[llvm] [SDAG] Promote extract subvector in more cases without falling back to build vectors. (PR #212156)

[via llvm-commits]

github-actions[bot] wrote:

test-suite diff from 131e31016ff94c8782d726baa3ed0160a480f3f3...20a8f423d585aece80534137c0b980d42fb50768: https://github.com/llvm/llvm-project/actions/runs/34187758794/artifacts/10043361234

Statistics: https://github.com/llvm/llvm-project/actions/runs/34187758794/artifacts/10043362269

## riscv64-linux-gnu `-march=rva23u64 -O3`
| ('Program', '')    |   ('size..text', 'base') |   ('size..text', 'head') |   ('size..text', 'diff') |
|:-------------------|-------------------------:|-------------------------:|-------------------------:|
| Geomean difference |                      nan |                      nan |                        0 |
## aarch64-linux-gnu `-march=armv9-a -O3`
| ('Program', '')                             |   ('size..text', 'base') |   ('size..text', 'head') |   ('size..text', 'diff') |
|:--------------------------------------------|-------------------------:|-------------------------:|-------------------------:|
| test-suite...ve-susan/automotive-susan.test |                    23884 |                    23912 |              0.00117233  |
| Geomean difference                          |                      nan |                      nan |              2.89173e-06 |
## x86_64-linux-gnu `-march=x86-64-v3 -O3`
| ('Program', '')    |   ('size..text', 'base') |   ('size..text', 'head') |   ('size..text', 'diff') |
|:-------------------|-------------------------:|-------------------------:|-------------------------:|
| Geomean difference |                      nan |                      nan |                        0 |


https://github.com/llvm/llvm-project/pull/212156