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V4 [PATCH 3/4] i386: Add -mbranches-within-32B-boundaries
- From: "H.J. Lu" <hjl dot tools at gmail dot com>
- To: binutils at sourceware dot org
- Date: Tue, 10 Dec 2019 08:21:55 -0800
- Subject: V4 [PATCH 3/4] i386: Add -mbranches-within-32B-boundaries
- References: <20191210162156.8480-1-hjl.tools@gmail.com>
Add -mbranches-within-32B-boundaries to enable
-malign-branch-boundary=32
-malign-branch=jcc+fused+jmp
-malign-branch-prefix-size=5
* config/tc-i386.c (OPTION_MBRANCHES_WITH_32B_BOUNDARIES): New.
(md_longopts): Add -mbranches-within-32B-boundaries.
(md_parse_option): Handle -mbranches-within-32B-boundaries.
(md_show_usage): Add -mbranches-within-32B-boundaries.
---
gas/config/tc-i386.c | 13 +++++++++++++
gas/doc/c-i386.texi | 11 +++++++++++
2 files changed, 24 insertions(+)
diff --git a/gas/config/tc-i386.c b/gas/config/tc-i386.c
index 0aeb07066b..10f81b69e9 100644
--- a/gas/config/tc-i386.c
+++ b/gas/config/tc-i386.c
@@ -11997,6 +11997,7 @@ const char *md_shortopts = "qnO::";
#define OPTION_MALIGN_BRANCH_BOUNDARY (OPTION_MD_BASE + 27)
#define OPTION_MALIGN_BRANCH_PREFIX_SIZE (OPTION_MD_BASE + 28)
#define OPTION_MALIGN_BRANCH (OPTION_MD_BASE + 29)
+#define OPTION_MBRANCHES_WITH_32B_BOUNDARIES (OPTION_MD_BASE + 30)
struct option md_longopts[] =
{
@@ -12035,6 +12036,7 @@ struct option md_longopts[] =
{"malign-branch-boundary", required_argument, NULL, OPTION_MALIGN_BRANCH_BOUNDARY},
{"malign-branch-prefix-size", required_argument, NULL, OPTION_MALIGN_BRANCH_PREFIX_SIZE},
{"malign-branch", required_argument, NULL, OPTION_MALIGN_BRANCH},
+ {"mbranches-within-32B-boundaries", no_argument, NULL, OPTION_MBRANCHES_WITH_32B_BOUNDARIES},
{"mamd64", no_argument, NULL, OPTION_MAMD64},
{"mintel64", no_argument, NULL, OPTION_MINTEL64},
{NULL, no_argument, NULL, 0}
@@ -12497,6 +12499,14 @@ md_parse_option (int c, const char *arg)
free (saved);
break;
+ case OPTION_MBRANCHES_WITH_32B_BOUNDARIES:
+ align_branch_power = 5;
+ align_branch_prefix_size = 5;
+ align_branch = (align_branch_jcc_bit
+ | align_branch_fused_bit
+ | align_branch_jmp_bit);
+ break;
+
case OPTION_MAMD64:
intel64 = 0;
break;
@@ -12760,6 +12770,9 @@ md_show_usage (FILE *stream)
-malign-branch-prefix-size=NUM (default: 5)\n\
align branches with NUM prefixes per instruction\n"));
fprintf (stream, _("\
+ -mbranches-within-32B-boundaries\n\
+ align branches within 32 byte boundary\n"));
+ fprintf (stream, _("\
-mamd64 accept only AMD64 ISA [default]\n"));
fprintf (stream, _("\
-mintel64 accept only Intel64 ISA\n"));
diff --git a/gas/doc/c-i386.texi b/gas/doc/c-i386.texi
index 74296e61f6..08f139cc15 100644
--- a/gas/doc/c-i386.texi
+++ b/gas/doc/c-i386.texi
@@ -449,6 +449,17 @@ This option specifies the maximum number of prefixes on an instruction
to align branches. @var{NUM} should be between 0 and 5. The default
@var{NUM} is 5.
+@cindex @samp{-mbranches-within-32B-boundaries} option, i386
+@cindex @samp{-mbranches-within-32B-boundaries} option, x86-64
+@item -mbranches-within-32B-boundaries
+This option aligns conditional jumps, fused conditional jumps and
+unconditional jumps within 32 byte boundary with up to 5 segment prefixes
+on an instruction. It is equivalent to
+@option{-malign-branch-boundary=32}
+@option{-malign-branch=jcc+fused+jmp}
+@option{-malign-branch-prefix-size=5}.
+The default doesn't align branches.
+
@cindex @samp{-mx86-used-note=} option, i386
@cindex @samp{-mx86-used-note=} option, x86-64
@item -mx86-used-note=@var{no}
--
2.21.0