[clang] [CIR] Add pass_object_size hidden parameter support (PR #191482)

[via cfe-commits]

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@@ -2581,11 +2581,37 @@ mlir::Value CIRGenFunction::emitVAArg(VAArgExpr *ve) {
   return cir::VAArgOp::create(builder, loc, type, vaList);
 }
 
+/// Checks if using the result of __builtin_object_size(p, @p from) in place of
+/// __builtin_object_size(p, @p to) is correct.
+///
+/// type=0 is the maximum object size; compatible with type=1 (maximum of the
+/// remaining bytes, which is always <= total size).  type=3 is the minimum
+/// remaining bytes; compatible with type=2 (minimum object size).
+static bool areBOSTypesCompatible(int from, int to) {
+  return from == to || (from == 0 && to == 1) || (from == 3 && to == 2);
+}
+
 mlir::Value CIRGenFunction::emitBuiltinObjectSize(const Expr *e, unsigned type,
                                                   cir::IntType resType,
                                                   mlir::Value emittedE,
                                                   bool isDynamic) {
-  assert(!cir::MissingFeatures::opCallImplicitObjectSizeArgs());
+  // If this is a pass_object_size parameter, load the implicit size arg.
+  if (auto *d = dyn_cast<DeclRefExpr>(e->IgnoreParenImpCasts())) {
+    auto *param = dyn_cast<ParmVarDecl>(d->getDecl());
+    auto *ps = d->getDecl()->getAttr<PassObjectSizeAttr>();
+    if (param && ps && areBOSTypesCompatible(ps->getType(), type)) {
+      auto iter = sizeArguments.find(param);
+      assert(iter != sizeArguments.end());
+
+      const ImplicitParamDecl *sizeDecl = iter->second;
+      auto dIter = localDeclMap.find(sizeDecl);
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adams381 wrote:

Done.

https://github.com/llvm/llvm-project/pull/191482