* [PATCH 0/2] provide toolchain abstracted __builtin_constant_p
@ 2024-03-20 21:33 Tyler Retzlaff
2024-03-20 21:33 ` [PATCH 1/2] eal: provide macro for GCC builtin constant intrinsic Tyler Retzlaff
2024-03-20 21:33 ` [PATCH 2/2] mempool: use rte constant macro instead of GCC builtin Tyler Retzlaff
0 siblings, 2 replies; 7+ messages in thread
From: Tyler Retzlaff @ 2024-03-20 21:33 UTC (permalink / raw)
To: dev; +Cc: Morten Brørup, Andrew Rybchenko, Tyler Retzlaff
Decouple direct dependency on GCC built-in __builtin_constant_p provide
a new macro __rte_constant(e) that expands to the built-in for GCC and
to false for MSVC.
Tyler Retzlaff (2):
eal: provide macro for GCC builtin constant intrinsic
mempool: use rte constant macro instead of GCC builtin
lib/eal/include/rte_common.h | 6 ++++++
lib/mempool/rte_mempool.h | 7 +++----
2 files changed, 9 insertions(+), 4 deletions(-)
--
1.8.3.1
^ permalink raw reply [flat|nested] 7+ messages in thread
* [PATCH 1/2] eal: provide macro for GCC builtin constant intrinsic
2024-03-20 21:33 [PATCH 0/2] provide toolchain abstracted __builtin_constant_p Tyler Retzlaff
@ 2024-03-20 21:33 ` Tyler Retzlaff
2024-03-26 9:57 ` Morten Brørup
2024-03-31 22:03 ` Stephen Hemminger
2024-03-20 21:33 ` [PATCH 2/2] mempool: use rte constant macro instead of GCC builtin Tyler Retzlaff
1 sibling, 2 replies; 7+ messages in thread
From: Tyler Retzlaff @ 2024-03-20 21:33 UTC (permalink / raw)
To: dev; +Cc: Morten Brørup, Andrew Rybchenko, Tyler Retzlaff
MSVC does not have a __builtin_constant_p intrinsic so provide
__rte_constant(e) that expands false for MSVC and to the intrinsic for
GCC.
Signed-off-by: Tyler Retzlaff <roretzla@linux.microsoft.com>
---
lib/eal/include/rte_common.h | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/lib/eal/include/rte_common.h b/lib/eal/include/rte_common.h
index 298a5c6..d520be6 100644
--- a/lib/eal/include/rte_common.h
+++ b/lib/eal/include/rte_common.h
@@ -44,6 +44,12 @@
#endif
#endif
+#ifdef RTE_TOOLCHAIN_MSVC
+#define __rte_constant(e) 0
+#else
+#define __rte_constant(e) __extension__(__builtin_constant_p(e))
+#endif
+
/*
* RTE_TOOLCHAIN_GCC is defined if the target is built with GCC,
* while a host application (like pmdinfogen) may have another compiler.
--
1.8.3.1
^ permalink raw reply [flat|nested] 7+ messages in thread
* [PATCH 2/2] mempool: use rte constant macro instead of GCC builtin
2024-03-20 21:33 [PATCH 0/2] provide toolchain abstracted __builtin_constant_p Tyler Retzlaff
2024-03-20 21:33 ` [PATCH 1/2] eal: provide macro for GCC builtin constant intrinsic Tyler Retzlaff
@ 2024-03-20 21:33 ` Tyler Retzlaff
2024-03-26 9:57 ` Morten Brørup
1 sibling, 1 reply; 7+ messages in thread
From: Tyler Retzlaff @ 2024-03-20 21:33 UTC (permalink / raw)
