[gcc(refs/users/aoliva/heads/testme)] Add leafy mode for zero-call-used-regs

[Alexandre Oliva <aoliva@gcc.gnu.org>]

https://gcc.gnu.org/g:8107c786ebc29b9f6b8b41b22f0b9acc1cc19faa

commit 8107c786ebc29b9f6b8b41b22f0b9acc1cc19faa
Author: Alexandre Oliva <oliva@adacore.com>
Date:   Thu Jun 8 01:34:48 2023 -0300

    Add leafy mode for zero-call-used-regs
    
    Introduce 'leafy' to auto-select between 'used' and 'all' for leaf and
    nonleaf functions, respectively.
    
    
    for  gcc/ChangeLog
    
            * doc/extend.texi (zero-call-used-regs): Document leafy and
            variants thereof.
            * flag-types.h (zero_regs_flags): Add LEAFY_MODE, as well as
            LEAFY and variants.
            * function.cc (gen_call_ued_regs_seq): Set only_used for leaf
            functions in leafy mode.
            * opts.cc (zero_call_used_regs_opts): Add leafy and variants.
    
    for  gcc/testsuite/ChangeLog
    
            * c-c++-common/zero-scratch-regs-leafy-1.c: New.
            * c-c++-common/zero-scratch-regs-leafy-2.c: New.
            * gcc.target/i386/zero-scratch-regs-leafy-1.c: New.
            * gcc.target/i386/zero-scratch-regs-leafy-2.c: New.

Diff:
---
 gcc/doc/extend.texi                                | 22 ++++++++++++++++++++--
 gcc/flag-types.h                                   |  5 +++++
 gcc/function.cc                                    |  3 +++
 gcc/opts.cc                                        |  4 ++++
 .../c-c++-common/zero-scratch-regs-leafy-1.c       | 15 +++++++++++++++
 .../c-c++-common/zero-scratch-regs-leafy-2.c       | 21 +++++++++++++++++++++
 .../gcc.target/i386/zero-scratch-regs-leafy-1.c    | 12 ++++++++++++
 .../gcc.target/i386/zero-scratch-regs-leafy-2.c    | 16 ++++++++++++++++
 8 files changed, 96 insertions(+), 2 deletions(-)

diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi
index e6e1236e338..6f3338ed397 100644
--- a/gcc/doc/extend.texi
+++ b/gcc/doc/extend.texi
@@ -4409,10 +4409,28 @@ zeros all call-used registers that pass arguments.
 @item all-gpr-arg
 zeros all call-used general purpose registers that pass
 arguments.
+
+@item leafy
+Same as @samp{used} in a leaf function, and same as @samp{all} in a
+nonleaf function.
+
+@item leafy-gpr
+Same as @samp{used-gpr} in a leaf function, and same as @samp{all-gpr}
+in a nonleaf function.
+
+@item leafy-arg
+Same as @samp{used-arg} in a leaf function, and same as @samp{all-arg}
+in a nonleaf function.
+
+@item leafy-gpr-arg
+Same as @samp{used-gpr-arg} in a leaf function, and same as
+@samp{all-gpr-arg} in a nonleaf function.
+
 @end table
 
-Of this list, @samp{used-arg}, @samp{used-gpr-arg}, @samp{all-arg},
-and @samp{all-gpr-arg} are mainly used for ROP mitigation.
+Of this list, @samp{used-arg}, @samp{used-gpr-arg}, @samp{leafy-arg},
+@samp{leafy-gpr-arg}, @samp{all-arg}, and @samp{all-gpr-arg} are mainly
+used for ROP mitigation.
 
 The default for the attribute is controlled by @option{-fzero-call-used-regs}.
 @end table
diff --git a/gcc/flag-types.h b/gcc/flag-types.h
index f83d165fbfe..6a2e1beb997 100644
--- a/gcc/flag-types.h
+++ b/gcc/flag-types.h
@@ -348,6 +348,7 @@ namespace zero_regs_flags {
   const unsigned int ONLY_GPR = 1UL << 2;
   const unsigned int ONLY_ARG = 1UL << 3;
   const unsigned int ENABLED = 1UL << 4;
+  const unsigned int LEAFY_MODE = 1UL << 5;
   const unsigned int USED_GPR_ARG = ENABLED | ONLY_USED | ONLY_GPR | ONLY_ARG;
   const unsigned int USED_GPR = ENABLED | ONLY_USED | ONLY_GPR;
   const unsigned int USED_ARG = ENABLED | ONLY_USED | ONLY_ARG;
@@ -356,6 +357,10 @@ namespace zero_regs_flags {
   const unsigned int ALL_GPR = ENABLED | ONLY_GPR;
   const unsigned int ALL_ARG = ENABLED | ONLY_ARG;
   const unsigned int ALL = ENABLED;
+  const unsigned int LEAFY_GPR_ARG = ENABLED | LEAFY_MODE | ONLY_GPR | ONLY_ARG;
+  const unsigned int LEAFY_GPR = ENABLED | LEAFY_MODE | ONLY_GPR;
+  const unsigned int LEAFY_ARG = ENABLED | LEAFY_MODE | ONLY_ARG;
+  const unsigned int LEAFY = ENABLED | LEAFY_MODE;
 }
 
