[clang] [compiler-rt] [llvm] [SystemZ] Add support for half (fp16) (PR #109164)

[Trevor Gross via cfe-commits]

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@@ -255,4 +255,9 @@ void RuntimeLibcallsInfo::initLibcalls(const Triple &TT) {
     }
     setLibcallName(RTLIB::MULO_I128, nullptr);
   }
+
+  if (TT.isSystemZ()) {
+    setLibcallName(RTLIB::FPROUND_F32_F16, "__truncsfhf2");
+    setLibcallName(RTLIB::FPEXT_F16_F32, "__extendhfsf2");
+  }
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tgross35 wrote:

Regarding how to build and link, they are in compiler-rt if that can be built https://github.com/llvm/llvm-project/blob/fa22100d57631bbb0a507dd27e3ebb24b1354623/compiler-rt/lib/builtins/truncsfhf2.c#L15. `__trunc` and `__extend` are what you want to emit here, I'm just not sure what exactly this file needs to do because it seems like `HasLegalHalfType` controls `__extend`/`__trunc` vs. `__gnu_` lowering somehow https://github.com/llvm/llvm-project/pull/109164#issuecomment-2433525551.

https://github.com/llvm/llvm-project/pull/109164