target/arm: Handle VPR semantics in existing code

When MVE is supported, the VPR register has a place on the exception
stack frame in a previously reserved slot just above the FPSCR.
It must also be zeroed in various situations when we invalidate
FPU context.

Update the code which handles the stack frames (exception entry and
exit code, VLLDM, and VLSTM) to save/restore VPR.

Update code which invalidates FP registers (mostly also exception
entry and exit code, but also VSCCLRM and the code in
full_vfp_access_check() that corresponds to the ExecuteFPCheck()
pseudocode) to zero VPR.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20210614151007.4545-4-peter.maydell@linaro.org

3 files changed, 57 insertions, 11 deletions

diff --git a/target/arm/m_helper.c b/target/arm/m_helper.c
index 074c543..7a1e35a 100644
--- a/target/arm/m_helper.c
+++ b/target/arm/m_helper.c
@@ -378,7 +378,7 @@ void HELPER(v7m_preserve_fp_state)(CPUARMState *env)
             uint32_t shi = extract64(dn, 32, 32);
 
             if (i >= 16) {
-                faddr += 8; /* skip the slot for the FPSCR */
+                faddr += 8; /* skip the slot for the FPSCR/VPR */
             }
             stacked_ok = stacked_ok &&
                 v7m_stack_write(cpu, faddr, slo, mmu_idx, STACK_LAZYFP) &&
@@ -388,6 +388,11 @@ void HELPER(v7m_preserve_fp_state)(CPUARMState *env)
         stacked_ok = stacked_ok &&
             v7m_stack_write(cpu, fpcar + 0x40,
                             vfp_get_fpscr(env), mmu_idx, STACK_LAZYFP);
+        if (cpu_isar_feature(aa32_mve, cpu)) {
+            stacked_ok = stacked_ok &&
+                v7m_stack_write(cpu, fpcar + 0x44,
+                                env->v7m.vpr, mmu_idx, STACK_LAZYFP);
+        }
     }
 
     /*
@@ -410,16 +415,19 @@ void HELPER(v7m_preserve_fp_state)(CPUARMState *env)
     env->v7m.fpccr[is_secure] &= ~R_V7M_FPCCR_LSPACT_MASK;
 
     if (ts) {
-        /* Clear s0 to s31 and the FPSCR */
+        /* Clear s0 to s31 and the FPSCR and VPR */
         int i;
 
         for (i = 0; i < 32; i += 2) {
             *aa32_vfp_dreg(env, i / 2) = 0;
         }
         vfp_set_fpscr(env, 0);
+        if (cpu_isar_feature(aa32_mve, cpu)) {
+            env->v7m.vpr = 0;
+        }
     }
     /*
-     * Otherwise s0 to s15 and FPSCR are UNKNOWN; we choose to leave them
+     * Otherwise s0 to s15, FPSCR and VPR are UNKNOWN; we choose to leave them
      * unchanged.
      */
 }
@@ -1044,6 +1052,7 @@ static void v7m_update_fpccr(CPUARMState *env, uint32_t frameptr,
 void HELPER(v7m_vlstm)(CPUARMState *env, uint32_t fptr)
 {
     /* fptr is the value of Rn, the frame pointer we store the FP regs to */
+    ARMCPU *cpu = env_archcpu(env);
     bool s = env->v7m.fpccr[M_REG_S] & R_V7M_FPCCR_S_MASK;
     bool lspact = env->v7m.fpccr[s] & R_V7M_FPCCR_LSPACT_MASK;
     uintptr_t ra = GETPC();
@@ -1092,9 +1101,12 @@ void HELPER(v7m_vlstm)(CPUARMState *env, uint32_t fptr)
             cpu_stl_data_ra(env, faddr + 4, shi, ra);
         }
         cpu_stl_data_ra(env, fptr + 0x40, vfp_get_fpscr(env), ra);
+        if (cpu_isar_feature(aa32_mve, cpu)) {
+            cpu_stl_data_ra(env, fptr + 0x44, env->v7m.vpr, ra);
+        }
 
