codegen: handle dead code with unsafe_store of FCA pointers

Fix #50125

Author: vtjnash

src/intrinsics.cpp

@@ -675,7 +675,7 @@ static jl_cgval_t emit_pointerref(jl_codectx_t &ctx, jl_cgval_t *argv)
         ai.decorateInst(load);
         return mark_julia_type(ctx, load, true, ety);
     }
-    else if (!jl_isbits(ety)) {
+    else if (!deserves_stack(ety)) {
         assert(jl_is_datatype(ety));
         uint64_t size = jl_datatype_size(ety);
         Value *strct = emit_allocobj(ctx, (jl_datatype_t*)ety);
@@ -747,7 +747,7 @@ static jl_cgval_t emit_pointerset(jl_codectx_t &ctx, jl_cgval_t *argv)
         jl_aliasinfo_t ai = jl_aliasinfo_t::fromTBAA(ctx, ctx.tbaa().tbaa_data);
         ai.decorateInst(store);
     }
-    else if (!jl_isbits(ety)) {
+    else if (x.ispointer()) {
         thePtr = emit_unbox(ctx, getInt8PtrTy(ctx.builder.getContext()), e, e.typ);
         uint64_t size = jl_datatype_size(ety);
         im1 = ctx.builder.CreateMul(im1, ConstantInt::get(ctx.types().T_size,