[clang] [clang][PowerPC] Add flag to enable compatibility with GNU for complex arguments (PR #77732)

[Eli Friedman via cfe-commits]

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@@ -78,6 +78,13 @@ class CodeGenOptions : public CodeGenOptionsBase {
     SRCK_InRegs    // Small structs in registers (-freg-struct-return).
   };
 
+  enum ComplexArgumentConventionKind {
+    CMPLX_Default,
+    CMPLX_OnStack,
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efriedma-quic wrote:

I don't think this needs to be a target-independent thing; this doesn't really generalize to other targets.  I mean, maybe different targets have sort of similar schemes, but the same ABI compatibility issue shouldn't exist anywhere else.  Maybe pass this as a target feature (ref getPPCTargetFeatures()).

https://github.com/llvm/llvm-project/pull/77732