         /*
-         * If TS is 0 then s0 to s15 and FPSCR are UNKNOWN; we choose to
+         * If TS is 0 then s0 to s15, FPSCR and VPR are UNKNOWN; we choose to
          * leave them unchanged, matching our choice in v7m_preserve_fp_state.
          */
         if (ts) {
@@ -1102,6 +1114,9 @@ void HELPER(v7m_vlstm)(CPUARMState *env, uint32_t fptr)
                 *aa32_vfp_dreg(env, i / 2) = 0;
             }
             vfp_set_fpscr(env, 0);
+            if (cpu_isar_feature(aa32_mve, cpu)) {
+                env->v7m.vpr = 0;
+            }
         }
     } else {
         v7m_update_fpccr(env, fptr, false);
@@ -1112,6 +1127,7 @@ void HELPER(v7m_vlstm)(CPUARMState *env, uint32_t fptr)
 
 void HELPER(v7m_vlldm)(CPUARMState *env, uint32_t fptr)
 {
+    ARMCPU *cpu = env_archcpu(env);
     uintptr_t ra = GETPC();
 
     /* fptr is the value of Rn, the frame pointer we load the FP regs from */
@@ -1144,7 +1160,7 @@ void HELPER(v7m_vlldm)(CPUARMState *env, uint32_t fptr)
             uint32_t faddr = fptr + 4 * i;
 
             if (i >= 16) {
-                faddr += 8; /* skip the slot for the FPSCR */
+                faddr += 8; /* skip the slot for the FPSCR and VPR */
             }
 
             slo = cpu_ldl_data_ra(env, faddr, ra);
@@ -1155,6 +1171,9 @@ void HELPER(v7m_vlldm)(CPUARMState *env, uint32_t fptr)
         }
         fpscr = cpu_ldl_data_ra(env, fptr + 0x40, ra);
         vfp_set_fpscr(env, fpscr);
+        if (cpu_isar_feature(aa32_mve, cpu)) {
+            env->v7m.vpr = cpu_ldl_data_ra(env, fptr + 0x44, ra);
+        }
     }
 
     env->v7m.control[M_REG_S] |= R_V7M_CONTROL_FPCA_MASK;
@@ -1298,7 +1317,7 @@ static bool v7m_push_stack(ARMCPU *cpu)
                     uint32_t shi = extract64(dn, 32, 32);
 
                     if (i >= 16) {
-                        faddr += 8; /* skip the slot for the FPSCR */
+                        faddr += 8; /* skip the slot for the FPSCR and VPR */
                     }
                     stacked_ok = stacked_ok &&
                         v7m_stack_write(cpu, faddr, slo,
@@ -1309,11 +1328,19 @@ static bool v7m_push_stack(ARMCPU *cpu)
                 stacked_ok = stacked_ok &&
                     v7m_stack_write(cpu, frameptr + 0x60,
                                     vfp_get_fpscr(env), mmu_idx, STACK_NORMAL);
+                if (cpu_isar_feature(aa32_mve, cpu)) {
+                    stacked_ok = stacked_ok &&
+                        v7m_stack_write(cpu, frameptr + 0x64,
+                                        env->v7m.vpr, mmu_idx, STACK_NORMAL);
+                }
                 if (cpacr_pass) {
                     for (i = 0; i < ((framesize == 0xa8) ? 32 : 16); i += 2) {
                         *aa32_vfp_dreg(env, i / 2) = 0;
                     }
                     vfp_set_fpscr(env, 0);
+                    if (cpu_isar_feature(aa32_mve, cpu)) {
+                        env->v7m.vpr = 0;
+                    }
                 }
             } else {
                 /* Lazy stacking enabled, save necessary info to stack later */
@@ -1536,13 +1563,16 @@ static void do_v7m_exception_exit(ARMCPU *cpu)
                     v7m_exception_taken(cpu, excret, true, false);
                 }
             }
-            /* Clear s0..s15 and FPSCR; TODO also VPR when MVE is implemented */
+            /* Clear s0..s15, FPSCR and VPR */
             int i;
 
             for (i = 0; i < 16; i += 2) {
                 *aa32_vfp_dreg(env, i / 2) = 0;
             }
             vfp_set_fpscr(env, 0);
+            if (cpu_isar_feature(aa32_mve, cpu)) {
+                env->v7m.vpr = 0;
+            }
         }
     }
 
