x86: don't use operand size override with NOP in 16-bit code

Since we don't key the NOP selection to user-controlled properties, we
may not use i386 features; otherwise we would violate a possible .arch
directive restricting ISA to pre-386.

gas/config/tc-i386.c

@@ -1291,6 +1291,7 @@ static const unsigned char f64_7[] =
 #define f64_8 (f64_9 + 1)		/* lea 0L(%rsi,%riz),%rsi */
 static const unsigned char f64_9[] =
   {0x2e,0x48,0x8d,0xb4,0x26,0x00,0x00,0x00,0x00}; /* lea %cs:0L(%rsi,%riz),%rsi */
+#define f16_2 (f64_3 + 1)		/* mov %si,%si	*/
 static const unsigned char f16_3[] =
   {0x8d,0x74,0x00};			/* lea 0(%si),%si	*/
 static const unsigned char f16_4[] =
@@ -1311,7 +1312,7 @@ static const unsigned char *const f64_patt[] = {
 };
 /* 16-bit NOPs patterns.  */
 static const unsigned char *const f16_patt[] = {
-  f32_1, f32_2, f16_3, f16_4
+  f32_1, f16_2, f16_3, f16_4
 };
 /* nopl (%[re]ax) */
 static const unsigned char alt_3[] =

gas/testsuite/gas/i386/nop-2.d

@@ -26,7 +26,7 @@ Disassembly of section .text:
  +[a-f0-9]+:	8d b4 00 00          	lea    0x0\(%si\),%si
  +[a-f0-9]+:	8d b4 00 00          	lea    0x0\(%si\),%si
  +[a-f0-9]+:	8d b4 00 00          	lea    0x0\(%si\),%si
- +[a-f0-9]+:	66 90                	xchg   %eax,%eax
+ +[a-f0-9]+:	89 f6                	mov    %si,%si
 
 0+26 <pseudo_30>:
  +[a-f0-9]+:	eb 1c                	jmp    44 <pseudo_129>

gas/testsuite/gas/i386/nops16-1.d

@@ -55,7 +55,7 @@ Disassembly of section .text:
 [ 	]*[a-f0-9]+:	8d b4 00 00          	lea    0x0\(%si\),%si
 [ 	]*[a-f0-9]+:	8d b4 00 00          	lea    0x0\(%si\),%si
 [ 	]*[a-f0-9]+:	8d b4 00 00          	lea    0x0\(%si\),%si
-[ 	]*[a-f0-9]+:	66 90                	xchg   %eax,%eax
+[ 	]*[a-f0-9]+:	89 f6                	mov    %si,%si
 
 0+80 <nop27>:
 [ 	]*[a-f0-9]+:	90                   	nop
@@ -118,7 +118,7 @@ Disassembly of section .text:
 [ 	]*[a-f0-9]+:	8d b4 00 00          	lea    0x0\(%si\),%si
 [ 	]*[a-f0-9]+:	8d b4 00 00          	lea    0x0\(%si\),%si
 [ 	]*[a-f0-9]+:	8d b4 00 00          	lea    0x0\(%si\),%si
-[ 	]*[a-f0-9]+:	66 90                	xchg   %eax,%eax
+[ 	]*[a-f0-9]+:	89 f6                	mov    %si,%si
 
 0+100 <nop23>:
 [ 	]*[a-f0-9]+:	90                   	nop
@@ -193,7 +193,7 @@ Disassembly of section .text:
 [ 	]*[a-f0-9]+:	8d b4 00 00          	lea    0x0\(%si\),%si
 [ 	]*[a-f0-9]+:	8d b4 00 00          	lea    0x0\(%si\),%si
 [ 	]*[a-f0-9]+:	8d b4 00 00          	lea    0x0\(%si\),%si
-[ 	]*[a-f0-9]+:	66 90                	xchg   %eax,%eax
+[ 	]*[a-f0-9]+:	89 f6                	mov    %si,%si
 
 0+180 <nop19>:
 [ 	]*[a-f0-9]+:	90                   	nop
@@ -280,7 +280,7 @@ Disassembly of section .text:
 [ 	]*[a-f0-9]+:	8d b4 00 00          	lea    0x0\(%si\),%si
 [ 	]*[a-f0-9]+:	8d b4 00 00          	lea    0x0\(%si\),%si
 [ 	]*[a-f0-9]+:	8d b4 00 00          	lea    0x0\(%si\),%si
-[ 	]*[a-f0-9]+:	66 90                	xchg   %eax,%eax
+[ 	]*[a-f0-9]+:	89 f6                	mov    %si,%si
 
 0+200 <nop15>:
 [ 	]*[a-f0-9]+:	90                   	nop
@@ -315,7 +315,7 @@ Disassembly of section .text:
 [ 	]*[a-f0-9]+:	eb 0a                	jmp    240 <nop11>
 [ 	]*[a-f0-9]+:	8d b4 00 00          	lea    0x0\(%si\),%si
 [ 	]*[a-f0-9]+:	8d b4 00 00          	lea    0x0\(%si\),%si
-[ 	]*[a-f0-9]+:	66 90                	xchg   %eax,%eax
+[ 	]*[a-f0-9]+:	89 f6                	mov    %si,%si
 
 0+240 <nop11>:
 [ 	]*[a-f0-9]+:	90                   	nop
@@ -336,7 +336,7 @@ Disassembly of section .text:
 [ 	]*[a-f0-9]+:	90                   	nop
 [ 	]*[a-f0-9]+:	8d b4 00 00          	lea    0x0\(%si\),%si
 [ 	]*[a-f0-9]+:	8d b4 00 00          	lea    0x0\(%si\),%si
-[ 	]*[a-f0-9]+:	66 90                	xchg   %eax,%eax
+[ 	]*[a-f0-9]+:	89 f6                	mov    %si,%si
 
 0+260 <nop9>:
 [ 	]*[a-f0-9]+:	90                   	nop
@@ -387,7 +387,7 @@ Disassembly of section .text:
 [ 	]*[a-f0-9]+:	90                   	nop
 [ 	]*[a-f0-9]+:	90                   	nop
 [ 	]*[a-f0-9]+:	8d b4 00 00          	lea    0x0\(%si\),%si
-[ 	]*[a-f0-9]+:	66 90                	xchg   %eax,%eax
+[ 	]*[a-f0-9]+:	89 f6                	mov    %si,%si
 
 0+2a0 <nop5>:
 [ 	]*[a-f0-9]+:	90                   	nop
@@ -450,5 +450,5 @@ Disassembly of section .text:
 [ 	]*[a-f0-9]+:	90                   	nop
 [ 	]*[a-f0-9]+:	90                   	nop
 [ 	]*[a-f0-9]+:	90                   	nop
-[ 	]*[a-f0-9]+:	66 90                	xchg   %eax,%eax
+[ 	]*[a-f0-9]+:	89 f6                	mov    %si,%si
 #pass

gas/testsuite/gas/i386/x86-64-nop-2.d

@@ -27,7 +27,7 @@ Disassembly of section .text:
  +[a-f0-9]+:	8d b4 00 00          	lea    0x0\(%si\),%si
  +[a-f0-9]+:	8d b4 00 00          	lea    0x0\(%si\),%si
  +[a-f0-9]+:	8d b4 00 00          	lea    0x0\(%si\),%si
- +[a-f0-9]+:	66 90                	xchg   %eax,%eax
+ +[a-f0-9]+:	89 f6                	mov    %si,%si
 
 0+26 <pseudo_30>:
  +[a-f0-9]+:	eb 1c                	jmp    44 <pseudo_129>