[AArch64][PATCH 2/3] Adjust a utility function for floating point values.

ARMv8.2 adds 16-bit floating point operations as an optional
extension. This patch adjusts the utility function expand_fp_imm to
support 16-bit values.

The function is intended to convert an 8-bit immediate representing a
floating point value to a representation that can be passed to
fprintf. Because of the limited use of the results, the only change made
to the function is to treat a request for a 16-bit float as a request
for a 32-bit float.

opcodes/
2015-11-27  Matthew Wahab  <matthew.wahab@arm.com>

	* aarch64-opc.c (half_conv_t): New.
	(expand_fp_imm): Replace is_dp flag with the parameter size to
	specify the number of bytes for the required expansion.  Treat
	a 16-bit expansion like a 32-bit expansion.  Add check for an
	unsupported size request.  Update comment.
	(aarch64_print_operand): Update to support 16-bit floating point
	values.  Update for changes to expand_fp_imm.

Change-Id: I1ae3df3864be375d71925197ab03397ed1ad2d15

opcodes/ChangeLog

@@ -1,3 +1,13 @@
+2015-11-27  Matthew Wahab  <matthew.wahab@arm.com>
+
+	* aarch64-opc.c (half_conv_t): New.
+        (expand_fp_imm): Replace is_dp flag with the parameter size to
+	specify the number of bytes for the required expansion.  Treat
+	a 16-bit expansion like a 32-bit expansion.  Add check for an
+	unsupported size request.  Update comment.
+	(aarch64_print_operand): Update to support 16-bit floating point
+	values.  Update for changes to expand_fp_imm.
+
 2015-11-27  Matthew Wahab  <matthew.wahab@arm.com>
 
 	* aarch64-tbl.h (aarch64_feature_fp_f16): New.

opcodes/aarch64-opc.c

@@ -2172,14 +2172,22 @@ typedef union
   float    f;
 } single_conv_t;
 
+typedef union
+{
+  uint32_t i;
+  float    f;
+} half_conv_t;
+
 /* IMM8 is an 8-bit floating-point constant with sign, 3-bit exponent and
    normalized 4 bits of precision, encoded in "a:b:c:d:e:f:g:h" or FLD_imm8
    (depending on the type of the instruction).  IMM8 will be expanded to a
-   single-precision floating-point value (IS_DP == 0) or a double-precision
+   single-precision floating-point value (SIZE == 4) or a double-precision
-   floating-point value (IS_DP == 1).  The expanded value is returned.  */
+   floating-point value (SIZE == 8).  A half-precision floating-point value
+   (SIZE == 2) is expanded to a single-precision floating-point value.  The
+   expanded value is returned.  */
 
 static uint64_t
-expand_fp_imm (int is_dp, uint32_t imm8)
+expand_fp_imm (int size, uint32_t imm8)
 {
   uint64_t imm;
   uint32_t imm8_7, imm8_6_0, imm8_6, imm8_6_repl4;
@@ -2189,7 +2197,7 @@ expand_fp_imm (int is_dp, uint32_t imm8)
   imm8_6 = imm8_6_0 >> 6;	/* imm8<6>   */
   imm8_6_repl4 = (imm8_6 << 3) | (imm8_6 << 2)
     | (imm8_6 << 1) | imm8_6;	/* Replicate(imm8<6>,4) */
-  if (is_dp)
+  if (size == 8)
     {
       imm = (imm8_7 << (63-32))		/* imm8<7>  */
 	| ((imm8_6 ^ 1) << (62-32))	/* NOT(imm8<6)	*/
@@ -2198,13 +2206,18 @@ expand_fp_imm (int is_dp, uint32_t imm8)
 	| (imm8_6_0 << (48-32));	/* imm8<6>:imm8<5:0>    */
       imm <<= 32;
     }
-  else
+  else if (size == 4 || size == 2)
     {
       imm = (imm8_7 << 31)	/* imm8<7>              */
 	| ((imm8_6 ^ 1) << 30)	/* NOT(imm8<6>)         */
 	| (imm8_6_repl4 << 26)	/* Replicate(imm8<6>,4) */
 	| (imm8_6_0 << 19);	/* imm8<6>:imm8<5:0>    */
     }
+  else
+    {
+      /* An unsupported size.  */
+      assert (0);
+    }
 
   return imm;
 }
@@ -2533,17 +2546,24 @@ aarch64_print_operand (char *buf, size_t size, bfd_vma pc,
     case AARCH64_OPND_SIMD_FPIMM:
       switch (aarch64_get_qualifier_esize (opnds[0].qualifier))
 	{
+	case 2:	/* e.g. FMOV <Hd>, #<imm>.  */
+	    {
+	      half_conv_t c;
+	      c.i = expand_fp_imm (2, opnd->imm.value);
+	      snprintf (buf, size,  "#%.18e", c.f);
+	    }
+	  break;
 	case 4:	/* e.g. FMOV <Vd>.4S, #<imm>.  */
 	    {
 	      single_conv_t c;
-	      c.i = expand_fp_imm (0, opnd->imm.value);
+	      c.i = expand_fp_imm (4, opnd->imm.value);
 	      snprintf (buf, size,  "#%.18e", c.f);
 	    }
 	  break;
 	case 8:	/* e.g. FMOV <Sd>, #<imm>.  */
 	    {
 	      double_conv_t c;
-	      c.i = expand_fp_imm (1, opnd->imm.value);
+	      c.i = expand_fp_imm (8, opnd->imm.value);
 	      snprintf (buf, size,  "#%.18e", c.d);
 	    }
 	  break;