File opencv-ppc64le-power9.patch of Package opencv

From 83026bfe871bb9b575f62df03743704a01c13fcd Mon Sep 17 00:00:00 2001
From: Alexander Smorkalov <2536374+asmorkalov@users.noreply.github.com>
Date: Mon, 10 Nov 2025 12:11:24 +0300
Subject: [PATCH] Merge pull request #27990 from asmorkalov:as/power9_build_fix

Fix missing vec_cvfo on IBM POWER9 due to unavailable VSX float64 conversion #27990

Replaces https://github.com/opencv/opencv/pull/27633
Closes https://github.com/opencv/opencv/issues/27635

### Pull Request Readiness Checklist

See details at https://github.com/opencv/opencv/wiki/How_to_contribute#making-a-good-pull-request

- [x] I agree to contribute to the project under Apache 2 License.
- [x] To the best of my knowledge, the proposed patch is not based on a code under GPL or another license that is incompatible with OpenCV
- [ ] The PR is proposed to the proper branch
- [ ] There is a reference to the original bug report and related work
- [ ] There is accuracy test, performance test and test data in opencv_extra repository, if applicable
      Patch to opencv_extra has the same branch name.
- [ ] The feature is well documented and sample code can be built with the project CMake
---
 .../core/include/opencv2/core/vsx_utils.hpp   | 23 +++++++++++++++++--
 1 file changed, 21 insertions(+), 2 deletions(-)

diff --git a/modules/core/include/opencv2/core/vsx_utils.hpp b/modules/core/include/opencv2/core/vsx_utils.hpp
index 4d5a694bae8e..aafc6c07b176 100644
--- a/modules/core/include/opencv2/core/vsx_utils.hpp
+++ b/modules/core/include/opencv2/core/vsx_utils.hpp
@@ -257,8 +257,27 @@ VSX_IMPL_1VRG(vec_udword2, vec_udword2, vpopcntd, vec_popcntu)
 VSX_IMPL_1VRG(vec_udword2, vec_dword2,  vpopcntd, vec_popcntu)
 
 // converts between single and double-precision
-VSX_REDIRECT_1RG(vec_float4,  vec_double2, vec_cvfo, vec_floate)
-VSX_REDIRECT_1RG(vec_double2, vec_float4,  vec_cvfo, vec_doubleo)
+// vec_floate and vec_doubleo are available since Power10 and z14
+#if defined(__POWER10__) || (defined(__powerpc64__) && defined(__ARCH_PWR10__)
+//  Use VSX double<->float conversion instructions (if supported by the architecture)
+    VSX_REDIRECT_1RG(vec_float4,  vec_double2, vec_cvfo, vec_floate)
+    VSX_REDIRECT_1RG(vec_double2, vec_float4,  vec_cvfo, vec_doubleo)
+#else
+//  Fallback: implement vec_cvfo using scalar operations (to ensure successful linking)
+    static inline vec_float4 vec_cvfo(const vec_double2& a)
+    {
+        float r0 = static_cast<float>(reinterpret_cast<const double*>(&a)[0]);
+        float r1 = static_cast<float>(reinterpret_cast<const double*>(&a)[1]);
+        return (vec_float4){r0, 0.f, r1, 0.f};
+    }
+
+    static inline vec_double2 vec_cvfo(const vec_float4& a)
+    {
+        double r0 = static_cast<double>(reinterpret_cast<const float*>(&a)[0]);
+        double r1 = static_cast<double>(reinterpret_cast<const float*>(&a)[2]);
+        return (vec_double2){r0, r1};
+    }
+#endif
 
 // converts word and doubleword to double-precision
 #undef vec_ctd