--- a/gas/config/tc-i386.c
+++ b/gas/config/tc-i386.c
@@ -4362,6 +4362,42 @@ optimize_encoding (void)
        */
       i.tm.base_opcode = 0x84 | (i.tm.base_opcode & 1);
     }
+  else if (i.tm.base_opcode == 0xba
+	   && i.tm.opcode_space == SPACE_0F
+	   && i.reg_operands == 1
+	   && i.op[0].imms->X_op == O_constant
+	   && i.op[0].imms->X_add_number >= 0)
+    {
+      /* Optimize: -O:
+	   btw $n, %rN -> btl $n, %rN (outside of 16-bit mode, n < 16)
+	   btq $n, %rN -> btl $n, %rN (in 64-bit mode, n < 32, N < 8)
+	   btl $n, %rN -> btw $n, %rN (in 16-bit mode, n < 16)
+
+	   With <BT> one of bts, btr, and bts also:
+	   <BT>w $n, %rN -> btl $n, %rN (in 32-bit mode, n < 16)
+	   <BT>l $n, %rN -> btw $n, %rN (in 16-bit mode, n < 16)
+       */
+      switch (flag_code)
+	{
+	case CODE_64BIT:
+	  if (i.tm.extension_opcode != 4)
+	    break;
+	  if (i.types[1].bitfield.qword
+	      && i.op[0].imms->X_add_number < 32
+	      && !(i.op[1].regs->reg_flags & RegRex))
+	    i.tm.opcode_modifier.size = SIZE32;
+	  /* Fall through.  */
+	case CODE_32BIT:
+	  if (i.types[1].bitfield.word
+	      && i.op[0].imms->X_add_number < 16)
+	    i.tm.opcode_modifier.size = SIZE32;
+	  break;
+	case CODE_16BIT:
+	  if (i.op[0].imms->X_add_number < 16)
+	    i.tm.opcode_modifier.size = SIZE16;
+	  break;
+	}
+    }
   else if (i.reg_operands == 3
 	   && i.op[0].regs == i.op[1].regs
 	   && !i.types[2].bitfield.xmmword
--- a/gas/testsuite/gas/i386/optimize-1.d
+++ b/gas/testsuite/gas/i386/optimize-1.d
@@ -147,4 +147,14 @@ Disassembly of section .text:
  +[a-f0-9]+:	62 .*	vporq  0x80\(%eax\),%ymm2,%ymm3
  +[a-f0-9]+:	62 .*	vpxord 0x80\(%eax\),%ymm2,%ymm3
  +[a-f0-9]+:	62 .*	vpxorq 0x80\(%eax\),%ymm2,%ymm3
+ +[a-f0-9]+:	0f ba e0 0f          	bt     \$0xf,%eax
+ +[a-f0-9]+:	66 0f ba e0 10       	bt     \$0x10,%ax
+ +[a-f0-9]+:	0f ba f8 0f          	btc    \$0xf,%eax
+ +[a-f0-9]+:	0f ba f0 0f          	btr    \$0xf,%eax
+ +[a-f0-9]+:	0f ba e8 0f          	bts    \$0xf,%eax
+ +[a-f0-9]+:	0f ba e0 0f          	bt     \$0xf,%eax
+ +[a-f0-9]+:	66 0f ba e0 10       	bt     \$0x10,%ax
+ +[a-f0-9]+:	0f ba f8 0f          	btc    \$0xf,%eax
+ +[a-f0-9]+:	0f ba f0 0f          	btr    \$0xf,%eax
+ +[a-f0-9]+:	0f ba e8 0f          	bts    \$0xf,%eax
