[AutoDiff] Registers VJPs for FloatingPoint.[maximum|minimum] (#35379)

Resolves TF-1134.

Author: vguerra

stdlib/public/Differentiation/FloatingPointDifferentiation.swift.gyb

@@ -282,4 +282,22 @@ where
     let y = squareRoot()
     return (y, { v in v / (2 * y) })
   }
+
+  @inlinable
+  @derivative(of: minimum)
+  static func _vjpMinimum(_ x: Self, _ y: Self) -> (
+    value: Self, pullback: (TangentVector) -> (TangentVector, TangentVector)
+  ) {
+    if x <= y || y.isNaN { return (x, { v in (v, .zero) }) }
+    return (y, { v in (.zero, v) })
+  }
+
+  @inlinable
+  @derivative(of: maximum)
+  static func _vjpMaximum(_ x: Self, _ y: Self) -> (
+    value: Self, pullback: (TangentVector) -> (TangentVector, TangentVector)
+  ) {
+    if x > y || y.isNaN { return (x, { v in (v, .zero) }) }
+    return (y, { v in (.zero, v) })
+  }
 }

test/AutoDiff/stdlib/floating_point.swift.gyb

@@ -83,6 +83,22 @@ FloatingPointDerivativeTests.test("${Self}.addingProduct") {
   expectEqual((1, 2, 3), gradient(at: ${Self}(10), 3, 2, in: { $0.addingProduct($1, $2) }))
 }
 
+FloatingPointDerivativeTests.test("${Self}.minimum") {
+  expectEqual((1.0, 0.0), gradient(at: ${Self}(1), ${Self}(2), in : { ${Self}.minimum($0, $1) }))
+  expectEqual((1.0, 0.0), gradient(at: ${Self}(1), ${Self}(1), in : { ${Self}.minimum($0, $1) }))
+  expectEqual((0.0, 1.0), gradient(at: ${Self}(2), ${Self}(1), in : { ${Self}.minimum($0, $1) }))
+  expectEqual((1.0, 0.0), gradient(at: ${Self}(1), .nan, in : { ${Self}.minimum($0, $1) }))
+  expectEqual((0.0, 1.0), gradient(at: .nan, ${Self}(1), in : { ${Self}.minimum($0, $1) }))
+}
+
+FloatingPointDerivativeTests.test("${Self}.maximum") {
+  expectEqual((0.0, 1.0), gradient(at: ${Self}(1), ${Self}(2), in : { ${Self}.maximum($0, $1) }))
+  expectEqual((0.0, 1.0), gradient(at: ${Self}(1), ${Self}(1), in : { ${Self}.maximum($0, $1) }))
+  expectEqual((1.0, 0.0), gradient(at: ${Self}(2), ${Self}(1), in : { ${Self}.maximum($0, $1) }))
+  expectEqual((1.0, 0.0), gradient(at: ${Self}(1), .nan, in : { ${Self}.maximum($0, $1) }))
+  expectEqual((0.0, 1.0), gradient(at: .nan, ${Self}(1), in : { ${Self}.maximum($0, $1) }))
+}
+
 %if Self == 'Float80':
 #endif
 %end