While auditing our ROP code generation for some test cases I wrote, I noticed
a few issues which I'm tracking in PR114759. The first issue I noticed is we
disable shrink-wrapping when using -mrop-protect, even in the cases where we
never emit the ROP instructions because they're not needed. The problem is
we disable shrink-wrapping too early, before we know whether we will need to
emit the ROP instructions or not. The fix is to delay disabling shrink
wrapping until we've decided whether we will or won't be emitting the ROP
instructions.
This patch passed bootstrap and regtesting on powerpc64le-linux with no
regressions, with the unpatched build FAILing the new test case and the
patched build PASSing the new test case.
Ok for trunk?
Peter
rs6000: ROP - Do not disable shrink-wrapping for leaf functions [PR114759]
Only disable shrink-wrapping when using -mrop-protect when we know we
will be emitting the ROP instructions (ie, non-leaf functions).
2024-06-17 Peter Bergner <berg...@linux.ibm.com>
gcc/
PR target/114759
* config/rs6000/rs6000.cc (rs6000_override_options_after_change): Move
the disabling of shrink-wrapping from here....
* config/rs6000/rs6000-logue.cc (rs6000_stack_info): ...to here.
gcc/testsuite/
PR target/114759
* gcc.target/powerpc/pr114759-1.c: New test.
---
gcc/config/rs6000/rs6000-logue.cc | 6 +++++-
gcc/config/rs6000/rs6000.cc | 4 ----
gcc/testsuite/gcc.target/powerpc/pr114759-1.c | 16 ++++++++++++++++
3 files changed, 21 insertions(+), 5 deletions(-)
create mode 100644 gcc/testsuite/gcc.target/powerpc/pr114759-1.c
diff --git a/gcc/config/rs6000/rs6000-logue.cc
b/gcc/config/rs6000/rs6000-logue.cc
index 193e2122c0f..659da0bd53f 100644
--- a/gcc/config/rs6000/rs6000-logue.cc
+++ b/gcc/config/rs6000/rs6000-logue.cc
@@ -720,7 +720,11 @@ rs6000_stack_info (void)
&& info->calls_p
&& DEFAULT_ABI == ABI_ELFv2
&& rs6000_rop_protect)
- info->rop_hash_size = 8;
+ {
+ /* If we are inserting ROP-protect instructions, disable shrink wrap. */
+ flag_shrink_wrap = 0;
+ info->rop_hash_size = 8;
+ }
else if (rs6000_rop_protect && DEFAULT_ABI != ABI_ELFv2)
{
/* We can't check this in rs6000_option_override_internal since
diff --git a/gcc/config/rs6000/rs6000.cc b/gcc/config/rs6000/rs6000.cc
index e4dc629ddcc..fd6e013c346 100644
--- a/gcc/config/rs6000/rs6000.cc
+++ b/gcc/config/rs6000/rs6000.cc
@@ -3427,10 +3427,6 @@ rs6000_override_options_after_change (void)
}
else if (!OPTION_SET_P (flag_cunroll_grow_size))
flag_cunroll_grow_size = flag_peel_loops || optimize >= 3;
-
- /* If we are inserting ROP-protect instructions, disable shrink wrap. */
- if (rs6000_rop_protect)
- flag_shrink_wrap = 0;
}
#ifdef TARGET_USES_LINUX64_OPT
diff --git a/gcc/testsuite/gcc.target/powerpc/pr114759-1.c
b/gcc/testsuite/gcc.target/powerpc/pr114759-1.c
new file mode 100644
index 00000000000..b4ba366402f
--- /dev/null
+++ b/gcc/testsuite/gcc.target/powerpc/pr114759-1.c
@@ -0,0 +1,16 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -mdejagnu-cpu=power10 -mrop-protect
-fdump-rtl-pro_and_epilogue" } */
+/* { dg-require-effective-target rop_ok } */
+
+/* Verify we still attempt shrink-wrapping when using -mrop-protect
+ and there are no function calls. */
+
+long
+foo (long arg)
+{
+ if (arg)
+ asm ("" ::: "r20");
+ return 0;
+}
+
+/* { dg-final { scan-rtl-dump-times "Performing shrink-wrapping" 1
"pro_and_epilogue" } } */
--
2.43.0
