[Qemu-devel] [PATCH] Honour current_tc for MIPS M{T,F}{HI,LO}

[Richard Sandiford]

I noticed while working on something else that the MIPS muldiv code
is careful to store in {HI,LO}[current_tc] but that the M{F,T}{HI,LO}
code always uses {HI,LO}[0].  I realise we don't really support MT yet,
but I thought I might as well have a stab at "fixing" it.

Following the current use of "current_tc_gprs", the patch introduces
a new TCG global, "current_tc_hi", to point at the current thread
context's HI array.  This is good for accessing LO as well,
and could be used for ACX in future.

HI and LO accesses are now more complicated than they were
when the gen_{load,store}_{HI,LO} accessor functions were removed,
so I've added them back.  I also added an accumulator register
parameter, ready for any future DSP support.

This might well not seem like the right approach, or it might
interfere with a longer-term plan.  If so, I apologise; please
feel free to ignore. ;)

Richard


Index: qemu/target-mips/cpu.h
===================================================================
--- qemu.orig/target-mips/cpu.h 2008-05-25 09:54:30.000000000 +0100
+++ qemu/target-mips/cpu.h      2008-05-25 09:56:19.000000000 +0100
@@ -159,6 +159,7 @@ struct CPUMIPSState {
     CPUMIPSFPUContext *fpu;
     uint32_t current_tc;
     target_ulong *current_tc_gprs;
+    target_ulong *current_tc_hi;
 
     uint32_t SEGBITS;
     target_ulong SEGMask;
Index: qemu/target-mips/translate.c
===================================================================
--- qemu.orig/target-mips/translate.c   2008-05-25 09:54:30.000000000 +0100
+++ qemu/target-mips/translate.c        2008-05-25 09:57:00.000000000 +0100
@@ -524,7 +524,7 @@ enum {
 };
 
 /* global register indices */
-static TCGv cpu_env, current_tc_gprs, cpu_T[2];
+static TCGv cpu_env, current_tc_gprs, current_tc_hi, cpu_T[2];
 
 /* The code generator doesn't like lots of temporaries, so maintain our own
    cache for reuse within a function.  */
@@ -633,6 +633,33 @@ static inline void gen_store_gpr (TCGv t
         tcg_gen_st_tl(t, current_tc_gprs, sizeof(target_ulong) * reg);
 }
 
+/* Moves to/from HI and LO registers.  */
+static inline void gen_load_LO (TCGv t, int reg)
+{
+    tcg_gen_ld_tl(t, current_tc_hi,
+                  offsetof(CPUState, LO)
+                  - offsetof(CPUState, HI)
+                  + sizeof(target_ulong) * reg);
+}
+
+static inline void gen_store_LO (TCGv t, int reg)
+{
+    tcg_gen_st_tl(t, current_tc_hi,
+                  offsetof(CPUState, LO)
+                  - offsetof(CPUState, HI)
+                  + sizeof(target_ulong) * reg);
+}
+
+static inline void gen_load_HI (TCGv t, int reg)
+{
+    tcg_gen_ld_tl(t, current_tc_hi, sizeof(target_ulong) * reg);
+}
+
+static inline void gen_store_HI (TCGv t, int reg)
+{
+    tcg_gen_st_tl(t, current_tc_hi, sizeof(target_ulong) * reg);
+}
+
 /* Moves to/from shadow registers. */
 static inline void gen_load_srsgpr (TCGv t, int reg)
 {
@@ -1917,23 +1944,23 @@ static void gen_HILO (DisasContext *ctx,
     }
     switch (opc) {
     case OPC_MFHI:
-        tcg_gen_ld_tl(cpu_T[0], cpu_env, offsetof(CPUState, HI[0]));
+        gen_load_HI(cpu_T[0], 0);
         gen_store_gpr(cpu_T[0], reg);
         opn = "mfhi";
         break;
     case OPC_MFLO:
-        tcg_gen_ld_tl(cpu_T[0], cpu_env, offsetof(CPUState, LO[0]));
+        gen_load_LO(cpu_T[0], 0);
         gen_store_gpr(cpu_T[0], reg);
         opn = "mflo";
         break;
     case OPC_MTHI:
         gen_load_gpr(cpu_T[0], reg);
-        tcg_gen_st_tl(cpu_T[0], cpu_env, offsetof(CPUState, HI[0]));
+        gen_store_HI(cpu_T[0], 0);
         opn = "mthi";
         break;
     case OPC_MTLO:
         gen_load_gpr(cpu_T[0], reg);
-        tcg_gen_st_tl(cpu_T[0], cpu_env, offsetof(CPUState, LO[0]));
+        gen_store_LO(cpu_T[0], 0);
         opn = "mtlo";
         break;
     default:
@@ -1961,9 +1988,6 @@ static void gen_muldiv (DisasContext *ct
                 TCGv r_tmp1 = new_tmp();
                 TCGv r_tmp2 = new_tmp();
                 TCGv r_tmp3 = new_tmp();
-                TCGv r_tc_off = new_tmp();
-                TCGv r_tc_off_tl = tcg_temp_new(TCG_TYPE_TL);
-                TCGv r_ptr = tcg_temp_new(TCG_TYPE_PTR);
 