To: dev; +Cc: Morten Brørup, Andrew Rybchenko, Tyler Retzlaff
Use newly introduced __rte_constant(e) macro instead of directly using
__builtin_constant_p() allowing mempool to be built by MSVC.
Signed-off-by: Tyler Retzlaff <roretzla@linux.microsoft.com>
---
lib/mempool/rte_mempool.h | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)
diff --git a/lib/mempool/rte_mempool.h b/lib/mempool/rte_mempool.h
index 23fd5c8..a3564fb 100644
--- a/lib/mempool/rte_mempool.h
+++ b/lib/mempool/rte_mempool.h
@@ -1521,7 +1521,7 @@ struct rte_mempool_cache *
/* The cache is a stack, so copy will be in reverse order. */
cache_objs = &cache->objs[cache->len];
- if (__extension__(__builtin_constant_p(n)) && n <= cache->len) {
+ if (__rte_constant(n) && n <= cache->len) {
/*
* The request size is known at build time, and
* the entire request can be satisfied from the cache,
@@ -1542,8 +1542,7 @@ struct rte_mempool_cache *
* If the request size 'n' is known at build time, the above comparison
* ensures that n > cache->len here, so omit RTE_MIN().
*/
- len = __extension__(__builtin_constant_p(n)) ? cache->len :
- RTE_MIN(n, cache->len);
+ len = __rte_constant(n) ? cache->len : RTE_MIN(n, cache->len);
cache->len -= len;
remaining = n - len;
for (index = 0; index < len; index++)
@@ -1554,7 +1553,7 @@ struct rte_mempool_cache *
* where the entire request can be satisfied from the cache
* has already been handled above, so omit handling it here.
*/
- if (!__extension__(__builtin_constant_p(n)) && remaining == 0) {
+ if (!__rte_constant(n) && remaining == 0) {
/* The entire request is satisfied from the cache. */
RTE_MEMPOOL_CACHE_STAT_ADD(cache, get_success_bulk, 1);
--
1.8.3.1
^ permalink raw reply [flat|nested] 7+ messages in thread
* RE: [PATCH 1/2] eal: provide macro for GCC builtin constant intrinsic
2024-03-20 21:33 ` [PATCH 1/2] eal: provide macro for GCC builtin constant intrinsic Tyler Retzlaff
@ 2024-03-26 9:57 ` Morten Brørup
2024-03-31 22:03 ` Stephen Hemminger
1 sibling, 0 replies; 7+ messages in thread
From: Morten Brørup @ 2024-03-26 9:57 UTC (permalink / raw)
To: Tyler Retzlaff, dev; +Cc: Andrew Rybchenko
> From: Tyler Retzlaff [mailto:roretzla@linux.microsoft.com]
> Sent: Wednesday, 20 March 2024 22.34
>
> MSVC does not have a __builtin_constant_p intrinsic so provide
> __rte_constant(e) that expands false for MSVC and to the intrinsic for
> GCC.
>
> Signed-off-by: Tyler Retzlaff <roretzla@linux.microsoft.com>
> ---
Reviewed-by: Morten Brørup <mb@smartsharesystems.com>
^ permalink raw reply [flat|nested] 7+ messages in thread
* RE: [PATCH 2/2] mempool: use rte constant macro instead of GCC builtin
2024-03-20 21:33 ` [PATCH 2/2] mempool: use rte constant macro instead of GCC builtin Tyler Retzlaff
@ 2024-03-26 9:57 ` Morten Brørup
0 siblings, 0 replies; 7+ messages in thread
From: Morten Brørup @ 2024-03-26 9:57 UTC (permalink / raw)
To: Tyler Retzlaff, dev; +Cc: Andrew Rybchenko
> From: Tyler Retzlaff [mailto:roretzla@linux.microsoft.com]
> Sent: Wednesday, 20 March 2024 22.34
>
> Use newly introduced __rte_constant(e) macro instead of directly using
> __builtin_constant_p() allowing mempool to be built by MSVC.
