x86: correct and simplify NOP disassembly

It's not just REX.W which is ignored with opcode 0x90. The same goes for
REX.R and REX.X as well as empty REX. None of these are forms of
"xchg %eax,%eax" (which would mean zero-extending %eax to %rax), so they
also shouldn't be disassembled this way.

While there simplify things: A single hook function suffices, thus
making it unnecessary to keep two expressions in sync. And checking
ins->address_mode for mode_64bit also is unnecessary, as "rex" can be
non-zero only in that case anyway.

diff --git a/gas/testsuite/gas/i386/ilp32/rex.d b/gas/testsuite/gas/i386/ilp32/rex.d
index d8bc1b528c3c646ff0805f1173eb5988b0accd49..63b696f22b83414303d9a2411a2a9daabc8cce7f 100644 (file)
--- a/gas/testsuite/gas/i386/ilp32/rex.d
+++ b/gas/testsuite/gas/i386/ilp32/rex.d
@@ -2,46 +2,4 @@
 #objdump: -dw
 #name: x86-64 (ILP32) manual rex prefix use
 #notarget: x86_64-*-elf*
-
-.*: +file format .*
-
-Disassembly of section .text:
-
-0+ <_start>:
-[       ]*[0-9a-f]+:[   ]+40 0f ae 00[  ]+rex fxsave[   ]+\(%rax\)
-[       ]*[0-9a-f]+:[   ]+48 0f ae 00[  ]+fxsave64[     ]+\(%rax\)
-[       ]*[0-9a-f]+:[   ]+41 0f ae 00[  ]+fxsave[       ]+\(%r8\)
-[       ]*[0-9a-f]+:[   ]+49 0f ae 00[  ]+fxsave64[     ]+\(%r8\)
-[       ]*[0-9a-f]+:[   ]+42 0f ae 04 05 00 00 00 00[   ]+fxsave[       ]+(0x0)?\(,%r8(,1)?\)
-[       ]*[0-9a-f]+:[   ]+4a 0f ae 04 05 00 00 00 00[   ]+fxsave64[     ]+(0x0)?\(,%r8(,1)?\)
-[       ]*[0-9a-f]+:[   ]+43 0f ae 04 00[       ]+fxsave[       ]+\(%r8,%r8(,1)?\)
-[       ]*[0-9a-f]+:[   ]+4b 0f ae 04 00[       ]+fxsave64[     ]+\(%r8,%r8(,1)?\)
-[       ]*[0-9a-f]+:[   ]+48 03 04 00[  ]+add[  ]+\(%rax,%rax(,1)?\),%rax
-[       ]*[0-9a-f]+:[   ]+44 03 04 00[  ]+add[  ]+\(%rax,%rax(,1)?\),%r8d
-[       ]*[0-9a-f]+:[   ]+41 03 04 00[  ]+add[  ]+\(%r8,%rax(,1)?\),%eax
-[       ]*[0-9a-f]+:[   ]+42 03 04 00[  ]+add[  ]+\(%rax,%r8(,1)?\),%eax
-[       ]*[0-9a-f]+:[   ]+49 03 04 00[  ]+add[  ]+\(%r8,%rax(,1)?\),%rax
-[       ]*[0-9a-f]+:[   ]+46 03 04 00[  ]+add[  ]+\(%rax,%r8(,1)?\),%r8d
-[       ]*[0-9a-f]+:[   ]+45 03 04 00[  ]+add[  ]+\(%r8,%rax(,1)?\),%r8d
-[       ]*[0-9a-f]+:[   ]+4a 03 04 00[  ]+add[  ]+\(%rax,%r8(,1)?\),%rax
-[       ]*[0-9a-f]+:[   ]+41\s+rex\.B
-[       ]*[0-9a-f]+:[   ]+9b dd 30\s+fsave\s+\(%rax\)
-[       ]*[0-9a-f]+:[   ]+9b 41 dd 30\s+fsave\s+\(%r8\)
-[       ]*[0-9a-f]+:[   ]+40 c5 f9 28 00[       ]+rex vmovapd \(%rax\),%xmm0
-[       ]*[0-9a-f]+:[   ]+40[   ]+rex
-[       ]*[0-9a-f]+:[   ]+41[   ]+rex.B
-[       ]*[0-9a-f]+:[   ]+42[   ]+rex.X
-[       ]*[0-9a-f]+:[   ]+43[   ]+rex.XB
-[       ]*[0-9a-f]+:[   ]+44[   ]+rex.R
-[       ]*[0-9a-f]+:[   ]+45[   ]+rex.RB
-[       ]*[0-9a-f]+:[   ]+46[   ]+rex.RX
-[       ]*[0-9a-f]+:[   ]+47[   ]+rex.RXB
-[       ]*[0-9a-f]+:[   ]+48[   ]+rex.W
-[       ]*[0-9a-f]+:[   ]+49[   ]+rex.WB
-[       ]*[0-9a-f]+:[   ]+4a[   ]+rex.WX
-[       ]*[0-9a-f]+:[   ]+4b[   ]+rex.WXB
-[       ]*[0-9a-f]+:[   ]+4c[   ]+rex.WR
-[       ]*[0-9a-f]+:[   ]+4d[   ]+rex.WRB
-[       ]*[0-9a-f]+:[   ]+4e[   ]+rex.WRX
-[       ]*[0-9a-f]+:[   ]+4f[   ]+rex.WRXB
-#pass
+#dump: ../rex.d

