target/arm: Factor out FWB=0 specific part of combine_cacheattrs()

Factor out the part of combine_cacheattrs() that is specific to
handling HCR_EL2.FWB == 0.  This is the part where we combine the
memory type and cacheability attributes.

The "force Outer Shareable for Device or Normal Inner-NC Outer-NC"
logic remains in combine_cacheattrs() because it holds regardless
(this is the equivalent of the pseudocode EffectiveShareability()
function).

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20220505183950.2781801-3-peter.maydell@linaro.org

target/arm/helper.c

@@ -12578,6 +12578,46 @@ static uint8_t combine_cacheattr_nibble(uint8_t s1, uint8_t s2)
     }
 }
 
+/*
+ * Combine the memory type and cacheability attributes of
+ * s1 and s2 for the HCR_EL2.FWB == 0 case, returning the
+ * combined attributes in MAIR_EL1 format.
+ */
+static uint8_t combined_attrs_nofwb(CPUARMState *env,
+                                    ARMCacheAttrs s1, ARMCacheAttrs s2)
+{
+    uint8_t s1lo, s2lo, s1hi, s2hi, s2_mair_attrs, ret_attrs;
+
+    s2_mair_attrs = convert_stage2_attrs(env, s2.attrs);
+
+    s1lo = extract32(s1.attrs, 0, 4);
+    s2lo = extract32(s2_mair_attrs, 0, 4);
+    s1hi = extract32(s1.attrs, 4, 4);
+    s2hi = extract32(s2_mair_attrs, 4, 4);
+
+    /* Combine memory type and cacheability attributes */
+    if (s1hi == 0 || s2hi == 0) {
+        /* Device has precedence over normal */
+        if (s1lo == 0 || s2lo == 0) {
+            /* nGnRnE has precedence over anything */
+            ret_attrs = 0;
+        } else if (s1lo == 4 || s2lo == 4) {
+            /* non-Reordering has precedence over Reordering */
+            ret_attrs = 4;  /* nGnRE */
+        } else if (s1lo == 8 || s2lo == 8) {
+            /* non-Gathering has precedence over Gathering */
+            ret_attrs = 8;  /* nGRE */
+        } else {
+            ret_attrs = 0xc; /* GRE */
+        }
+    } else { /* Normal memory */
+        /* Outer/inner cacheability combine independently */
+        ret_attrs = combine_cacheattr_nibble(s1hi, s2hi) << 4
+                  | combine_cacheattr_nibble(s1lo, s2lo);
+    }
+    return ret_attrs;
+}
+
 /* Combine S1 and S2 cacheability/shareability attributes, per D4.5.4
  * and CombineS1S2Desc()
  *
@@ -12588,26 +12628,17 @@ static uint8_t combine_cacheattr_nibble(uint8_t s1, uint8_t s2)
 static ARMCacheAttrs combine_cacheattrs(CPUARMState *env,
                                         ARMCacheAttrs s1, ARMCacheAttrs s2)
 {
-    uint8_t s1lo, s2lo, s1hi, s2hi;
     ARMCacheAttrs ret;
     bool tagged = false;
-    uint8_t s2_mair_attrs;
 
     assert(s2.is_s2_format && !s1.is_s2_format);
     ret.is_s2_format = false;
 
-    s2_mair_attrs = convert_stage2_attrs(env, s2.attrs);
-
     if (s1.attrs == 0xf0) {
         tagged = true;
         s1.attrs = 0xff;
     }
 
-    s1lo = extract32(s1.attrs, 0, 4);
-    s2lo = extract32(s2_mair_attrs, 0, 4);
-    s1hi = extract32(s1.attrs, 4, 4);
-    s2hi = extract32(s2_mair_attrs, 4, 4);
-
     /* Combine shareability attributes (table D4-43) */
     if (s1.shareability == 2 || s2.shareability == 2) {
         /* if either are outer-shareable, the result is outer-shareable */
@@ -12621,37 +12652,18 @@ static ARMCacheAttrs combine_cacheattrs(CPUARMState *env,
     }
 
     /* Combine memory type and cacheability attributes */
-    if (s1hi == 0 || s2hi == 0) {
-        /* Device has precedence over normal */
-        if (s1lo == 0 || s2lo == 0) {
-            /* nGnRnE has precedence over anything */
-            ret.attrs = 0;
-        } else if (s1lo == 4 || s2lo == 4) {
-            /* non-Reordering has precedence over Reordering */
-            ret.attrs = 4;  /* nGnRE */
-        } else if (s1lo == 8 || s2lo == 8) {
-            /* non-Gathering has precedence over Gathering */
-            ret.attrs = 8;  /* nGRE */
-        } else {
-            ret.attrs = 0xc; /* GRE */
-        }
+    ret.attrs = combined_attrs_nofwb(env, s1, s2);
 
-        /* Any location for which the resultant memory type is any
-         * type of Device memory is always treated as Outer Shareable.
-         */
+    /*
+     * Any location for which the resultant memory type is any
+     * type of Device memory is always treated as Outer Shareable.
+     * Any location for which the resultant memory type is Normal
+     * Inner Non-cacheable, Outer Non-cacheable is always treated
+     * as Outer Shareable.
+     * TODO: FEAT_XS adds another value (0x40) also meaning iNCoNC
+     */
+    if ((ret.attrs & 0xf0) == 0 || ret.attrs == 0x44) {
         ret.shareability = 2;
-    } else { /* Normal memory */
-        /* Outer/inner cacheability combine independently */
-        ret.attrs = combine_cacheattr_nibble(s1hi, s2hi) << 4
-                  | combine_cacheattr_nibble(s1lo, s2lo);
-
-        if (ret.attrs == 0x44) {
-            /* Any location for which the resultant memory type is Normal
-             * Inner Non-cacheable, Outer Non-cacheable is always treated
-             * as Outer Shareable.
-             */
-            ret.shareability = 2;
-        }
     }
 
     /* TODO: CombineS1S2Desc does not consider transient, only WB, RWA. */