[llvm] [llvm][GlobalOpt] Optimize statically resolvable IFuncs (PR #80606)

[Nikita Popov via llvm-commits]

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@@ -2404,6 +2405,42 @@ static bool OptimizeEmptyGlobalCXXDtors(Function *CXAAtExitFn) {
   return Changed;
 }
 
+static Function *hasSideeffectFreeStaticResolution(GlobalIFunc &IF) {
+  Function *Resolver = IF.getResolverFunction();
+  if (!Resolver)
+    return nullptr;
+
+  Function *Callee = nullptr;
+  for (BasicBlock &BB : *Resolver) {
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nikic wrote:

This doesn't account for divergence effects (infinite loops). I'd recommend to only handle the case with a single basic block and rely on preceding simplification to reduce it to that form. (Unless there is a phase-ordering reason to believe this will not happen?)

https://github.com/llvm/llvm-project/pull/80606