[gcc(refs/users/aoliva/heads/testme)] strub: enable conditional support

[Alexandre Oliva]

https://gcc.gnu.org/g:f8134d5fb8918da05c1b3fdaba0740d2cdc0540e

commit f8134d5fb8918da05c1b3fdaba0740d2cdc0540e
Author: Alexandre Oliva <oliva@gnu.org>
Date:   Wed Dec 6 19:36:02 2023 -0300

    strub: enable conditional support

Diff:
---
 gcc/config/i386/i386.cc   |  4 ++++
 gcc/config/nvptx/nvptx.cc |  3 +++
 gcc/ipa-strub.cc          | 27 +++++++++++++++++++++++++++
 gcc/target.def            |  8 ++++++++
 4 files changed, 42 insertions(+)

diff --git a/gcc/config/i386/i386.cc b/gcc/config/i386/i386.cc
index 7c5cab4e2c6..f933c9c23c7 100644
--- a/gcc/config/i386/i386.cc
+++ b/gcc/config/i386/i386.cc
@@ -26658,6 +26658,10 @@ ix86_libm_function_max_error (unsigned cfn, machine_mode mode,
 #define TARGET_RUN_TARGET_SELFTESTS selftest::ix86_run_selftests
 #endif /* #if CHECKING_P */
 
+// ??? for testing only
+#undef TARGET_HAVE_STRUB_SUPPORT_FOR
+#define TARGET_HAVE_STRUB_SUPPORT_FOR hook_bool_tree_false
+
 struct gcc_target targetm = TARGET_INITIALIZER;
 
 #include "gt-i386.h"
diff --git a/gcc/config/nvptx/nvptx.cc b/gcc/config/nvptx/nvptx.cc
index ae20802c879..3fb1deb70fd 100644
--- a/gcc/config/nvptx/nvptx.cc
+++ b/gcc/config/nvptx/nvptx.cc
@@ -7789,6 +7789,9 @@ nvptx_asm_output_def_from_decls (FILE *stream, tree name, tree value)
 #undef TARGET_LIBC_HAS_FUNCTION
 #define TARGET_LIBC_HAS_FUNCTION nvptx_libc_has_function
 
+#undef TARGET_HAVE_STRUB_SUPPORT_FOR
+#define TARGET_HAVE_STRUB_SUPPORT_FOR hook_bool_tree_false
+
 struct gcc_target targetm = TARGET_INITIALIZER;
 
 #include "gt-nvptx.h"
diff --git a/gcc/ipa-strub.cc b/gcc/ipa-strub.cc
index 293bec132b8..a13ef09b559 100644
--- a/gcc/ipa-strub.cc
+++ b/gcc/ipa-strub.cc
@@ -60,6 +60,7 @@ along with GCC; see the file COPYING3.  If not see
 #include "ipa-strub.h"
 #include "symtab-thunks.h"
 #include "attr-fnspec.h"
+#include "target.h"
 
 /* This file introduces two passes that, together, implement
    machine-independent stack scrubbing, strub for short.  It arranges
@@ -639,9 +640,35 @@ can_strub_p (cgraph_node *node, bool report = false)
 {
   bool result = true;
 
+  if (!targetm.have_strub_support_for (node->decl))
+    {
+      result = false;
+
+      if (!report)
+	return result;
+
+      sorry_at (DECL_SOURCE_LOCATION (node->decl),
+		"%qD is not eligible for %<strub%>"
+		" on the target system",
+		node->decl);
+    }
+
   if (!report && strub_always_inline_p (node))
     return result;
 
+  if (flag_split_stack)
+    {
+      result = false;
+
+      if (!report)
+	return result;
+
+      sorry_at (DECL_SOURCE_LOCATION (node->decl),
+		"%qD is not eligible for %<strub%>"
+		" because %<-fsplit-stack%> is enabled",
+		node->decl);
+    }
+
   if (lookup_attribute ("noipa", DECL_ATTRIBUTES (node->decl)))
     {
       result = false;
diff --git a/gcc/target.def b/gcc/target.def
index 52b83e091b9..08218f3a42a 100644
--- a/gcc/target.def
+++ b/gcc/target.def
@@ -4457,6 +4457,14 @@ otherwise return false.  The default implementation always returns true.",
  bool, (void),
  hook_bool_void_true)
 
+DEFHOOK
+(have_strub_support_for,
+ "Returns true if the target supports stack scrubbing for the given function\n\
+or type, otherwise return false.  The default implementation always returns\n\
+true.",
+ bool, (tree),
+ hook_bool_tree_true)
+
 DEFHOOK
 (have_speculation_safe_value,
 "This hook is used to determine the level of target support for\n\