Rollup merge of rust-lang#100556 - Alex-Velez:patch-1, r=scottmcm

Clamp Function for f32 and f64

I thought the clamp function could use a little improvement for readability purposes. The function now returns early in order to skip the extra bound checks.

If there was a reason for binding `self` to `x` or if this code is incorrect, please correct me :)

Author: matthiaskrgr

library/core/src/num/f32.rs

@@ -1282,15 +1282,14 @@ impl f32 {
     #[must_use = "method returns a new number and does not mutate the original value"]
     #[stable(feature = "clamp", since = "1.50.0")]
     #[inline]
-    pub fn clamp(self, min: f32, max: f32) -> f32 {
+    pub fn clamp(mut self, min: f32, max: f32) -> f32 {
         assert!(min <= max);
-        let mut x = self;
-        if x < min {
-            x = min;
+        if self < min {
+            self = min;
         }
-        if x > max {
-            x = max;
+        if self > max {
+            self = max;
         }
-        x
+        self
     }
 }

library/core/src/num/f64.rs

@@ -1280,15 +1280,14 @@ impl f64 {
     #[must_use = "method returns a new number and does not mutate the original value"]
     #[stable(feature = "clamp", since = "1.50.0")]
     #[inline]
-    pub fn clamp(self, min: f64, max: f64) -> f64 {
+    pub fn clamp(mut self, min: f64, max: f64) -> f64 {
         assert!(min <= max);
-        let mut x = self;
-        if x < min {
-            x = min;
+        if self < min {
+            self = min;
         }
-        if x > max {
-            x = max;
+        if self > max {
+            self = max;
         }
-        x
+        self
     }
 }

src/test/assembly/x86_64-floating-point-clamp.rs

@@ -0,0 +1,25 @@
+// Floating-point clamp is designed to be implementable as max+min,
+// so check to make sure that's what it's actually emitting.
+
+// assembly-output: emit-asm
+// compile-flags: --crate-type=lib -O -C llvm-args=-x86-asm-syntax=intel
+// only-x86_64
+
+// CHECK-LABEL: clamp_demo:
+#[no_mangle]
+pub fn clamp_demo(a: f32, x: f32, y: f32) -> f32 {
+    // CHECK: maxss
+    // CHECK: minss
+    a.clamp(x, y)
+}
+
+// CHECK-LABEL: clamp12_demo:
+#[no_mangle]
+pub fn clamp12_demo(a: f32) -> f32 {
+    // CHECK: movss   xmm1
+    // CHECK-NEXT: maxss   xmm1, xmm0
+    // CHECK-NEXT: movss   xmm0
+    // CHECK-NEXT: minss   xmm0, xmm1
+    // CHECK: ret
+    a.clamp(1.0, 2.0)
+}