From: Jan Beulich <jbeulich@sourceware.org>
To: bfd-cvs@sourceware.org
Subject: [binutils-gdb] x86: adjust NOP generation after potential non-insn
Date: Fri, 1 Dec 2023 07:30:11 +0000 (GMT) [thread overview]
Message-ID: <20231201073011.C50423858C30@sourceware.org> (raw)
https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=0aa5d0c9e90a2bf26a99a0354ef500e971341de8
commit 0aa5d0c9e90a2bf26a99a0354ef500e971341de8
Author: Jan Beulich <jbeulich@suse.com>
Date: Fri Dec 1 08:29:11 2023 +0100
x86: adjust NOP generation after potential non-insn
Just like avoiding to do certain transformations potentially affected by
stand-alone prefixes or direct data emission, also avoid emitting
optimized NOPs right afterwards; insert a plain old NOP first in such
cases.
Diff:
---
gas/config/tc-i386.c | 8 ++++++++
gas/config/tc-i386.h | 6 +++++-
2 files changed, 13 insertions(+), 1 deletion(-)
diff --git a/gas/config/tc-i386.c b/gas/config/tc-i386.c
index e984923ec35..4f3864f2ba7 100644
--- a/gas/config/tc-i386.c
+++ b/gas/config/tc-i386.c
@@ -1529,6 +1529,14 @@ i386_generate_nops (fragS *fragP, char *where, offsetT count, int limit)
else if (fragP->fr_type != rs_machine_dependent)
fragP->fr_var = count;
+ /* Emit a plain NOP first when the last thing we saw may not have been
+ a proper instruction (e.g. a stand-alone prefix or .byte). */
+ if (!fragP->tc_frag_data.last_insn_normal)
+ {
+ *where++ = 0x90;
+ --count;
+ }
+
if ((count / max_single_nop_size) > max_number_of_nops)
{
/* Generate jump over NOPs. */
diff --git a/gas/config/tc-i386.h b/gas/config/tc-i386.h
index c3022149fbe..6d6f0b93681 100644
--- a/gas/config/tc-i386.h
+++ b/gas/config/tc-i386.h
@@ -321,6 +321,7 @@ struct i386_tc_frag_data
unsigned int branch_type : 3;
unsigned int cpunop : 1;
unsigned int isanop : 1;
+ unsigned int last_insn_normal : 1;
};
/* We need to emit the right NOP pattern in .align frags. This is
@@ -347,7 +348,10 @@ struct i386_tc_frag_data
(FRAGP)->tc_frag_data.cmp_size = 0; \
(FRAGP)->tc_frag_data.classified = 0; \
(FRAGP)->tc_frag_data.branch_type = 0; \
- (FRAGP)->tc_frag_data.mf_type = 0; \
+ (FRAGP)->tc_frag_data.mf_type = 0; \
+ (FRAGP)->tc_frag_data.last_insn_normal \
+ = (seg_info(now_seg)->tc_segment_info_data.last_insn.kind \
+ == last_insn_other); \
} \
while (0)
reply other threads:[~2023-12-01 7:30 UTC|newest]
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