From ed0d8fa3e8c061fdd22fb95f6cfadbada864118d Mon Sep 17 00:00:00 2001
From: AngelicosPhosphoros <xuzin.timur@gmail.com>
Date: Sat, 3 Apr 2021 20:58:15 +0300
Subject: [PATCH] Optimize PartialOrd le

Closes https://github.com/rust-lang/rust/issues/73338
This change stops default implementation of `le()` method from generating jumps.
---
 library/core/src/cmp.rs                       |  3 +-
 src/test/codegen/issue-73338-effecient-cmp.rs | 39 +++++++++++++++++++
 2 files changed, 41 insertions(+), 1 deletion(-)
 create mode 100644 src/test/codegen/issue-73338-effecient-cmp.rs

diff --git a/library/core/src/cmp.rs b/library/core/src/cmp.rs
index 5bab1fb93db..adb033e6bdf 100644
--- a/library/core/src/cmp.rs
+++ b/library/core/src/cmp.rs
@@ -981,7 +981,8 @@ pub trait PartialOrd<Rhs: ?Sized = Self>: PartialEq<Rhs> {
     #[must_use]
     #[stable(feature = "rust1", since = "1.0.0")]
     fn le(&self, other: &Rhs) -> bool {
-        matches!(self.partial_cmp(other), Some(Less | Equal))
+        // Pattern `Some(Less | Eq)` optimizes worse than negating `None | Some(Greater)`.
+        !matches!(self.partial_cmp(other), None | Some(Greater))
     }
 
     /// This method tests greater than (for `self` and `other`) and is used by the `>` operator.
diff --git a/src/test/codegen/issue-73338-effecient-cmp.rs b/src/test/codegen/issue-73338-effecient-cmp.rs
new file mode 100644
index 00000000000..85c2bbfd040
--- /dev/null
+++ b/src/test/codegen/issue-73338-effecient-cmp.rs
@@ -0,0 +1,39 @@
+// This test checks that comparison operation
+// generated by #[derive(PartialOrd)]
+// doesn't contain jumps for C enums
+
+// compile-flags: -Copt-level=3
+
+#![crate_type="lib"]
+
+#[repr(u32)]
+#[derive(Copy, Clone, Eq, PartialEq, PartialOrd)]
+pub enum Foo {
+    Zero,
+    One,
+    Two,
+}
+
+#[no_mangle]
+pub fn compare_less(a: Foo, b: Foo)->bool{
+    // CHECK-NOT: br {{.*}}
+    a < b
+}
+
+#[no_mangle]
+pub fn compare_le(a: Foo, b: Foo)->bool{
+    // CHECK-NOT: br {{.*}}
+    a <= b
+}
+
+#[no_mangle]
+pub fn compare_ge(a: Foo, b: Foo)->bool{
+    // CHECK-NOT: br {{.*}}
+    a >= b
+}
+
+#[no_mangle]
+pub fn compare_greater(a: Foo, b: Foo)->bool{
+    // CHECK-NOT: br {{.*}}
+    a > b
+}