[RFC PATCH v2 21/22] target/mips/tx79: Move RDHWR usermode kludge to trans_SQ()

[Philippe Mathieu-Daudé]

Now than SQ is properly implemented, we can move the RDHWR
kludge required to have usermode working with recent glibc.

Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
---
v2: { RDHWR_user } (rth)
---
 target/mips/tx79.decode      |  5 +++-
 target/mips/translate.c      | 56 ------------------------------------
 target/mips/tx79_translate.c | 31 ++++++++++++++++++++
 3 files changed, 35 insertions(+), 57 deletions(-)

diff --git a/target/mips/tx79.decode b/target/mips/tx79.decode
index f1cb7ebfa3c..4e8acb7ab9a 100644
--- a/target/mips/tx79.decode
+++ b/target/mips/tx79.decode
@@ -73,4 +73,7 @@ PCPYH           011100 00000 ..... ..... 11011 101001   @rt_rd
 # SPECIAL
 
 LQ              011110 ..... ..... ................     @ldst
-SQ              011111 ..... ..... ................     @ldst
+{
+  RDHWR_user    011111 00000 ..... ..... 00000 111011   @rt_rd
+  SQ            011111 ..... ..... ................     @ldst
+}
diff --git a/target/mips/translate.c b/target/mips/translate.c
index 0d20a0e3b84..b01022a6ad7 100644
--- a/target/mips/translate.c
+++ b/target/mips/translate.c
@@ -1167,7 +1167,6 @@ enum {
 
 enum {
     MMI_OPC_CLASS_MMI = 0x1C << 26,    /* Same as OPC_SPECIAL2 */
-    MMI_OPC_SQ        = 0x1F << 26,    /* Same as OPC_SPECIAL3 */
 };
 
 /*
@@ -24428,53 +24427,6 @@ static void decode_mmi(CPUMIPSState *env, DisasContext 
*ctx)
     }
 }
 
-static void gen_mmi_sq(DisasContext *ctx, int base, int rt, int offset)
-{
-    gen_reserved_instruction(ctx);    /* TODO: MMI_OPC_SQ */
-}
-
-/*
- * The TX79-specific instruction Store Quadword
- *
- * +--------+-------+-------+------------------------+
- * | 011111 |  base |   rt  |           offset       | SQ
- * +--------+-------+-------+------------------------+
- *      6       5       5                 16
- *
- * has the same opcode as the Read Hardware Register instruction
- *
- * +--------+-------+-------+-------+-------+--------+
- * | 011111 | 00000 |   rt  |   rd  | 00000 | 111011 | RDHWR
- * +--------+-------+-------+-------+-------+--------+
- *      6       5       5       5       5        6
- *
- * that is required, trapped and emulated by the Linux kernel. However, all
- * RDHWR encodings yield address error exceptions on the TX79 since the SQ
- * offset is odd. Therefore all valid SQ instructions can execute normally.
- * In user mode, QEMU must verify the upper and lower 11 bits to distinguish
- * between SQ and RDHWR, as the Linux kernel does.
- */
-static void decode_mmi_sq(CPUMIPSState *env, DisasContext *ctx)
-{
-    int base = extract32(ctx->opcode, 21, 5);
-    int rt = extract32(ctx->opcode, 16, 5);
-    int offset = extract32(ctx->opcode, 0, 16);
-
-#ifdef CONFIG_USER_ONLY
-    uint32_t op1 = MASK_SPECIAL3(ctx->opcode);
-    uint32_t op2 = extract32(ctx->opcode, 6, 5);
-
-    if (base == 0 && op2 == 0 && op1 == OPC_RDHWR) {
-        int rd = extract32(ctx->opcode, 11, 5);
-
-        gen_rdhwr(ctx, rt, rd, 0);
-        return;
-    }
-#endif
-
-    gen_mmi_sq(ctx, base, rt, offset);
-}
-
 #endif
 
 static void decode_opc_special3(CPUMIPSState *env, DisasContext *ctx)
@@ -24664,15 +24616,7 @@ static bool decode_opc_legacy(CPUMIPSState *env, 
DisasContext *ctx)
         decode_opc_special2_legacy(env, ctx);
         break;
     case OPC_SPECIAL3:
-#if defined(TARGET_MIPS64)
-        if (ctx->insn_flags & INSN_R5900) {
-            decode_mmi_sq(env, ctx);    /* MMI_OPC_SQ */
-        } else {
-            decode_opc_special3(env, ctx);
-        }
-#else
         decode_opc_special3(env, ctx);
-#endif
         break;
     case OPC_REGIMM:
         op1 = MASK_REGIMM(ctx->opcode);
diff --git a/target/mips/tx79_translate.c b/target/mips/tx79_translate.c
index e32c6218852..5e69783420a 100644
--- a/target/mips/tx79_translate.c
+++ b/target/mips/tx79_translate.c
@@ -396,6 +396,37 @@ static bool trans_SQ(DisasContext *ctx, arg_itype *a)
     return true;
 }
 
+/*
+ * The TX79-specific instruction Store Quadword
+ *
+ * +--------+-------+-------+------------------------+
+ * | 011111 |  base |   rt  |           offset       | SQ
+ * +--------+-------+-------+------------------------+
+ *      6       5       5                 16
+ *
+ * has the same opcode as the Read Hardware Register instruction
+ *
+ * +--------+-------+-------+-------+-------+--------+
+ * | 011111 | 00000 |   rt  |   rd  | 00000 | 111011 | RDHWR
+ * +--------+-------+-------+-------+-------+--------+
+ *      6       5       5       5       5        6
+ *
+ * that is required, trapped and emulated by the Linux kernel. However, all
+ * RDHWR encodings yield address error exceptions on the TX79 since the SQ
+ * offset is odd. Therefore all valid SQ instructions can execute normally.
+ * In user mode, QEMU must verify the upper and lower 11 bits to distinguish
+ * between SQ and RDHWR, as the Linux kernel does.
+ */
+static bool trans_RDHWR_user(DisasContext *ctx, arg_rtype *a)
+{
+#if defined(CONFIG_USER_ONLY)
+    gen_rdhwr(ctx, a->rt, a->rd, 0);
+    return true;
+#else
+    return false;
+#endif
+}
+
 /*
  *     Multiply and Divide (19 instructions)
  *     -------------------------------------
-- 
2.26.2