> -#if defined(USE_HTM_FASTPATH) && !defined(HTM_CUSTOM_FASTPATH)
> +#ifdef USE_HTM_FASTPATH
> // HTM fastpath. Only chosen in the absence of transaction_cancel to allow
> // using an uninstrumented code path.
> // The fastpath is enabled only by dispatch_htm's method group, which uses
> @@ -187,6 +187,7 @@ GTM::gtm_thread::begin_transaction (uint32_t prop, const
> gtm_jmpbuf *jb)
> // indeed in serial mode, and HW transactions should never need serial mode
> // for any internal changes (e.g., they never abort visibly to the STM code
> // and thus do not trigger the standard retry handling).
> +#ifndef HTM_CUSTOM_FASTPATH
> if (likely(htm_fastpath && (prop & pr_hasNoAbort)))
> {
> for (uint32_t t = htm_fastpath; t; t--)
> @@ -237,6 +238,49 @@ GTM::gtm_thread::begin_transaction (uint32_t prop, const
> gtm_jmpbuf *jb)
> }
> }
> }
> +#else
> + // If we have a custom HTM fastpath in ITM_beginTransaction, we implement
> + // just the retry policy here. We communicate with the custom fastpath
Don't you want this logic arranged as
#ifdef HTM_CUSTOM_FASTPATH
... your new code
#elif defined(USE_HTM_FASTPATH)
... existing htm code
#endif
> + /* Store edi for future HTM fast path retries. */
> + movl %edi, -8(%rsp)
> + orl $pr_HTMRetryableAbort, %edi
> + /* Let the C++ code handle the retry policy. */
> +no_htm:
Note for future porting of this code to i386 or win64 -- there is no redzone.
It might just be cleaner to go ahead and allocate the stack frame always, even
if we don't store anything into it along the htm fastpath.
> - subq $56, %rsp
> - cfi_def_cfa_offset(64)
> + subq $64, %rsp
> + cfi_def_cfa_offset(72)
You now have an abi-misaligned stack. Since the return address is pushed by
the call, an aligned stack frame allocation is (N + 8) % 16 == 0.
> + // Accessed from assembly language, thus the "asm" specifier on
> + // the name, avoiding complex name mangling.
> +#ifdef __USER_LABEL_PREFIX__
> +#define UPFX1(t) UPFX(t)
> +#define UPFX(t) #t
> + static gtm_rwlock serial_lock
> + __asm__(UPFX1(__USER_LABEL_PREFIX__) "gtm_serial_lock");
> +#else
> + static gtm_rwlock serial_lock
> + __asm__("gtm_serial_lock");
> +#endif
Now that we have 3 copies of this, we should simplify things. E.g.
#ifdef __USER_LABEL_PREFIX__
# define UPFX1(X) #X
# define UPFX UPFX1(__USER_LABEL_PREFIX__)
#else
# define UPFX
#endif
static gtm_rwlock serial_lock __asm__(UPFX "gtm_serial_lock");
or something.
r~
