target/arm: Move vfp_expand_imm() to translate.[ch]

We want to use vfp_expand_imm() in the AArch32 VFP decode;
move it from the a64-only header/source file to the
AArch32 one (which is always compiled even for AArch64).

Backports commit d6a092d479333b5f20a647a912a31b0102d37335 from qemu

qemu/target/arm/translate-a64.c

@@ -6511,38 +6511,6 @@ static void disas_fp_3src(DisasContext *s, uint32_t insn)
     }
 }
 
-/* The imm8 encodes the sign bit, enough bits to represent an exponent in
- * the range 01....1xx to 10....0xx, and the most significant 4 bits of
- * the mantissa; see VFPExpandImm() in the v8 ARM ARM.
- */
-uint64_t vfp_expand_imm(int size, uint8_t imm8)
-{
-    uint64_t imm;
-
-    switch (size) {
-    case MO_64:
-        imm = (extract32(imm8, 7, 1) ? 0x8000 : 0) |
-            (extract32(imm8, 6, 1) ? 0x3fc0 : 0x4000) |
-            extract32(imm8, 0, 6);
-        imm <<= 48;
-        break;
-    case MO_32:
-        imm = (extract32(imm8, 7, 1) ? 0x8000 : 0) |
-            (extract32(imm8, 6, 1) ? 0x3e00 : 0x4000) |
-            (extract32(imm8, 0, 6) << 3);
-        imm <<= 16;
-        break;
-    case MO_16:
-        imm = (extract32(imm8, 7, 1) ? 0x8000 : 0) |
-            (extract32(imm8, 6, 1) ? 0x3000 : 0x4000) |
-            (extract32(imm8, 0, 6) << 6);
-        break;
-    default:
-        g_assert_not_reached();
-    }
-    return imm;
-}
-
 /* Floating point immediate
  *   31  30  29 28       24 23  22  21 20        13 12   10 9    5 4    0
  * +---+---+---+-----------+------+---+------------+-------+------+------+

qemu/target/arm/translate-a64.h

@@ -39,7 +39,6 @@ void write_fp_dreg(DisasContext *s, int reg, TCGv_i64 v);
 TCGv_ptr get_fpstatus_ptr(DisasContext *, bool);
 bool logic_imm_decode_wmask(uint64_t *result, unsigned int immn,
                             unsigned int imms, unsigned int immr);
-uint64_t vfp_expand_imm(int size, uint8_t imm8);
 bool sve_access_check(DisasContext *s);
 
 /* We should have at some point before trying to access an FP register

qemu/target/arm/translate-vfp.inc.c

@@ -30,6 +30,39 @@
 #include "decode-vfp.inc.c"
 #include "decode-vfp-uncond.inc.c"
 
+/*
+ * The imm8 encodes the sign bit, enough bits to represent an exponent in
+ * the range 01....1xx to 10....0xx, and the most significant 4 bits of
+ * the mantissa; see VFPExpandImm() in the v8 ARM ARM.
+ */
+uint64_t vfp_expand_imm(int size, uint8_t imm8)
+{
+    uint64_t imm;
+
+    switch (size) {
+    case MO_64:
+        imm = (extract32(imm8, 7, 1) ? 0x8000 : 0) |
+            (extract32(imm8, 6, 1) ? 0x3fc0 : 0x4000) |
+            extract32(imm8, 0, 6);
+        imm <<= 48;
+        break;
+    case MO_32:
+        imm = (extract32(imm8, 7, 1) ? 0x8000 : 0) |
+            (extract32(imm8, 6, 1) ? 0x3e00 : 0x4000) |
+            (extract32(imm8, 0, 6) << 3);
+        imm <<= 16;
+        break;
+    case MO_16:
+        imm = (extract32(imm8, 7, 1) ? 0x8000 : 0) |
+            (extract32(imm8, 6, 1) ? 0x3000 : 0x4000) |
+            (extract32(imm8, 0, 6) << 6);
+        break;
+    default:
+        g_assert_not_reached();
+    }
+    return imm;
+}
+
 /*
  * Return the offset of a 16-bit half of the specified VFP single-precision
  * register. If top is true, returns the top 16 bits; otherwise the bottom

qemu/target/arm/translate.h

@@ -242,6 +242,13 @@ static inline void gen_ss_advance(DisasContext *s)
     }
 }
 
+/*
+ * Given a VFP floating point constant encoded into an 8 bit immediate in an
+ * instruction, expand it to the actual constant value of the specified
+ * size, as per the VFPExpandImm() pseudocode in the Arm ARM.
+ */
+uint64_t vfp_expand_imm(int size, uint8_t imm8);
+
 /* Vector operations shared between ARM and AArch64.  */
 extern const GVecGen3 cmtst_op[4];
 extern const GVecGen3 mla_op[4];