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7b78b6a78d
Implement `SpecOptionPartialEq` for `cmp::Ordering` Noticed as I continue to explore options for having code using `partial_cmp` optimize better. Before: ```llvm ; Function Attrs: mustprogress nofree nosync nounwind willreturn uwtable define noundef zeroext i1 `@ordering_eq(i8` noundef %0, i8 noundef %1) unnamed_addr #0 { start: %2 = icmp eq i8 %0, 2 br i1 %2, label %bb1.i, label %bb3.i bb1.i: ; preds = %start %3 = icmp eq i8 %1, 2 br label %"_ZN55_$LT$T$u20$as$u20$core..option..SpecOptionPartialEq$GT$2eq17hb7e7beacecde585fE.exit" bb3.i: ; preds = %start %.not.i = icmp ne i8 %1, 2 %4 = icmp eq i8 %0, %1 %spec.select.i = and i1 %.not.i, %4 br label %"_ZN55_$LT$T$u20$as$u20$core..option..SpecOptionPartialEq$GT$2eq17hb7e7beacecde585fE.exit" "_ZN55_$LT$T$u20$as$u20$core..option..SpecOptionPartialEq$GT$2eq17hb7e7beacecde585fE.exit": ; preds = %bb1.i, %bb3.i %.0.i = phi i1 [ %3, %bb1.i ], [ %spec.select.i, %bb3.i ] ret i1 %.0.i } ``` After: ```llvm ; Function Attrs: mustprogress nofree norecurse nosync nounwind readnone willreturn uwtable define noundef zeroext i1 `@ordering_eq(i8` noundef %0, i8 noundef %1) unnamed_addr #1 { start: %2 = icmp eq i8 %0, %1 ret i1 %2 } ``` (Which <https://alive2.llvm.org/ce/z/-rop5r> says LLVM *could* just do itself, but there's probably an issue already open for that problem from when this was originally looked at for `Option<NonZeroU8>` and friends.)
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