target/arm: Use MVFR1 feature bits to gate A32/T32 FP16 instructions

Instead of gating the A32/T32 FP16 conversion instructions on
the ARM_FEATURE_VFP_FP16 flag, switch to our new approach of
looking at ID register bits. In this case MVFR1 fields FPHP
and SIMDHP indicate the presence of these insns.

This change doesn't alter behaviour for any of our CPUs.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20190222170936.13268-2-peter.maydell@linaro.org

4 files changed, 54 insertions, 14 deletions

diff --git a/target/arm/cpu.c b/target/arm/cpu.c
index 4d7f6a3bc0..a3baf4eeed 100644
--- a/target/arm/cpu.c
+++ b/target/arm/cpu.c
@@ -1014,7 +1014,6 @@ static void arm_cpu_realizefn(DeviceState *dev, Error **errp)
     }
     if (arm_feature(env, ARM_FEATURE_VFP4)) {
         set_feature(env, ARM_FEATURE_VFP3);
-        set_feature(env, ARM_FEATURE_VFP_FP16);
     }
     if (arm_feature(env, ARM_FEATURE_VFP3)) {
         set_feature(env, ARM_FEATURE_VFP);
@@ -1675,7 +1674,6 @@ static void cortex_a9_initfn(Object *obj)
     cpu->dtb_compatible = "arm,cortex-a9";
     set_feature(&cpu->env, ARM_FEATURE_V7);
     set_feature(&cpu->env, ARM_FEATURE_VFP3);
-    set_feature(&cpu->env, ARM_FEATURE_VFP_FP16);
     set_feature(&cpu->env, ARM_FEATURE_NEON);
     set_feature(&cpu->env, ARM_FEATURE_THUMB2EE);
     set_feature(&cpu->env, ARM_FEATURE_EL3);
diff --git a/target/arm/cpu.h b/target/arm/cpu.h
index 1eea1a408b..36ea3b5856 100644
--- a/target/arm/cpu.h
+++ b/target/arm/cpu.h
@@ -1730,6 +1730,27 @@ FIELD(ID_DFR0, MPROFDBG, 20, 4)
 FIELD(ID_DFR0, PERFMON, 24, 4)
 FIELD(ID_DFR0, TRACEFILT, 28, 4)
 
+FIELD(MVFR0, SIMDREG, 0, 4)
+FIELD(MVFR0, FPSP, 4, 4)
+FIELD(MVFR0, FPDP, 8, 4)
+FIELD(MVFR0, FPTRAP, 12, 4)
+FIELD(MVFR0, FPDIVIDE, 16, 4)
+FIELD(MVFR0, FPSQRT, 20, 4)
+FIELD(MVFR0, FPSHVEC, 24, 4)
+FIELD(MVFR0, FPROUND, 28, 4)
+
+FIELD(MVFR1, FPFTZ, 0, 4)
+FIELD(MVFR1, FPDNAN, 4, 4)
+FIELD(MVFR1, SIMDLS, 8, 4)
+FIELD(MVFR1, SIMDINT, 12, 4)
+FIELD(MVFR1, SIMDSP, 16, 4)
+FIELD(MVFR1, SIMDHP, 20, 4)
+FIELD(MVFR1, FPHP, 24, 4)
+FIELD(MVFR1, SIMDFMAC, 28, 4)
+
+FIELD(MVFR2, SIMDMISC, 0, 4)
+FIELD(MVFR2, FPMISC, 4, 4)
+
 QEMU_BUILD_BUG_ON(ARRAY_SIZE(((ARMCPU *)0)->ccsidr) <= R_V7M_CSSELR_INDEX_MASK);
 
 /* If adding a feature bit which corresponds to a Linux ELF
@@ -1747,7 +1768,6 @@ enum arm_features {
     ARM_FEATURE_THUMB2,
     ARM_FEATURE_PMSA,   /* no MMU; may have Memory Protection Unit */
     ARM_FEATURE_VFP3,
-    ARM_FEATURE_VFP_FP16,
     ARM_FEATURE_NEON,
     ARM_FEATURE_M, /* Microcontroller profile.  */
     ARM_FEATURE_OMAPCP, /* OMAP specific CP15 ops handling.  */
@@ -3294,6 +3314,21 @@ static inline bool isar_feature_aa32_fp16_arith(const ARMISARegisters *id)
 }
 
