[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
18 files changed: