Provide more atomic ops

[taiki-e]

The following are the atomic operations supported by the x86 lock prefix.

ADD, ADC, AND, BTC, BTR, BTS, CMPXCHG, CMPXCH8B, CMPXCHG16B, DEC, INC, NEG, NOT, OR, SBB, SUB, XOR, XADD, and XCHG.

We currently do not provide corresponding operations for BTC, BTR, BTS, NEG, and NOT. ^{1 2}

NEG and NOT don't return the previous value, but can be provided in a way like #47.

• BTS (fetch_bit_set?); done in Add bit_{set,clear,toggle} to Atomic{I,U}* and AtomicPtr #72
• BTR (fetch_bit_reset or fetch_bit_clear?); done in Add bit_{set,clear,toggle} to Atomic{I,U}* and AtomicPtr #72
• BTC (fetch_bit_toggle?); done in Add bit_{set,clear,toggle} to Atomic{I,U}* and AtomicPtr #72
• NEG (fetch_neg, neg); done in Add fetch_neg/neg/fetch_not/not #54
• NOT (fetch_not, not); done in Add fetch_neg/neg/fetch_not/not #54

Footnotes

1. To be exact, BTC, BTR, and BTS are available via other operations on Rust 1.65+, but LLVM only generates lock bt{s,r,c} for immediate bit offsets (as of LLVM 15). EDIT: see https://github.com/taiki-e/portable-atomic/issues/48#issuecomment-1453473831 ↩

2. As for NOT, an equivalent is available via fetch_xor(-1i*)/fetch_xor(u*::MAX), though, LLVM does not lower it to lock not. ↩

[taiki-e]

LLVM only generates lock bt{s,r,c} for immediate bit offsets (as of LLVM 15).

Ok, I confirmed LLVM 16 generates lock bt{s,r,c} for both immediate and register bit offsets.

Section .text.case1::example::fetch_bit_set::h2f09b9d099cdaf68:

<case1::example::fetch_bit_set::h2f09b9d099cdaf68>:
   0: lock
   1: btsq	$0x3e, (%rdi)
   6: setb	%al
   9: retq

Section .text.case1::example::fetch_bit_reset::hf6782daec0285b9e:

<case1::example::fetch_bit_reset::hf6782daec0285b9e>:
   0: lock
   1: btrq	$0x3e, (%rdi)
   6: setb	%al
   9: retq

Section .text.case1::example::fetch_bit_toggle::h6562ca191492438e:

<case1::example::fetch_bit_toggle::h6562ca191492438e>:
   0: lock
   1: btcq	$0x3e, (%rdi)
   6: setb	%al
   9: retq

Section .text.case1::fetch_bit_set::h225c90620db049f0:

<case1::fetch_bit_set::h225c90620db049f0>:
   0: andl	$0x3f, %esi
   3: lock
   4: btsq	%rsi, (%rdi)
   8: setb	%al
   b: retq

Section .text.case1::fetch_bit_reset::hc81cc2390d523ce9:

<case1::fetch_bit_reset::hc81cc2390d523ce9>:
   0: andl	$0x3f, %esi
   3: lock
   4: btrq	%rsi, (%rdi)
   8: setb	%al
   b: retq

Section .text.case1::fetch_bit_toggle::h7889c81a712fcbda:

<case1::fetch_bit_toggle::h7889c81a712fcbda>:
   0: andl	$0x3f, %esi
   3: lock
   4: btcq	%rsi, (%rdi)
   8: setb	%al
   b: retq