nvptx: stack size limits are relevant for execution only

For non-'dg-do run' test cases, that means: big 'dg-require-stack-size' need
not be UNSUPPORTED (and indeed now do all PASS), 'dg-add-options stack_size'
need not define (and thus limit) 'STACK_SIZE' (and still do all PASS).

Re "Find 'dg-do-what' in an outer frame", currently (sources not completely
clean, though), we've got:

    $ git grep -F 'check_effective_target_stack_size: found dg-do-what at level ' -- build-gcc/\*.log | sort | uniq -c
          6 build-gcc/gcc/testsuite/gcc/gcc.log:check_effective_target_stack_size: found dg-do-what at level 2
        267 build-gcc/gcc/testsuite/gcc/gcc.log:check_effective_target_stack_size: found dg-do-what at level 3
        239 build-gcc/gcc/testsuite/gcc/gcc.log:check_effective_target_stack_size: found dg-do-what at level 4

	gcc/testsuite/
	* lib/target-supports.exp (check_effective_target_stack_size): For
	nvptx target, stack size limits are relevant for execution only.
	gcc/
	* doc/sourcebuild.texi (stack_size): Update.

2 files changed, 20 insertions, 0 deletions

diff --git a/gcc/doc/sourcebuild.texi b/gcc/doc/sourcebuild.texi
index de1aa8c..8bf7014 100644
--- a/gcc/doc/sourcebuild.texi
+++ b/gcc/doc/sourcebuild.texi
@@ -2932,6 +2932,10 @@ Target has limited stack size.  The stack size limit can be obtained using the
 STACK_SIZE macro defined by @ref{stack_size_ao,,@code{dg-add-options} feature
 @code{stack_size}}.
 
+Note that for certain targets, stack size limits are relevant for
+execution only, and therefore considered only if @code{dg-do run} is
+in effect, otherwise unlimited.
+
 @item static
 Target supports @option{-static}.
 
diff --git a/gcc/testsuite/lib/target-supports.exp b/gcc/testsuite/lib/target-supports.exp
index 0ea8bcb..1080a5c 100644
--- a/gcc/testsuite/lib/target-supports.exp
+++ b/gcc/testsuite/lib/target-supports.exp
@@ -649,6 +649,22 @@ proc check_effective_target_trampolines { } {
 # Return 1 if target has limited stack size.
 
 proc check_effective_target_stack_size { } {
+    # For nvptx target, stack size limits are relevant for execution only.
+    if { [istarget nvptx-*-*] } {
+	# Find 'dg-do-what' in an outer frame.
+	set level 1
+	while true {
+	    upvar $level dg-do-what dg-do-what
+	    if [info exists dg-do-what] then break
+	    incr level
+	}
+	verbose "check_effective_target_stack_size: found dg-do-what at level $level" 2
+
+	if { ![string equal [lindex ${dg-do-what} 0] run] } {
+	    return 0
+	}
+    }
+
     if [target_info exists gcc,stack_size] {
 	return 1
     }