[llvm] [SDAG] Add missing float type legalizations for FMODF (PR #128055)

[Eli Friedman via llvm-commits]

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@@ -2616,6 +2624,18 @@ bool SelectionDAG::expandMultipleResultFPLibCall(
 
   auto [Call, CallChain] = TLI->LowerCallTo(CLI);
 
+  if (CallRetResNo && !Node->hasAnyUseOfValue(*CallRetResNo)) {
+    // This is needed for x87, which uses a floating-point stack. If (for
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efriedma-quic wrote:

My primary issue with the chain barrier is it doesn't generalize properly.  For example, say you have a libcall that returns a complex number as an fp0/fp1 pair, and subsequent code throws away fp1.  You run into basically the same issue, and there isn't any way to use a chain barrier to resolve it because the chain barrier itself would be dead.  (I don't think we currently generate any complex libcalls, but there's no fundamental reason for that.)

https://github.com/llvm/llvm-project/pull/128055