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* [PATCH] i386: Insert ENDBR for NOTE_INSN_DELETED_LABEL only if needed
@ 2019-02-15  4:13 H.J. Lu
  2019-02-16 15:02 ` V2 " H.J. Lu
  0 siblings, 1 reply; 13+ messages in thread
From: H.J. Lu @ 2019-02-15  4:13 UTC (permalink / raw)
  To: gcc-patches; +Cc: Uros Bizjak, Jan Hubicka

NOTE_INSN_DELETED_LABEL is used to mark what used to be a 'code_label',
but was not used for other purposes than taking its address and was
transformed to mark that no code jumps to it.  NOTE_INSN_DELETED_LABEL
is generated only in 3 places:

1. When delete_insn sees an unused label which is an explicit label in
the input source code or its address is taken, it turns the label into
a NOTE_INSN_DELETED_LABEL note.
2. When rtl_tidy_fallthru_edge deletes a tablejump, it turns the
tablejump into a NOTE_INSN_DELETED_LABEL note.
3. ix86_init_large_pic_reg creats a NOTE_INSN_DELETED_LABEL note, .L2,
to initialize large model PIC register:

L2:
	movabsq	$_GLOBAL_OFFSET_TABLE_-.L2, %r11
	leaq	.L2(%rip), %rax
	movabsq	$val@GOT, %rdx
	addq	%r11, %rax

Among of them, ENDBR is needed only when the label address is taken.
rest_of_insert_endbranch has

          if ((LABEL_P (insn) && LABEL_PRESERVE_P (insn))
              || (NOTE_P (insn)
                  && NOTE_KIND (insn) == NOTE_INSN_DELETED_LABEL))
            /* TODO.  Check /s bit also.  */
            {
              cet_eb = gen_nop_endbr ();
              emit_insn_after (cet_eb, insn);
              continue;
            }

For NOTE_INSN_DELETED_LABEL, we should check if forced_labels to see
if its address is taken.  Also ix86_init_large_pic_reg shouldn't set
LABEL_PRESERVE_P (in_struct) since NOTE_INSN_DELETED_LABEL is suffcient
to keep the label.

gcc/

	PR target/89355
	* config/i386/i386.c (rest_of_insert_endbranch): Check
	forced_labels to see if the address of NOTE_INSN_DELETED_LABEL
	is taken.
	(ix86_init_large_pic_reg): Don't set LABEL_PRESERVE_P.

gcc/testsuite/

	PR target/89355
	* gcc.target/i386/cet-label-3.c: New test.
	* gcc.target/i386/cet-label-4.c: Likewise.
	* gcc.target/i386/cet-label-5.c: Likewise.
---
 gcc/config/i386/i386.c                      |  9 +++++---
 gcc/testsuite/gcc.target/i386/cet-label-3.c | 23 +++++++++++++++++++++
 gcc/testsuite/gcc.target/i386/cet-label-4.c | 12 +++++++++++
 gcc/testsuite/gcc.target/i386/cet-label-5.c | 13 ++++++++++++
 4 files changed, 54 insertions(+), 3 deletions(-)
 create mode 100644 gcc/testsuite/gcc.target/i386/cet-label-3.c
 create mode 100644 gcc/testsuite/gcc.target/i386/cet-label-4.c
 create mode 100644 gcc/testsuite/gcc.target/i386/cet-label-5.c

diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
index fd05873ba39..ed53fbea9ae 100644
--- a/gcc/config/i386/i386.c
+++ b/gcc/config/i386/i386.c
@@ -2734,10 +2734,14 @@ rest_of_insert_endbranch (void)
 	      continue;
 	    }
 
