x86: fix "REP RET" with -madd-bnd-prefix

Just like any other branches, RET should gain a BND prefix also when
already prefixed in source by REP.

8 files changed, 45 insertions, 8 deletions

diff --git a/gas/ChangeLog b/gas/ChangeLog
index d49fc11..6de7a61 100644
--- a/gas/ChangeLog
+++ b/gas/ChangeLog
@@ -1,3 +1,16 @@
+2018-07-11  Jan Beulich  <jbeulich@suse.com>
+
+	* config/tc-i386.c (md_assemble): Also replace an already
+	present REP prefix.
+	* testsuite/gas/i386/mpx-add-bnd-prefix.s,
+	testsuite/gas/i386/x86-64-mpx-add-bnd-prefix.s: Test RET with
+	all REP flavors.
+	* testsuite/gas/i386/mpx-add-bnd-prefix.d,
+	testsuite/gas/i386/x86-64-mpx-add-bnd-prefix.d: Adjust
+	expectations.
+	* testsuite/gas/i386/mpx-add-bnd-prefix.e,
+	testsuite/gas/i386/x86-64-mpx-add-bnd-prefix.e: New.
+
 2018-07-09  Jeff Law  <law@redhat.com>
 
 	* testsuite/nds32/ji-jr.d: Fix name tag.
diff --git a/gas/config/tc-i386.c b/gas/config/tc-i386.c
index 2d20f1c..a7b8400 100644
--- a/gas/config/tc-i386.c
+++ b/gas/config/tc-i386.c
@@ -4112,10 +4112,16 @@ md_assemble (char *line)
     }
 
   /* Insert BND prefix.  */
-  if (add_bnd_prefix
-      && i.tm.opcode_modifier.bndprefixok
-      && !i.prefix[BND_PREFIX])
-    add_prefix (BND_PREFIX_OPCODE);
+  if (add_bnd_prefix && i.tm.opcode_modifier.bndprefixok)
+    {
+      if (!i.prefix[BND_PREFIX])
+	add_prefix (BND_PREFIX_OPCODE);
+      else if (i.prefix[BND_PREFIX] != BND_PREFIX_OPCODE)
+	{
+	  as_warn (_("replacing `rep'/`repe' prefix by `bnd'"));
+	  i.prefix[BND_PREFIX] = BND_PREFIX_OPCODE;
+	}
+    }
 
   /* Check string instruction segment overrides.  */
   if (i.tm.opcode_modifier.isstring && i.mem_operands != 0)
diff --git a/gas/testsuite/gas/i386/mpx-add-bnd-prefix.d b/gas/testsuite/gas/i386/mpx-add-bnd-prefix.d
index 571f0da..30f6502 100644
--- a/gas/testsuite/gas/i386/mpx-add-bnd-prefix.d
+++ b/gas/testsuite/gas/i386/mpx-add-bnd-prefix.d
@@ -1,4 +1,5 @@
 #as: -madd-bnd-prefix
+#stderr: mpx-add-bnd-prefix.e
 #objdump: -drw
 #name: Check -madd-bnd-prefix
 
