enhance maintainability of jl_ir_ accessors

[aviatesk]

By allowing us to change data size at one place when we make a change to the layout of compressed IR.

[Keno]

Yes, this is what I had in mind, plus some asserts in the serializer that asserts that the offset matches what is being written.

[aviatesk]

plus some asserts in the serializer that asserts that the offset matches what is being written

Do you mean something like this?

diff --git a/src/ircode.c b/src/ircode.c
index 8516cf9817..fb322a37a9 100644
--- a/src/ircode.c
+++ b/src/ircode.c
@@ -825,12 +825,16 @@ JL_DLLEXPORT jl_string_t *jl_compress_ir(jl_method_t *m, jl_code_info_t *code)
     jl_code_info_flags_t flags = code_info_flags(code->inferred, code->propagate_inbounds, code->has_fcall,
                                                  code->nospecializeinfer, code->inlining, code->constprop);
     write_uint8(s.s, flags.packed);
+    assert(sizeof(flags.packed) == ir_datasize_flags);
     write_uint8(s.s, code->purity.bits);
+    assert(sizeof(code->purity.bits) == ir_datasize_purity);
     write_uint16(s.s, code->inlining_cost);
+    assert(sizeof(code->inlining_cost) == ir_datasize_inlining_cost);
 
-    size_t nslots = jl_array_nrows(code->slotflags);
+    int32_t nslots = jl_array_nrows(code->slotflags);
     assert(nslots >= m->nargs && nslots < INT32_MAX); // required by generated functions
     write_int32(s.s, nslots);
+    assert(sizeof(nslots) == ir_datasize_nslots);
     ios_write(s.s, jl_array_data(code->slotflags, const char), nslots);
 
     // N.B.: The layout of everything before this point is explicitly referenced

[Keno]

Yes, although those could probably be static asserts, since they're constexpr, which would help even if you're not building in debug mode. The intention is for something to fail loudly if things get messed up.

[aviatesk]

Hmm, it looks like they aren't constexprs in the CI setup? I couldn't reproduce it locally..