Re: PATCH: Add check_lto_available

[Richard Earnshaw <rearnsha@arm.com>]

HJ,

Why does this patch try to produce a shared object as part of
determining whether LTO works?  If you have LTO but not shared object
support in a toolchain this means we don't test LTO properly.

R.

On 07/12/12 17:58, H.J. Lu wrote:
> Hi,
> 
> I checked in this patch to add check_lto_available to check if
> compiler supports LTO.
> 
> 
> H.J.
> ---
> Index: ChangeLog
> ===================================================================
> RCS file: /cvs/src/src/ld/testsuite/ChangeLog,v
> retrieving revision 1.1637
> diff -u -p -r1.1637 ChangeLog
> --- ChangeLog	7 Dec 2012 17:53:03 -0000	1.1637
> +++ ChangeLog	7 Dec 2012 17:55:20 -0000
> @@ -1,5 +1,10 @@
>  2012-12-07  H.J. Lu  <hongjiu.lu@intel.com>
>  
> +	* lib/ld-lib.exp (check_lto_available): New.  Check if compiler
> +	supports LTO.
> +
> +2012-12-07  H.J. Lu  <hongjiu.lu@intel.com>
> +
>  	* lib/ld-lib.exp (run_cc_link_tests): Properly check linker
>  	warnings.
>  
> Index: lib/ld-lib.exp
> ===================================================================
> RCS file: /cvs/src/src/ld/testsuite/lib/ld-lib.exp,v
> retrieving revision 1.99
> diff -u -p -r1.99 ld-lib.exp
> --- lib/ld-lib.exp	7 Dec 2012 17:53:04 -0000	1.99
> +++ lib/ld-lib.exp	7 Dec 2012 17:55:20 -0000
> @@ -1614,6 +1614,34 @@ proc check_plugin_api_available { } {
>      return $plugin_api_available_saved
>  }
>  
> +# Returns true if the target compiler supports LTO
> +proc check_lto_available { } {
> +    global lto_available_saved
> +    global CC
> +    if {![info exists lto_available_saved]} {
> +	# Check if gcc supports -flto -fuse-linker-plugin
> +	if { [which $CC] == 0 } {
> +	    set lto_available_saved 0
> +	    return 0
> +	}
> +	set basename "lto"
> +	set src ${basename}[pid].c
> +	set output ${basename}[pid].so
> +	set f [open $src "w"]
> +	puts $f ""
> +	close $f
> +	set status [remote_exec host $CC "-shared -B[pwd]/tmpdir/ld/ -flto -fuse-linker-plugin $src -o $output"]
> +	if { [lindex $status 0] == 0 } {
> +	    set lto_available_saved 1
> +	} else {
> +	    set lto_available_saved 0
> +	}
> +	file delete $src
> +	file delete $output
> +    }
> +    return $lto_available_saved
> +}
> +
>  # Check if the assembler supports CFI statements.
>  
>  proc check_as_cfi { } {
>