I suggest lifting the pointers to a C autos, and setting struct field to NULL, then call SvREFCNT_dec. Analyse if SvREFCNT_dec_NN is appropriate.

xhv_class_superclass can be NULL if the class has no base class defined.

I don't think there's any value re-ordering here, since we only write to xhv_class_superclass after the REFCNT_dec.

I think it's unlikely the cache line will expire - this is a reference to an existing class, so it's just going to reduce the reference count and test it.

My rational for the change is so the CC has the opportunity to not write the int literal that is part of ->xhv_class_superclass 2x in machine code. I doubt the offset of ->xhv_class_superclass is 0x0. Its more likely to be 0x18 or 0x30 or 0x10. Foo-arch RISC CPUs may or may not not allow writing a +/- (U8) 0xF0 literal, that will be embedded inside the ld/st/mov opcode. So on Foo RISC CPU arch, Either the user wants load/store opcodes, or the user wants integer algebra opcodes. Can't have your cake and eat it too,

I have a personal policy to write C code, pretending that certain Intel x86 only op codes do not exist in my head, and to avoid writing C code, that will emit those certain Intel x86 only op,

Specifically I try to not use Intel's lea op, which is unique on planet earth. No other CPU has ever had an op that does a1 = a1+a2+(a3<<a4) ; AND that op DOES NOT CHANGE EFLAGS/jmp status control bits,

I also avoid Intel's swiss army knife of pre-calculus math exams, the 2 byte ling SIB operand specifier. I prefer to stick to old fashioned 1 byte long modR/M operands.

lea and sib is easily fixed by just factoring out some math from your struct deref statements in your inner loop.
Change int i = 0; i++; to using a real pointer, that gets bumped by sizeof(c_struct) and < compare against a read END pointer in your loop. All those LEA and SIB ops fluffery has been factored out by hand in C pretty easily.

ARM32 CPUs can't store more than a U8 literal in THUMB machine code, and can't store more than a 2^12 (4096) integer literal operand in 4byte OPs ARM. All C lang literals > 0x100 or > 4096, become separate instruction LOAD DblWrdRegX2, *(U32*)(IP+(0xff*4); opcodes, Seeing all those >0x80 >0x100 >0x1000 src code literal ints/src code struct derefs on large structs, turning to separate mov opcodes, to GET MY OWN CONST LITERALS THAT I TYPED IN BASE 10!!! It makes my stomach feel sick reason Arm32 asm code,

So to solve every possible flaw and defect,, on every CPU arch, for all CPU archs past present and future, on every commercial grade and hobby grade C compiler from any vendor, combine whit any CC -O -m -arch cmd line args. and so I know I wrote good clean code and I dont need to decompile it because I can trust that the CC, any CC, I used, it did the best choice that I wanted.

So solve all over that, just lift the ptr_to_dotr from malloc mem first, to a C auto/volatile register, assign NULL to the malloc mem you just lifted, then pass [IRL there is no"pass"its already inside RCX or RDI] the lifted ptr stored in a volatile register to the heavy weight C and invoke the heavy weight C call.

benefit is minimal phy mem interactions, minimum computing abs addrs of data vars from offsets into structs.

3 aux->xhv_class_superclass statements become

void ** p = &aux->xhv_class_superclass;
if(*p) {
    void * p2 = *p;
    *p = NULL;
    foo_free(p2);
}

not

if(aux->xhv_class_superclass) 
    foo_free(aux->xhv_class_superclass);
aux->xhv_class_superclass = NULL;

What if var aux happens to be a c stack var and not a non vol register? Maybe foo_free() changed the ptr inside C stack var aux that was stored/splilled to phy vir memory? escape analysis? How do you know what the the e-liberal/e-conservative/e-communist/e-fascist parties at IEEE going to vote on for next month's draft spec of https://developers.redhat.com/articles/2022/06/02/use-compiler-flags-stack-protection-gcc-and-clang#safestack_and_shadow_stack ?

so worst case possible, aux->xhv_class_superclass = NULL; has 2 read ops, 1 xor op, 1 write op. my perfect version eliminated the 2 read ops,
earlier by doing

void ** p = &aux->xhv_class_superclass;
if(*p) {

Add _NN(), cv already proved to be derefable

Done

Pass the HEK* maybe, or U32 hash. hv_delete_ent() maybe??? XS api is not fully there for exotic with HEK with hash, not fetch, HV operations.

hv_delete_ent() would require making a SV, this would only be efficient for the (I think) atypical case of the key being an SVKEY.

hv_delete_ent() would require making a SV, this would only be efficient for the (I think) atypical case of the key being an SVKEY.

# define hv_deletehek(hv, hek, flags) \
    hv_common((hv), NULL, HEK_KEY(hek), HEK_LEN(hek), HEK_UTF8(hek), \
              (flags)|HV_DELETE, NULL, HEK_HASH(hek))

usng this vs hv_delete() is still a better choice, U32 has wasnt recalculated.

Unrealistic bc there arent supposd 2 exit outside TIEHASH

#define HePV(he,lp)		((HeKLEN(he) == HEf_SVKEY) ? SvPV(HeKEY_sv(he),lp) :((lp = HeKLEN(he)), HeKEY(he)))

If santa says youver been a good boy HeKEY_sv(he) will be a SVLEN()==0 HEK* COW. Note either way, you get 2 accelerated hash lookup data structures here, either an unreliatic SV*, or a HEK * from shared HEK POOL. Its wrong to use const RO "CString" hv_delete() here, you have the meta data to do something better,

sv_2mortal(isaname); to isaname = sv_2mortal(isaname);, use the free retval register.

Done

is there a better way of doing this other than a trip through SvPV(3args)'s S_uiv_2buf(), or worse going to libc sprintf with dozens of lock aq/releases, and maybe some kernel calls to the FS. I would just have 4 byte / 8 byte UVs stored straight as raw unprintable binary with SvPOK_on(). Hash algo/perl just sees char strings, vs turning them into longer less dense ascii bytes.

This code was only re-indented

factor out HeVAL(he), get the SV*. its too many layers deep of derefs in code, and probably does optimize, but its 3 or 4 derefs now from the C auto. if accidents happen with multi eval, they will be smaller.

This code was only re-indented

idk if this is a loop, but if it is, y not reuse the sv_2mortal(newSVuv()); ?

It is a loop, but this code was only re-indented.

Likely wants to be ::fail()

Fixed, thanks.