Improve documentation of noinline and noipa attributes [PR108470]

gcc/ChangeLog
	PR ipa/108470
	* doc/extend.texi (Common Function Attributes): Document that
	noinline also disables some interprocedural optimizations and
	improve flow to the part about using inline asm instead to
	disable calls from being optimized away completely.  Remove the
	sentence that says noipa is mainly for internal compiler testing.

diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi
index d879ad544b54bd4e8c85827ec8ae858e2275cad0..616e26d47dc2d556996a4037bb73c753209a4e03 100644 (file)
--- a/gcc/doc/extend.texi
+++ b/gcc/doc/extend.texi
@@ -3666,13 +3666,17 @@ propagation.
 @cindex @code{noinline} function attribute
 @item noinline
 This function attribute prevents a function from being considered for
-inlining.
+inlining.  It also disables some other interprocedural optimizations; it's
+preferable to use the more comprehensive @code{noipa} attribute instead
+if that is your goal.
+
 @c Don't enumerate the optimizations by name here; we try to be
 @c future-compatible with this mechanism.
-If the function does not have side effects, there are optimizations
-other than inlining that cause function calls to be optimized away,
-although the function call is live.  To keep such calls from being
-optimized away, put
+Even if a function is declared with the @code{noinline} attribute,
+there are optimizations other than inlining that can cause calls to be
+optimized away if it does not have side effects, although the function
+call is live.  To keep such calls from being optimized away, put
+
 @smallexample
 asm ("");
 @end smallexample
@@ -3691,8 +3695,7 @@ the body.  This attribute implies @code{noinline}, @code{noclone} and
 to a combination of other attributes, because its purpose is to suppress
 existing and future optimizations employing interprocedural analysis,
 including those that do not have an attribute suitable for disabling
-them individually.  This attribute is supported mainly for the purpose
-of testing the compiler.
+them individually.
 
 @cindex @code{nonnull} function attribute
 @cindex functions with non-null pointer arguments