[llvm] [SelectionDAG] Preserve fast math flags when legalizing/promoting (PR #130124)

[John Brawn via llvm-commits]

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@@ -5075,6 +5075,9 @@ void SelectionDAGLegalize::PromoteNode(SDNode *Node) {
   if (Node->getOpcode() == ISD::BR_CC ||
       Node->getOpcode() == ISD::SELECT_CC)
     OVT = Node->getOperand(2).getSimpleValueType();
+  // Preserve fast math flags
+  SDNodeFlags FastMathFlags = Node->getFlags() & SDNodeFlags::FastMathFlags;
+  SelectionDAG::FlagInserter FlagsInserter(DAG, FastMathFlags);
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john-brawn-arm wrote:

I'll clean up the now-redundant setting of flags later in this function in a follow-on patch.

https://github.com/llvm/llvm-project/pull/130124