diff --git a/base/pointer.jl b/base/pointer.jl
index 924a5c18ca1d3..0813d0a0c9735 100644
--- a/base/pointer.jl
+++ b/base/pointer.jl
@@ -56,8 +56,8 @@ function unsafe_convert end
 
 unsafe_convert(::Type{Ptr{UInt8}}, x::Symbol) = ccall(:jl_symbol_name, Ptr{UInt8}, (Any,), x)
 unsafe_convert(::Type{Ptr{Int8}}, x::Symbol) = ccall(:jl_symbol_name, Ptr{Int8}, (Any,), x)
-unsafe_convert(::Type{Ptr{UInt8}}, s::String) = convert(Ptr{UInt8}, pointer_from_objref(s)+sizeof(Int))
-unsafe_convert(::Type{Ptr{Int8}}, s::String) = convert(Ptr{Int8}, pointer_from_objref(s)+sizeof(Int))
+unsafe_convert(::Type{Ptr{UInt8}}, s::String) = ccall(:jl_string_ptr, Ptr{UInt8}, (Any,), s)
+unsafe_convert(::Type{Ptr{Int8}}, s::String) = ccall(:jl_string_ptr, Ptr{Int8}, (Any,), s)
 # convert strings to String etc. to pass as pointers
 cconvert(::Type{Ptr{UInt8}}, s::AbstractString) = String(s)
 cconvert(::Type{Ptr{Int8}}, s::AbstractString) = String(s)
diff --git a/src/ccall.cpp b/src/ccall.cpp
index ce5fc1fc160bc..6ce7ab59caf24 100644
--- a/src/ccall.cpp
+++ b/src/ccall.cpp
@@ -1227,6 +1227,10 @@ std::string generate_func_sig(const char *fname)
             continue;
         attributes = attributes.addAttributes(jl_LLVMContext, i + 1, as);
     }
+    // If return value is boxed it must be non-null.
+    if (retboxed)
+        attributes = attributes.addAttribute(jl_LLVMContext, AttributeList::ReturnIndex,
+                                             Attribute::NonNull);
     if (rt == jl_bottom_type) {
         attributes = attributes.addAttribute(jl_LLVMContext,
                                              AttributeList::FunctionIndex,
@@ -1692,8 +1696,25 @@ static jl_cgval_t emit_ccall(jl_codectx_t &ctx, jl_value_t **args, size_t nargs)
     else if (is_libjulia_func(jl_string_ptr)) {
         assert(lrt == T_size);
         assert(!isVa && !llvmcall && nccallargs == 1);
-        Value *obj = ctx.builder.CreatePtrToInt(emit_pointer_from_objref(ctx, boxed(ctx, argv[0])), T_size);
-        Value *strp = ctx.builder.CreateAdd(obj, ConstantInt::get(T_size, sizeof(void*)));
+        auto obj = emit_bitcast(ctx, emit_pointer_from_objref(ctx, boxed(ctx, argv[0])),
+                                T_pprjlvalue);
+        // The inbounds gep makes it more clear to LLVM that the resulting value is not
+        // a null pointer.
+        auto strp = ctx.builder.CreateConstInBoundsGEP1_32(T_prjlvalue, obj, 1);
+        strp = ctx.builder.CreatePtrToInt(strp, T_size);
+        JL_GC_POP();
+        return mark_or_box_ccall_result(ctx, strp, retboxed, rt, unionall, static_rt);
+    }
+    else if (is_libjulia_func(jl_symbol_name)) {
+        assert(lrt == T_size);
+        assert(!isVa && !llvmcall && nccallargs == 1);
+        auto obj = emit_bitcast(ctx, emit_pointer_from_objref(ctx, boxed(ctx, argv[0])),
+                                T_pprjlvalue);
+        // The inbounds gep makes it more clear to LLVM that the resulting value is not
+        // a null pointer.
+        auto strp = ctx.builder.CreateConstInBoundsGEP1_32(
+            T_prjlvalue, obj, (sizeof(jl_sym_t) + sizeof(void*) - 1) / sizeof(void*));
+        strp = ctx.builder.CreatePtrToInt(strp, T_size);
         JL_GC_POP();
         return mark_or_box_ccall_result(ctx, strp, retboxed, rt, unionall, static_rt);
     }
diff --git a/src/codegen.cpp b/src/codegen.cpp
index 18196377995a0..f3d746e4bfae0 100644
--- a/src/codegen.cpp
+++ b/src/codegen.cpp
@@ -361,7 +361,7 @@ static AttributeList get_attrs_sext(LLVMContext &C)
 {
     return AttributeList::get(C,
                 AttributeSet(),
-                AttributeSet(),
+                Attributes(C, {Attribute::NonNull}),
                 {Attributes(C, {Attribute::SExt})});
 }
 
