x86: Clear modrm if not needed

The MODRM byte can be checked to display the instruction name only if the
MODRM byte needed.  Clear modrm if the MODRM byte isn't needed so that
modrm field checks in putop like, modrm.mod == N with N != 0, can be done
without checking need_modrm.

gas/

	PR binutils/26705
	* testsuite/gas/i386/x86-64-suffix.s: Add "mov %rsp,%rbp" before
	sysretq.
	* testsuite/gas/i386/x86-64-suffix-intel.d: Updated.
	* testsuite/gas/i386/x86-64-suffix.d: Likewise.

opcodes/

	PR binutils/26705
	* i386-dis.c (print_insn): Clear modrm if not needed.
	(putop): Check need_modrm for modrm.mod != 3.  Don't check
	need_modrm for modrm.mod == 3.

6 files changed, 29 insertions, 4 deletions

diff --git a/gas/ChangeLog b/gas/ChangeLog
index 56796ff..ae5a614 100644
--- a/gas/ChangeLog
+++ b/gas/ChangeLog
@@ -1,3 +1,11 @@
+2020-10-05  H.J. Lu  <hongjiu.lu@intel.com>
+
+	PR binutils/26705
+	* testsuite/gas/i386/x86-64-suffix.s: Add "mov %rsp,%rbp" before
+	sysretq.
+	* testsuite/gas/i386/x86-64-suffix-intel.d: Updated.
+	* testsuite/gas/i386/x86-64-suffix.d: Likewise.
+
 2020-10-05  Nick Clifton  <nickc@redhat.com>
 
 	PR 26253
diff --git a/gas/testsuite/gas/i386/x86-64-suffix-intel.d b/gas/testsuite/gas/i386/x86-64-suffix-intel.d
index 74c8eaa..55d4a8d 100644
--- a/gas/testsuite/gas/i386/x86-64-suffix-intel.d
+++ b/gas/testsuite/gas/i386/x86-64-suffix-intel.d
@@ -18,11 +18,13 @@ Disassembly of section .text:
 [ 	]*[a-f0-9]+:	cf                   	iretd  
 [ 	]*[a-f0-9]+:	48 cf                	iretq  
 [ 	]*[a-f0-9]+:	0f 07                	sysretd 
+[ 	]*[a-f0-9]+:	48 89 e5             	mov    rbp,rsp
 [ 	]*[a-f0-9]+:	48 0f 07             	sysretq 
 [ 	]*[a-f0-9]+:	66 cf                	iretw  
 [ 	]*[a-f0-9]+:	cf                   	iretd  
 [ 	]*[a-f0-9]+:	cf                   	iretd  
 [ 	]*[a-f0-9]+:	48 cf                	iretq  
 [ 	]*[a-f0-9]+:	0f 07                	sysretd 
+[ 	]*[a-f0-9]+:	48 89 e5             	mov    rbp,rsp
 [ 	]*[a-f0-9]+:	48 0f 07             	sysretq 
 #pass
diff --git a/gas/testsuite/gas/i386/x86-64-suffix.d b/gas/testsuite/gas/i386/x86-64-suffix.d
index d81ac45..5ae1173 100644
--- a/gas/testsuite/gas/i386/x86-64-suffix.d
+++ b/gas/testsuite/gas/i386/x86-64-suffix.d
@@ -17,11 +17,13 @@ Disassembly of section .text:
 [ 	]*[a-f0-9]+:	cf                   	iretl  
 [ 	]*[a-f0-9]+:	48 cf                	iretq  
 [ 	]*[a-f0-9]+:	0f 07                	sysretl 
+[ 	]*[a-f0-9]+:	48 89 e5             	movq   %rsp,%rbp
 [ 	]*[a-f0-9]+:	48 0f 07             	sysretq 
 [ 	]*[a-f0-9]+:	66 cf                	iretw  
 [ 	]*[a-f0-9]+:	cf                   	iretl  
 [ 	]*[a-f0-9]+:	cf                   	iretl  
 [ 	]*[a-f0-9]+:	48 cf                	iretq  
 [ 	]*[a-f0-9]+:	0f 07                	sysretl 
+[ 	]*[a-f0-9]+:	48 89 e5             	movq   %rsp,%rbp
 [ 	]*[a-f0-9]+:	48 0f 07             	sysretq 
 #pass
diff --git a/gas/testsuite/gas/i386/x86-64-suffix.s b/gas/testsuite/gas/i386/x86-64-suffix.s
index 2261c2c..a226836 100644
--- a/gas/testsuite/gas/i386/x86-64-suffix.s
+++ b/gas/testsuite/gas/i386/x86-64-suffix.s
@@ -14,6 +14,7 @@ foo:
 	iretl
 	iretq
 	sysretl
+	mov	%rsp,%rbp
 	sysretq
 
