[PATCH] D107420: [WIP][sema] Disallow __builtin_mul_overflow under special condition.

[Freddy, Ye via Phabricator via cfe-commits]

FreddyYe updated this revision to Diff 364154.
FreddyYe marked 2 inline comments as done.
FreddyYe added a comment.

Address comments. I'll refactor clang-format later. Pls help review the new condition and diagnostic.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D107420/new/

https://reviews.llvm.org/D107420

Files:
  clang/include/clang/Basic/DiagnosticSemaKinds.td
  clang/lib/Sema/SemaChecking.cpp
  clang/test/Sema/builtins-overflow.c


Index: clang/test/Sema/builtins-overflow.c
===================================================================
--- clang/test/Sema/builtins-overflow.c
+++ clang/test/Sema/builtins-overflow.c
@@ -38,4 +38,10 @@
     _ExtInt(129) result;
     _Bool status = __builtin_mul_overflow(x, y, &result); // expected-error {{__builtin_mul_overflow does not support signed _ExtInt operands of more than 128 bits}}
   }
+  {
+    _ExtInt(128) x = 1;
+    _ExtInt(128) y = 1;
+    unsigned _ExtInt(128) result;
+    _Bool status = __builtin_mul_overflow(x, y, &result); // expected-error {{__builtin_mul_overflow does not support special combination operands (signed, signed, unsigned*) of more than 64 bits}}
+  }
 }
Index: clang/lib/Sema/SemaChecking.cpp
===================================================================
--- clang/lib/Sema/SemaChecking.cpp
+++ clang/lib/Sema/SemaChecking.cpp
@@ -328,6 +328,20 @@
   // Disallow signed ExtIntType args larger than 128 bits to mul function until
   // we improve backend support.
   if (BuiltinID == Builtin::BI__builtin_mul_overflow) {
+    const auto LeftTy = TheCall->getArg(0)->getType();
+    const auto RightTy = TheCall->getArg(1)->getType();
+    const auto ResultPointeeTy = TheCall->getArg(2)->getType()->getPointeeType();
+    // Input combination below will also emit an integer value larger than
+    // 128 bits in the backend, disallow same as above.
+    if (!ResultTy->isSignedIntegerType() &&
+        S.getASTContext().getIntWidth(ResultTy) >= 128 &&
+        (LeftTy->isSignedIntegerType() || RightTy->isSignedIntegerType()) &&
+        (S.getASTContext().getIntWidth(LeftTy) + S.getASTContext().getIntWidth(RightTy)) > 128 &&
+        ) {
+      return S.Diag(TheCall->getArg(0)->getBeginLoc(),
+                    diag::err_overflow_builtin_special_combination_max_size)
+             << 127;
+    }
     for (unsigned I = 0; I < 3; ++I) {
       const auto Arg = TheCall->getArg(I);
       // Third argument will be a pointer.
Index: clang/include/clang/Basic/DiagnosticSemaKinds.td
===================================================================
--- clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -8348,6 +8348,9 @@
 def err_overflow_builtin_ext_int_max_size : Error<
   "__builtin_mul_overflow does not support signed _ExtInt operands of more "
   "than %0 bits">;
+def err_overflow_builtin_special_combination_max_size : Error<
+  "__builtin_mul_overflow does not suport unsigned overflow check after convention "
+  "more than %0 bits">;
 
 def err_atomic_load_store_uses_lib : Error<
   "atomic %select{load|store}0 requires runtime support that is not "


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