 #pass
--- a/gas/testsuite/gas/i386/optimize-1.s
+++ b/gas/testsuite/gas/i386/optimize-1.s
@@ -170,3 +170,16 @@ _start:
 	vporq		128(%eax), %ymm2, %ymm3
 	vpxord		128(%eax), %ymm2, %ymm3
 	vpxorq		128(%eax), %ymm2, %ymm3
+
+	bt	$15, %ax
+	bt	$16, %ax
+	btc	$15, %ax
+	btr	$15, %ax
+	bts	$15, %ax
+
+	.code16
+	bt	$15, %eax
+	bt	$16, %eax
+	btc	$15, %eax
+	btr	$15, %eax
+	bts	$15, %eax
--- a/gas/testsuite/gas/i386/optimize-1a.d
+++ b/gas/testsuite/gas/i386/optimize-1a.d
@@ -148,4 +148,14 @@ Disassembly of section .text:
  +[a-f0-9]+:	62 .*	vporq  0x80\(%eax\),%ymm2,%ymm3
  +[a-f0-9]+:	62 .*	vpxord 0x80\(%eax\),%ymm2,%ymm3
  +[a-f0-9]+:	62 .*	vpxorq 0x80\(%eax\),%ymm2,%ymm3
+ +[a-f0-9]+:	0f ba e0 0f          	bt     \$0xf,%eax
+ +[a-f0-9]+:	66 0f ba e0 10       	bt     \$0x10,%ax
+ +[a-f0-9]+:	0f ba f8 0f          	btc    \$0xf,%eax
+ +[a-f0-9]+:	0f ba f0 0f          	btr    \$0xf,%eax
+ +[a-f0-9]+:	0f ba e8 0f          	bts    \$0xf,%eax
+ +[a-f0-9]+:	0f ba e0 0f          	bt     \$0xf,%eax
+ +[a-f0-9]+:	66 0f ba e0 10       	bt     \$0x10,%ax
+ +[a-f0-9]+:	0f ba f8 0f          	btc    \$0xf,%eax
+ +[a-f0-9]+:	0f ba f0 0f          	btr    \$0xf,%eax
+ +[a-f0-9]+:	0f ba e8 0f          	bts    \$0xf,%eax
 #pass
--- a/gas/testsuite/gas/i386/optimize-4.d
+++ b/gas/testsuite/gas/i386/optimize-4.d
@@ -147,6 +147,16 @@ Disassembly of section .text:
  +[a-f0-9]+:	62 .*	vporq  0x80\(%eax\),%ymm2,%ymm3
  +[a-f0-9]+:	62 .*	vpxord 0x80\(%eax\),%ymm2,%ymm3
  +[a-f0-9]+:	62 .*	vpxorq 0x80\(%eax\),%ymm2,%ymm3
+ +[a-f0-9]+:	0f ba e0 0f          	bt     \$0xf,%eax
+ +[a-f0-9]+:	66 0f ba e0 10       	bt     \$0x10,%ax
+ +[a-f0-9]+:	0f ba f8 0f          	btc    \$0xf,%eax
+ +[a-f0-9]+:	0f ba f0 0f          	btr    \$0xf,%eax
+ +[a-f0-9]+:	0f ba e8 0f          	bts    \$0xf,%eax
+ +[a-f0-9]+:	0f ba e0 0f          	bt     \$0xf,%eax
+ +[a-f0-9]+:	66 0f ba e0 10       	bt     \$0x10,%ax
+ +[a-f0-9]+:	0f ba f8 0f          	btc    \$0xf,%eax
+ +[a-f0-9]+:	0f ba f0 0f          	btr    \$0xf,%eax
+ +[a-f0-9]+:	0f ba e8 0f          	bts    \$0xf,%eax
  +[a-f0-9]+:	62 f1 f5 08 55 e9    	\{evex\} vandnpd %xmm1,%xmm1,%xmm5
  +[a-f0-9]+:	62 f1 f5 08 55 e9    	\{evex\} vandnpd %xmm1,%xmm1,%xmm5
 #pass
