[SYCL] Fix acos edge case (#14026)

Author: jzc

libdevice/fallback-complex-fp64.cpp

@@ -311,8 +311,8 @@ double __complex__ __devicelib_cacos(double __complex__ z) {
       return CMPLX(z_real, -z_imag);
     return CMPLX(z_real, z_real);
   }
-  if (__spirv_IsInf(z_real))
-    return CMPLX(__pi / 2.0, -z_real);
+  if (__spirv_IsInf(z_imag))
+    return CMPLX(__pi / 2.0, -z_imag);
   if (z_real == 0 && (z_imag == 0 || __spirv_IsNan(z_imag)))
     return CMPLX(__pi / 2.0, -z_imag);
   double __complex__ w =

sycl/test-e2e/Regression/acos.cpp

@@ -0,0 +1,39 @@
+// REQUIRES: aspect-fp64
+// UNSUPPORTED: cuda || hip
+
+// RUN: %{build} -o %t.out
+// RUN: %{run} %t.out
+#include <complex>
+#include <sycl/detail/core.hpp>
+#include <sycl/usm.hpp>
+
+using namespace sycl;
+using T = std::complex<double>;
+
+int main() {
+  queue q;
+  const double pi = std::atan2(+0., -0.);
+  T data[][2] = {{{-2, -INFINITY}, {pi / 2, INFINITY}},
+                 {{-0., INFINITY}, {pi / 2, -INFINITY}}};
+  int N = std::size(data);
+  auto *p = malloc_shared<T>(N, q);
+
+  q.single_task([=] {
+     for (int i = 0; i < N; ++i) {
+       p[i] = std::acos(data[i][0]);
+     }
+   }).wait();
+
+  int fails = 0;
+  for (int i = 0; i < N; ++i) {
+    auto actual = p[i];
+    auto expected = data[i][1];
+    if (expected != actual) {
+      std::cout << i << " fail:"
+                << "expected = " << expected << ", actual = " << actual << "\n";
+      ++fails;
+    }
+  }
+
+  return fails;
+}