 	.intel_syntax noprefix
@@ -22,4 +23,5 @@ foo:
 	iret
 	iretq
 	sysretd
+	mov	rbp,rsp
 	sysretq
diff --git a/opcodes/ChangeLog b/opcodes/ChangeLog
index c57c0b1..f1b4273 100644
--- a/opcodes/ChangeLog
+++ b/opcodes/ChangeLog
@@ -1,3 +1,10 @@
+2020-10-05  H.J. Lu  <hongjiu.lu@intel.com>
+
+	PR binutils/26705
+	* i386-dis.c (print_insn): Clear modrm if not needed.
+	(putop): Check need_modrm for modrm.mod != 3.  Don't check
+	need_modrm for modrm.mod == 3.
+
 2020-09-28  Przemyslaw Wirkus  <przemyslaw.wirkus@arm.com>
 
 	* aarch64-opc.c: Added ETMv4 system registers TRCACATRn, TRCACVRn,
diff --git a/opcodes/i386-dis.c b/opcodes/i386-dis.c
index 67d5b6a..f4f35bc 100644
--- a/opcodes/i386-dis.c
+++ b/opcodes/i386-dis.c
@@ -9927,7 +9927,7 @@ print_insn (bfd_vma pc, disassemble_info *info)
       FETCH_DATA (info, codep + 1);
       threebyte = *codep;
       dp = &dis386_twobyte[threebyte];
-      need_modrm = twobyte_has_modrm[*codep];
+      need_modrm = twobyte_has_modrm[threebyte];
       codep++;
     }
   else
@@ -9954,6 +9954,8 @@ print_insn (bfd_vma pc, disassemble_info *info)
       modrm.reg = (*codep >> 3) & 7;
       modrm.rm = *codep & 7;
     }
+  else
+    memset (&modrm, 0, sizeof (modrm));
 
   need_vex = 0;
   memset (&vex, 0, sizeof (vex));
@@ -10644,7 +10646,8 @@ putop (const char *in_template, int sizeflag)
 	case 'A':
 	  if (intel_syntax)
 	    break;
-	  if (modrm.mod != 3 || (sizeflag & SUFFIX_ALWAYS))
+	  if ((need_modrm && modrm.mod != 3)
+	      || (sizeflag & SUFFIX_ALWAYS))
 	    *obufp++ = 'b';
 	  break;
 	case 'B':
@@ -10796,7 +10799,7 @@ putop (const char *in_template, int sizeflag)
 	case 'P':
 	  if (l == 0)
 	    {
-	      if (((need_modrm && modrm.mod == 3) || !cond)
+	      if ((modrm.mod == 3 || !cond)
 		  && !(sizeflag & SUFFIX_ALWAYS))
 		break;
 	  /* Fall through.  */
@@ -10840,7 +10843,8 @@ putop (const char *in_template, int sizeflag)
 	      if (intel_syntax && !alt)
 		break;
 	      USED_REX (REX_W);
-	      if (modrm.mod != 3 || (sizeflag & SUFFIX_ALWAYS))
+	      if ((need_modrm && modrm.mod != 3)
+		  || (sizeflag & SUFFIX_ALWAYS))
 		{
 		  if (rex & REX_W)
 		    *obufp++ = 'q';