RISC-V: Describe -march behavior for dependent extensions

gcc/ChangeLog:

	* doc/invoke.texi: Describe -march behavior for dependent extensions on
	RISC-V.

diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 68ebd79d6761481784808be7504a21d1e98fce09..b37c7af7a3905a1f8a28ba445d1ecb5e4fcc4e6d 100644 (file)
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -31063,6 +31063,10 @@ If both @option{-march} and @option{-mcpu=} are not specified, the default for
 this argument is system dependent, users who want a specific architecture
 extensions should specify one explicitly.
 
+When the RISC-V specifications define an extension as depending on other
+extensions, GCC will implicitly add the dependent extensions to the enabled
+extension set if they weren't added explicitly.
+
 @opindex mcpu
 @item -mcpu=@var{processor-string}
 Use architecture of and optimize the output for the given processor, specified