Add a mir-opt test for *debug* MIR from derive(PartialOrd, Ord)

Because the follow-up commits will affect it, and the goal is to show how.

Author: scottmcm

tests/mir-opt/pre-codegen/derived_ord_debug.rs

@@ -0,0 +1,18 @@
+//@ compile-flags: -Copt-level=0 -Zmir-opt-level=1 -Cdebuginfo=limited
+// EMIT_MIR_FOR_EACH_PANIC_STRATEGY
+
+#![crate_type = "lib"]
+
+#[derive(PartialOrd, Ord, PartialEq, Eq)]
+pub struct MultiField(char, i16);
+
+// EMIT_MIR derived_ord_debug.{impl#0}-partial_cmp.PreCodegen.after.mir
+// EMIT_MIR derived_ord_debug.{impl#1}-cmp.PreCodegen.after.mir
+
+// CHECK-LABEL: partial_cmp(_1: &MultiField, _2: &MultiField) -> Option<std::cmp::Ordering>
+// CHECK: = <char as PartialOrd>::partial_cmp(
+// CHECK: = <i16 as PartialOrd>::partial_cmp(
+
+// CHECK-LABEL: cmp(_1: &MultiField, _2: &MultiField) -> std::cmp::Ordering
+// CHECK: = <char as Ord>::cmp(
+// CHECK: = <i16 as Ord>::cmp(

tests/mir-opt/pre-codegen/derived_ord_debug.{impl#0}-partial_cmp.PreCodegen.after.panic-abort.mir

@@ -0,0 +1,52 @@
+// MIR for `<impl at $DIR/derived_ord_debug.rs:6:10: 6:20>::partial_cmp` after PreCodegen
+
+fn <impl at $DIR/derived_ord_debug.rs:6:10: 6:20>::partial_cmp(_1: &MultiField, _2: &MultiField) -> Option<std::cmp::Ordering> {
+    debug self => _1;
+    debug other => _2;
+    let mut _0: std::option::Option<std::cmp::Ordering>;
+    let _3: &char;
+    let _4: &char;
+    let mut _5: std::option::Option<std::cmp::Ordering>;
+    let mut _6: isize;
+    let mut _7: i8;
+    let _8: &i16;
+    let _9: &i16;
+    scope 1 {
+        debug cmp => _5;
+    }
+
+    bb0: {
+        _3 = &((*_1).0: char);
+        _4 = &((*_2).0: char);
+        _5 = <char as PartialOrd>::partial_cmp(copy _3, copy _4) -> [return: bb1, unwind unreachable];
+    }
+
+    bb1: {
+        _6 = discriminant(_5);
+        switchInt(move _6) -> [1: bb2, 0: bb4, otherwise: bb6];
+    }
+
+    bb2: {
+        _7 = discriminant(((_5 as Some).0: std::cmp::Ordering));
+        switchInt(move _7) -> [0: bb3, otherwise: bb4];
+    }
+
+    bb3: {
+        _8 = &((*_1).1: i16);
+        _9 = &((*_2).1: i16);
+        _0 = <i16 as PartialOrd>::partial_cmp(copy _8, copy _9) -> [return: bb5, unwind unreachable];
+    }
+
+    bb4: {
+        _0 = copy _5;
+        goto -> bb5;
+    }
+
+    bb5: {
+        return;
+    }
+
+    bb6: {
+        unreachable;
+    }
+}

tests/mir-opt/pre-codegen/derived_ord_debug.{impl#0}-partial_cmp.PreCodegen.after.panic-unwind.mir

