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unroll: Drop the unused unrolled and unrolled_none macros

PATCH Applied Tzu-Ching Yang 3 participants 4 messages Oct 23 – Nov 3 Crypto API

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Tzu-Ching Yang

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#0 lore raw

PATCH v2 1/1 unroll: Drop the unused unrolled and unrolled_none macros

unrolled and unrolled_none are object-like macros with lower-case names, and neither has had a user since commit c6594d642717 ("unroll:
add generic loop unroll helpers") added them in February 2025.

The name unrolled also breaks code that uses it for something else. On GCC the macro expands to an empty _Pragma(), so a function parameter named unrolled compiles with only -Wunknown-pragmas warnings (errors only with CONFIG_WERROR) and silently loses its name:

	int add(int unrolled, int x) { return unrolled + x; }

builds as "return x;" with GCC 11 to 16 (GCC 8 to 10 and Clang reject it).

Drop both macros, and retitle the kernel-doc comment from unrolled to unrolled_count(), the macro its usage example shows. unrolled_full and unrolled_count() stay; any clash with their names fails to build instead of compiling silently.

Suggested-by Alexander Lobakin <[email protected]>
Link https://lore.kernel.org/all/[email protected]/ open here
Signed-off-by Tzu-Ching Yang <[email protected]>

---
v2: drop the two unused macros instead of making all three function-like (Alexander Lobakin).
v1: https://lore.kernel.org/all/[email protected]/

Eric, this version no longer touches lib/crypto/. Would you still take it through libcrypto-next, or should it go through Andrew's -mm tree (unroll.h has no MAINTAINERS entry)?

Testing: an x86_64 defconfig build with the includers of <linux/unroll.h> enabled (BLAKE2b/s, LSMs, IMA/EVM, BPF LSM, vhost, i40e/ice/idpf; no debug info) gives byte-identical objects, modules and vmlinux before and after, with GCC 11.5, GCC 16.2 and Clang 23. In a file that includes only <linux/unroll.h>, a variable, member or parameter named unrolled or unrolled_none now builds without warnings with GCC 8.1 to 16.2 and Clang 17 to 23.

Based on libcrypto-next (20ec6916d871); applies as is to next-20261022, which has no users of the two macros either.

 include/linux/unroll.h | 13 ++-----------
 1 file changed, 2 insertions(+), 11 deletions(-)
include/linux/unroll.h +2 -11
index 186b71de7..d027b37f6 100644
@@ -16,7 +16,8 @@
 #endif
 
 /**
- * unrolled - loop attributes to ask the compiler to unroll it
+ * unrolled_count() - loop attribute to ask the compiler to unroll it
+ * @n: unroll each @n iterations of the loop
  *
  * Usage:
  *

@@ -34,12 +35,6 @@
  * provides best performance and object code size.
  * Available only on Clang and GCC 8.x onwards.
  */
-
-/* Ask the compiler to pick an optimal unroll count, Clang only */
-#define unrolled							\
-	__pick_unrolled(clang loop unroll(enable), /* nothing */)
-
-/* Unroll each @n iterations of the loop */
 #define unrolled_count(n)						\
 	__pick_unrolled(clang loop unroll_count(n), GCC unroll n)
 

@@ -47,10 +42,6 @@
 #define unrolled_full							\
 	__pick_unrolled(clang loop unroll(full), GCC unroll 65534)
 
-/* Never unroll the loop */
-#define unrolled_none							\
-	__pick_unrolled(clang loop unroll(disable), GCC unroll 1)
-
 #define UNROLL(N, MACRO, args...) CONCATENATE(__UNROLL_, N)(MACRO, args)
 
 #define __UNROLL_0(MACRO, args...)

base-commit: 20ec6916d8712e84d58e8c688a25cd368ddeb82b

Signature · 1 line
2.34.1
Reviewed-by on v2 1/1
#1 lore raw
Quoted 14 lines · Tzu-Ching Yang

unrolled and unrolled_none are object-like macros with lower-case names, and neither has had a user since commit c6594d642717 ("unroll:
add generic loop unroll helpers") added them in February 2025.

The name unrolled also breaks code that uses it for something else. On GCC the macro expands to an empty _Pragma(), so a function parameter named unrolled compiles with only -Wunknown-pragmas warnings (errors only with CONFIG_WERROR) and silently loses its name:

	int add(int unrolled, int x) { return unrolled + x; }

builds as "return x;" with GCC 11 to 16 (GCC 8 to 10 and Clang reject it).

