diff mbox series

[2/9] target/arm: Make vfp_get_fpscr() call vfp_get_{fpcr, fpsr}

Message ID 20240628142347.1283015-3-peter.maydell@linaro.org (mailing list archive)
State New, archived
Headers show
Series target/arm: Refactor FPCR/FPSR handling to prepare for FEAT_AFP | expand

Commit Message

Peter Maydell June 28, 2024, 2:23 p.m. UTC 
In AArch32, the floating point control and status bits are all in a
single register, FPSCR.  In AArch64, these were split into separate
FPCR and FPSR registers, but the bit layouts remained the same, with
no overlaps, so that you could construct an FPSCR value by ORing FPCR
and FPSR, or equivalently could produce FPSR and FPCR by masking an
FPSCR value.  For QEMU's implementation, we opted to use masking to
produce FPSR and FPCR, because we started with an AArch32
implementation of FPSCR.

The addition of the (AArch64-only) FEAT_AFP adds new bits to the FPCR
which overlap with some bits in the FPSR.  This means we'll no longer
be able to consider the FPSCR-encoded value as the primary one, but
instead need to treat FPSR/FPCR as the primary encoding and construct
the FPSCR from those.  (This remains possible because the FEAT_AFP
bits in FPCR don't appear in the FPSCR.)

As the first step in this refactoring, make vfp_get_fpscr() call
vfp_get_fpcr() and vfp_get_fpsr(), instead of the other way around.

Note that vfp_get_fpcsr_from_host() returns only bits in the FPSR
(for the cumulative fp exception bits), so we can simply rename
it without needing to add a new function for getting FPCR bits.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 target/arm/cpu.h        | 24 +++++++++++++++---------
 target/arm/vfp_helper.c | 34 ++++++++++++++++++++++------------
 2 files changed, 37 insertions(+), 21 deletions(-)

Comments

Richard Henderson June 28, 2024, 3:37 p.m. UTC | #1 
On 6/28/24 07:23, Peter Maydell wrote:
> In AArch32, the floating point control and status bits are all in a
> single register, FPSCR.  In AArch64, these were split into separate
> FPCR and FPSR registers, but the bit layouts remained the same, with
> no overlaps, so that you could construct an FPSCR value by ORing FPCR
> and FPSR, or equivalently could produce FPSR and FPCR by masking an
> FPSCR value.  For QEMU's implementation, we opted to use masking to
> produce FPSR and FPCR, because we started with an AArch32
> implementation of FPSCR.
> 
> The addition of the (AArch64-only) FEAT_AFP adds new bits to the FPCR
> which overlap with some bits in the FPSR.  This means we'll no longer
> be able to consider the FPSCR-encoded value as the primary one, but
> instead need to treat FPSR/FPCR as the primary encoding and construct
> the FPSCR from those.  (This remains possible because the FEAT_AFP
> bits in FPCR don't appear in the FPSCR.)
> 
> As the first step in this refactoring, make vfp_get_fpscr() call
> vfp_get_fpcr() and vfp_get_fpsr(), instead of the other way around.
> 
> Note that vfp_get_fpcsr_from_host() returns only bits in the FPSR
> (for the cumulative fp exception bits), so we can simply rename
> it without needing to add a new function for getting FPCR bits.
> 
> Signed-off-by: Peter Maydell<peter.maydell@linaro.org>
> ---
>   target/arm/cpu.h        | 24 +++++++++++++++---------
>   target/arm/vfp_helper.c | 34 ++++++++++++++++++++++------------
>   2 files changed, 37 insertions(+), 21 deletions(-)

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>

r~
diff mbox series

Patch

diff --git a/target/arm/cpu.h b/target/arm/cpu.h
index 3841359d0f1..68a9922f88e 100644
--- a/target/arm/cpu.h
+++ b/target/arm/cpu.h
@@ -1714,10 +1714,21 @@  void vfp_set_fpscr(CPUARMState *env, uint32_t val);
 #define FPCR_NZCV_MASK (FPCR_N | FPCR_Z | FPCR_C | FPCR_V)
 #define FPCR_NZCVQC_MASK (FPCR_NZCV_MASK | FPCR_QC)
 
