implement min and max floating point intrinsics

Author: RalfJung

src/intrinsic.rs

@@ -1,3 +1,4 @@
+use rustc_apfloat::Float;
 use rustc::mir;
 use rustc::mir::interpret::{InterpResult, PointerArithmetic};
 use rustc::ty::layout::{self, LayoutOf, Size};
@@ -242,6 +243,28 @@ pub trait EvalContextExt<'a, 'mir, 'tcx: 'a+'mir>: crate::MiriEvalContextExt<'a,
                 this.binop_ignore_overflow(op, a, b, dest)?;
             }
 
+            "minnumf32" | "maxnumf32" => {
+                let a = this.read_scalar(args[0])?.to_f32()?;
+                let b = this.read_scalar(args[1])?.to_f32()?;
+                let res = if intrinsic_name.get().starts_with("min") {
+                    a.min(b)
+                } else {
+                    a.max(b)
+                };
+                this.write_scalar(Scalar::from_f32(res), dest)?;
+            }
+
+            "minnumf64" | "maxnumf64" => {
+                let a = this.read_scalar(args[0])?.to_f64()?;
+                let b = this.read_scalar(args[1])?.to_f64()?;
+                let res = if intrinsic_name.get().starts_with("min") {
+                    a.min(b)
+                } else {
+                    a.max(b)
+                };
+                this.write_scalar(Scalar::from_f64(res), dest)?;
+            }
+
             "exact_div" => {
                 // Performs an exact division, resulting in undefined behavior where
                 // `x % y != 0` or `y == 0` or `x == T::min_value() && y == -1`

src/lib.rs

@@ -6,8 +6,8 @@
 extern crate log;
 // From rustc.
 extern crate syntax;
-#[macro_use]
-extern crate rustc;
+extern crate rustc_apfloat;
+#[macro_use] extern crate rustc;
 extern crate rustc_data_structures;
 extern crate rustc_mir;
 extern crate rustc_target;

tests/run-pass/floats.rs

@@ -1,4 +1,3 @@
-
 fn main() {
     assert_eq!(6.0_f32*6.0_f32, 36.0_f32);
     assert_eq!(6.0_f64*6.0_f64, 36.0_f64);
@@ -12,4 +11,18 @@ fn main() {
     assert_eq!(5.0f32 as u32, 5);
     assert_eq!(5.0f32 as i32, 5);
     assert_eq!(-5.0f32 as i32, -5);
+
+    assert_eq!((1.0 as f32).max(-1.0), 1.0);
+    assert_eq!((1.0 as f32).min(-1.0), -1.0);
+    assert_eq!(std::f32::NAN.min(9.0), 9.0);
+    assert_eq!(std::f32::NAN.max(-9.0), -9.0);
+    assert_eq!((9.0 as f32).min(std::f32::NAN), 9.0);
+    assert_eq!((-9.0 as f32).max(std::f32::NAN), -9.0);
+
+    assert_eq!((1.0 as f64).max(-1.0), 1.0);
+    assert_eq!((1.0 as f64).min(-1.0), -1.0);
+    assert_eq!(std::f64::NAN.min(9.0), 9.0);
+    assert_eq!(std::f64::NAN.max(-9.0), -9.0);
+    assert_eq!((9.0 as f64).min(std::f64::NAN), 9.0);
+    assert_eq!((-9.0 as f64).max(std::f64::NAN), -9.0);
 }