@@ -369,7 +369,7 @@ static AttributeList get_attrs_zext(LLVMContext &C)
 {
     return AttributeList::get(C,
                 AttributeSet(),
-                AttributeSet(),
+                Attributes(C, {Attribute::NonNull}),
                 {Attributes(C, {Attribute::ZExt})});
 }
 
@@ -614,7 +614,7 @@ static const auto jl_newbits_func = new JuliaFunction{
                 {T_prjlvalue, T_pint8}, false); },
     [](LLVMContext &C) { return AttributeList::get(C,
             AttributeSet(),
-            Attributes(C, {Attribute::NoAlias, Attribute::NonNull}),
+            Attributes(C, {Attribute::NonNull}),
             None); },
 };
 static const auto jl_typeof_func = new JuliaFunction{
@@ -769,9 +769,9 @@ BOX_FUNC(uint32, T_prjlvalue, T_int32, get_attrs_zext);
 BOX_FUNC(int64, T_prjlvalue, T_int64, get_attrs_sext);
 BOX_FUNC(uint64, T_prjlvalue, T_int64, get_attrs_zext);
 BOX_FUNC(char, T_prjlvalue, T_char, get_attrs_zext);
-BOX_FUNC(float32, T_prjlvalue, T_float32, nullptr);
-BOX_FUNC(float64, T_prjlvalue, T_float64, nullptr);
-BOX_FUNC(ssavalue, T_prjlvalue, T_size, nullptr);
+BOX_FUNC(float32, T_prjlvalue, T_float32, get_func_attrs);
+BOX_FUNC(float64, T_prjlvalue, T_float64, get_func_attrs);
+BOX_FUNC(ssavalue, T_prjlvalue, T_size, get_func_attrs);
 #undef BOX_FUNC
 
 
@@ -805,7 +805,7 @@ static const auto pointer_from_objref_func = new JuliaFunction{
             {PointerType::get(T_jlvalue, AddressSpace::Derived)}, false); },
     [](LLVMContext &C) { return AttributeList::get(C,
             AttributeSet::get(C, makeArrayRef({Attribute::get(C, Attribute::ReadNone), Attribute::get(C, Attribute::NoUnwind)})),
-            AttributeSet(),
+            Attributes(C, {Attribute::NonNull}),
             None); },
 };
 
diff --git a/src/julia.h b/src/julia.h
index 6ee5c5bce69de..166c6b59f2806 100644
--- a/src/julia.h
+++ b/src/julia.h
@@ -1012,6 +1012,7 @@ STATIC_INLINE jl_value_t *jl_field_type_concrete(jl_datatype_t *st JL_PROPAGATES
 #define jl_datatype_nfields(t) (((jl_datatype_t*)(t))->layout->nfields)
 #define jl_datatype_isinlinealloc(t) (((jl_datatype_t *)(t))->isinlinealloc)
 
+JL_DLLEXPORT void *jl_symbol_name(jl_sym_t *s);
 // inline version with strong type check to detect typos in a `->name` chain
 STATIC_INLINE char *jl_symbol_name_(jl_sym_t *s) JL_NOTSAFEPOINT
 {