[llvm] [LLVM][Tablegen] Add Default arguments support for Intrinsics in TableGen (PR #198557)

[Rahul Joshi via llvm-commits]

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@@ -4983,6 +5013,55 @@ static Value *upgradeConvertIntrinsicCall(StringRef Name, CallBase *CI,
   return nullptr;
 }
 
+static bool upgradeIntrinsicCallWithDefaultArgs(CallBase *CI, Function *NewFn,
+                                                IRBuilder<> &Builder) {
+  Intrinsic::ID IID = NewFn->getIntrinsicID();
+
+  auto [FirstDefault, Defaults] = Intrinsic::getAllDefaultArgValues(IID);
+  if (Defaults.empty())
+    return false;
+
+  unsigned OldArgCount = CI->arg_size();
+  unsigned NewArgCount = NewFn->arg_size();
+
+  // If the caller already supplied all arguments (or more), nothing to do.
+  // This mirrors C++ semantics: an explicitly-passed value is never overridden.
+  if (OldArgCount >= NewArgCount)
+    return false;
+
+  // Start with the existing arguments from the old call.
+  SmallVector<Value *, 8> NewArgs(CI->args());
+
+  // Fill in each missing trailing argument from the table.
+  FunctionType *NewFT = NewFn->getFunctionType();
+  for (unsigned Idx = OldArgCount; Idx < NewArgCount; ++Idx) {
+    if (Idx < FirstDefault || Idx >= FirstDefault + Defaults.size())
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jurahul wrote:

should this be assert instead?

https://github.com/llvm/llvm-project/pull/198557