From 975638b2d76ce6f26965ac3160c5af8029e16c29 Mon Sep 17 00:00:00 2001
From: Thomas Schwinge <tschwinge@baylibre.com>
Date: Mon, 16 Dec 2024 11:48:11 +0100
Subject: [PATCH] nvptx: Add effective-target 'nvptx_softstack', use for
 effective-target 'alloca'

..., and thereby making the check for effective-target 'alloca' more explicit.
As of commit 5012919d0bd344ac1888e8e531072f0ccbe24d2c (Subversion r242503)
"nvptx backend prerequisites for OpenMP offloading", the check for
effective-target 'alloca' did "use a compile test"; let's make this more
explicit: supported for '-msoft-stack', not supported otherwise.

	gcc/testsuite/
	* lib/target-supports.exp
	(check_effective_target_nvptx_softstack): New.
	(check_effective_target_alloca) [nvptx]: Use it.
	gcc/
	* doc/sourcebuild.texi (Effective-Target Keywords): Document
	'nvptx_softstack'.
---
 gcc/doc/sourcebuild.texi              |  3 +++
 gcc/testsuite/lib/target-supports.exp | 19 +++++++++++++++----
 2 files changed, 18 insertions(+), 4 deletions(-)

diff --git a/gcc/doc/sourcebuild.texi b/gcc/doc/sourcebuild.texi
index f32f50b9c03..0e0a7c806eb 100644
--- a/gcc/doc/sourcebuild.texi
+++ b/gcc/doc/sourcebuild.texi
@@ -2433,6 +2433,9 @@ nvptx code by default compiles for at least PTX ISA version 6.0.
 @item nvptx_runtime_alias_ptx
 The nvptx runtime environment supports the PTX ISA directive
 @code{.alias}.
+
+@item nvptx_softstack
+nvptx @option{-msoft-stack} is enabled.
 @end table
 
 @subsubsection PowerPC-specific attributes
diff --git a/gcc/testsuite/lib/target-supports.exp b/gcc/testsuite/lib/target-supports.exp
index e6a876d9301..d7d7217be05 100644
--- a/gcc/testsuite/lib/target-supports.exp
+++ b/gcc/testsuite/lib/target-supports.exp
@@ -1009,10 +1009,11 @@ proc check_effective_target_alloca {} {
       return 0
     }
     if { [istarget nvptx-*-*] } {
-	return [check_no_compiler_messages alloca assembly {
-	    void f (void*);
-	    void g (int n) { f (__builtin_alloca (n)); }
-	}]
+	if { ![check_effective_target_nvptx_softstack] } {
+	    return 0
+	} else {
+	    return 1
+	}
     }
     return 1
 }
@@ -14099,6 +14100,16 @@ proc check_effective_target_nvptx_default_ptx_isa_version_at_least_6_0 { } {
     return [check_nvptx_default_ptx_isa_version_at_least 6 0]
 }
 
+# Return 1 if nvptx '-msoft-stack' is enabled.
+
+proc check_effective_target_nvptx_softstack { } {
+    return [check_no_compiler_messages nvptx_softstack assembly {
+	#if !defined(__nvptx_softstack__)
+	#error !__nvptx_softstack__
+	#endif
+    }]
+}
+
 # Return 1 if nvptx code with PTX ISA version major.minor or higher can be run.
 
 proc check_nvptx_runtime_ptx_isa_version_at_least { major minor } {