Re: [Qemu-arm] [PATCH 08/15] target/arm: Define and use XPSR bit masks

["Edgar E. Iglesias" <edgar.iglesias@gmail.com>]

On Wed, Aug 02, 2017 at 05:43:54PM +0100, Peter Maydell wrote:
> The M profile XPSR is almost the same format as the A profile CPSR,
> but not quite. Define some XPSR_* macros and use them where we
> definitely dealing with an XPSR rather than reusing the CPSR ones.
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

Reviewed-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com>


> ---
>  target/arm/cpu.h    | 38 ++++++++++++++++++++++++++++----------
>  target/arm/helper.c | 15 ++++++++-------
>  2 files changed, 36 insertions(+), 17 deletions(-)
> 
> diff --git a/target/arm/cpu.h b/target/arm/cpu.h
> index b64474c..1f06de0 100644
> --- a/target/arm/cpu.h
> +++ b/target/arm/cpu.h
> @@ -883,6 +883,22 @@ void pmccntr_sync(CPUARMState *env);
>  /* Mask of bits which may be set by exception return copying them from SPSR */
>  #define CPSR_ERET_MASK (~CPSR_RESERVED)
>  
> +/* Bit definitions for M profile XPSR. Most are the same as CPSR. */
> +#define XPSR_EXCP 0x1ffU
> +#define XPSR_SPREALIGN (1U << 9) /* Only set in exception stack frames */
> +#define XPSR_IT_2_7 CPSR_IT_2_7
> +#define XPSR_GE CPSR_GE
> +#define XPSR_SFPA (1U << 20) /* Only set in exception stack frames */
> +#define XPSR_T (1U << 24) /* Not the same as CPSR_T ! */
> +#define XPSR_IT_0_1 CPSR_IT_0_1
> +#define XPSR_Q CPSR_Q
> +#define XPSR_V CPSR_V
> +#define XPSR_C CPSR_C
> +#define XPSR_Z CPSR_Z
> +#define XPSR_N CPSR_N
> +#define XPSR_NZCV CPSR_NZCV
> +#define XPSR_IT CPSR_IT
> +
>  #define TTBCR_N      (7U << 0) /* TTBCR.EAE==0 */
>  #define TTBCR_T0SZ   (7U << 0) /* TTBCR.EAE==1 */
>  #define TTBCR_PD0    (1U << 4)
> @@ -987,26 +1003,28 @@ static inline uint32_t xpsr_read(CPUARMState *env)
>  /* Set the xPSR.  Note that some bits of mask must be all-set or all-clear.  */
>  static inline void xpsr_write(CPUARMState *env, uint32_t val, uint32_t mask)
>  {
> -    if (mask & CPSR_NZCV) {
> -        env->ZF = (~val) & CPSR_Z;
> +    if (mask & XPSR_NZCV) {
> +        env->ZF = (~val) & XPSR_Z;
>          env->NF = val;
>          env->CF = (val >> 29) & 1;
>          env->VF = (val << 3) & 0x80000000;
>      }
> -    if (mask & CPSR_Q)
> -        env->QF = ((val & CPSR_Q) != 0);
> -    if (mask & (1 << 24))
> -        env->thumb = ((val & (1 << 24)) != 0);
> -    if (mask & CPSR_IT_0_1) {
> +    if (mask & XPSR_Q) {
> +        env->QF = ((val & XPSR_Q) != 0);
> +    }
> +    if (mask & XPSR_T) {
> +        env->thumb = ((val & XPSR_T) != 0);
> +    }
> +    if (mask & XPSR_IT_0_1) {
>          env->condexec_bits &= ~3;
>          env->condexec_bits |= (val >> 25) & 3;
>      }
> -    if (mask & CPSR_IT_2_7) {
> +    if (mask & XPSR_IT_2_7) {
>          env->condexec_bits &= 3;
>          env->condexec_bits |= (val >> 8) & 0xfc;
>      }
> -    if (mask & 0x1ff) {
> -        env->v7m.exception = val & 0x1ff;
> +    if (mask & XPSR_EXCP) {
> +        env->v7m.exception = val & XPSR_EXCP;
>      }
>  }
>  
> diff --git a/target/arm/helper.c b/target/arm/helper.c
> index cb88c66..f087d42 100644
> --- a/target/arm/helper.c
> +++ b/target/arm/helper.c
> @@ -6119,7 +6119,7 @@ static void v7m_push_stack(ARMCPU *cpu)
>      /* Align stack pointer if the guest wants that */
>      if ((env->regs[13] & 4) && (env->v7m.ccr & R_V7M_CCR_STKALIGN_MASK)) {
>          env->regs[13] -= 4;
> -        xpsr |= 0x200;
> +        xpsr |= XPSR_SPREALIGN;
>      }
>      /* Switch to the handler mode.  */
>      v7m_push(env, xpsr);
> @@ -6244,10 +6244,11 @@ static void do_v7m_exception_exit(ARMCPU *cpu)
>          env->regs[15] &= ~1U;
>      }
>      xpsr = v7m_pop(env);
> -    xpsr_write(env, xpsr, 0xfffffdff);
> +    xpsr_write(env, xpsr, ~XPSR_SPREALIGN);
>      /* Undo stack alignment.  */
> -    if (xpsr & 0x200)
> +    if (xpsr & XPSR_SPREALIGN) {
>          env->regs[13] |= 4;
> +    }
>  
>      /* The restored xPSR exception field will be zero if we're
>       * resuming in Thread mode. If that doesn't match what the
> @@ -8693,10 +8694,10 @@ uint32_t HELPER(v7m_mrs)(CPUARMState *env, uint32_t reg)
>      case 0 ... 7: /* xPSR sub-fields */
>          mask = 0;
>          if ((reg & 1) && el) {
> -            mask |= 0x000001ff; /* IPSR (unpriv. reads as zero) */
> +            mask |= XPSR_EXCP; /* IPSR (unpriv. reads as zero) */
>          }
>          if (!(reg & 4)) {
> -            mask |= 0xf8000000; /* APSR */
> +            mask |= XPSR_NZCV | XPSR_Q; /* APSR */
>          }
>          /* EPSR reads as zero */
>          return xpsr_read(env) & mask;
> @@ -8754,10 +8755,10 @@ void HELPER(v7m_msr)(CPUARMState *env, uint32_t maskreg, uint32_t val)
>              uint32_t apsrmask = 0;
>  
>              if (mask & 8) {
> -                apsrmask |= 0xf8000000; /* APSR NZCVQ */
> +                apsrmask |= XPSR_NZCV | XPSR_Q;
>              }
>              if ((mask & 4) && arm_feature(env, ARM_FEATURE_THUMB_DSP)) {
> -                apsrmask |= 0x000f0000; /* APSR GE[3:0] */
> +                apsrmask |= XPSR_GE;
>              }
>              xpsr_write(env, val, apsrmask);
>          }
> -- 
> 2.7.4
> 
>