Splitting pow's derivative test cases.

We now have 3 sections for the tests: negative base, 0 base and
positive base.

Author: vguerra

test/AutoDiff/stdlib/tgmath_derivatives.swift.gyb

@@ -141,37 +141,62 @@ DerivativeTests.test("${op}_${T}") {
   // pow
   let eps:${T} = 0.01
   let ulps:${T} = eps/eps.ulp
-  for a in -3...3 {
+
+  // Checks for negative base.
+  for a in -3..<0 {
     let x = ${T}(a)
     for b in -3...3 {
       let y = ${T}(b)
-      var expectedValues: (dx: ${T}, dy: ${T})?
-      if x.isZero {
-        if y.isLess(than: 0) {
-          expectedValues = (dx: ${T}.infinity, dy: ${T}.nan)
-        } else if y.isZero {
-          expectedValues = (dx: ${T}.nan, dy: ${T}.zero)
-        } else if !y.isEqual(to: 1) {
-          expectedValues = (dx: ${T}.zero, dy: ${T}.zero)
-        }
-      } else if x.isLess(than: 2) {
-        expectedValues = (dx: y * pow(x, y - 1), ${T}.zero)
-      }
-      if let (expectedDx, expectedDy) = expectedValues {
-        let dpow = ${op}(at: x, y, in: pow)
+      let expectedDx =  y * pow(x, y - 1)
+      let expectedDy = ${T}.zero
+      let dpow = ${op}(at: x, y, in: pow)
 %if op == 'gradient':
-        expectEqualWithTolerance(TestLiteralType(expectedDx), dpow.0)
-        expectEqualWithTolerance(TestLiteralType(expectedDy), dpow.1)
+      expectEqualWithTolerance(TestLiteralType(expectedDx), dpow.0)
+      expectEqualWithTolerance(TestLiteralType(expectedDy), dpow.1)
 %else: # if op == 'derivative'
-        expectEqualWithTolerance(TestLiteralType(expectedDx + expectedDy), dpow)
+      expectEqualWithTolerance(TestLiteralType(expectedDx + expectedDy), dpow)
 %end
-      } else {
+    }
+  }
+
+  // Checks for 0 base.
+  for b in -3...3 {
+    let y = ${T}(b)
+    var expectedValues: (dx: ${T}, dy: ${T})?
+    if y.isLess(than: 0) {
+      expectedValues = (dx: ${T}.infinity, dy: ${T}.nan)
+    } else if y.isZero {
+      expectedValues = (dx: ${T}.nan, dy: ${T}.zero)
+    } else if !y.isEqual(to: 1) {
+      expectedValues = (dx: ${T}.zero, dy: ${T}.zero)
+    }
+    if let (expectedDx, expectedDy) = expectedValues {
+      let dpow = ${op}(at: 0.0, y, in: pow)
+%if op == 'gradient':
+      expectEqualWithTolerance(TestLiteralType(expectedDx), dpow.0)
+      expectEqualWithTolerance(TestLiteralType(expectedDy), dpow.1)
+%else: # if op == 'derivative'
+      expectEqualWithTolerance(TestLiteralType(expectedDx + expectedDy), dpow)
+%end
+    } else {
+%if op == 'gradient':
+      checkGradient({ pow($0, $1) }, 0.0, y, ulps: ulps)
+%else: # if op == 'derivative'
+      checkDerivative({ pow($0, $1) }, 0.0, y, ulps: ulps)
+%end
+    }
+  }
+
+  // Checks for positive base.
+  for a in 1...3 {
+    let x = ${T}(a)
+    for b in -3...3 {
+      let y = ${T}(b)
 %if op == 'gradient':
-          checkGradient({ pow($0, $1) }, x, y, ulps: ulps)
+      checkGradient({ pow($0, $1) }, x, y, ulps: ulps)
 %else: # if op == 'derivative'
-          checkDerivative({ pow($0, $1) }, x, y, ulps: ulps)
+      checkDerivative({ pow($0, $1) }, x, y, ulps: ulps)
 %end
-      }
     }
   }
 }