target/arm: Fix VPT advance when ECI is non-zero

We were not paying attention to the ECI state when advancing the VPT
state.  Architecturally, VPT state advance happens for every beat
(see the pseudocode VPTAdvance()), so on every beat the 4 bits of
VPR.P0 corresponding to the current beat are inverted if required,
and at the end of beats 1 and 3 the VPR MASK fields are updated.
This means that if the ECI state says we should not be executing all
4 beats then we need to skip some of the updating of the VPR that we
currently do in mve_advance_vpt().

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

1 files changed, 17 insertions, 7 deletions

diff --git a/target/arm/mve_helper.c b/target/arm/mve_helper.c
index ffff280..bc89ce9 100644
--- a/target/arm/mve_helper.c
+++ b/target/arm/mve_helper.c
@@ -110,6 +110,8 @@ static void mve_advance_vpt(CPUARMState *env)
     /* Advance the VPT and ECI state if necessary */
     uint32_t vpr = env->v7m.vpr;
     unsigned mask01, mask23;
+    uint16_t inv_mask;
+    uint16_t eci_mask = mve_eci_mask(env);
 
     if ((env->condexec_bits & 0xf) == 0) {
         env->condexec_bits = (env->condexec_bits == (ECI_A0A1A2B0 << 4)) ?
@@ -121,17 +123,25 @@ static void mve_advance_vpt(CPUARMState *env)
         return;
     }
 
+    /* Invert P0 bits if needed, but only for beats we actually executed */
     mask01 = FIELD_EX32(vpr, V7M_VPR, MASK01);
     mask23 = FIELD_EX32(vpr, V7M_VPR, MASK23);
-    if (mask01 > 8) {
-        /* high bit set, but not 0b1000: invert the relevant half of P0 */
-        vpr ^= 0xff;
+    /* Start by assuming we invert all bits corresponding to executed beats */
+    inv_mask = eci_mask;
+    if (mask01 <= 8) {
+        /* MASK01 says don't invert low half of P0 */
+        inv_mask &= ~0xff;
     }
-    if (mask23 > 8) {
-        /* high bit set, but not 0b1000: invert the relevant half of P0 */
-        vpr ^= 0xff00;
+    if (mask23 <= 8) {
+        /* MASK23 says don't invert high half of P0 */
+        inv_mask &= ~0xff00;
     }
-    vpr = FIELD_DP32(vpr, V7M_VPR, MASK01, mask01 << 1);
+    vpr ^= inv_mask;
+    /* Only update MASK01 if beat 1 executed */
+    if (eci_mask & 0xf0) {
+        vpr = FIELD_DP32(vpr, V7M_VPR, MASK01, mask01 << 1);
+    }
+    /* Beat 3 always executes, so update MASK23 */
     vpr = FIELD_DP32(vpr, V7M_VPR, MASK23, mask23 << 1);
     env->v7m.vpr = vpr;
 }