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authorGravatar Abseil Team <absl-team@google.com>2021-02-18 17:10:44 -0800
committerGravatar Derek Mauro <dmauro@google.com>2021-02-18 20:12:44 -0500
commitb5173c8d45bbb1eae9900eea6231823041cac64f (patch)
tree2c77d97d1d71034368d74afac5ab86282ff569c2 /absl/base
parentf3697b4fedc2d8f2311eaaebed051f6a44182bb2 (diff)
Export of internal Abseil changes
-- f27dbf50d5db12279ab018f11c93ad1704043006 by Derek Mauro <dmauro@google.com>: Internal change PiperOrigin-RevId: 358298501 -- 864c141a59e20e96234c06700d7519d43bc73d71 by Derek Mauro <dmauro@google.com>: Annotates the duration-to-int64 and duration-to-double conversion functions as "pure" to potentially optimize out repeated calls with the same argument This adds an ABSL_ATTRIBUTE_PURE_FUNCTION macro for this purpose. PiperOrigin-RevId: 358247225 GitOrigin-RevId: f27dbf50d5db12279ab018f11c93ad1704043006 Change-Id: I5c2238911711b15d9d3ae53da44db788f20b402b
Diffstat (limited to 'absl/base')
-rw-r--r--absl/base/attributes.h21
1 files changed, 21 insertions, 0 deletions
diff --git a/absl/base/attributes.h b/absl/base/attributes.h
index faa5b27e..cf2cb550 100644
--- a/absl/base/attributes.h
+++ b/absl/base/attributes.h
@@ -678,4 +678,25 @@
#define ABSL_CONST_INIT
#endif // ABSL_HAVE_CPP_ATTRIBUTE(clang::require_constant_initialization)
+// ABSL_ATTRIBUTE_PURE_FUNCTION
+//
+// ABSL_ATTRIBUTE_PURE_FUNCTION is used to annotate declarations of "pure"
+// functions. A function is pure if its return value is only a function of its
+// arguments. The pure attribute prohibits a function from modifying the state
+// of the program that is observable by means other than inspecting the
+// function's return value. Declaring such functions with the pure attribute
+// allows the compiler to avoid emitting some calls in repeated invocations of
+// the function with the same argument values.
+//
+// Example:
+//
+// ABSL_ATTRIBUTE_PURE_FUNCTION int64_t ToInt64Milliseconds(Duration d);
+#if ABSL_HAVE_CPP_ATTRIBUTE(gnu::pure)
+#define ABSL_ATTRIBUTE_PURE_FUNCTION [[gnu::pure]]
+#elif ABSL_HAVE_ATTRIBUTE(pure)
+#define ABSL_ATTRIBUTE_PURE_FUNCTION __attribute__((pure))
+#else
+#define ABSL_ATTRIBUTE_PURE_FUNCTION
+#endif
+
#endif // ABSL_BASE_ATTRIBUTES_H_