[llvm] [SDAG] Add missing ppc_fp128 ExpandFloatRes for sincos[pi] (PR #128514)

[Benjamin Maxwell via llvm-commits]

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@@ -49,3 +49,49 @@ define { ppc_fp128, ppc_fp128 } @test_sincospi_ppcf128(ppc_fp128 %a) {
   %result = call { ppc_fp128, ppc_fp128 } @llvm.sincospi.ppcf128(ppc_fp128 %a)
   ret { ppc_fp128, ppc_fp128 } %result
 }
+
+; FIXME: Recognise this as a tail call and omit the stack frame:
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MacDue wrote:

> the return needs to be the immediate next instruction after the call

That is what codegen emits, the stores and extractvalues fold away to nothing, though the tail call logic does not recognise this. 

https://github.com/llvm/llvm-project/pull/128514