std: Restore conventional `compareFn` behavior for `binarySearch`

PR #20927 made some improvements to the `binarySearch` API, but one
change I found surprising was the relationship between the left-hand and
right-hand parameters of `compareFn` was inverted. This is different
from how comparison functions typically behave, both in other parts of
Zig (e.g. `std.math.order`) and in other languages (e.g. C's `bsearch`).
Unless a strong reason can be identified and documented for doing
otherwise, I think it'll be better to stick with convention.

While writing this patch and changing things back to the way they were,
the predicates of `lowerBound` and `upperBound` seemed to be the only
areas that benefited from the inversion. I don't think that benefit is
worth the cost, personally. Calling `Order.invert()` in the predicates
accomplishes the same goal.

3 files changed, 4 insertions, 4 deletions

diff --git a/lib/std/debug/Coverage.zig b/lib/std/debug/Coverage.zig
index 2d0e054673..58e600dc63 100644
--- a/lib/std/debug/Coverage.zig
+++ b/lib/std/debug/Coverage.zig
@@ -196,7 +196,7 @@ pub fn resolveAddressesDwarf(
             const table_addrs = slc.line_table.keys();
             line_table_i = std.sort.upperBound(u64, table_addrs, pc, struct {
                 fn order(context: u64, item: u64) std.math.Order {
-                    return std.math.order(item, context);
+                    return std.math.order(context, item);
                 }
             }.order);
         }
diff --git a/lib/std/debug/Dwarf.zig b/lib/std/debug/Dwarf.zig
index d36e4f961d..73b1871c46 100644
--- a/lib/std/debug/Dwarf.zig
+++ b/lib/std/debug/Dwarf.zig
@@ -182,7 +182,7 @@ pub const CompileUnit = struct {
         pub fn findSource(slc: *const SrcLocCache, address: u64) !LineEntry {
             const index = std.sort.upperBound(u64, slc.line_table.keys(), address, struct {
                 fn order(context: u64, item: u64) std.math.Order {
-                    return std.math.order(item, context);
+                    return std.math.order(context, item);
                 }
             }.order);
             if (index == 0) return missing();
diff --git a/lib/std/debug/SelfInfo.zig b/lib/std/debug/SelfInfo.zig
index 76c0505e96..5e9afc8cfd 100644
--- a/lib/std/debug/SelfInfo.zig
+++ b/lib/std/debug/SelfInfo.zig
@@ -1624,12 +1624,12 @@ pub fn unwindFrameDwarf(
     } else {
         const index = std.sort.binarySearch(Dwarf.FrameDescriptionEntry, di.fde_list.items, context.pc, struct {
             pub fn compareFn(pc: usize, item: Dwarf.FrameDescriptionEntry) std.math.Order {
-                if (pc < item.pc_begin) return .gt;
+                if (pc < item.pc_begin) return .lt;
 
                 const range_end = item.pc_begin + item.pc_range;
                 if (pc < range_end) return .eq;
 
-                return .lt;
+                return .gt;
             }
         }.compareFn);