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Diffstat (limited to 'gas/doc/c-hppa.texi')
| -rw-r--r-- | gas/doc/c-hppa.texi | 45 |
1 files changed, 41 insertions, 4 deletions
diff --git a/gas/doc/c-hppa.texi b/gas/doc/c-hppa.texi index 7e9ea30..9970188 100644 --- a/gas/doc/c-hppa.texi +++ b/gas/doc/c-hppa.texi @@ -245,14 +245,51 @@ identified by keywords. The keywords recognized are @samp{quad=@var{expr}} beginning of this subsection; a power of two), @samp{access=@var{expr}} (value for ``access rights'' field), @samp{sort=@var{expr}} (sorting order for this subspace in link), @samp{code_only} (subsection contains only code), -@samp{unloadable} (subsection cannot be loaded into memory), @samp{common} -(subsection is common block), @samp{dup_comm} (initialized data may have -duplicate names), or @samp{zero} (subsection is all zeros, do not write in -object file). +@samp{unloadable} (subsection cannot be loaded into memory), @samp{comdat} +(subsection is comdat), @samp{common} (subsection is common block), +@samp{dup_comm} (subsection may have duplicate names), or @samp{zero} +(subsection is all zeros, do not write in object file). @code{.nsubspa} always creates a new subspace with the given name, even if one with the same name already exists. +@samp{comdat}, @samp{common} and @samp{dup_comm} can be used to implement +various flavors of one-only support when using the SOM linker. The SOM +linker only supports specific combinations of these flags. The details +are not documented. A brief description is provided here. + +@samp{comdat} provides a form of linkonce support. It is useful for +both code and data subspaces. A @samp{comdat} subspace has a key symbol +marked by the @samp{is_comdat} flag or @samp{ST_COMDAT}. Only the first +subspace for any given key is selected. The key symbol becomes universal +in shared links. This is similar to the behavior of @samp{secondary_def} +symbols. + +@samp{common} provides Fortran named common support. It is only useful +for data subspaces. Symbols with the flag @samp{is_common} retain this +flag in shared links. Referencing a @samp{is_common} symbol in a shared +library from outside the library doesn't work. Thus, @samp{is_common} +symbols must be output whenever they are needed. + +@samp{common} and @samp{dup_comm} together provide Cobol common support. +The subspaces in this case must all be the same length. Otherwise, this +support is similar to the Fortran common support. + +@samp{dup_comm} by itself provides a type of one-only support for code. +Only the first @samp{dup_comm} subspace is selected. There is a rather +complex algorithm to compare subspaces. Code symbols marked with the +@samp{dup_common} flag are hidden. This support was intended for "C++ +duplicate inlines". + +A simplified technique is used to mark the flags of symbols based on +the flags of their subspace. A symbol with the scope SS_UNIVERSAL and +type ST_ENTRY, ST_CODE or ST_DATA is marked with the corresponding +settings of @samp{comdat}, @samp{common} and @samp{dup_comm} from the +subspace, respectively. This avoids having to introduce additional +directives to mark these symbols. The HP assembler sets @samp{is_common} +from @samp{common}. However, it doesn't set the @samp{dup_common} from +@samp{dup_comm}. It doesn't have @samp{comdat} support. + @item .version "@var{str}" Write @var{str} as version identifier in object code. @end table |