<linux/compiler_types.h>: Add the __signed_scalar_typeof() helper

Define __signed_scalar_typeof() to declare a signed scalar type, leaving
non-scalar types unchanged.

To be used to clean up the scheduler load-balancing code a bit.

[ mingo: Split off this patch from the scheduler patch. ]

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Shrikanth Hegde <sshegde@linux.ibm.com>
Cc: Valentin Schneider <vschneid@redhat.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://patch.msgid.link/20251127154725.413564507@infradead.org

diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h
index 1280693766b9dd844ec7ca83053381799be12456..280b4ac0990ff3373d1dae1d3f6f86971aa1c043 100644 (file)
--- a/include/linux/compiler_types.h
+++ b/include/linux/compiler_types.h
@@ -586,6 +586,25 @@ struct ftrace_likely_data {
                         __scalar_type_to_expr_cases(long long),        \
                         default: (x)))
 
+/*
+ * __signed_scalar_typeof(x) - Declare a signed scalar type, leaving
+ *                            non-scalar types unchanged.
+ */
+
+#define __scalar_type_to_signed_cases(type)                            \
+               unsigned type:  (signed type)0,                         \
+               signed type:    (signed type)0
+
+#define __signed_scalar_typeof(x) typeof(                              \
+               _Generic((x),                                           \
+                        char:  (signed char)0,                         \
+                        __scalar_type_to_signed_cases(char),           \
+                        __scalar_type_to_signed_cases(short),          \
+                        __scalar_type_to_signed_cases(int),            \
+                        __scalar_type_to_signed_cases(long),           \
+                        __scalar_type_to_signed_cases(long long),      \
+                        default: (x)))
+
 /* Is this type a native word size -- useful for atomic operations */
 #define __native_word(t) \
        (sizeof(t) == sizeof(char) || sizeof(t) == sizeof(short) || \