>
> Signed-off-by: Tyler Retzlaff <roretzla@linux.microsoft.com>
> ---
Reviewed-by: Morten Brørup <mb@smartsharesystems.com>
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH 1/2] eal: provide macro for GCC builtin constant intrinsic
2024-03-20 21:33 ` [PATCH 1/2] eal: provide macro for GCC builtin constant intrinsic Tyler Retzlaff
2024-03-26 9:57 ` Morten Brørup
@ 2024-03-31 22:03 ` Stephen Hemminger
2024-04-01 8:34 ` Morten Brørup
1 sibling, 1 reply; 7+ messages in thread
From: Stephen Hemminger @ 2024-03-31 22:03 UTC (permalink / raw)
To: Tyler Retzlaff; +Cc: dev, Morten Brørup, Andrew Rybchenko
On Wed, 20 Mar 2024 14:33:35 -0700
Tyler Retzlaff <roretzla@linux.microsoft.com> wrote:
> +#ifdef RTE_TOOLCHAIN_MSVC
> +#define __rte_constant(e) 0
> +#else
> +#define __rte_constant(e) __extension__(__builtin_constant_p(e))
> +#endif
> +
I did some looking around and some other project have macros
for expressing constant expression vs constant.
Implementing this with some form of sizeof math is possible.
For example in linux/compiler.h
/*
* This returns a constant expression while determining if an argument is
* a constant expression, most importantly without evaluating the argument.
* Glory to Martin Uecker <Martin.Uecker@med.uni-goettingen.de>
*
* Details:
* - sizeof() return an integer constant expression, and does not evaluate
* the value of its operand; it only examines the type of its operand.
* - The results of comparing two integer constant expressions is also
* an integer constant expression.
* - The first literal "8" isn't important. It could be any literal value.
* - The second literal "8" is to avoid warnings about unaligned pointers;
* this could otherwise just be "1".
* - (long)(x) is used to avoid warnings about 64-bit types on 32-bit
* architectures.
* - The C Standard defines "null pointer constant", "(void *)0", as
* distinct from other void pointers.
* - If (x) is an integer constant expression, then the "* 0l" resolves
* it into an integer constant expression of value 0. Since it is cast to
* "void *", this makes the second operand a null pointer constant.
* - If (x) is not an integer constant expression, then the second operand
* resolves to a void pointer (but not a null pointer constant: the value
* is not an integer constant 0).
* - The conditional operator's third operand, "(int *)8", is an object
* pointer (to type "int").
* - The behavior (including the return type) of the conditional operator
* ("operand1 ? operand2 : operand3") depends on the kind of expressions
* given for the second and third operands. This is the central mechanism
* of the macro:
* - When one operand is a null pointer constant (i.e. when x is an integer
* constant expression) and the other is an object pointer (i.e. our
* third operand), the conditional operator returns the type of the
* object pointer operand (i.e. "int *). Here, within the sizeof(), we
* would then get:
* sizeof(*((int *)(...)) == sizeof(int) == 4
* - When one operand is a void pointer (i.e. when x is not an integer
* constant expression) and the other is an object pointer (i.e. our
* third operand), the conditional operator returns a "void *" type.
* Here, within the sizeof(), we would then get:
* sizeof(*((void *)(...)) == sizeof(void) == 1
* - The equality comparison to "sizeof(int)" therefore depends on (x):
* sizeof(int) == sizeof(int) (x) was a constant expression
* sizeof(int) != sizeof(void) (x) was not a constant expression
*/
#define __is_constexpr(x) \
(sizeof(int) == sizeof(*(8 ? ((void *)((long)(x) * 0l)) : (int *)8)))
^ permalink raw reply [flat|nested] 7+ messages in thread
* RE: [PATCH 1/2] eal: provide macro for GCC builtin constant intrinsic
2024-03-31 22:03 ` Stephen Hemminger
@ 2024-04-01 8:34 ` Morten Brørup
0 siblings, 0 replies; 7+ messages in thread
From: Morten Brørup @ 2024-04-01 8:34 UTC (permalink / raw)
To: Stephen Hemminger, Tyler Retzlaff; +Cc: dev, Andrew Rybchenko
> From: Stephen Hemminger [mailto:stephen@networkplumber.org]
> Sent: Monday, 1 April 2024 00.03
>
> On Wed, 20 Mar 2024 14:33:35 -0700
> Tyler Retzlaff <roretzla@linux.microsoft.com> wrote:
>
> > +#ifdef RTE_TOOLCHAIN_MSVC
> > +#define __rte_constant(e) 0
> > +#else
> > +#define __rte_constant(e) __extension__(__builtin_constant_p(e))
> > +#endif
> > +
>
>
> I did some looking around and some other project have macros
> for expressing constant expression vs constant.
