[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:

If x87 is the only issue you're worried about here, modifying the way the x86 call lowering works might be the right approach.  Instead of representing the floating-point return value with CopyFromReg, introduce "X86ISD::PopX87Reg".  That way it's more explicit why it's important to preserve, and target-independent code doesn't need any special logic for it.

A fully generic barrier seems like it's just making everything harder to understand.

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