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[PATCH] x86: tighten condition for emitting LOCK on control register accesses
- From: "Jan Beulich" <JBeulich at suse dot com>
- To: <binutils at sourceware dot org>
- Cc: "H.J. Lu" <hjl dot tools at gmail dot com>
- Date: Wed, 30 May 2018 01:42:04 -0600
- Subject: [PATCH] x86: tighten condition for emitting LOCK on control register accesses
The control register is never expressed by REX.B; this bit only affects
the involved GPR. Also only one of the operands can have its "control"
flag set, so only check the correct operand.
gas/
2018-05-30 Jan Beulich <jbeulich@suse.com>
* config/tc-i386.c (build_modrm_byte): Drop REX_B from condition
checking for the need of emitting LOCK. Check "control" bit just
once.
--- a/gas/config/tc-i386.c
+++ b/gas/config/tc-i386.c
@@ -6894,12 +6894,11 @@ build_modrm_byte (void)
if ((i.op[source].regs->reg_flags & RegVRex) != 0)
i.vrex |= REX_R;
}
- if (flag_code != CODE_64BIT && (i.rex & (REX_R | REX_B)))
+ if (flag_code != CODE_64BIT && (i.rex & REX_R))
{
- if (!i.types[0].bitfield.control
- && !i.types[1].bitfield.control)
+ if (!i.types[i.tm.operand_types[0].bitfield.regmem].bitfield.control)
abort ();
- i.rex &= ~(REX_R | REX_B);
+ i.rex &= ~REX_R;
add_prefix (LOCK_PREFIX_OPCODE);
}
}