--- a/gas/testsuite/gas/i386/optimize-5.d
+++ b/gas/testsuite/gas/i386/optimize-5.d
@@ -147,6 +147,16 @@ Disassembly of section .text:
  +[a-f0-9]+:	62 .*	vporq  0x80\(%eax\),%ymm2,%ymm3
  +[a-f0-9]+:	62 .*	vpxord 0x80\(%eax\),%ymm2,%ymm3
  +[a-f0-9]+:	62 .*	vpxorq 0x80\(%eax\),%ymm2,%ymm3
+ +[a-f0-9]+:	0f ba e0 0f          	bt     \$0xf,%eax
+ +[a-f0-9]+:	66 0f ba e0 10       	bt     \$0x10,%ax
+ +[a-f0-9]+:	0f ba f8 0f          	btc    \$0xf,%eax
+ +[a-f0-9]+:	0f ba f0 0f          	btr    \$0xf,%eax
+ +[a-f0-9]+:	0f ba e8 0f          	bts    \$0xf,%eax
+ +[a-f0-9]+:	0f ba e0 0f          	bt     \$0xf,%eax
+ +[a-f0-9]+:	66 0f ba e0 10       	bt     \$0x10,%ax
+ +[a-f0-9]+:	0f ba f8 0f          	btc    \$0xf,%eax
+ +[a-f0-9]+:	0f ba f0 0f          	btr    \$0xf,%eax
+ +[a-f0-9]+:	0f ba e8 0f          	bts    \$0xf,%eax
  +[a-f0-9]+:	62 f1 f5 08 55 e9    	\{evex\} vandnpd %xmm1,%xmm1,%xmm5
  +[a-f0-9]+:	62 f1 f5 08 55 e9    	\{evex\} vandnpd %xmm1,%xmm1,%xmm5
  +[a-f0-9]+:	62 f1 7d 28 6f d1    	vmovdqa32 %ymm1,%ymm2
--- a/gas/testsuite/gas/i386/x86-64-optimize-1.d
+++ b/gas/testsuite/gas/i386/x86-64-optimize-1.d
@@ -58,4 +58,17 @@ Disassembly of section .text:
  +[a-f0-9]+:	48 b8 00 00 00 00 01 00 00 00 	movabs \$0x100000000,%rax
  +[a-f0-9]+:	31 c0                	xor    %eax,%eax
  +[a-f0-9]+:	45 31 f6             	xor    %r14d,%r14d
+ +[a-f0-9]+:	0f ba e0 0f          	bt     \$0xf,%eax
+ +[a-f0-9]+:	66 0f ba e0 10       	bt     \$0x10,%ax
+ +[a-f0-9]+:	41 0f ba e0 0f       	bt     \$0xf,%r8d
+ +[a-f0-9]+:	66 41 0f ba e0 10    	bt     \$0x10,%r8w
+ +[a-f0-9]+:	0f ba e0 1f          	bt     \$0x1f,%eax
+ +[a-f0-9]+:	48 0f ba e0 20       	bt     \$0x20,%rax
+ +[a-f0-9]+:	49 0f ba e0 1f       	bt     \$0x1f,%r8
+ +[a-f0-9]+:	66 0f ba f8 0f       	btc    \$0xf,%ax
+ +[a-f0-9]+:	48 0f ba f8 1f       	btc    \$0x1f,%rax
+ +[a-f0-9]+:	66 0f ba f0 0f       	btr    \$0xf,%ax
+ +[a-f0-9]+:	48 0f ba f0 1f       	btr    \$0x1f,%rax
+ +[a-f0-9]+:	66 0f ba e8 0f       	bts    \$0xf,%ax
+ +[a-f0-9]+:	48 0f ba e8 1f       	bts    \$0x1f,%rax
 #pass
--- a/gas/testsuite/gas/i386/x86-64-optimize-1.s
+++ b/gas/testsuite/gas/i386/x86-64-optimize-1.s
@@ -53,3 +53,16 @@ _start:
 	movq	$0x100000000,%rax
 	clrq	%rax
 	clrq	%r14
+	bt	$15, %ax