Quoted 8 lines

Drop both macros, and retitle the kernel-doc comment from unrolled to unrolled_count(), the macro its usage example shows. unrolled_full and unrolled_count() stay; any clash with their names fails to build instead of compiling silently.

Suggested-by Alexander Lobakin <[email protected]>
Link https://lore.kernel.org/all/[email protected]/ open here
Signed-off-by Tzu-Ching Yang <[email protected]>
Reviewed-by Eric Biggers <[email protected]>
Quoted 7 lines

v2: drop the two unused macros instead of making all three function-like (Alexander Lobakin).
v1: https://lore.kernel.org/all/[email protected]/

Eric, this version no longer touches lib/crypto/. Would you still take it through libcrypto-next, or should it go through Andrew's -mm tree (unroll.h has no MAINTAINERS entry)?

Either way is fine with me. It's one of the unowned files, which are always problematic. If Andrew hasn't taken it by the time -rc1 rolls around, I'll apply it to libcrypto-next: it's at least somewhat related, given that lib/crypto/ is one of the few users of this file.

- Eric

#2 lore raw
Quoted 30 lines · On Sat, 24 Oct 2026 11:15:20 -0700 Eric Biggers <[email protected]> wrote:
Quoted 14 lines · Tzu-Ching Yang

unrolled and unrolled_none are object-like macros with lower-case names, and neither has had a user since commit c6594d642717 ("unroll:
add generic loop unroll helpers") added them in February 2025.

The name unrolled also breaks code that uses it for something else. On GCC the macro expands to an empty _Pragma(), so a function parameter named unrolled compiles with only -Wunknown-pragmas warnings (errors only with CONFIG_WERROR) and silently loses its name:

	int add(int unrolled, int x) { return unrolled + x; }

builds as "return x;" with GCC 11 to 16 (GCC 8 to 10 and Clang reject it).

Quoted 8 lines

Drop both macros, and retitle the kernel-doc comment from unrolled to unrolled_count(), the macro its usage example shows. unrolled_full and unrolled_count() stay; any clash with their names fails to build instead of compiling silently.

Suggested-by Alexander Lobakin <[email protected]>
Link https://lore.kernel.org/all/[email protected]/ open here
Signed-off-by Tzu-Ching Yang <[email protected]>
Reviewed-by Eric Biggers <[email protected]>
Quoted 4 lines

v2: drop the two unused macros instead of making all three function-like (Alexander Lobakin).
v1: https://lore.kernel.org/all/[email protected]/

Quoted 8 lines
Quoted 3 lines

Eric, this version no longer touches lib/crypto/. Would you still take it through libcrypto-next, or should it go through Andrew's -mm tree (unroll.h has no MAINTAINERS entry)?

Either way is fine with me. It's one of the unowned files, which are always problematic. If Andrew hasn't taken it by the time -rc1 rolls around, I'll apply it to libcrypto-next: it's at least somewhat related, given that lib/crypto/ is one of the few users of this file.

That sounds good.

I'm only looking at bugfixes at present. Non-fixes get parked for consideration after -rc1.

Applied
#3 lore raw
In reply to Tzu-Ching Yang
Quoted 22 lines · Tzu-Ching Yang

unrolled and unrolled_none are object-like macros with lower-case names, and neither has had a user since commit c6594d642717 ("unroll:
add generic loop unroll helpers") added them in February 2025.

The name unrolled also breaks code that uses it for something else. On GCC the macro expands to an empty _Pragma(), so a function parameter named unrolled compiles with only -Wunknown-pragmas warnings (errors only with CONFIG_WERROR) and silently loses its name:

	int add(int unrolled, int x) { return unrolled + x; }

builds as "return x;" with GCC 11 to 16 (GCC 8 to 10 and Clang reject it).

Drop both macros, and retitle the kernel-doc comment from unrolled to unrolled_count(), the macro its usage example shows. unrolled_full and unrolled_count() stay; any clash with their names fails to build instead of compiling silently.

Suggested-by Alexander Lobakin <[email protected]>
Link https://lore.kernel.org/all/[email protected]/ open here
Signed-off-by Tzu-Ching Yang <[email protected]>
Quoted 8 lines

---
v2: drop the two unused macros instead of making all three function-like (Alexander Lobakin).
v1: https://lore.kernel.org/all/[email protected]/

Eric, this version no longer touches lib/crypto/. Would you still take it through libcrypto-next, or should it go through Andrew's -mm tree (unroll.h has no MAINTAINERS entry)?

Applied to https://git.kernel.org/pub/scm/linux/kernel/git/ebiggers/linux.git/log/?h=libcrypto-next

- Eric