[Qemu-devel] [PATCH] target-mips: Add missing calls to synchronise SoftFloat status

[Qemu-devel] [PATCH] target-mips: Add missing calls to synchronise SoftFloat status

[Maciej W. Rozycki]

Add missing calls to synchronise the SoftFloat status with the CP1.FSCR:

+ for the rounding and flush-to-zero modes upon processor reset,

+ for the flush-to-zero mode on FSCR updates through the GDB stub.

Refactor code accordingly and remove the redundant RESTORE_ROUNDING_MODE 
macro.

Signed-off-by: Thomas Schwinge <thomas@codesourcery.com>
Signed-off-by: Maciej W. Rozycki <macro@codesourcery.com>
---
qemu-mips-softfloat-status.diff
Index: qemu-git-trunk/target-mips/cpu.h
===================================================================
--- qemu-git-trunk.orig/target-mips/cpu.h	2014-12-02 16:29:15.000000000 +0000
+++ qemu-git-trunk/target-mips/cpu.h	2014-12-02 16:32:49.127585631 +0000
@@ -777,6 +777,18 @@ target_ulong exception_resume_pc (CPUMIP
 extern unsigned int ieee_rm[];
 int ieee_ex_to_mips(int xcpt);
 
+static inline void restore_rounding_mode(CPUMIPSState *env)
+{
+    set_float_rounding_mode(ieee_rm[env->active_fpu.fcr31 & 3],
+                            &env->active_fpu.fp_status);
+}
+
+static inline void restore_flush_mode(CPUMIPSState *env)
+{
+    set_flush_to_zero((env->active_fpu.fcr31 & (1 << 24)) != 0,
+                      &env->active_fpu.fp_status);
+}
+
 static inline void cpu_get_tb_cpu_state(CPUMIPSState *env, target_ulong *pc,
                                         target_ulong *cs_base, int *flags)
 {
Index: qemu-git-trunk/target-mips/gdbstub.c
===================================================================
--- qemu-git-trunk.orig/target-mips/gdbstub.c	2014-12-02 16:29:15.000000000 +0000
+++ qemu-git-trunk/target-mips/gdbstub.c	2014-12-02 16:32:49.127585631 +0000
@@ -74,10 +74,6 @@ int mips_cpu_gdb_read_register(CPUState 
     return 0;
 }
 
-#define RESTORE_ROUNDING_MODE \
-    set_float_rounding_mode(ieee_rm[env->active_fpu.fcr31 & 3], \
-                            &env->active_fpu.fp_status)
-
 int mips_cpu_gdb_write_register(CPUState *cs, uint8_t *mem_buf, int n)
 {
     MIPSCPU *cpu = MIPS_CPU(cs);
@@ -95,7 +91,9 @@ int mips_cpu_gdb_write_register(CPUState
         case 70:
             env->active_fpu.fcr31 = tmp & 0xFF83FFFF;
             /* set rounding mode */
-            RESTORE_ROUNDING_MODE;
+            restore_rounding_mode(env);
+            /* set flush-to-zero mode */
+            restore_flush_mode(env);
             break;
         case 71:
             /* FIR is read-only.  Ignore writes.  */
Index: qemu-git-trunk/target-mips/op_helper.c
===================================================================
--- qemu-git-trunk.orig/target-mips/op_helper.c	2014-12-02 16:29:14.000000000 +0000
+++ qemu-git-trunk/target-mips/op_helper.c	2014-12-02 16:32:49.127585631 +0000
@@ -2280,18 +2280,6 @@ unsigned int ieee_rm[] = {
     float_round_down
 };
 