+	bt	$16, %ax
+	bt	$15, %r8w
+	bt	$16, %r8w
+	bt	$31, %rax
+	bt	$32, %rax
+	bt	$31, %r8
+	btc	$15, %ax
+	btc	$31, %rax
+	btr	$15, %ax
+	btr	$31, %rax
+	bts	$15, %ax
+	bts	$31, %rax
--- a/opcodes/i386-opc.tbl
+++ b/opcodes/i386-opc.tbl
@@ -536,13 +536,13 @@ xlat, 0xd7, 0, No_wSuf|No_lSuf|No_sSuf|N
 bsf, 0xfbc, i386, Modrm|CheckOperandSize|No_bSuf|No_sSuf|RepPrefixOk, { Reg16|Reg32|Reg64|Word|Dword|Qword|Unspecified|BaseIndex, Reg16|Reg32|Reg64 }
 bsr, 0xfbd, i386, Modrm|CheckOperandSize|No_bSuf|No_sSuf|RepPrefixOk, { Reg16|Reg32|Reg64|Word|Dword|Qword|Unspecified|BaseIndex, Reg16|Reg32|Reg64 }
 bt, 0xfa3, i386, Modrm|CheckOperandSize|No_bSuf|No_sSuf, { Reg16|Reg32|Reg64, Reg16|Reg32|Reg64|Word|Dword|Qword|Unspecified|BaseIndex }
-bt, 0xfba/4, i386, Modrm|No_bSuf|No_sSuf, { Imm8, Reg16|Reg32|Reg64|Word|Dword|Qword|Unspecified|BaseIndex }
+bt, 0xfba/4, i386, Modrm|No_bSuf|No_sSuf|Optimize, { Imm8, Reg16|Reg32|Reg64|Unspecified|BaseIndex }
 btc, 0xfbb, i386, Modrm|CheckOperandSize|No_bSuf|No_sSuf|HLEPrefixLock, { Reg16|Reg32|Reg64, Reg16|Reg32|Reg64|Word|Dword|Qword|Unspecified|BaseIndex }
-btc, 0xfba/7, i386, Modrm|No_bSuf|No_sSuf|HLEPrefixLock, { Imm8, Reg16|Reg32|Reg64|Word|Dword|Qword|Unspecified|BaseIndex }
+btc, 0xfba/7, i386, Modrm|No_bSuf|No_sSuf|Optimize|HLEPrefixLock, { Imm8, Reg16|Reg32|Reg64|Unspecified|BaseIndex }
 btr, 0xfb3, i386, Modrm|CheckOperandSize|No_bSuf|No_sSuf|HLEPrefixLock, { Reg16|Reg32|Reg64, Reg16|Reg32|Reg64|Word|Dword|Qword|Unspecified|BaseIndex }
-btr, 0xfba/6, i386, Modrm|No_bSuf|No_sSuf|HLEPrefixLock, { Imm8, Reg16|Reg32|Reg64|Word|Dword|Qword|Unspecified|BaseIndex }
+btr, 0xfba/6, i386, Modrm|No_bSuf|No_sSuf|Optimize|HLEPrefixLock, { Imm8, Reg16|Reg32|Reg64|Unspecified|BaseIndex }
 bts, 0xfab, i386, Modrm|CheckOperandSize|No_bSuf|No_sSuf|HLEPrefixLock, { Reg16|Reg32|Reg64, Reg16|Reg32|Reg64|Word|Dword|Qword|Unspecified|BaseIndex }
-bts, 0xfba/5, i386, Modrm|No_bSuf|No_sSuf|HLEPrefixLock, { Imm8, Reg16|Reg32|Reg64|Word|Dword|Qword|Unspecified|BaseIndex }
+bts, 0xfba/5, i386, Modrm|No_bSuf|No_sSuf|Optimize|HLEPrefixLock, { Imm8, Reg16|Reg32|Reg64|Unspecified|BaseIndex }
 
 // Interrupts & op. sys insns.
 // See gas/config/tc-i386.c for conversion of 'int $3' into the special
