[Qemu-devel] [PATCH 2/2] target/arm: Only implement doubles if the FPU supports them

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

The architecture permits FPUs which have only single-precision
support, not double-precision; Cortex-M4 and Cortex-M33 are
both like that. Add the necessary checks on the MVFR0 FPDP
field so that we UNDEF any double-precision instructions on
CPUs like this.

Note that even if FPDP==0 the insns like VMOV-to/from-gpreg,
VLDM/VSTM, VLDR/VSTR which take double precision registers
still exist.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 target/arm/cpu.h               |  6 +++
 target/arm/translate-vfp.inc.c | 84 ++++++++++++++++++++++++++++++++++
 2 files changed, 90 insertions(+)

diff --git a/target/arm/cpu.h b/target/arm/cpu.h
index 92298624215..29be1f7ea97 100644
--- a/target/arm/cpu.h
+++ b/target/arm/cpu.h
@@ -3382,6 +3382,12 @@ static inline bool isar_feature_aa32_fpshvec(const ARMISARegisters *id)
     return FIELD_EX64(id->mvfr0, MVFR0, FPSHVEC) > 0;
 }
 
+static inline bool isar_feature_aa32_fpdp(const ARMISARegisters *id)
+{
+    /* Return true if CPU supports double precision floating point */
+    return FIELD_EX64(id->mvfr0, MVFR0, FPDP) > 0;
+}
+
 /*
  * We always set the FP and SIMD FP16 fields to indicate identical
  * levels of support (assuming SIMD is implemented at all), so
diff --git a/target/arm/translate-vfp.inc.c b/target/arm/translate-vfp.inc.c
index 85187bcc9dc..a3df81d3b07 100644
--- a/target/arm/translate-vfp.inc.c
+++ b/target/arm/translate-vfp.inc.c
@@ -173,6 +173,11 @@ static bool trans_VSEL(DisasContext *s, arg_VSEL *a)
         ((a->vm | a->vn | a->vd) & 0x10)) {
         return false;
     }
+
+    if (dp && !dc_isar_feature(aa32_fpdp, s)) {
+        return false;
+    }
+
     rd = a->vd;
     rn = a->vn;
     rm = a->vm;
@@ -301,6 +306,11 @@ static bool trans_VMINMAXNM(DisasContext *s, arg_VMINMAXNM *a)
         ((a->vm | a->vn | a->vd) & 0x10)) {
         return false;
     }
+
+    if (dp && !dc_isar_feature(aa32_fpdp, s)) {
+        return false;
+    }
+
     rd = a->vd;
     rn = a->vn;
     rm = a->vm;
@@ -382,6 +392,11 @@ static bool trans_VRINT(DisasContext *s, arg_VRINT *a)
         ((a->vm | a->vd) & 0x10)) {
         return false;
     }
+
+    if (dp && !dc_isar_feature(aa32_fpdp, s)) {
+        return false;
+    }
+
     rd = a->vd;
     rm = a->vm;
 
@@ -440,6 +455,11 @@ static bool trans_VCVT(DisasContext *s, arg_VCVT *a)
     if (dp && !dc_isar_feature(aa32_fp_d32, s) && (a->vm & 0x10)) {
         return false;
     }
+
+    if (dp && !dc_isar_feature(aa32_fpdp, s)) {
+        return false;
+    }
+
     rd = a->vd;
     rm = a->vm;
 
@@ -1268,6 +1288,10 @@ static bool do_vfp_3op_dp(DisasContext *s, VFPGen3OpDPFn *fn,
         return false;
     }
 
+    if (!dc_isar_feature(aa32_fpdp, s)) {
+        return false;
+    }
+
     if (!dc_isar_feature(aa32_fpshvec, s) &&
         (veclen != 0 || s->vec_stride != 0)) {
         return false;
@@ -1413,6 +1437,10 @@ static bool do_vfp_2op_dp(DisasContext *s, VFPGen2OpDPFn *fn, int vd, int vm)
         return false;
     }
 
+    if (!dc_isar_feature(aa32_fpdp, s)) {
+        return false;
+    }
+
     if (!dc_isar_feature(aa32_fpshvec, s) &&
         (veclen != 0 || s->vec_stride != 0)) {
         return false;
@@ -1773,6 +1801,10 @@ static bool trans_VFM_dp(DisasContext *s, arg_VFM_dp *a)
         return false;
     }
 
