[llvm] [LLVM] New NoDivergenceSource function attribute (PR #111832)

[Jay Foad via llvm-commits]

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@@ -32,7 +32,14 @@ bool llvm::GenericUniformityAnalysisImpl<SSAContext>::markDefsDivergent(
 
 template <> void llvm::GenericUniformityAnalysisImpl<SSAContext>::initialize() {
   for (auto &I : instructions(F)) {
-    if (TTI->isSourceOfDivergence(&I))
+    bool NoDivergenceSource = false;
+    if (auto Call = dyn_cast<CallInst>(&I)) {
+      if (Function *Callee = Call->getCalledFunction()) {
+        if (Callee->hasFnAttribute(Attribute::NoDivergenceSource))
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jayfoad wrote:

Great. Then I think this patch should check attributes on the call. It seems reasonable that a call could be "no divergence source" either with an unknown callee (e.g. an indirect call) or because the frontend knows something about that specific call site even though the callee could in general introduce divergence.

https://github.com/llvm/llvm-project/pull/111832