[Qemu-devel] [5937] SH4: Implement FD bit

[Aurelien Jarno]

Revision: 5937
          http://svn.sv.gnu.org/viewvc/?view=rev&root=qemu&revision=5937
Author:   aurel32
Date:     2008-12-07 22:46:31 +0000 (Sun, 07 Dec 2008)

Log Message:
-----------
SH4: Implement FD bit

SH4 manual say that if a floating point instruction is executed while
FD bit in the status register is 1, an exception should be raised. QEMU
presently does not do that, so the kernel does not initialize FP state
for any thread, nor does it save/restore FP state. The most apparent
consequence is that while recent gcc/libc expect double-precision mode
to be set by kernel, they run in single-precision mode, and all FP code
produces wrong values.

This patch fixes this. It also fixes a couple of places where PC was
not updated before handling an exception, although both those places
deal with invalid instruction and don't lead to any user-visible bugs.

(Vladimir Prus)

Modified Paths:
--------------
    trunk/target-sh4/cpu.h
    trunk/target-sh4/helper.h
    trunk/target-sh4/op_helper.c
    trunk/target-sh4/translate.c

Modified: trunk/target-sh4/cpu.h
===================================================================
--- trunk/target-sh4/cpu.h      2008-12-07 20:35:00 UTC (rev 5936)
+++ trunk/target-sh4/cpu.h      2008-12-07 22:46:31 UTC (rev 5937)
@@ -279,7 +279,8 @@
     *flags = (env->flags & (DELAY_SLOT | DELAY_SLOT_CONDITIONAL
                     | DELAY_SLOT_TRUE | DELAY_SLOT_CLEARME))   /* Bits  0- 3 */
             | (env->fpscr & (FPSCR_FR | FPSCR_SZ | FPSCR_PR))  /* Bits 19-21 */
-            | (env->sr & (SR_MD | SR_RB));                     /* Bits 29-30 */
+            | (env->sr & (SR_MD | SR_RB))                      /* Bits 29-30 */
+            | (env->sr & SR_FD);                               /* Bit 15 */
 }
 
 #endif                         /* _CPU_SH4_H */

Modified: trunk/target-sh4/helper.h
===================================================================
--- trunk/target-sh4/helper.h   2008-12-07 20:35:00 UTC (rev 5936)
+++ trunk/target-sh4/helper.h   2008-12-07 22:46:31 UTC (rev 5937)
@@ -3,6 +3,8 @@
 DEF_HELPER_0(ldtlb, void)
 DEF_HELPER_0(raise_illegal_instruction, void)
 DEF_HELPER_0(raise_slot_illegal_instruction, void)
+DEF_HELPER_0(raise_fpu_disable, void)
+DEF_HELPER_0(raise_slot_fpu_disable, void)
 DEF_HELPER_0(debug, void)
 DEF_HELPER_1(sleep, void, i32)
 DEF_HELPER_1(trapa, void, i32)

Modified: trunk/target-sh4/op_helper.c
===================================================================
--- trunk/target-sh4/op_helper.c        2008-12-07 20:35:00 UTC (rev 5936)
+++ trunk/target-sh4/op_helper.c        2008-12-07 22:46:31 UTC (rev 5937)
@@ -89,6 +89,18 @@
     cpu_loop_exit();
 }
 
+void helper_raise_fpu_disable(void)
+{
+  env->exception_index = 0x800;
+  cpu_loop_exit();
+}
+
+void helper_raise_slot_fpu_disable(void)
+{
+  env->exception_index = 0x820;
+  cpu_loop_exit();
+}
+
 void helper_debug(void)
 {
     env->exception_index = EXCP_DEBUG;

Modified: trunk/target-sh4/translate.c
===================================================================
--- trunk/target-sh4/translate.c        2008-12-07 20:35:00 UTC (rev 5936)
+++ trunk/target-sh4/translate.c        2008-12-07 22:46:31 UTC (rev 5937)
@@ -447,17 +447,35 @@
 #define DREG(x) FREG(x) /* Assumes lsb of (x) is always 0 */
 
 #define CHECK_NOT_DELAY_SLOT \
-  if (ctx->flags & (DELAY_SLOT | DELAY_SLOT_CONDITIONAL)) \
-  {gen_helper_raise_slot_illegal_instruction(); ctx->bstate = BS_EXCP; \
-   return;}
+  if (ctx->flags & (DELAY_SLOT | DELAY_SLOT_CONDITIONAL))     \
+  {                                                           \
+      tcg_gen_movi_i32(cpu_pc, ctx->pc-2);                    \
+      gen_helper_raise_slot_illegal_instruction();            \
+      ctx->bstate = BS_EXCP;                                  \
+      return;                                                 \
+  }
 
 #define CHECK_PRIVILEGED                                      \
   if (IS_USER(ctx)) {                                         \
+      tcg_gen_movi_i32(cpu_pc, ctx->pc);                      \
       gen_helper_raise_illegal_instruction();                 \
       ctx->bstate = BS_EXCP;                                  \
       return;                                                 \
   }
 
+#define CHECK_FPU_ENABLED                                       \
+  if (ctx->flags & SR_FD) {                                     \
+      if (ctx->flags & (DELAY_SLOT | DELAY_SLOT_CONDITIONAL)) { \
+          tcg_gen_movi_i32(cpu_pc, ctx->pc-2);                  \
+          gen_helper_raise_slot_fpu_disable();                  \
+      } else {                                                  \
+          tcg_gen_movi_i32(cpu_pc, ctx->pc);                    \
+          gen_helper_raise_fpu_disable();                       \
+      }                                                         \
+      ctx->bstate = BS_EXCP;                                    \
+      return;                                                   \
+  }
+
 static void _decode_opc(DisasContext * ctx)
 {
 #if 0
@@ -1454,12 +1472,14 @@
        LDST(mach, 0x400a, 0x4006, 0x000a, 0x4002, {})
        LDST(macl, 0x401a, 0x4016, 0x001a, 0x4012, {})
        LDST(pr,   0x402a, 0x4026, 0x002a, 0x4022, {})
-       LDST(fpul, 0x405a, 0x4056, 0x005a, 0x4052, {})
+       LDST(fpul, 0x405a, 0x4056, 0x005a, 0x4052, {CHECK_FPU_ENABLED})
     case 0x406a:               /* lds Rm,FPSCR */
+       CHECK_FPU_ENABLED
        gen_helper_ld_fpscr(REG(B11_8));
        ctx->bstate = BS_STOP;
        return;
     case 0x4066:               /* lds.l @Rm+,FPSCR */
+       CHECK_FPU_ENABLED
        {
            TCGv addr = tcg_temp_new();
            tcg_gen_qemu_ld32s(addr, REG(B11_8), ctx->memidx);
@@ -1470,9 +1490,11 @@
        }
        return;
     case 0x006a:               /* sts FPSCR,Rn */
+       CHECK_FPU_ENABLED
        tcg_gen_andi_i32(REG(B11_8), cpu_fpscr, 0x003fffff);
        return;
     case 0x4062:               /* sts FPSCR,@-Rn */
+       CHECK_FPU_ENABLED
        {
            TCGv addr, val;
            val = tcg_temp_new();