                 tcg_gen_ext_i32_tl(r_tmp1, cpu_T[0]);
                 tcg_gen_ext_i32_tl(r_tmp2, cpu_T[1]);
@@ -1971,16 +1995,11 @@ static void gen_muldiv (DisasContext *ct
                 tcg_gen_rem_i32(r_tmp1, r_tmp1, r_tmp2);
                 tcg_gen_trunc_tl_i32(cpu_T[0], r_tmp3);
                 tcg_gen_trunc_tl_i32(cpu_T[1], r_tmp1);
+                gen_store_LO(cpu_T[0], 0);
+                gen_store_HI(cpu_T[1], 0);
                 dead_tmp(r_tmp1);
                 dead_tmp(r_tmp2);
                 dead_tmp(r_tmp3);
-                tcg_gen_ld_i32(r_tc_off, cpu_env, offsetof(CPUState, 
current_tc));
-                tcg_gen_muli_i32(r_tc_off, r_tc_off, sizeof(target_ulong));
-                tcg_gen_ext_i32_ptr(r_tc_off_tl, r_tc_off);
-                tcg_gen_add_ptr(r_ptr, cpu_env, r_tc_off_tl);
-                tcg_gen_st_tl(cpu_T[0], r_ptr, offsetof(CPUState, LO));
-                tcg_gen_st_tl(cpu_T[1], r_ptr, offsetof(CPUState, HI));
-                dead_tmp(r_tc_off);
             }
             gen_set_label(l1);
         }
@@ -1995,9 +2014,6 @@ static void gen_muldiv (DisasContext *ct
                 TCGv r_tmp1 = new_tmp();
                 TCGv r_tmp2 = new_tmp();
                 TCGv r_tmp3 = new_tmp();
-                TCGv r_tc_off = new_tmp();
-                TCGv r_tc_off_tl = tcg_temp_new(TCG_TYPE_TL);
-                TCGv r_ptr = tcg_temp_new(TCG_TYPE_PTR);
 
                 tcg_gen_ext_i32_tl(r_tmp1, cpu_T[0]);
                 tcg_gen_ext_i32_tl(r_tmp2, cpu_T[1]);
@@ -2005,16 +2021,11 @@ static void gen_muldiv (DisasContext *ct
                 tcg_gen_remu_i32(r_tmp1, r_tmp1, r_tmp2);
                 tcg_gen_trunc_tl_i32(cpu_T[0], r_tmp3);
                 tcg_gen_trunc_tl_i32(cpu_T[1], r_tmp1);
+                gen_store_LO(cpu_T[0], 0);
+                gen_store_HI(cpu_T[1], 0);
                 dead_tmp(r_tmp1);
                 dead_tmp(r_tmp2);
                 dead_tmp(r_tmp3);
-                tcg_gen_ld_i32(r_tc_off, cpu_env, offsetof(CPUState, 
current_tc));
-                tcg_gen_muli_i32(r_tc_off, r_tc_off, sizeof(target_ulong));
-                tcg_gen_ext_i32_ptr(r_tc_off_tl, r_tc_off);
-                tcg_gen_add_ptr(r_ptr, cpu_env, r_tc_off_tl);
-                tcg_gen_st_tl(cpu_T[0], r_ptr, offsetof(CPUState, LO));
-                tcg_gen_st_tl(cpu_T[1], r_ptr, offsetof(CPUState, HI));
-                dead_tmp(r_tc_off);
             }
             gen_set_label(l1);
         }
@@ -2035,9 +2046,6 @@ static void gen_muldiv (DisasContext *ct
 
             tcg_gen_brcondi_tl(TCG_COND_EQ, cpu_T[1], 0, l1);
             {
-                TCGv r_tc_off = new_tmp();
-                TCGv r_tc_off_tl = tcg_temp_new(TCG_TYPE_TL);
-                TCGv r_ptr = tcg_temp_new(TCG_TYPE_PTR);
                 int l2 = gen_new_label();
                 int l3 = gen_new_label();
 
