[PATCH v2 02/10] target/arm: Implement v8.1M NOCP handling

[Peter Maydell]

>From v8.1M, disabled-coprocessor handling changes slightly:
 * coprocessors 8, 9, 14 and 15 are also governed by the
   cp10 enable bit, like cp11
 * an extra range of instruction patterns is considered
   to be inside the coprocessor space

We previously marked these up with TODO comments; implement the
correct behaviour.

Unfortunately there is no ID register field which indicates this
behaviour.  We could in theory test an unrelated ID register which
indicates guaranteed-to-be-in-v8.1M behaviour like ID_ISAR0.CmpBranch
>= 3 (low-overhead-loops), but it seems better to simply define a new
ARM_FEATURE_V8_1M feature flag and use it for this and other
new-in-v8.1M behaviour that isn't identifiable from the ID registers.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 target/arm/cpu.h               |  1 +
 target/arm/m-nocp.decode       | 10 ++++++----
 target/arm/translate-vfp.c.inc | 17 +++++++++++++++--
 3 files changed, 22 insertions(+), 6 deletions(-)

diff --git a/target/arm/cpu.h b/target/arm/cpu.h
index cfff1b5c8fe..74392fa0295 100644
--- a/target/arm/cpu.h
+++ b/target/arm/cpu.h
@@ -1985,6 +1985,7 @@ enum arm_features {
     ARM_FEATURE_VBAR, /* has cp15 VBAR */
     ARM_FEATURE_M_SECURITY, /* M profile Security Extension */
     ARM_FEATURE_M_MAIN, /* M profile Main Extension */
+    ARM_FEATURE_V8_1M, /* M profile extras only in v8.1M and later */
 };
 
 static inline int arm_feature(CPUARMState *env, int feature)
diff --git a/target/arm/m-nocp.decode b/target/arm/m-nocp.decode
index 7182d7d1217..28c8ac6b94c 100644
--- a/target/arm/m-nocp.decode
+++ b/target/arm/m-nocp.decode
@@ -29,14 +29,16 @@
 # If the coprocessor is not present or disabled then we will generate
 # the NOCP exception; otherwise we let the insn through to the main decode.
 
+&nocp cp
+
 {
   # Special cases which do not take an early NOCP: VLLDM and VLSTM
   VLLDM_VLSTM  1110 1100 001 l:1 rn:4 0000 1010 0000 0000
   # TODO: VSCCLRM (new in v8.1M) is similar:
   #VSCCLRM      1110 1100 1-01 1111 ---- 1011 ---- ---0
 
-  NOCP         111- 1110 ---- ---- ---- cp:4 ---- ----
-  NOCP         111- 110- ---- ---- ---- cp:4 ---- ----
-  # TODO: From v8.1M onwards we will also want this range to NOCP
-  #NOCP_8_1     111- 1111 ---- ---- ---- ---- ---- ---- cp=10
+  NOCP         111- 1110 ---- ---- ---- cp:4 ---- ---- &nocp
+  NOCP         111- 110- ---- ---- ---- cp:4 ---- ---- &nocp
+  # From v8.1M onwards this range will also NOCP:
+  NOCP_8_1     111- 1111 ---- ---- ---- ---- ---- ---- &nocp cp=10
 }
diff --git a/target/arm/translate-vfp.c.inc b/target/arm/translate-vfp.c.inc
index 28e0dba5f14..cc9ffb95887 100644
--- a/target/arm/translate-vfp.c.inc
+++ b/target/arm/translate-vfp.c.inc
@@ -3459,7 +3459,7 @@ static bool trans_VLLDM_VLSTM(DisasContext *s, 
arg_VLLDM_VLSTM *a)
     return true;
 }
 
-static bool trans_NOCP(DisasContext *s, arg_NOCP *a)
+static bool trans_NOCP(DisasContext *s, arg_nocp *a)
 {
     /*
      * Handle M-profile early check for disabled coprocessor:
@@ -3472,7 +3472,11 @@ static bool trans_NOCP(DisasContext *s, arg_NOCP *a)
     if (a->cp == 11) {
         a->cp = 10;
     }
-    /* TODO: in v8.1M cp 8, 9, 14, 15 also are governed by the cp10 enable */
+    if (arm_dc_feature(s, ARM_FEATURE_V8_1M) &&
+        (a->cp == 8 || a->cp == 9 || a->cp == 14 || a->cp == 15)) {
+        /* in v8.1M cp 8, 9, 14, 15 also are governed by the cp10 enable */
+        a->cp = 10;
+    }
 
     if (a->cp != 10) {
         gen_exception_insn(s, s->pc_curr, EXCP_NOCP,
@@ -3489,6 +3493,15 @@ static bool trans_NOCP(DisasContext *s, arg_NOCP *a)
     return false;
 }
 
+static bool trans_NOCP_8_1(DisasContext *s, arg_nocp *a)
+{
+    /* This range needs a coprocessor check for v8.1M and later only */
+    if (!arm_dc_feature(s, ARM_FEATURE_V8_1M)) {
+        return false;
+    }
+    return trans_NOCP(s, a);
+}
+
 static bool trans_VINS(DisasContext *s, arg_VINS *a)
 {
     TCGv_i32 rd, rm;
-- 
2.20.1