@@ -0,0 +1,52 @@
+// MIR for `<impl at $DIR/derived_ord_debug.rs:6:10: 6:20>::partial_cmp` after PreCodegen
+
+fn <impl at $DIR/derived_ord_debug.rs:6:10: 6:20>::partial_cmp(_1: &MultiField, _2: &MultiField) -> Option<std::cmp::Ordering> {
+    debug self => _1;
+    debug other => _2;
+    let mut _0: std::option::Option<std::cmp::Ordering>;
+    let _3: &char;
+    let _4: &char;
+    let mut _5: std::option::Option<std::cmp::Ordering>;
+    let mut _6: isize;
+    let mut _7: i8;
+    let _8: &i16;
+    let _9: &i16;
+    scope 1 {
+        debug cmp => _5;
+    }
+
+    bb0: {
+        _3 = &((*_1).0: char);
+        _4 = &((*_2).0: char);
+        _5 = <char as PartialOrd>::partial_cmp(copy _3, copy _4) -> [return: bb1, unwind continue];
+    }
+
+    bb1: {
+        _6 = discriminant(_5);
+        switchInt(move _6) -> [1: bb2, 0: bb4, otherwise: bb6];
+    }
+
+    bb2: {
+        _7 = discriminant(((_5 as Some).0: std::cmp::Ordering));
+        switchInt(move _7) -> [0: bb3, otherwise: bb4];
+    }
+
+    bb3: {
+        _8 = &((*_1).1: i16);
+        _9 = &((*_2).1: i16);
+        _0 = <i16 as PartialOrd>::partial_cmp(copy _8, copy _9) -> [return: bb5, unwind continue];
+    }
+
+    bb4: {
+        _0 = copy _5;
+        goto -> bb5;
+    }
+
+    bb5: {
+        return;
+    }
+
+    bb6: {
+        unreachable;
+    }
+}

tests/mir-opt/pre-codegen/derived_ord_debug.{impl#1}-cmp.PreCodegen.after.panic-abort.mir

@@ -0,0 +1,42 @@
+// MIR for `<impl at $DIR/derived_ord_debug.rs:6:22: 6:25>::cmp` after PreCodegen
+
+fn <impl at $DIR/derived_ord_debug.rs:6:22: 6:25>::cmp(_1: &MultiField, _2: &MultiField) -> std::cmp::Ordering {
+    debug self => _1;
+    debug other => _2;
+    let mut _0: std::cmp::Ordering;
+    let _3: &char;
+    let _4: &char;
+    let mut _5: std::cmp::Ordering;
+    let mut _6: i8;
+    let _7: &i16;
+    let _8: &i16;
+    scope 1 {
+        debug cmp => _5;
+    }
+
+    bb0: {
+        _3 = &((*_1).0: char);
+        _4 = &((*_2).0: char);
+        _5 = <char as Ord>::cmp(copy _3, copy _4) -> [return: bb1, unwind unreachable];
+    }
+
+    bb1: {
+        _6 = discriminant(_5);
+        switchInt(move _6) -> [0: bb2, otherwise: bb3];
+    }
+
+    bb2: {
+        _7 = &((*_1).1: i16);
+        _8 = &((*_2).1: i16);
+        _0 = <i16 as Ord>::cmp(copy _7, copy _8) -> [return: bb4, unwind unreachable];
+    }
+
+    bb3: {
+        _0 = copy _5;
+        goto -> bb4;
+    }
+
+    bb4: {
+        return;
+    }
+}

tests/mir-opt/pre-codegen/derived_ord_debug.{impl#1}-cmp.PreCodegen.after.panic-unwind.mir

@@ -0,0 +1,42 @@
+// MIR for `<impl at $DIR/derived_ord_debug.rs:6:22: 6:25>::cmp` after PreCodegen
+
+fn <impl at $DIR/derived_ord_debug.rs:6:22: 6:25>::cmp(_1: &MultiField, _2: &MultiField) -> std::cmp::Ordering {
+    debug self => _1;
+    debug other => _2;
+    let mut _0: std::cmp::Ordering;
+    let _3: &char;
+    let _4: &char;
+    let mut _5: std::cmp::Ordering;
+    let mut _6: i8;
+    let _7: &i16;
+    let _8: &i16;
+    scope 1 {
+        debug cmp => _5;
+    }
+
+    bb0: {
+        _3 = &((*_1).0: char);
+        _4 = &((*_2).0: char);
+        _5 = <char as Ord>::cmp(copy _3, copy _4) -> [return: bb1, unwind continue];
+    }
+
+    bb1: {
+        _6 = discriminant(_5);
+        switchInt(move _6) -> [0: bb2, otherwise: bb3];
+    }
+
+    bb2: {
+        _7 = &((*_1).1: i16);
+        _8 = &((*_2).1: i16);
+        _0 = <i16 as Ord>::cmp(copy _7, copy _8) -> [return: bb4, unwind continue];
+    }
+
+    bb3: {
+        _0 = copy _5;
+        goto -> bb4;
+    }
+
+    bb4: {
+        return;
+    }
+}