From: Jan Beulich <jbeulich@suse.com>
Date: Fri, 14 Feb 2020 13:04:23 +0000 (+0100)
Subject: x86: adjust segment override prefix emission
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=b6773884364e0275a793adad4b025913fa155d5a;p=binutils-gdb.git

x86: adjust segment override prefix emission

Since we already suppress the prefix altogether when it's the default
one for the chosen addressing mode, let's do so also when instruction
prefix and override specified with the memory operand match. (Note that
insn prefix specified segment overrides never get discarded.)
---

diff --git a/gas/ChangeLog b/gas/ChangeLog
index 0cbd2a5bbff..56d50719a2a 100644
--- a/gas/ChangeLog
+++ b/gas/ChangeLog
@@ -1,3 +1,11 @@
+2020-02-14  Jan Beulich  <jbeulich@suse.com>
+
+	* config/tc-i386.c (process_operands): Also skip segment
+	override prefix emission if it matches an already present one.
+	* testsuite/gas/i386/prefix32.s: Add double segment override
+	cases.
+	* testsuite/gas/i386/prefix32.l: Adjust expectations.
+
 2020-02-14  Jan Beulich  <jbeulich@suse.com>
 
 	* config/tc-i386.c (process_operands): Drop ineffectual segment
diff --git a/gas/config/tc-i386.c b/gas/config/tc-i386.c
index d7d45de76e0..0e60919e492 100644
--- a/gas/config/tc-i386.c
+++ b/gas/config/tc-i386.c
@@ -7178,11 +7178,13 @@ duplicate:
     }
 
   /* If a segment was explicitly specified, and the specified segment
-     is not the default, use an opcode prefix to select it.  If we
-     never figured out what the default segment is, then default_seg
-     will be zero at this point, and the specified segment prefix will
-     always be used.  */
-  if ((i.seg[0]) && (i.seg[0] != default_seg))
+     is neither the default nor the one already recorded from a prefix,
+     use an opcode prefix to select it.  If we never figured out what
+     the default segment is, then default_seg will be zero at this
+     point, and the specified segment prefix will always be used.  */
+  if (i.seg[0]
+      && i.seg[0] != default_seg
+      && i.seg[0]->seg_prefix != i.prefix[SEG_PREFIX])
     {
       if (!add_prefix (i.seg[0]->seg_prefix))
 	return 0;
diff --git a/gas/testsuite/gas/i386/prefix32.l b/gas/testsuite/gas/i386/prefix32.l
index 41c8d8801c0..09a00cd03d9 100644
--- a/gas/testsuite/gas/i386/prefix32.l
+++ b/gas/testsuite/gas/i386/prefix32.l
@@ -8,6 +8,7 @@
 .*:19: Error: same type of prefix .*
 .*:20: Error: data size .* `vaddps'
 .*:21: Error: data size .* `vaddpd'
+.*:25: Error: same type of prefix .*
 GAS LISTING .*
 #...
 [ 	]*1[ 	]+\.text
@@ -33,4 +34,10 @@ GAS LISTING .*
 [ 	]*20[ 	]+data16 vaddps	%xmm0, %xmm0, %xmm0
 [ 	]*21[ 	]+data16 vaddpd	%xmm0, %xmm0, %xmm0
 [ 	]*22[ 	]*
-[ 	]*23[ 	]*[\?]+ 0+[ \t]+\.p2align	4,0
+[ 	]*23[ 	]+\.Lsegment:
+[ 	]*24[ 	]+\?\?\?\? 368B4500[ 	]+ss mov		%ss:\(%ebp\), %eax
+[ 	]*25[ 	]+ss mov		%ds:\(%ebp\), %eax
+[ 	]*26[ 	]+\?\?\?\? 3E8B4500[ 	]+ds mov		%ss:\(%ebp\), %eax
+[ 	]*27[ 	]+\?\?\?\? 3E8B4500[ 	]+ds mov		%ds:\(%ebp\), %eax
+[ 	]*28[ 	]*
+#pass
diff --git a/gas/testsuite/gas/i386/prefix32.s b/gas/testsuite/gas/i386/prefix32.s
index 1ffdff13250..a4382a2b616 100644
--- a/gas/testsuite/gas/i386/prefix32.s
+++ b/gas/testsuite/gas/i386/prefix32.s
@@ -20,4 +20,10 @@ prefix:
 	data16 vaddps	%xmm0, %xmm0, %xmm0
 	data16 vaddpd	%xmm0, %xmm0, %xmm0
 
+.Lsegment:
+	ss mov		%ss:(%ebp), %eax
+	ss mov		%ds:(%ebp), %eax
+	ds mov		%ss:(%ebp), %eax
+	ds mov		%ds:(%ebp), %eax
+
 	.p2align	4,0