+	  /* NB: Add an ENDBR for NOTE_INSN_DELETED_LABEL only if its
+	     addresss is taken.  */
 	  if ((LABEL_P (insn) && LABEL_PRESERVE_P (insn))
 	      || (NOTE_P (insn)
-		  && NOTE_KIND (insn) == NOTE_INSN_DELETED_LABEL))
-	    /* TODO.  Check /s bit also.  */
+		  && NOTE_KIND (insn) == NOTE_INSN_DELETED_LABEL
+		  && vec_safe_contains<rtx_insn *>
+		       (forced_labels,
+			static_cast<rtx_code_label *> (insn))))
 	    {
 	      cet_eb = gen_nop_endbr ();
 	      emit_insn_after (cet_eb, insn);
@@ -7002,7 +7006,6 @@ ix86_init_large_pic_reg (unsigned int tmp_regno)
   gcc_assert (Pmode == DImode);
   label = gen_label_rtx ();
   emit_label (label);
-  LABEL_PRESERVE_P (label) = 1;
   tmp_reg = gen_rtx_REG (Pmode, tmp_regno);
   gcc_assert (REGNO (pic_offset_table_rtx) != tmp_regno);
   emit_insn (gen_set_rip_rex64 (pic_offset_table_rtx,
diff --git a/gcc/testsuite/gcc.target/i386/cet-label-3.c b/gcc/testsuite/gcc.target/i386/cet-label-3.c
new file mode 100644
index 00000000000..9f427a866f3
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/cet-label-3.c
@@ -0,0 +1,23 @@
+/* PR target/89355  */
+/* { dg-do compile } */
+/* { dg-options "-O2 -fcf-protection" } */
+/* { dg-final { scan-assembler-times "endbr32" 1 { target ia32 } } } */
+/* { dg-final { scan-assembler-times "endbr64" 1 { target { ! ia32 } } } } */
+int
+test (int* val)
+{
+  int status = 99;
+
+  if (!val)
+    {
+      status = 22;
+      goto end;
+    }
+
+  extern int x;
+  *val = x;
+
+  status = 0;
+end:
+  return status;
+}
diff --git a/gcc/testsuite/gcc.target/i386/cet-label-4.c b/gcc/testsuite/gcc.target/i386/cet-label-4.c
new file mode 100644
index 00000000000..d743d2bf202
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/cet-label-4.c
@@ -0,0 +1,12 @@
+/* PR target/89355  */
+/* { dg-do compile { target { fpic && lp64 } } } */
+/* { dg-options "-O2 -fcf-protection -fPIC -mcmodel=large" } */
+/* { dg-final { scan-assembler-times "endbr64" 1 } } */
+
+extern int val;
+
+int
+test (void)
+{
+  return val;
+}
diff --git a/gcc/testsuite/gcc.target/i386/cet-label-5.c b/gcc/testsuite/gcc.target/i386/cet-label-5.c
new file mode 100644
index 00000000000..4d5ca816598
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/cet-label-5.c
@@ -0,0 +1,13 @@
+/* PR target/89355  */
+/* { dg-do compile } */
+/* { dg-options "-O2 -fcf-protection -Wno-return-local-addr" } */
+/* { dg-final { scan-assembler-times "endbr32" 2 { target ia32 } } } */
+/* { dg-final { scan-assembler-times "endbr64" 2 { target { ! ia32 } } } } */
+
+void *
+func (void)
+{
+  return &&bar;
+bar:
+  return 0;
+}
-- 
2.20.1

^ permalink raw reply	[flat|nested] 13+ messages in thread
end of thread, other threads:[~2019-05-31 18:03 UTC | newest]

Thread overview: 13+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2019-02-15  4:13 [PATCH] i386: Insert ENDBR for NOTE_INSN_DELETED_LABEL only if needed H.J. Lu
2019-02-16 15:02 ` V2 " H.J. Lu
2019-05-21 21:48   ` PING^1: " H.J. Lu
2019-05-28  7:21     ` Uros Bizjak
2019-05-28  9:22   ` Jakub Jelinek
2019-05-28 15:16     ` H.J. Lu
2019-05-28 15:31       ` Jakub Jelinek
2019-05-28 15:34         ` H.J. Lu
2019-05-28 16:11           ` Jakub Jelinek
2019-05-28 17:37             ` Jeff Law
2019-05-31 17:39               ` [PATCH] Don't insert ENDBR after NOTE_INSN_DELETED_LABEL H.J. Lu
2019-05-31 18:03                 ` Jakub Jelinek
2019-05-31 18:26                   ` H.J. Lu

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