>
> Implementing this with some form of sizeof math is possible.
> For example in linux/compiler.h
>
> /*
> * This returns a constant expression while determining if an argument
> is
> * a constant expression, most importantly without evaluating the
> argument.
> * Glory to Martin Uecker <Martin.Uecker@med.uni-goettingen.de>
> *
> * Details:
> * - sizeof() return an integer constant expression, and does not
> evaluate
> * the value of its operand; it only examines the type of its operand.
> * - The results of comparing two integer constant expressions is also
> * an integer constant expression.
> * - The first literal "8" isn't important. It could be any literal
> value.
> * - The second literal "8" is to avoid warnings about unaligned
> pointers;
> * this could otherwise just be "1".
> * - (long)(x) is used to avoid warnings about 64-bit types on 32-bit
> * architectures.
> * - The C Standard defines "null pointer constant", "(void *)0", as
> * distinct from other void pointers.
> * - If (x) is an integer constant expression, then the "* 0l" resolves
> * it into an integer constant expression of value 0. Since it is cast
> to
> * "void *", this makes the second operand a null pointer constant.
> * - If (x) is not an integer constant expression, then the second
> operand
> * resolves to a void pointer (but not a null pointer constant: the
> value
> * is not an integer constant 0).
> * - The conditional operator's third operand, "(int *)8", is an object
> * pointer (to type "int").
> * - The behavior (including the return type) of the conditional
> operator
> * ("operand1 ? operand2 : operand3") depends on the kind of
> expressions
> * given for the second and third operands. This is the central
> mechanism
> * of the macro:
> * - When one operand is a null pointer constant (i.e. when x is an
> integer
> * constant expression) and the other is an object pointer (i.e. our
> * third operand), the conditional operator returns the type of the
> * object pointer operand (i.e. "int *). Here, within the sizeof(),
> we
> * would then get:
> * sizeof(*((int *)(...)) == sizeof(int) == 4
> * - When one operand is a void pointer (i.e. when x is not an integer
> * constant expression) and the other is an object pointer (i.e. our
> * third operand), the conditional operator returns a "void *" type.
> * Here, within the sizeof(), we would then get:
> * sizeof(*((void *)(...)) == sizeof(void) == 1
> * - The equality comparison to "sizeof(int)" therefore depends on (x):
> * sizeof(int) == sizeof(int) (x) was a constant expression
> * sizeof(int) != sizeof(void) (x) was not a constant expression
> */
> #define __is_constexpr(x) \
> (sizeof(int) == sizeof(*(8 ? ((void *)((long)(x) * 0l)) : (int
> *)8)))
Nice!
If the author is willing to license it under the BSD license, we can copy it as is.
We might want to add a couple of build time checks to verify that it does what is expected; to catch any changes in compiler behavior.
^ permalink raw reply [flat|nested] 7+ messages in thread
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2024-03-20 21:33 [PATCH 0/2] provide toolchain abstracted __builtin_constant_p Tyler Retzlaff
2024-03-20 21:33 ` [PATCH 1/2] eal: provide macro for GCC builtin constant intrinsic Tyler Retzlaff
2024-03-26 9:57 ` Morten Brørup
2024-03-31 22:03 ` Stephen Hemminger
2024-04-01 8:34 ` Morten Brørup
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