diff --git a/llvm/lib/Transforms/Scalar/RewriteStatepointsForGC.cpp b/llvm/lib/Transforms/Scalar/RewriteStatepointsForGC.cpp
--- a/llvm/lib/Transforms/Scalar/RewriteStatepointsForGC.cpp
+++ b/llvm/lib/Transforms/Scalar/RewriteStatepointsForGC.cpp
@@ -529,10 +529,12 @@
     assert(cast<PointerType>(Def->getType())->getAddressSpace() ==
                cast<PointerType>(CI->getType())->getAddressSpace() &&
            "unsupported addrspacecast");
-    // If we find a cast instruction here, it means we've found a cast which is
-    // not simply a pointer cast (i.e. an inttoptr).  We don't know how to
-    // handle int->ptr conversion.
-    assert(!isa<CastInst>(Def) && "shouldn't find another cast here");
+    // If we find an inttoptr, we'll assume that's the base pointer.
+    // Optimization passes can generate inttoptrs from loads from memory,
+    // which we consider base pointers, so we treat inttoptr the same way.
+    if ((CI = dyn_cast<CastInst>(Def)) &&
+        CI->getOpcode() == Instruction::CastOps::IntToPtr)
+      return BaseDefiningValueResult(Def, true);
     return findBaseDefiningValue(Def);
   }
 
diff --git a/llvm/test/Transforms/RewriteStatepointsForGC/base-inttoptr.ll b/llvm/test/Transforms/RewriteStatepointsForGC/base-inttoptr.ll
new file mode 100644
--- /dev/null
+++ b/llvm/test/Transforms/RewriteStatepointsForGC/base-inttoptr.ll
@@ -0,0 +1,13 @@
+; RUN: opt -S -rewrite-statepoints-for-gc < %s | FileCheck %s
+
+; Regression test to make sure RS4GC can handle inttoptr casts, which can be generated by other optimization passes
+; CHECK: test
+target triple = "x86_64-unknown-linux-gnu"
+
+declare void @foo()
+
+define i8 addrspace(1)* @test(i64 %i) gc "statepoint-example" {
+    %p = inttoptr i64 %i to i8 addrspace(1)*
+    call void @foo()
+    ret i8 addrspace(1)* %p
+}