[PATCH 1/3] target/arm: Convert Neon 3-same-fp size field to MO_* in decode

[Peter Maydell <peter.maydell@linaro.org>]

In the Neon instructions, some instruction formats have a 2-bit size
field which corresponds exactly to QEMU's MO_8/16/32/64.  However the
floating-point insns in the 3-same group have a 1-bit size field
which is "0 for 32-bit float and 1 for 16-bit float".  Currently we
pass these values directly through to trans_ functions, which means
that when reading a particular trans_ function you need to know if
that insn uses a 2-bit size or a 1-bit size.

Move the handling of the 1-bit size to the decodetree file, so that
all these insns consistently pass a size to the trans_ function which
is an MO_8/16/32/64 value.

In this commit we switch over the insns using the 3same_fp and
3same_fp_q0 formats.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
I wanted to call the field %3same_fp_size, but decodetree
doesn't seem to allow a field starting with a digit, even
though it does allow a format that starts with a digit.
So it's %fp_3same_size...
---
 target/arm/neon-dp.decode       | 15 ++++++++++-----
 target/arm/translate-neon.c.inc | 16 +++++++++++-----
 2 files changed, 21 insertions(+), 10 deletions(-)

diff --git a/target/arm/neon-dp.decode b/target/arm/neon-dp.decode
index 1e9e8592917..f453833396f 100644
--- a/target/arm/neon-dp.decode
+++ b/target/arm/neon-dp.decode
@@ -45,11 +45,16 @@
 @3same_q0        .... ... . . . size:2 .... .... .... . 0 . . .... \
                  &3same vm=%vm_dp vn=%vn_dp vd=%vd_dp q=0
 
-# For FP insns the high bit of 'size' is used as part of opcode decode
-@3same_fp        .... ... . . . . size:1 .... .... .... . q:1 . . .... \
-                 &3same vm=%vm_dp vn=%vn_dp vd=%vd_dp
-@3same_fp_q0     .... ... . . . . size:1 .... .... .... . 0 . . .... \
-                 &3same vm=%vm_dp vn=%vn_dp vd=%vd_dp q=0
+# For FP insns the high bit of 'size' is used as part of opcode decode,
+# and the 'size' bit is 0 for 32-bit float and 1 for 16-bit float.
+# This converts this encoding to the same MO_8/16/32/64 values that the
+# integer neon insns use.
+%fp_3same_size   20:1 !function=neon_3same_fp_size
+
+@3same_fp        .... ... . . . . . .... .... .... . q:1 . . .... \
+                 &3same vm=%vm_dp vn=%vn_dp vd=%vd_dp size=%fp_3same_size
+@3same_fp_q0     .... ... . . . . . .... .... .... . 0 . . .... \
+                 &3same vm=%vm_dp vn=%vn_dp vd=%vd_dp q=0 size=%fp_3same_size
 
 VHADD_S_3s       1111 001 0 0 . .. .... .... 0000 . . . 0 .... @3same
 VHADD_U_3s       1111 001 1 0 . .. .... .... 0000 . . . 0 .... @3same
diff --git a/target/arm/translate-neon.c.inc b/target/arm/translate-neon.c.inc
index 2d4926316a4..255c1cf8a2a 100644
--- a/target/arm/translate-neon.c.inc
+++ b/target/arm/translate-neon.c.inc
@@ -49,6 +49,12 @@ static inline int rsub_8(DisasContext *s, int x)
     return 8 - x;
 }
 
+static inline int neon_3same_fp_size(DisasContext *s, int x)
+{
+    /* Convert 0==fp32, 1==fp16 into a MO_* value */
+    return MO_32 - x;
+}
+
 /* Include the generated Neon decoder */
 #include "decode-neon-dp.c.inc"
 #include "decode-neon-ls.c.inc"
@@ -1049,7 +1055,7 @@ DO_3SAME_VQDMULH(VQRDMULH, qrdmulh)
     WRAP_FP_GVEC(gen_##INSN##_fp16_3s, FPST_STD_F16, HFUNC)             \
     static bool trans_##INSN##_fp_3s(DisasContext *s, arg_3same *a)     \
     {                                                                   \
-        if (a->size != 0) {                                             \
+        if (a->size == MO_16) {                                         \
             if (!dc_isar_feature(aa32_fp16_arith, s)) {                 \
                 return false;                                           \
             }                                                           \
@@ -1088,7 +1094,7 @@ static bool trans_VMAXNM_fp_3s(DisasContext *s, arg_3same *a)
         return false;
     }
 
-    if (a->size != 0) {
+    if (a->size == MO_16) {
         if (!dc_isar_feature(aa32_fp16_arith, s)) {
             return false;
         }
@@ -1103,7 +1109,7 @@ static bool trans_VMINNM_fp_3s(DisasContext *s, arg_3same *a)
         return false;
     }
 
-    if (a->size != 0) {
+    if (a->size == MO_16) {
         if (!dc_isar_feature(aa32_fp16_arith, s)) {
             return false;
         }
@@ -1135,7 +1141,7 @@ static bool do_3same_fp_pair(DisasContext *s, arg_3same *a,
     assert(a->q == 0); /* enforced by decode patterns */
 
 
-    fpstatus = fpstatus_ptr(a->size != 0 ? FPST_STD_F16 : FPST_STD);
+    fpstatus = fpstatus_ptr(a->size == MO_16 ? FPST_STD_F16 : FPST_STD);
     tcg_gen_gvec_3_ptr(vfp_reg_offset(1, a->vd),
                        vfp_reg_offset(1, a->vn),
                        vfp_reg_offset(1, a->vm),
@@ -1152,7 +1158,7 @@ static bool do_3same_fp_pair(DisasContext *s, arg_3same *a,
 #define DO_3S_FP_PAIR(INSN,FUNC)                                    \
     static bool trans_##INSN##_fp_3s(DisasContext *s, arg_3same *a) \
     {                                                               \
-        if (a->size != 0) {                                         \
+        if (a->size == MO_16) {                                     \
             if (!dc_isar_feature(aa32_fp16_arith, s)) {             \
                 return false;                                       \
             }                                                       \
-- 
2.20.1