-static inline uint32_t vfp_get_fpsr(CPUARMState *env)
-{
-    return vfp_get_fpscr(env) & FPSR_MASK;
-}
+/**
+ * vfp_get_fpsr: read the AArch64 FPSR
+ * @env: CPU context
+ *
+ * Return the current AArch64 FPSR value
+ */
+uint32_t vfp_get_fpsr(CPUARMState *env);
+
+/**
+ * vfp_get_fpcr: read the AArch64 FPCR
+ * @env: CPU context
+ *
+ * Return the current AArch64 FPCR value
+ */
+uint32_t vfp_get_fpcr(CPUARMState *env);
 
 static inline void vfp_set_fpsr(CPUARMState *env, uint32_t val)
 {
@@ -1725,11 +1736,6 @@  static inline void vfp_set_fpsr(CPUARMState *env, uint32_t val)
     vfp_set_fpscr(env, new_fpscr);
 }
 
-static inline uint32_t vfp_get_fpcr(CPUARMState *env)
-{
-    return vfp_get_fpscr(env) & FPCR_MASK;
-}
-
 static inline void vfp_set_fpcr(CPUARMState *env, uint32_t val)
 {
     uint32_t new_fpscr = (vfp_get_fpscr(env) & ~FPCR_MASK) | (val & FPCR_MASK);
diff --git a/target/arm/vfp_helper.c b/target/arm/vfp_helper.c
index dd67825270b..a87d39e4d9b 100644
--- a/target/arm/vfp_helper.c
+++ b/target/arm/vfp_helper.c
@@ -85,7 +85,7 @@  static inline int vfp_exceptbits_to_host(int target_bits)
     return host_bits;
 }
 
-static uint32_t vfp_get_fpscr_from_host(CPUARMState *env)
+static uint32_t vfp_get_fpsr_from_host(CPUARMState *env)
 {
     uint32_t i;
 
@@ -156,7 +156,7 @@  static void vfp_set_fpscr_to_host(CPUARMState *env, uint32_t val)
 
 #else
 
-static uint32_t vfp_get_fpscr_from_host(CPUARMState *env)
+static uint32_t vfp_get_fpsr_from_host(CPUARMState *env)
 {
     return 0;
 }
@@ -167,26 +167,36 @@  static void vfp_set_fpscr_to_host(CPUARMState *env, uint32_t val)
 
 #endif
 
-uint32_t HELPER(vfp_get_fpscr)(CPUARMState *env)
+uint32_t vfp_get_fpcr(CPUARMState *env)
 {
-    uint32_t i, fpscr;
-
-    fpscr = env->vfp.xregs[ARM_VFP_FPSCR]
-            | (env->vfp.vec_len << 16)
-            | (env->vfp.vec_stride << 20);
+    uint32_t fpcr = (env->vfp.xregs[ARM_VFP_FPSCR] & FPCR_MASK)
+        | (env->vfp.vec_len << 16)
+        | (env->vfp.vec_stride << 20);
 
     /*
      * M-profile LTPSIZE is the same bits [18:16] as A-profile Len; whichever
      * of the two is not applicable to this CPU will always be zero.
      */
-    fpscr |= env->v7m.ltpsize << 16;
+    fpcr |= env->v7m.ltpsize << 16;
 
-    fpscr |= vfp_get_fpscr_from_host(env);
+    return fpcr;
+}
+
+uint32_t vfp_get_fpsr(CPUARMState *env)
+{
+    uint32_t fpsr = env->vfp.xregs[ARM_VFP_FPSCR] & FPSR_MASK;
+    uint32_t i;
+
+    fpsr |= vfp_get_fpsr_from_host(env);
 
     i = env->vfp.qc[0] | env->vfp.qc[1] | env->vfp.qc[2] | env->vfp.qc[3];
-    fpscr |= i ? FPCR_QC : 0;
+    fpsr |= i ? FPCR_QC : 0;
+    return fpsr;
+}
 
-    return fpscr;
+uint32_t HELPER(vfp_get_fpscr)(CPUARMState *env)
+{
+    return (vfp_get_fpcr(env) & FPCR_MASK) | (vfp_get_fpsr(env) & FPSR_MASK);
 }
 
 uint32_t vfp_get_fpscr(CPUARMState *env)