target/arm: Enable FPSCR.QC bit for MVE

MVE has an FPSCR.QC bit similar to the A-profile Neon one; when MVE
is implemented make the bit writeable, both in the generic "load and
store FPSCR" helper functions and in the code for handling the NZCVQC
sysreg which we had previously left as "TODO when we implement MVE".

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20210614151007.4545-3-peter.maydell@linaro.org

diff --git a/target/arm/translate-vfp.c b/target/arm/translate-vfp.c
index d01e465..728856d 100644 (file)
--- a/target/arm/translate-vfp.c
+++ b/target/arm/translate-vfp.c
@@ -784,10 +784,17 @@ static bool gen_M_fp_sysreg_write(DisasContext *s, int regno,
     {
         TCGv_i32 fpscr;
         tmp = loadfn(s, opaque);
-        /*
-         * TODO: when we implement MVE, write the QC bit.
-         * For non-MVE, QC is RES0.
-         */
+        if (dc_isar_feature(aa32_mve, s)) {
+            /* QC is only present for MVE; otherwise RES0 */
+            TCGv_i32 qc = tcg_temp_new_i32();
+            tcg_gen_andi_i32(qc, tmp, FPCR_QC);
+            /*
+             * The 4 vfp.qc[] fields need only be "zero" vs "non-zero";
+             * here writing the same value into all elements is simplest.
+             */
+            tcg_gen_gvec_dup_i32(MO_32, offsetof(CPUARMState, vfp.qc),
+                                 16, 16, qc);
+        }
         tcg_gen_andi_i32(tmp, tmp, FPCR_NZCV_MASK);
         fpscr = load_cpu_field(vfp.xregs[ARM_VFP_FPSCR]);
         tcg_gen_andi_i32(fpscr, fpscr, ~FPCR_NZCV_MASK);
@@ -869,6 +876,11 @@ static bool gen_M_fp_sysreg_read(DisasContext *s, int regno,
         break;
     }
 
+    if (regno == ARM_VFP_FPSCR_NZCVQC && !dc_isar_feature(aa32_mve, s)) {
+        /* QC is RES0 without MVE, so NZCVQC simplifies to NZCV */
+        regno = QEMU_VFP_FPSCR_NZCV;
+    }
+
     switch (regno) {
     case ARM_VFP_FPSCR:
         tmp = tcg_temp_new_i32();
@@ -876,11 +888,11 @@ static bool gen_M_fp_sysreg_read(DisasContext *s, int regno,
         storefn(s, opaque, tmp);
         break;
     case ARM_VFP_FPSCR_NZCVQC:
-        /*
-         * TODO: MVE has a QC bit, which we probably won't store
-         * in the xregs[] field. For non-MVE, where QC is RES0,
-         * we can just fall through to the FPSCR_NZCV case.
-         */
+        tmp = tcg_temp_new_i32();
+        gen_helper_vfp_get_fpscr(tmp, cpu_env);
+        tcg_gen_andi_i32(tmp, tmp, FPCR_NZCVQC_MASK);
+        storefn(s, opaque, tmp);
+        break;
     case QEMU_VFP_FPSCR_NZCV:
         /*
          * Read just NZCV; this is a special case to avoid the

diff --git a/target/arm/vfp_helper.c b/target/arm/vfp_helper.c
index 496f003..8a71660 100644 (file)
--- a/target/arm/vfp_helper.c
+++ b/target/arm/vfp_helper.c
@@ -220,7 +220,8 @@ void HELPER(vfp_set_fpscr)(CPUARMState *env, uint32_t val)
                                      FPCR_LTPSIZE_LENGTH);
     }
 
-    if (arm_feature(env, ARM_FEATURE_NEON)) {
+    if (arm_feature(env, ARM_FEATURE_NEON) ||
+        cpu_isar_feature(aa32_mve, cpu)) {
         /*
          * The bit we set within fpscr_q is arbitrary; the register as a
          * whole being zero/non-zero is what counts.