 /* Settings of flag_incremental_link.  */
diff --git a/gcc/function.cc b/gcc/function.cc
index edf0b2ec6cf..ebca0628a26 100644
--- a/gcc/function.cc
+++ b/gcc/function.cc
@@ -5894,6 +5894,9 @@ gen_call_used_regs_seq (rtx_insn *ret, unsigned int zero_regs_type)
   only_used = zero_regs_type & ONLY_USED;
   only_arg = zero_regs_type & ONLY_ARG;
 
+  if ((zero_regs_type & LEAFY_MODE) && leaf_function_p ())
+    only_used = true;
+
   /* For each of the hard registers, we should zero it if:
 	    1. it is a call-used register;
 	and 2. it is not a fixed register;
diff --git a/gcc/opts.cc b/gcc/opts.cc
index fb2e5388ab1..9cc8998cfe1 100644
--- a/gcc/opts.cc
+++ b/gcc/opts.cc
@@ -2114,6 +2114,10 @@ const struct zero_call_used_regs_opts_s zero_call_used_regs_opts[] =
   ZERO_CALL_USED_REGS_OPT (all-gpr, zero_regs_flags::ALL_GPR),
   ZERO_CALL_USED_REGS_OPT (all-arg, zero_regs_flags::ALL_ARG),
   ZERO_CALL_USED_REGS_OPT (all, zero_regs_flags::ALL),
+  ZERO_CALL_USED_REGS_OPT (leafy-gpr-arg, zero_regs_flags::LEAFY_GPR_ARG),
+  ZERO_CALL_USED_REGS_OPT (leafy-gpr, zero_regs_flags::LEAFY_GPR),
+  ZERO_CALL_USED_REGS_OPT (leafy-arg, zero_regs_flags::LEAFY_ARG),
+  ZERO_CALL_USED_REGS_OPT (leafy, zero_regs_flags::LEAFY),
 #undef ZERO_CALL_USED_REGS_OPT
   {NULL, 0U}
 };
diff --git a/gcc/testsuite/c-c++-common/zero-scratch-regs-leafy-1.c b/gcc/testsuite/c-c++-common/zero-scratch-regs-leafy-1.c
new file mode 100644
index 00000000000..c1a0c31ba1c
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/zero-scratch-regs-leafy-1.c
@@ -0,0 +1,15 @@
+/* { dg-do run } */
+/* { dg-options "-O2 -fzero-call-used-regs=leafy" } */
+
+volatile int result = 0;
+int 
+__attribute__((noipa))
+foo (int x)
+{
+  return x;
+}
+int main()
+{
+  result = foo (2);
+  return 0;
+}
diff --git a/gcc/testsuite/c-c++-common/zero-scratch-regs-leafy-2.c b/gcc/testsuite/c-c++-common/zero-scratch-regs-leafy-2.c
new file mode 100644
index 00000000000..d450620c1fc
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/zero-scratch-regs-leafy-2.c
@@ -0,0 +1,21 @@
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+
+#include <assert.h>
+int result = 0;
+
+int 
+__attribute__((noipa))
+__attribute__ ((zero_call_used_regs("leafy")))
+foo1 (int x)
+{
+  return (x + 1);
+}
+
+int 
+__attribute__((noipa))
+__attribute__ ((zero_call_used_regs("leafy")))
+foo2 (int x)
+{
+  return foo1 (x + 2);
+}
diff --git a/gcc/testsuite/gcc.target/i386/zero-scratch-regs-leafy-1.c b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-leafy-1.c
new file mode 100644
index 00000000000..2277710c771
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-leafy-1.c
@@ -0,0 +1,12 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fzero-call-used-regs=leafy -fno-stack-protector -fno-PIC" } */
+
+void
+foo (void)
+{
+}
+
+/* { dg-final { scan-assembler-not "vzeroall" } } */
+/* { dg-final { scan-assembler-not "%xmm" } } */
+/* { dg-final { scan-assembler-not "xorl\[ \t\]+%" } } */
+/* { dg-final { scan-assembler-not "movl\[ \t\]+%" } } */
diff --git a/gcc/testsuite/gcc.target/i386/zero-scratch-regs-leafy-2.c b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-leafy-2.c
new file mode 100644
index 00000000000..24b85c3dbb7
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-leafy-2.c
@@ -0,0 +1,16 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fzero-call-used-regs=leafy-gpr -fno-stack-protector -fno-PIC" } */
+
+extern int bar (int);
+
+void
+foo (void)
+{
+  int x = bar (0);
+  if (x)
+    bar (1);
+}
+
+/* { dg-final { scan-assembler "xorl\[ \t\]+%eax, %eax" } } */
+/* { dg-final { scan-assembler "xorl\[ \t\]+%edx, %edx" } } */
+/* { dg-final { scan-assembler "xorl\[ \t\]+%ecx, %ecx" } } */