diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -351,6 +351,9 @@
 
 Improvements to Clang's diagnostics
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+- Clang now supports implicit conversion warnings (``-Wsign-conversion``,
+  ``Wshorten-64-to-32``, etc) for compound assignment operators (like +=, -=, <<=, >>= etc) 
+  with integral operands.
 - Clang will now check compile-time determinable string literals as format strings.
   Fixes `Issue 55805: <https://github.com/llvm/llvm-project/issues/55805>`_.
 - ``-Wformat`` now recognizes ``%b`` for the ``printf``/``scanf`` family of
diff --git a/clang/lib/Sema/SemaChecking.cpp b/clang/lib/Sema/SemaChecking.cpp
--- a/clang/lib/Sema/SemaChecking.cpp
+++ b/clang/lib/Sema/SemaChecking.cpp
@@ -13508,8 +13508,13 @@
   }
 }
 
+static void CheckImplicitConversion(Sema &S, Expr *E, QualType T,
+                                    SourceLocation CC,
+                                    bool *ICContext = nullptr,
+                                    bool IsListInit = false);
+
 /// Analyze the given compound assignment for the possible losing of
-/// floating-point precision.
+/// floating-point precision and for implicit conversions for integral operands.
 static void AnalyzeCompoundAssignment(Sema &S, BinaryOperator *E) {
   assert(isa<CompoundAssignOperator>(E) &&
          "Must be compound assignment operation");
@@ -13526,8 +13531,17 @@
                         ->getComputationResultType()
                         ->getAs<BuiltinType>();
 
+  // Check for implicit conversions for compound assignment statements with
+  // intergral operands.
+  // FIXME: should this handle floating-point as well?
+  if (E->getLHS()->getType()->isIntegerType() &&
+      E->getRHS()->getType()->isIntegerType() && !E->isShiftAssignOp())
+    CheckImplicitConversion(S, E->getRHS(), E->getType(),
+                            E->getRHS()->getExprLoc());
+
   // The below checks assume source is floating point.
-  if (!ResultBT || !RBT || !RBT->isFloatingPoint()) return;
+  if (!ResultBT || !RBT || !RBT->isFloatingPoint())
+    return;
 
   // If source is floating point but target is an integer.
   if (ResultBT->isInteger())
@@ -13816,9 +13830,8 @@
 }
 
 static void CheckImplicitConversion(Sema &S, Expr *E, QualType T,
-                                    SourceLocation CC,
-                                    bool *ICContext = nullptr,
-                                    bool IsListInit = false) {
+                                    SourceLocation CC, bool *ICContext,
+                                    bool IsListInit) {
   if (E->isTypeDependent() || E->isValueDependent()) return;
 
   const Type *Source = S.Context.getCanonicalType(E->getType()).getTypePtr();
diff --git a/clang/test/Sema/conversion-64-32.c b/clang/test/Sema/conversion-64-32.c
--- a/clang/test/Sema/conversion-64-32.c
+++ b/clang/test/Sema/conversion-64-32.c
@@ -17,3 +17,36 @@
 int test2(long v) {
   return v / 2; // expected-warning {{implicit conversion loses integer precision: 'long' to 'int'}}
 }
+
+// rdar://10466193
+void test3(int i, long long ll) {
+  i += ll; // expected-warning {{implicit conversion loses integer precision}}
+  i -= ll; // expected-warning {{implicit conversion loses integer precision}}
+  i *= ll; // expected-warning {{implicit conversion loses integer precision}}
+  i /= ll; // expected-warning {{implicit conversion loses integer precision}}
+}
+
+void test4(int i, long long ll) {
+  i += i-ll; // expected-warning {{implicit conversion loses integer precision}}
+  i += i+ll; // expected-warning {{implicit conversion loses integer precision}}
+  i -= i-ll; // expected-warning {{implicit conversion loses integer precision}}
+  i -= i+ll; // expected-warning {{implicit conversion loses integer precision}}
+}
+
+void test5(int i, int j, long long ll) {
+  i += (i-j)*ll; // expected-warning {{implicit conversion loses integer precision}}
+  i += (i+j)*ll; // expected-warning {{implicit conversion loses integer precision}}
+  i -= ll/(i-j); // expected-warning {{implicit conversion loses integer precision}}
+  i -= ll/(i-j); // expected-warning {{implicit conversion loses integer precision}}
+}
+
+void test6(char c) {
+  c <<= 999999; // expected-warning {{shift count >= width of type}} \
+                  // cxx17-warning {{shift count >= width of type}} \
+                  // ref-warning {{shift count >= width of type}} \
+                  // ref-cxx17-warning {{shift count >= width of type}}
+  c >>= 999999; // expected-warning {{shift count >= width of type}} \
+                  // cxx17-warning {{shift count >= width of type}} \
+                  // ref-warning {{shift count >= width of type}} \
+                  // ref-cxx17-warning {{shift count >= width of type}}
+}