Add a MIR pre-codegen test for derived PartialOrd

Author: scottmcm

Diff for: tests/mir-opt/pre-codegen/derived_ord.rs

@@ -0,0 +1,9 @@
+// skip-filecheck
+//@ compile-flags: -O -Zmir-opt-level=2 -Cdebuginfo=0
+
+#![crate_type = "lib"]
+
+#[derive(PartialOrd, PartialEq)]
+pub struct MultiField(char, i16);
+
+// EMIT_MIR derived_ord.{impl#0}-partial_cmp.PreCodegen.after.mir

Diff for: tests/mir-opt/pre-codegen/derived_ord.{impl#0}-partial_cmp.PreCodegen.after.mir

@@ -0,0 +1,159 @@
+// MIR for `<impl at $DIR/derived_ord.rs:6:10: 6:20>::partial_cmp` after PreCodegen
+
+fn <impl at $DIR/derived_ord.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 mut _3: &char;
+    let mut _4: &char;
+    let mut _10: std::option::Option<std::cmp::Ordering>;
+    let mut _11: &i16;
+    let mut _12: &i16;
+    let _18: std::option::Option<std::cmp::Ordering>;
+    scope 1 {
+        debug cmp => _18;
+    }
+    scope 2 (inlined std::cmp::impls::<impl PartialOrd for char>::partial_cmp) {
+        debug self => _3;
+        debug other => _4;
+        let mut _9: std::cmp::Ordering;
+        scope 3 (inlined std::cmp::impls::<impl Ord for char>::cmp) {
+            debug self => _3;
+            debug other => _4;
+            let mut _5: char;
+            let mut _6: char;
+            let mut _7: bool;
+            let mut _8: bool;
+        }
+    }
+    scope 4 (inlined std::cmp::impls::<impl PartialOrd for i16>::partial_cmp) {
+        debug self => _11;
+        debug other => _12;
+        let mut _17: std::cmp::Ordering;
+        scope 5 (inlined std::cmp::impls::<impl Ord for i16>::cmp) {
+            debug self => _11;
+            debug other => _12;
+            let mut _13: i16;
+            let mut _14: i16;
+            let mut _15: bool;
+            let mut _16: bool;
+        }
+    }
+
+    bb0: {
+        StorageLive(_3);
+        _3 = &((*_1).0: char);
+        StorageLive(_4);
+        _4 = &((*_2).0: char);
+        StorageLive(_9);
+        StorageLive(_5);
+        StorageLive(_6);
+        StorageLive(_7);
+        _5 = ((*_1).0: char);
+        _6 = ((*_2).0: char);
+        _7 = Lt(_5, _6);
+        switchInt(move _7) -> [0: bb1, otherwise: bb10];
+    }
+
+    bb1: {
+        StorageLive(_8);
+        _8 = Eq(_5, _6);
+        switchInt(move _8) -> [0: bb2, otherwise: bb3];
+    }
+
+    bb2: {
+        _9 = const Greater;
+        StorageDead(_8);
+        StorageDead(_7);
+        StorageDead(_6);
+        StorageDead(_5);
+        _10 = Option::<std::cmp::Ordering>::Some(move _9);
+        StorageDead(_9);
+        StorageDead(_4);
+        StorageDead(_3);
+        goto -> bb11;
+    }
+
+    bb3: {
+        StorageDead(_8);
+        StorageDead(_7);
+        StorageDead(_6);
+        StorageDead(_5);
+        StorageDead(_9);
+        StorageDead(_4);
+        StorageDead(_3);
+        StorageLive(_11);
+        _11 = &((*_1).1: i16);
+        StorageLive(_12);
+        _12 = &((*_2).1: i16);
+        StorageLive(_17);
+        StorageLive(_13);
+        StorageLive(_14);
+        StorageLive(_15);
+        _13 = ((*_1).1: i16);
+        _14 = ((*_2).1: i16);
+        _15 = Lt(_13, _14);
+        switchInt(move _15) -> [0: bb4, otherwise: bb8];
+    }
+
+    bb4: {
+        StorageLive(_16);
+        _16 = Eq(_13, _14);
+        switchInt(move _16) -> [0: bb5, otherwise: bb6];
+    }
+
+    bb5: {
+        _17 = const Greater;
+        goto -> bb7;
+    }
+
+    bb6: {
+        _17 = const Equal;
+        goto -> bb7;
+    }
+
+    bb7: {
+        StorageDead(_16);
+        goto -> bb9;
+    }
+
+    bb8: {
+        _17 = const Less;
+        goto -> bb9;
+    }
+
+    bb9: {
+        StorageDead(_15);
+        StorageDead(_14);
+        StorageDead(_13);
+        _0 = Option::<std::cmp::Ordering>::Some(move _17);
+        StorageDead(_17);
+        StorageDead(_12);
+        StorageDead(_11);
+        goto -> bb12;
+    }
+
+    bb10: {
+        _9 = const Less;
+        StorageDead(_7);
+        StorageDead(_6);
+        StorageDead(_5);
+        _10 = Option::<std::cmp::Ordering>::Some(move _9);
+        StorageDead(_9);
+        StorageDead(_4);
+        StorageDead(_3);
+        goto -> bb11;
+    }
+
+    bb11: {
+        StorageLive(_18);
+        _18 = _10;
+        _0 = _10;
+        StorageDead(_18);
+        goto -> bb12;
+    }
+
+    bb12: {
+        return;
+    }
+}