+    if (!dc_isar_feature(aa32_fpdp, s)) {
+        return false;
+    }
+
     if (!vfp_access_check(s)) {
         return true;
     }
@@ -1878,6 +1910,10 @@ static bool trans_VMOV_imm_dp(DisasContext *s, arg_VMOV_imm_dp *a)
         return false;
     }
 
+    if (!dc_isar_feature(aa32_fpdp, s)) {
+        return false;
+    }
+
     if (!dc_isar_feature(aa32_fpshvec, s) &&
         (veclen != 0 || s->vec_stride != 0)) {
         return false;
@@ -2028,6 +2064,10 @@ static bool trans_VCMP_dp(DisasContext *s, arg_VCMP_dp *a)
         return false;
     }
 
+    if (!dc_isar_feature(aa32_fpdp, s)) {
+        return false;
+    }
+
     if (!vfp_access_check(s)) {
         return true;
     }
@@ -2097,6 +2137,10 @@ static bool trans_VCVT_f64_f16(DisasContext *s, arg_VCVT_f64_f16 *a)
         return false;
     }
 
+    if (!dc_isar_feature(aa32_fpdp, s)) {
+        return false;
+    }
+
     if (!vfp_access_check(s)) {
         return true;
     }
@@ -2159,6 +2203,10 @@ static bool trans_VCVT_f16_f64(DisasContext *s, arg_VCVT_f16_f64 *a)
         return false;
     }
 
+    if (!dc_isar_feature(aa32_fpdp, s)) {
+        return false;
+    }
+
     if (!vfp_access_check(s)) {
         return true;
     }
@@ -2215,6 +2263,10 @@ static bool trans_VRINTR_dp(DisasContext *s, arg_VRINTR_dp *a)
         return false;
     }
 
+    if (!dc_isar_feature(aa32_fpdp, s)) {
+        return false;
+    }
+
     if (!vfp_access_check(s)) {
         return true;
     }
@@ -2272,6 +2324,10 @@ static bool trans_VRINTZ_dp(DisasContext *s, arg_VRINTZ_dp *a)
         return false;
     }
 
+    if (!dc_isar_feature(aa32_fpdp, s)) {
+        return false;
+    }
+
     if (!vfp_access_check(s)) {
         return true;
     }
@@ -2327,6 +2383,10 @@ static bool trans_VRINTX_dp(DisasContext *s, arg_VRINTX_dp *a)
         return false;
     }
 
+    if (!dc_isar_feature(aa32_fpdp, s)) {
+        return false;
+    }
+
     if (!vfp_access_check(s)) {
         return true;
     }
@@ -2351,6 +2411,10 @@ static bool trans_VCVT_sp(DisasContext *s, arg_VCVT_sp *a)
         return false;
     }
 
+    if (!dc_isar_feature(aa32_fpdp, s)) {
+        return false;
+    }
+
     if (!vfp_access_check(s)) {
         return true;
     }
@@ -2375,6 +2439,10 @@ static bool trans_VCVT_dp(DisasContext *s, arg_VCVT_dp *a)
         return false;
     }
 
+    if (!dc_isar_feature(aa32_fpdp, s)) {
+        return false;
+    }
+
     if (!vfp_access_check(s)) {
         return true;
     }
@@ -2425,6 +2493,10 @@ static bool trans_VCVT_int_dp(DisasContext *s, arg_VCVT_int_dp *a)
         return false;
     }
 
+    if (!dc_isar_feature(aa32_fpdp, s)) {
+        return false;
+    }
+
     if (!vfp_access_check(s)) {
         return true;
     }
@@ -2461,6 +2533,10 @@ static bool trans_VJCVT(DisasContext *s, arg_VJCVT *a)
         return false;
     }
 
+    if (!dc_isar_feature(aa32_fpdp, s)) {
+        return false;
+    }
+
     if (!vfp_access_check(s)) {
         return true;
     }
@@ -2550,6 +2626,10 @@ static bool trans_VCVT_fix_dp(DisasContext *s, arg_VCVT_fix_dp *a)
         return false;
     }
 
+    if (!dc_isar_feature(aa32_fpdp, s)) {
+        return false;
+    }
+
     if (!vfp_access_check(s)) {
         return true;
     }
@@ -2642,6 +2722,10 @@ static bool trans_VCVT_dp_int(DisasContext *s, arg_VCVT_dp_int *a)
         return false;
     }
 
+    if (!dc_isar_feature(aa32_fpdp, s)) {
+        return false;
+    }
+
     if (!vfp_access_check(s)) {
         return true;
     }
-- 
2.20.1