sim/testsuite: Support "requires: simoption <--name-of-option>"

Simulator features can be present or not, typically
depending on different-valued configure options, like
--enable-sim-hardware[=off|=on].  To avoid failures in
test-suite-runs when testing such configurations, a new
predicate is needed, as neither "target", "progos" nor
"mach" fits cleanly.

The immediate need was to check for presence of a simulator
option, but rather than a specialized "requires-simoption:"
predicate I thought I'd handle the general (parametrized)
need, so here's a generic predicate machinery and a (first)
predicate to use together with it; checking whether a
particular option is supported, by looking at "run --help"
output.  This was inspired by the check_effective_target_
machinery in the gcc test-suite.

Multiple "requires: <requirement> <parameter>" form a list of
predicates (with parameters), to be used as a conjunction.

sim/testsuite:
	* lib/sim-defs.exp (sim_check_requires_simoption): New function.
	(run_sim_test): Support "requires: <requirement> <parameter>".

sim/testsuite/lib/sim-defs.exp

@@ -261,6 +261,41 @@ proc sim_run { prog sim_opts prog_opts redir options } {
     return [list $return_code $output]
 }
 
+# Support function for "#requires: simoption <xx>":
+# Looks in "run --help" output for <xx>, returns 1 iff <xx> is mentioned
+# there and looks like an option name, otherwise 0.
+
+proc sim_check_requires_simoption { optname } {
+    global sim_path
+    set testrun "$sim_path --help"
+    verbose -log "Checking for simoption `$optname'" 3
+    remote_spawn host $testrun
+    set result [remote_wait host 240]
+
+    set return_code [lindex $result 0]
+    if { $return_code != 0 } {
+	perror "Can't execute `$testrun' to check for `$optname'"
+	return 0
+    }
+
+    set output [lindex $result 1]
+    # Remove \r as for regular runs.
+    regsub -all -- "\r" $output "" output
+
+    # The option output format for --help for each line where an
+    # option name is mentioned, is assumed to be two space followed
+    # by the option name followed by a space or left square bracket,
+    # like in (optname=--foo): "  --foo " or "  --foo[this|that]".
+    # Beware not to match "  --foo-bar" nor "  --foobar".
+    if [string match "*\n  $optname\[\[ \]*" $output] {
+	verbose -log "Found `$optname'" 3
+	return 1
+    }
+    verbose -log "Did not find `$optname'" 3
+
+    return 0
+}
+
 # Run testcase NAME.
 # NAME is either a fully specified file name, or just the file name in which
 # case $srcdir/$subdir will be prepended.
@@ -326,6 +361,7 @@ proc run_sim_test { name requested_machs } {
     set opts(cc) ""
     set opts(progopts) ""
     set opts(progos) ""
+    set opts(requires) {}
     set opts(sim) ""
     set opts(status) "0"
     set opts(output) ""
@@ -375,6 +411,14 @@ proc run_sim_test { name requested_machs } {
 	    set opt_val "$opts($opt_name) $opt_val"
 	}
 
+	# Similar for "requires", except we append a pair to a list, and
+	# that doesn't match the processing in the rest of the loop, so we
+	# "continue" early.
+	if { $opt_name == "requires" } {
+	    lappend opts($opt_name) [split $opt_val " "]
+	    continue
+	}
+
 	foreach m $opt_machs {
 	    set opts($opt_name,$m) $opt_val
 	}
@@ -449,6 +493,22 @@ proc run_sim_test { name requested_machs } {
 	    set opts(cc,$mach) $opts(cc)
 	}
 
+	foreach req $opts(requires) {
+	    set what [lindex $req 0]
+	    set what_opt [lindex $req 1]
+	    verbose -log "requires: <$what> <$what_opt>"
+	    if { [info procs sim_check_requires_${what}] != [list] } {
+		if ![sim_check_requires_${what} $what_opt] {
+		    untested $subdir/$name
+		    return
+		}
+	    } {
+		perror "unknown requirement `requires: $what' in file $file"
+		unresolved $subdir/$name
+		return
+	    }
+	}
+
 	if [string match "*.c" $sourcefile] {
 	    # If we don't have a compiler available, skip tests :(.
 	    if { $global_cc_works == 0 } {