@@ -18,7 +19,9 @@ Disassembly of section .text:
 0+14 <foo>:
 [ 	]*[a-f0-9]+:	f2 c3                	bnd ret 
 [ 	]*[a-f0-9]+:	f2 c3                	bnd ret 
-[ 	]*[a-f0-9]+:	f2 e8 f6 ff ff ff    	bnd call 14 <foo>
+[ 	]*[a-f0-9]+:	f2 c3                	bnd ret 
+[ 	]*[a-f0-9]+:	f2 c3                	bnd ret 
+[ 	]*[a-f0-9]+:	f2 e8 f2 ff ff ff    	bnd call 14 <foo>
 [ 	]*[a-f0-9]+:	01 c3                	add    %eax,%ebx
-[ 	]*[a-f0-9]+:	e2 f2                	loop   14 <foo>
+[ 	]*[a-f0-9]+:	e2 ee                	loop   14 <foo>
 #pass
diff --git a/gas/testsuite/gas/i386/mpx-add-bnd-prefix.e b/gas/testsuite/gas/i386/mpx-add-bnd-prefix.e
new file mode 100644
index 0000000..4e99ad0
--- /dev/null
+++ b/gas/testsuite/gas/i386/mpx-add-bnd-prefix.e
@@ -0,0 +1,3 @@
+.*: Assembler messages:
+.*:12: Warning: .*rep.*bnd.*
+.*:13: Warning: .*rep.*bnd.*
diff --git a/gas/testsuite/gas/i386/mpx-add-bnd-prefix.s b/gas/testsuite/gas/i386/mpx-add-bnd-prefix.s
index 638dafa..a75faa7 100644
--- a/gas/testsuite/gas/i386/mpx-add-bnd-prefix.s
+++ b/gas/testsuite/gas/i386/mpx-add-bnd-prefix.s
@@ -8,6 +8,9 @@
 	jmp	*(%ebx)
 	ret
 foo:
+	# Use of REP/REPE prefix - converted to BND with warning
+	rep ret
+	repe ret
 	# Use of REPNE prefix - we shouldn't get any error
 	repne ret
 	# BND prefix already exists - we shouldn't get any error here
diff --git a/gas/testsuite/gas/i386/x86-64-mpx-add-bnd-prefix.d b/gas/testsuite/gas/i386/x86-64-mpx-add-bnd-prefix.d
index cef644f..139faae 100644
--- a/gas/testsuite/gas/i386/x86-64-mpx-add-bnd-prefix.d
+++ b/gas/testsuite/gas/i386/x86-64-mpx-add-bnd-prefix.d
@@ -1,4 +1,5 @@
 #as: -madd-bnd-prefix
+#stderr: x86-64-mpx-add-bnd-prefix.e
 #objdump: -drw
 #name: Check -madd-bnd-prefix (x86-64)
 
@@ -18,7 +19,9 @@ Disassembly of section .text:
 0+14 <foo>:
 [ 	]*[a-f0-9]+:	f2 c3                	bnd retq 
 [ 	]*[a-f0-9]+:	f2 c3                	bnd retq 
-[ 	]*[a-f0-9]+:	f2 e8 f6 ff ff ff    	bnd callq 14 <foo>
+[ 	]*[a-f0-9]+:	f2 c3                	bnd retq 
+[ 	]*[a-f0-9]+:	f2 c3                	bnd retq 
+[ 	]*[a-f0-9]+:	f2 e8 f2 ff ff ff    	bnd callq 14 <foo>
 [ 	]*[a-f0-9]+:	48 01 c3             	add    %rax,%rbx
-[ 	]*[a-f0-9]+:	e2 f1                	loop   14 <foo>
+[ 	]*[a-f0-9]+:	e2 ed                	loop   14 <foo>
 #pass
diff --git a/gas/testsuite/gas/i386/x86-64-mpx-add-bnd-prefix.e b/gas/testsuite/gas/i386/x86-64-mpx-add-bnd-prefix.e
new file mode 100644
index 0000000..4e99ad0
--- /dev/null
+++ b/gas/testsuite/gas/i386/x86-64-mpx-add-bnd-prefix.e
@@ -0,0 +1,3 @@
+.*: Assembler messages:
+.*:12: Warning: .*rep.*bnd.*
+.*:13: Warning: .*rep.*bnd.*
diff --git a/gas/testsuite/gas/i386/x86-64-mpx-add-bnd-prefix.s b/gas/testsuite/gas/i386/x86-64-mpx-add-bnd-prefix.s
index f9a900c..c1be9ef 100644
--- a/gas/testsuite/gas/i386/x86-64-mpx-add-bnd-prefix.s
+++ b/gas/testsuite/gas/i386/x86-64-mpx-add-bnd-prefix.s
@@ -8,6 +8,9 @@
 	jmp	*(%rbx)
 	ret
 foo:
+	# Use of REP/REPE prefix - converted to BND with warning
+	rep ret
+	repe ret
 	# Use of REPNE prefix - we shouldn't get any error
 	repne ret
 	# BND prefix already exists - we shouldn't get any error here