7f
   orr x0, x9, x8, lsl #7
```

Reviewed By: dmgreen

Differential Revision: https://reviews.llvm.org/D135102

0 files changed, 0 insertions, 0 deletions