@@ -2051,13 +2059,8 @@ static void gen_muldiv (DisasContext *ct
                 tcg_gen_rem_i64(cpu_T[1], cpu_T[0], cpu_T[1]);
                 gen_set_label(l3);
 
-                tcg_gen_ld_i32(r_tc_off, cpu_env, offsetof(CPUState, 
current_tc));
-                tcg_gen_muli_i32(r_tc_off, r_tc_off, sizeof(target_ulong));
-                tcg_gen_ext_i32_ptr(r_tc_off_tl, r_tc_off);
-                tcg_gen_add_ptr(r_ptr, cpu_env, r_tc_off_tl);
-                tcg_gen_st_tl(cpu_T[0], r_ptr, offsetof(CPUState, LO));
-                tcg_gen_st_tl(cpu_T[1], r_ptr, offsetof(CPUState, HI));
-                dead_tmp(r_tc_off);
+                gen_store_LO(cpu_T[0], 0);
+                gen_store_HI(cpu_T[1], 0);
             }
             gen_set_label(l1);
         }
@@ -2071,19 +2074,11 @@ static void gen_muldiv (DisasContext *ct
             {
                 TCGv r_tmp1 = tcg_temp_new(TCG_TYPE_I64);
                 TCGv r_tmp2 = tcg_temp_new(TCG_TYPE_I64);
-                TCGv r_tc_off = new_tmp();
-                TCGv r_tc_off_tl = tcg_temp_new(TCG_TYPE_TL);
-                TCGv r_ptr = tcg_temp_new(TCG_TYPE_PTR);
 
                 tcg_gen_divu_i64(r_tmp1, cpu_T[0], cpu_T[1]);
                 tcg_gen_remu_i64(r_tmp2, cpu_T[0], cpu_T[1]);
-                tcg_gen_ld_i32(r_tc_off, cpu_env, offsetof(CPUState, 
current_tc));
-                tcg_gen_muli_i32(r_tc_off, r_tc_off, sizeof(target_ulong));
-                tcg_gen_ext_i32_ptr(r_tc_off_tl, r_tc_off);
-                tcg_gen_add_ptr(r_ptr, cpu_env, r_tc_off_tl);
-                tcg_gen_st_tl(r_tmp1, r_ptr, offsetof(CPUState, LO));
-                tcg_gen_st_tl(r_tmp2, r_ptr, offsetof(CPUState, HI));
-                dead_tmp(r_tc_off);
+                gen_store_LO(r_tmp1, 0);
+                gen_store_HI(r_tmp2, 0);
             }
             gen_set_label(l1);
         }
@@ -8432,6 +8427,10 @@ static void mips_tcg_init(void)
                                          TCG_AREG0,
                                          offsetof(CPUState, current_tc_gprs),
                                          "current_tc_gprs");
+    current_tc_hi = tcg_global_mem_new(TCG_TYPE_PTR,
+                                       TCG_AREG0,
+                                       offsetof(CPUState, current_tc_hi),
+                                       "current_tc_hi");
 #if TARGET_LONG_BITS > HOST_LONG_BITS
     cpu_T[0] = tcg_global_mem_new(TCG_TYPE_TL,
                                   TCG_AREG0, offsetof(CPUState, t0), "T0");
Index: qemu/target-mips/translate_init.c
===================================================================
--- qemu.orig/target-mips/translate_init.c      2008-05-25 09:54:30.000000000 
+0100
+++ qemu/target-mips/translate_init.c   2008-05-25 09:56:19.000000000 +0100
@@ -547,6 +547,7 @@ static int cpu_mips_register (CPUMIPSSta
     env->CP0_SRSCtl = def->CP0_SRSCtl;
     env->current_tc = 0;
     env->current_tc_gprs = &env->gpr[env->current_tc][0];
+    env->current_tc_hi = &env->HI[env->current_tc][0];
     env->SEGBITS = def->SEGBITS;
     env->SEGMask = (target_ulong)((1ULL << def->SEGBITS) - 1);
 #if defined(TARGET_MIPS64)