[gcc(refs/users/aoliva/heads/testme)] hardcfr: optionally disable in leaf functions

[Alexandre Oliva]

https://gcc.gnu.org/g:e6c234f7f21c6ecd7096fb743d8c3589c8746cf0

commit e6c234f7f21c6ecd7096fb743d8c3589c8746cf0
Author: Alexandre Oliva <oliva@adacore.com>
Date:   Thu Jun 8 01:35:27 2023 -0300

    hardcfr: optionally disable in leaf functions
    
    Introduce -fhardcfr-skip-leaf to avoid control flow redundancy
    instrumentation of leaf functions, where the benefit is far more
    limited.
    
    
    for  gcc/ChangeLog
    
            * common.opt (fhardcfr-skip-leaf): New.
            * doc/invoke.texi: Document it.
            * gimple-harden-control-flow.cc
            (pass_harden_control_flow_redundancy::execute): Honor it.
    
    for  gcc/testsuite/ChangeLog
    
            * c-c++-common/torture/harden-cfr-skip-leaf.c: New.

Diff:
---
 gcc/common.opt                                     |  4 ++++
 gcc/doc/invoke.texi                                |  8 +++++--
 gcc/gimple-harden-control-flow.cc                  | 27 ++++++++++++++++++++++
 .../c-c++-common/torture/harden-cfr-skip-leaf.c    | 10 ++++++++
 4 files changed, 47 insertions(+), 2 deletions(-)

diff --git a/gcc/common.opt b/gcc/common.opt
index 574299edace..feea4920c9d 100644
--- a/gcc/common.opt
+++ b/gcc/common.opt
@@ -1805,6 +1805,10 @@ fharden-control-flow-redundancy
 Common Var(flag_harden_control_flow_redundancy) Optimization
 Harden control flow by recording and checking execution paths.
 
+fhardcfr-skip-leaf
+Common Var(flag_harden_control_flow_redundancy_skip_leaf) Optimization
+Disable CFR in leaf functions.
+
 fhardcfr-check-returning-calls
 Common Var(flag_harden_control_flow_redundancy_check_returning_calls) Init(-1) Optimization
 Check CFR execution paths also before calls followed by returns of their results.
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 3d9c5f753a4..2703a914dca 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -635,8 +635,8 @@ Objective-C and Objective-C++ Dialects}.
 -fsanitize-undefined-trap-on-error  -fbounds-check
 -fcf-protection=@r{[}full@r{|}branch@r{|}return@r{|}none@r{|}check@r{]}
 -fharden-compares -fharden-conditional-branches
--fharden-control-flow-redundancy  -fhardcfr-check-exceptions
--fhardcfr-check-returning-calls
+-fharden-control-flow-redundancy  -fhardcfr-skip-leaf
+-fhardcfr-check-exceptions  -fhardcfr-check-returning-calls
 -fhardcfr-check-noreturn-calls=@r{[}always@r{|}not-always@r{|}nothrow@r{|}never@r{]}
 -fstack-protector  -fstack-protector-all  -fstack-protector-strong
 -fstack-protector-explicit  -fstack-check
@@ -17263,6 +17263,10 @@ would also have verification issued before the call, but these
 possibilities are merely theoretical, as these conditions can only be
 met when using custom compiler plugins.
 
+@opindex fhardcfr-skip-leaf
+@item -fhardcfr-skip-leaf
+Disable @option{-fharden-control-flow-redundancy} in leaf functions.
+
 @opindex fhardcfr-check-exceptions
 @opindex fno-hardcfr-check-exceptions
 @item -fhardcfr-check-exceptions
diff --git a/gcc/gimple-harden-control-flow.cc b/gcc/gimple-harden-control-flow.cc
index 3e6fe2db479..3998fd0d293 100644
--- a/gcc/gimple-harden-control-flow.cc
+++ b/gcc/gimple-harden-control-flow.cc
@@ -1114,6 +1114,33 @@ pass_harden_control_flow_redundancy::execute (function *fun)
   basic_block bb;
   basic_block bb_eh_cleanup = NULL;
 
+  if (flag_harden_control_flow_redundancy_skip_leaf)
+    {
+      bool found_calls_p = false;
+
+      FOR_EACH_BB_FN (bb, fun)
+	{
+	  for (gimple_stmt_iterator gsi = gsi_last_bb (bb);
+	       !gsi_end_p (gsi); gsi_prev (&gsi))
+	    if (is_a <gcall *> (gsi_stmt (gsi)))
+	      {
+		found_calls_p = true;
+		break;
+	      }
+	  if (found_calls_p)
+	    break;
+	}
+
+      if (!found_calls_p)
+	{
+	  if (dump_file)
+	    fprintf (dump_file,
+		     "Disabling CFR for leaf function, as requested\n");
+
+	  return 0;
+	}
+    }
+
   if (check_at_escaping_exceptions)
     {
       int lp_eh_cleanup = -1;
diff --git a/gcc/testsuite/c-c++-common/torture/harden-cfr-skip-leaf.c b/gcc/testsuite/c-c++-common/torture/harden-cfr-skip-leaf.c
new file mode 100644
index 00000000000..85ecaa04d04
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/torture/harden-cfr-skip-leaf.c
@@ -0,0 +1,10 @@
+/* { dg-do run } */
+/* { dg-options "-fharden-control-flow-redundancy -fhardcfr-skip-leaf -fdump-tree-hardcfr -ffat-lto-objects" } */
+
+/* Test skipping instrumentation of leaf functions.  */
+
+#include "harden-cfr.c"
+
+/* { dg-final { scan-tree-dump-times "__builtin_trap" 0 "hardcfr" } } */
+/* Only main isn't leaf.  */
+/* { dg-final { scan-tree-dump-times "__hardcfr_check" 2 "hardcfr" } } */