[llvm] [flang][rt] Attempt to support some complex pow on the device (PR #135741)

[Slava Zakharin via llvm-commits]

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@@ -65,21 +66,23 @@ template <typename C, typename I> C tgpowi(C base, I exp) {
 #ifndef _MSC_VER
 // With most compilers, C complex is implemented as a builtin type that may have
 // specific ABI requirements
-extern "C" float _Complex RTNAME(cpowi)(float _Complex base, std::int32_t exp) {
+extern "C" RT_API_ATTRS CppTypeFor<TypeCategory::Complex, 4> RTNAME(cpowi)(
+    CppTypeFor<TypeCategory::Complex, 4> base, std::int32_t exp) {
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vzakhari wrote:

Sorry, I do not know where we stand with passing the complex values from Flang to the runtime, but the C complex was used here to match the ABI of pure C complex.  The discussion was here: https://reviews.llvm.org/D134889

This change may be unsafe, but this needs to be investigated.

https://github.com/llvm/llvm-project/pull/135741