[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:f9b0e7992963ace4b3167f7bfdc822c80c2d3f63

commit f9b0e7992963ace4b3167f7bfdc822c80c2d3f63
Author: Alexandre Oliva <oliva@adacore.com>
Date:   Wed Oct 19 20:36:28 2022 -0300

    Add leafy mode for zero-call-used-regs

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 3532728aa1a..16f161ebf8a 100644
--- a/gcc/doc/extend.texi
+++ b/gcc/doc/extend.texi
@@ -4402,10 +4402,28 @@ 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 d6d3b0e7800..268bf028ada 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 6474a663b30..16582e69804 100644
--- a/gcc/function.cc
+++ b/gcc/function.cc
@@ -5879,6 +5879,9 @@ 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 ae079fcd20e..39f6a1b278d 100644
--- a/gcc/opts.cc
+++ b/gcc/opts.cc
@@ -2099,6 +2099,10 @@ 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" } } */