[llvm] [SCCP] Support constant structure in PhiNode (PR #163713)

[via llvm-commits]

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@@ -2125,6 +2143,21 @@ void SCCPInstVisitor::handleCallResult(CallBase &CB) {
   }
 }
 
+bool SCCPInstVisitor::isInstUnderDefined(Instruction &Inst) {
+  // For structure Type, we handle each member seperately.
+  // A structure object won't be considered as overDefined when
+  // there is at least one member can become constant.
+  if (StructType *STy = dyn_cast<StructType>(Inst.getType())) {
+    for (unsigned i = 0, e = STy->getNumElements(); i < e; ++i) {
+      if (!getStructValueState(&Inst, i).isOverdefined())
+        return false;
+    }
+    return true;
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aokblast wrote:

> Not really sure how this is related -- I was just suggesting to write the same loop you currently have in a different way. But looking again, given that this is a counter loop, the result would probably not really be better, so it's fine to just leave it as-is.

I assume that you want me to write something like return all_of(**LatticeVector**, isOverDefined); But when getting **LatticeVector** by **getStructLatticeValueFor**. It panic when one of any member is not presented in the map.

In other word, the original implementation by using getStructValueState(V, I) has a side effect that can insert (V, I) to map when the node does not exist.


https://github.com/llvm/llvm-project/pull/163713