simd-wide-sum test: adapt for LLVM 17 codegen change
After 0d4a709bb8
LLVM becomes more clever and turns ```@wider_reduce_loop``` into an alias:
https://buildkite.com/llvm-project/rust-llvm-integrate-prototype/builds/17806#0186da6b-582c-46bf-a227-1565fa0859ac/743-766
This adapts the test to prevent this.
The files here use the LLVM FileCheck framework, documented at https://llvm.org/docs/CommandGuide/FileCheck.html.
One extension worth noting is the use of revisions as custom prefixes for FileCheck. If your codegen test has different behavior based on the chosen target or different compiler flags that you want to exercise, you can use a revisions annotation, like so:
// revisions: aaa bbb
// [bbb] compile-flags: --flags-for-bbb
After specifying those variations, you can write different expected, or
explicitly unexpected output by using <prefix>-SAME:
and <prefix>-NOT:
,
like so:
// CHECK: expected code
// aaa-SAME: emitted-only-for-aaa
// aaa-NOT: emitted-only-for-bbb
// bbb-NOT: emitted-only-for-aaa
// bbb-SAME: emitted-only-for-bbb