[clang] [llvm] [SCCP] Infer return attributes in SCCP as well (PR #106732)

[via cfe-commits]

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@@ -354,6 +354,36 @@ bool SCCPSolver::removeNonFeasibleEdges(BasicBlock *BB, DomTreeUpdater &DTU,
   return true;
 }
 
+void SCCPSolver::inferReturnAttributes() const {
+  for (const auto &I : getTrackedRetVals()) {
+    Function *F = I.first;
+    const ValueLatticeElement &ReturnValue = I.second;
+
+    // If there is a known constant range for the return value, add range
+    // attribute to the return value.
+    if (ReturnValue.isConstantRange() &&
+        !ReturnValue.getConstantRange().isSingleElement()) {
+      // Do not add range metadata if the return value may include undef.
+      if (ReturnValue.isConstantRangeIncludingUndef())
+        continue;
+
+      // Take the intersection of the existing attribute and the inferred range.
+      ConstantRange CR = ReturnValue.getConstantRange();
+      if (F->hasRetAttribute(Attribute::Range))
+        CR = CR.intersectWith(F->getRetAttribute(Attribute::Range).getRange());
+      F->addRangeRetAttr(CR);
+      continue;
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goldsteinn wrote:

Do we ever want to infer `nonnull` in addition to `range` attr?

https://github.com/llvm/llvm-project/pull/106732