-static inline void restore_rounding_mode(CPUMIPSState *env)
-{
-    set_float_rounding_mode(ieee_rm[env->active_fpu.fcr31 & 3],
-                            &env->active_fpu.fp_status);
-}
-
-static inline void restore_flush_mode(CPUMIPSState *env)
-{
-    set_flush_to_zero((env->active_fpu.fcr31 & (1 << 24)) != 0,
-                      &env->active_fpu.fp_status);
-}
-
 target_ulong helper_cfc1(CPUMIPSState *env, uint32_t reg)
 {
     target_ulong arg1 = 0;
Index: qemu-git-trunk/target-mips/translate.c
===================================================================
--- qemu-git-trunk.orig/target-mips/translate.c	2014-12-02 16:29:14.000000000 +0000
+++ qemu-git-trunk/target-mips/translate.c	2014-12-02 16:32:49.127585631 +0000
@@ -19615,6 +19615,8 @@ void cpu_state_reset(CPUMIPSState *env)
     }
 
     compute_hflags(env);
+    restore_rounding_mode(env);
+    restore_flush_mode(env);
     cs->exception_index = EXCP_NONE;
 }
 

Re: [Qemu-devel] [PATCH] target-mips: Add missing calls to synchronise SoftFloat status

[Peter Maydell]

On 2 December 2014 at 17:02, Maciej W. Rozycki <macro@codesourcery.com> wrote:
> Add missing calls to synchronise the SoftFloat status with the CP1.FSCR:
>
> + for the rounding and flush-to-zero modes upon processor reset,
>
> + for the flush-to-zero mode on FSCR updates through the GDB stub.
>
> Refactor code accordingly and remove the redundant RESTORE_ROUNDING_MODE
> macro.

> @@ -95,7 +91,9 @@ int mips_cpu_gdb_write_register(CPUState
>          case 70:
>              env->active_fpu.fcr31 = tmp & 0xFF83FFFF;
>              /* set rounding mode */
> -            RESTORE_ROUNDING_MODE;
> +            restore_rounding_mode(env);
> +            /* set flush-to-zero mode */
> +            restore_flush_mode(env);
>              break;

> @@ -19615,6 +19615,8 @@ void cpu_state_reset(CPUMIPSState *env)
>      }
>
>      compute_hflags(env);
> +    restore_rounding_mode(env);
> +    restore_flush_mode(env);
>      cs->exception_index = EXCP_NONE;

Is there ever a situation where you would want to
resynchronise only one of these two things? If not,
why not just have one function for synchronising
softfloat state from the FCR?

thanks
-- PMM

Re: [Qemu-devel] [PATCH] target-mips: Add missing calls to synchronise SoftFloat status

[Maciej W. Rozycki]

On Tue, 2 Dec 2014, Peter Maydell wrote:

> Is there ever a situation where you would want to
> resynchronise only one of these two things? If not,
> why not just have one function for synchronising
> softfloat state from the FCR?

 Good point, I think these are safe and cheap enough to be always called 
together.  It sounds like a good idea for a future improvement.  
Thanks!

  Maciej

Re: [Qemu-devel] [PATCH] target-mips: Add missing calls to synchronise SoftFloat status

[Leon Alrae]

On 02/12/2014 17:02, Maciej W. Rozycki wrote:
> Add missing calls to synchronise the SoftFloat status with the CP1.FSCR:
> 
> + for the rounding and flush-to-zero modes upon processor reset,
> 
> + for the flush-to-zero mode on FSCR updates through the GDB stub.
> 
> Refactor code accordingly and remove the redundant RESTORE_ROUNDING_MODE 
> macro.
> 
> Signed-off-by: Thomas Schwinge <thomas@codesourcery.com>
> Signed-off-by: Maciej W. Rozycki <macro@codesourcery.com>
> ---
> qemu-mips-softfloat-status.diff
> Index: qemu-git-trunk/target-mips/cpu.h
> Index: qemu-git-trunk/target-mips/gdbstub.c
> Index: qemu-git-trunk/target-mips/op_helper.c
> Index: qemu-git-trunk/target-mips/translate.c

Reviewed-by: Leon Alrae <leon.alrae@imgtec.com>