target/arm: Separate decode from handling of coproc insns

As a prelude to making coproc insns use decodetree, split out the
part of disas_coproc_insn() which does instruction decoding from the
part which does the actual work, and make do_coproc_insn() handle the
UNDEF-on-bad-permissions and similar cases itself rather than
returning 1 to eventually percolate up to a callsite that calls
unallocated_encoding() for it.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20200803111849.13368-3-peter.maydell@linaro.org

target/arm/translate.c

@@ -4544,34 +4544,12 @@ void gen_gvec_uaba(unsigned vece, uint32_t rd_ofs, uint32_t rn_ofs,
     tcg_gen_gvec_3(rd_ofs, rn_ofs, rm_ofs, opr_sz, max_sz, &ops[vece]);
 }
 
-static int disas_coproc_insn(DisasContext *s, uint32_t insn)
+static void do_coproc_insn(DisasContext *s, int cpnum, int is64,
+                           int opc1, int crn, int crm, int opc2,
+                           bool isread, int rt, int rt2)
 {
-    int cpnum, is64, crn, crm, opc1, opc2, isread, rt, rt2;
     const ARMCPRegInfo *ri;
 
-    cpnum = (insn >> 8) & 0xf;
-
-    is64 = (insn & (1 << 25)) == 0;
-    if (!is64 && ((insn & (1 << 4)) == 0)) {
-        /* cdp */
-        return 1;
-    }
-
-    crm = insn & 0xf;
-    if (is64) {
-        crn = 0;
-        opc1 = (insn >> 4) & 0xf;
-        opc2 = 0;
-        rt2 = (insn >> 16) & 0xf;
-    } else {
-        crn = (insn >> 16) & 0xf;
-        opc1 = (insn >> 21) & 7;
-        opc2 = (insn >> 5) & 7;
-        rt2 = 0;
-    }
-    isread = (insn >> 20) & 1;
-    rt = (insn >> 12) & 0xf;
-
     ri = get_arm_cp_reginfo(s->cp_regs,
             ENCODE_CP_REG(cpnum, is64, s->ns, crn, crm, opc1, opc2));
     if (ri) {
@@ -4579,7 +4557,8 @@ static int disas_coproc_insn(DisasContext *s, uint32_t insn)
 
         /* Check access permissions */
         if (!cp_access_ok(s->current_el, ri, isread)) {
-            return 1;
+            unallocated_encoding(s);
+            return;
         }
 
         if (s->hstr_active || ri->accessfn ||
@@ -4653,14 +4632,15 @@ static int disas_coproc_insn(DisasContext *s, uint32_t insn)
         /* Handle special cases first */
         switch (ri->type & ~(ARM_CP_FLAG_MASK & ~ARM_CP_SPECIAL)) {
         case ARM_CP_NOP:
-            return 0;
+            return;
         case ARM_CP_WFI:
             if (isread) {
-                return 1;
+                unallocated_encoding(s);
+                return;
             }
             gen_set_pc_im(s, s->base.pc_next);
             s->base.is_jmp = DISAS_WFI;
-            return 0;
+            return;
         default:
             break;
         }
@@ -4720,7 +4700,7 @@ static int disas_coproc_insn(DisasContext *s, uint32_t insn)
             /* Write */
             if (ri->type & ARM_CP_CONST) {
                 /* If not forbidden by access permissions, treat as WI */
-                return 0;
+                return;
             }
 
             if (is64) {
@@ -4786,7 +4766,7 @@ static int disas_coproc_insn(DisasContext *s, uint32_t insn)
             gen_lookup_tb(s);
         }
 
-        return 0;
+        return;
     }
 
     /* Unknown register; this might be a guest error or a QEMU
@@ -4806,7 +4786,39 @@ static int disas_coproc_insn(DisasContext *s, uint32_t insn)
                       s->ns ? "non-secure" : "secure");
     }
 
-    return 1;
+    unallocated_encoding(s);
+    return;
+}
+
+static int disas_coproc_insn(DisasContext *s, uint32_t insn)
+{
+    int cpnum, is64, crn, crm, opc1, opc2, isread, rt, rt2;
+
+    cpnum = (insn >> 8) & 0xf;
+
+    is64 = (insn & (1 << 25)) == 0;
+    if (!is64 && ((insn & (1 << 4)) == 0)) {
+        /* cdp */
+        return 1;
+    }
+
+    crm = insn & 0xf;
+    if (is64) {
+        crn = 0;
+        opc1 = (insn >> 4) & 0xf;
+        opc2 = 0;
+        rt2 = (insn >> 16) & 0xf;
+    } else {
+        crn = (insn >> 16) & 0xf;
+        opc1 = (insn >> 21) & 7;
+        opc2 = (insn >> 5) & 7;
+        rt2 = 0;
+    }
+    isread = (insn >> 20) & 1;
+    rt = (insn >> 12) & 0xf;
+
+    do_coproc_insn(s, cpnum, is64, opc1, crn, crm, opc2, isread, rt, rt2);
+    return 0;
 }
 
 /* Decode XScale DSP or iWMMXt insn (in the copro space, cp=0 or 1) */