diff --git a/gas/testsuite/gas/i386/rex.d b/gas/testsuite/gas/i386/rex.d
index 22c0c7f30a64f0f0f7dd505eca36561b047253fd..87856be1920bd48699f17f220138130ca777fc73 100644 (file)
--- a/gas/testsuite/gas/i386/rex.d
+++ b/gas/testsuite/gas/i386/rex.d
@@ -23,6 +23,11 @@ Disassembly of section .text:
 [       ]*[0-9a-f]+:[   ]+46 03 04 00[  ]+add[  ]+\(%rax,%r8(,1)?\),%r8d
 [       ]*[0-9a-f]+:[   ]+45 03 04 00[  ]+add[  ]+\(%r8,%rax(,1)?\),%r8d
 [       ]*[0-9a-f]+:[   ]+4a 03 04 00[  ]+add[  ]+\(%rax,%r8(,1)?\),%rax
+[       ]*[0-9a-f]+:[   ]+40 90[        ]+rex nop
+[       ]*[0-9a-f]+:[   ]+48 90[        ]+rex\.W nop
+[       ]*[0-9a-f]+:[   ]+44 90[        ]+rex\.R nop
+[       ]*[0-9a-f]+:[   ]+42 90[        ]+rex\.X nop
+[       ]*[0-9a-f]+:[   ]+41 90[        ]+xchg[         ]+%eax,%r8d
 [       ]*[0-9a-f]+:[   ]+41\s+rex\.B
 [       ]*[0-9a-f]+:[   ]+9b dd 30\s+fsave\s+\(%rax\)
 [       ]*[0-9a-f]+:[   ]+9b 41 dd 30\s+fsave\s+\(%r8\)

diff --git a/gas/testsuite/gas/i386/rex.s b/gas/testsuite/gas/i386/rex.s
index c1490ccdeef47ad29b341bf075d9565470bbe763..2a861be1eaed567dc02c6c55e01fed3214768569 100644 (file)
--- a/gas/testsuite/gas/i386/rex.s
+++ b/gas/testsuite/gas/i386/rex.s
@@ -20,6 +20,12 @@ _start:
        rex.b add       (%rax,%rax), %r8d
        rex.x add       (%rax,%rax), %rax
 
+       rex nop
+       rex.w nop
+       rex.r nop
+       rex.x nop
+       rex.b nop
+
        .byte 0x41,0x9b,0xdd,0x30
        fsave (%r8)
 

diff --git a/opcodes/i386-dis.c b/opcodes/i386-dis.c
index 101eeea150c34447a7f29754e7a934253c263e8b..1e3266329c1b80af7ef8432f48f0f23d04da3ad1 100644 (file)
--- a/opcodes/i386-dis.c
+++ b/opcodes/i386-dis.c
@@ -98,8 +98,7 @@ static void VPCOM_Fixup (instr_info *, int, int);
 static void OP_0f07 (instr_info *, int, int);
 static void OP_Monitor (instr_info *, int, int);
 static void OP_Mwait (instr_info *, int, int);
-static void NOP_Fixup1 (instr_info *, int, int);
-static void NOP_Fixup2 (instr_info *, int, int);
+static void NOP_Fixup (instr_info *, int, int);
 static void OP_3DNowSuffix (instr_info *, int, int);
 static void CMP_Fixup (instr_info *, int, int);
 static void BadOp (instr_info *);
@@ -2913,9 +2912,9 @@ static const struct dis386 reg_table[][8] = {
 static const struct dis386 prefix_table[][4] = {
   /* PREFIX_90 */
   {
-    { "xchgS", { { NOP_Fixup1, eAX_reg }, { NOP_Fixup2, eAX_reg } }, 0 },
+    { "xchgS", { { NOP_Fixup, 0 }, { NOP_Fixup, 1 } }, 0 },
     { "pause", { XX }, 0 },
-    { "xchgS", { { NOP_Fixup1, eAX_reg }, { NOP_Fixup2, eAX_reg } }, 0 },
+    { "xchgS", { { NOP_Fixup, 0 }, { NOP_Fixup, 1 } }, 0 },
     { NULL, { { NULL, 0 } }, PREFIX_IGNORED }
   },
 
@@ -12724,25 +12723,14 @@ OP_0f07 (instr_info *ins, int bytemode, int sizeflag)
    32bit mode and "xchg %rax,%rax" in 64bit mode.  */
 
 static void
-NOP_Fixup1 (instr_info *ins, int bytemode, int sizeflag)
+NOP_Fixup (instr_info *ins, int opnd, int sizeflag)
 {
-  if ((ins->prefixes & PREFIX_DATA) != 0
-      || (ins->rex != 0
-         && ins->rex != 0x48
-         && ins->address_mode == mode_64bit))
-    OP_REG (ins, bytemode, sizeflag);
-  else
+  if ((ins->prefixes & PREFIX_DATA) == 0 && (ins->rex & REX_B) == 0)
     strcpy (ins->obuf, "nop");
-}
-
-static void
-NOP_Fixup2 (instr_info *ins, int bytemode, int sizeflag)
-{
-  if ((ins->prefixes & PREFIX_DATA) != 0
-      || (ins->rex != 0
-         && ins->rex != 0x48
-         && ins->address_mode == mode_64bit))
-    OP_IMREG (ins, bytemode, sizeflag);
+  else if (opnd == 0)
+    OP_REG (ins, eAX_reg, sizeflag);
+  else
+    OP_IMREG (ins, eAX_reg, sizeflag);
 }
 
 static const char *const Suffix3DNow[] = {