Improve -mlfence-after-load

  1.Implict load for POP/POPF/POPA/XLATB, no load for Anysize insns
  2. Add -mlfence-before-ret=shl/yes, adjust operand size of
  or/not/shl according to ret's.
  3. Issue warning for REP CMPS/SCAS since they would affect control
  flow behavior.
  4. Adjust testcases and documents.

gas/Changelog:
	* config/tc-i386.c (lfence_before_ret_shl): New member.
	(load_insn_p): implict load for POP/POPA/POPF/XLATB, no load
	for Anysize insns.
	(insert_after_load): Issue warning for REP CMPS/SCAS.
	(insert_before_before): Handle iret, Handle
	-mlfence-before-ret=shl, Adjust operand size of or/not/shl to ret's,
	(md_parse_option): Change -mlfence-before-ret=[none|not|or] to
	-mlfence-before-ret=[none/not/or/shl/yes].
	Enable -mlfence-before-ret=shl when
	-mlfence-beofre-indirect-branch=all and no explict -mlfence-before-ret option.
	(md_show_usage): Ditto.
	* doc/c-i386.texi: Ditto.
	* testsuite/gas/i386/i386.exp: Add new testcases.
	* testsuite/gas/i386/lfence-load-b.d: New.
	* testsuite/gas/i386/lfence-load-b.e: New.
	* testsuite/gas/i386/lfence-load.d: Modified.
	* testsuite/gas/i386/lfence-load.e: New.
	* testsuite/gas/i386/lfence-load.s: Modified.
	* testsuite/gas/i386/lfence-ret-a.d: Modified.
	* testsuite/gas/i386/lfence-ret-b.d: Modified.
	* testsuite/gas/i386/lfence-ret-c.d: New.
	* testsuite/gas/i386/lfence-ret-d.d: New.
	* testsuite/gas/i386/lfence-ret.s: Modified.
	* testsuite/gas/i386/x86-64-lfence-load-b.d: New.
	* testsuite/gas/i386/x86-64-lfence-load.d: Modified.
	* testsuite/gas/i386/x86-64-lfence-load.s: Modified.
	* testsuite/gas/i386/x86-64-lfence-ret-a.d: Modified.
	* testsuite/gas/i386/x86-64-lfence-ret-b.d: Modified.
	* testsuite/gas/i386/x86-64-lfence-ret-c.d: New.
	* testsuite/gas/i386/x86-64-lfence-ret-d.d: New
	* testsuite/gas/i386/x86-64-lfence-ret-e.d: New.
	* testsuite/gas/i386/x86-64-lfence-ret.e: New.
	* testsuite/gas/i386/x86-64-lfence-ret.s: New.

1 files changed, 8 insertions, 4 deletions

diff --git a/gas/doc/c-i386.texi b/gas/doc/c-i386.texi
index 628fb1a..4acece4 100644
--- a/gas/doc/c-i386.texi
+++ b/gas/doc/c-i386.texi
@@ -488,6 +488,8 @@ before indirect near branch instructions.
 @option{-mlfence-before-indirect-branch=@var{all}} will generate lfence
 before indirect near branch via register and issue a warning before
 indirect near branch via memory.
+It also implicitly sets @option{-mlfence-before-ret=@var{shl}} when
+there's no explict @option{-mlfence-before-ret=}.
 @option{-mlfence-before-indirect-branch=@var{register}} will generate
 lfence before indirect near branch via register.
 @option{-mlfence-before-indirect-branch=@var{memory}} will issue a
@@ -501,15 +503,17 @@ after loading branch target register.
 @cindex @samp{-mlfence-before-ret=} option, i386
 @cindex @samp{-mlfence-before-ret=} option, x86-64
 @item -mlfence-before-ret=@var{none}
+@item -mlfence-before-ret=@var{shl}
 @item -mlfence-before-ret=@var{or}
+@item -mlfence-before-ret=@var{yes}
 @itemx -mlfence-before-ret=@var{not}
 These options control whether the assembler should generate lfence
 before ret.  @option{-mlfence-before-ret=@var{or}} will generate
 generate or instruction with lfence.
-@option{-mlfence-before-ret=@var{not}} will generate not instruction
-with lfence.
-@option{-mlfence-before-ret=@var{none}} will not generate lfence,
-which is the default.
+@option{-mlfence-before-ret=@var{shl/yes}} will generate shl instruction
+with lfence. @option{-mlfence-before-ret=@var{not}} will generate not
+instruction with lfence. @option{-mlfence-before-ret=@var{none}} will not
+generate lfence, which is the default.
 
 @cindex @samp{-mx86-used-note=} option, i386
 @cindex @samp{-mx86-used-note=} option, x86-64