 /*
+ * We always set the FP and SIMD FP16 fields to indicate identical
+ * levels of support (assuming SIMD is implemented at all), so
+ * we only need one set of accessors.
+ */
+static inline bool isar_feature_aa32_fp16_spconv(const ARMISARegisters *id)
+{
+    return FIELD_EX64(id->mvfr1, MVFR1, FPHP) > 0;
+}
+
+static inline bool isar_feature_aa32_fp16_dpconv(const ARMISARegisters *id)
+{
+    return FIELD_EX64(id->mvfr1, MVFR1, FPHP) > 1;
+}
+
+/*
  * 64-bit feature tests via id registers.
  */
 static inline bool isar_feature_aa64_aes(const ARMISARegisters *id)
diff --git a/target/arm/kvm32.c b/target/arm/kvm32.c
index a75e04cc8f..327375f625 100644
--- a/target/arm/kvm32.c
+++ b/target/arm/kvm32.c
@@ -125,9 +125,6 @@ bool kvm_arm_get_host_cpu_features(ARMHostCPUFeatures *ahcf)
     if (extract32(id_pfr0, 12, 4) == 1) {
         set_feature(&features, ARM_FEATURE_THUMB2EE);
     }
-    if (extract32(ahcf->isar.mvfr1, 20, 4) == 1) {
-        set_feature(&features, ARM_FEATURE_VFP_FP16);
-    }
     if (extract32(ahcf->isar.mvfr1, 12, 4) == 1) {
         set_feature(&features, ARM_FEATURE_NEON);
     }
diff --git a/target/arm/translate.c b/target/arm/translate.c
index c1175798ac..b7702fb49f 100644
--- a/target/arm/translate.c
+++ b/target/arm/translate.c
@@ -3663,17 +3663,27 @@ static int disas_vfp_insn(DisasContext *s, uint32_t insn)
                      * UNPREDICTABLE if bit 8 is set prior to ARMv8
                      * (we choose to UNDEF)
                      */
-                    if ((dp && !arm_dc_feature(s, ARM_FEATURE_V8)) ||
-                        !arm_dc_feature(s, ARM_FEATURE_VFP_FP16)) {
-                        return 1;
+                    if (dp) {
+                        if (!dc_isar_feature(aa32_fp16_dpconv, s)) {
+                            return 1;
+                        }
+                    } else {
+                        if (!dc_isar_feature(aa32_fp16_spconv, s)) {
+                            return 1;
+                        }
                     }
                     rm_is_dp = false;
                     break;
                 case 0x06: /* vcvtb.f16.f32, vcvtb.f16.f64 */
                 case 0x07: /* vcvtt.f16.f32, vcvtt.f16.f64 */
-                    if ((dp && !arm_dc_feature(s, ARM_FEATURE_V8)) ||
-                        !arm_dc_feature(s, ARM_FEATURE_VFP_FP16)) {
-                        return 1;
+                    if (dp) {
+                        if (!dc_isar_feature(aa32_fp16_dpconv, s)) {
+                            return 1;
+                        }
+                    } else {
+                        if (!dc_isar_feature(aa32_fp16_spconv, s)) {
+                            return 1;
+                        }
                     }
                     rd_is_dp = false;
                     break;
@@ -7876,7 +7886,7 @@ static int disas_neon_data_insn(DisasContext *s, uint32_t insn)
                     TCGv_ptr fpst;
                     TCGv_i32 ahp;
 
-                    if (!arm_dc_feature(s, ARM_FEATURE_VFP_FP16) ||
+                    if (!dc_isar_feature(aa32_fp16_spconv, s) ||
                         q || (rm & 1)) {
                         return 1;
                     }
@@ -7908,7 +7918,7 @@ static int disas_neon_data_insn(DisasContext *s, uint32_t insn)
                 {
                     TCGv_ptr fpst;
                     TCGv_i32 ahp;
-                    if (!arm_dc_feature(s, ARM_FEATURE_VFP_FP16) ||
+                    if (!dc_isar_feature(aa32_fp16_spconv, s) ||
                         q || (rd & 1)) {
                         return 1;
                     }