@@ -1771,7 +1801,7 @@ static void do_v7m_exception_exit(ARMCPU *cpu)
                     uint32_t faddr = frameptr + 0x20 + 4 * i;
 
                     if (i >= 16) {
-                        faddr += 8; /* Skip the slot for the FPSCR */
+                        faddr += 8; /* Skip the slot for the FPSCR and VPR */
                     }
 
                     pop_ok = pop_ok &&
@@ -1790,6 +1820,11 @@ static void do_v7m_exception_exit(ARMCPU *cpu)
                 if (pop_ok) {
                     vfp_set_fpscr(env, fpscr);
                 }
+                if (cpu_isar_feature(aa32_mve, cpu)) {
+                    pop_ok = pop_ok &&
+                        v7m_stack_read(cpu, &env->v7m.vpr,
+                                       frameptr + 0x64, mmu_idx);
+                }
                 if (!pop_ok) {
                     /*
                      * These regs are 0 if security extension present;
@@ -1799,6 +1834,9 @@ static void do_v7m_exception_exit(ARMCPU *cpu)
                         *aa32_vfp_dreg(env, i / 2) = 0;
                     }
                     vfp_set_fpscr(env, 0);
+                    if (cpu_isar_feature(aa32_mve, cpu)) {
+                        env->v7m.vpr = 0;
+                    }
                 }
             }
         }
diff --git a/target/arm/translate-m-nocp.c b/target/arm/translate-m-nocp.c
index d47eb8e..365810e 100644
--- a/target/arm/translate-m-nocp.c
+++ b/target/arm/translate-m-nocp.c
@@ -173,7 +173,10 @@ static bool trans_VSCCLRM(DisasContext *s, arg_VSCCLRM *a)
         btmreg++;
     }
     assert(btmreg == topreg + 1);
-    /* TODO: when MVE is implemented, zero VPR here */
+    if (dc_isar_feature(aa32_mve, s)) {
+        TCGv_i32 z32 = tcg_const_i32(0);
+        store_cpu_field(z32, v7m.vpr);
+    }
     return true;
 }
 
diff --git a/target/arm/translate-vfp.c b/target/arm/translate-vfp.c
index 728856d..49f4434 100644
--- a/target/arm/translate-vfp.c
+++ b/target/arm/translate-vfp.c
@@ -180,8 +180,8 @@ static bool full_vfp_access_check(DisasContext *s, bool ignore_vfp_enabled)
 
         if (s->v7m_new_fp_ctxt_needed) {
             /*
-             * Create new FP context by updating CONTROL.FPCA, CONTROL.SFPA
-             * and the FPSCR.
+             * Create new FP context by updating CONTROL.FPCA, CONTROL.SFPA,
+             * the FPSCR, and VPR.
              */
             TCGv_i32 control, fpscr;
             uint32_t bits = R_V7M_CONTROL_FPCA_MASK;
@@ -189,6 +189,11 @@ static bool full_vfp_access_check(DisasContext *s, bool ignore_vfp_enabled)
             fpscr = load_cpu_field(v7m.fpdscr[s->v8m_secure]);
             gen_helper_vfp_set_fpscr(cpu_env, fpscr);
             tcg_temp_free_i32(fpscr);
+            if (dc_isar_feature(aa32_mve, s)) {
+                TCGv_i32 z32 = tcg_const_i32(0);
+                store_cpu_field(z32, v7m.vpr);
+            }
+
             /*
              * We don't need to arrange to end the TB, because the only
              * parts of FPSCR which we cache in the TB flags are the VECLEN