tests: relax expectations after llvm change 902ddda120a5

[durin42]

LLVM 22 is able to drop assumes that seem to not help further optimizations, which actually seems to dramatically help further optimizations in some of our small test cases.

I'm a little unclear how to fix the last failure, in tests/codegen-llvm/issues/issue-122600-ptr-discriminant-update.rs:

-; Function Attrs: mustprogress nofree norecurse nosync nounwind willreturn memory(argmem: readwrite, inaccessiblemem: write) uwtable
+; Function Attrs: mustprogress nofree norecurse nosync nounwind nonlazybind willreturn memory(argmem: readwrite, inaccessiblemem: write) uwtable
 define void @update(ptr noundef captures(none) %s) unnamed_addr #0 {
 start:
-  %_3.sroa.0.0.copyload = load i8, ptr %s, align 1
-  %0 = trunc nuw i8 %_3.sroa.0.0.copyload to i1
-  %1 = xor i1 %0, true
-  tail call void @llvm.assume(i1 %1)
   store i8 1, ptr %s, align 1
   ret void
 }

I'm just not conversant enough in LLVM IR to follow the changes here.

@rustbot label llvm-main
r? nikic

[durin42]

@rustbot label +S-waiting-on-author -S-waiting-on-review

Well that's annoying, I'll have to figure out how to make it pass on LLVM 21 as well as 22.

[durin42]

Updated, all three tests should now pass on LLVM 22+ and LLVM < 22. I decided to just accept the two disappeared instructions in issue-122600-ptr-discriminant-update.rs since it sounds like the CHECK-NOT bits were the actually-important parts.

[durin42]

@rustbot label -S-waiting-on-author +S-waiting-on-review