target/arm: Split out FPSCR.QC to a vector field

Change the representation of this field such that it is easy
to set from vector code.

Backports commit a4d5846245c5e029e5aa3945a9bda1de1c3fedbf from qemu

qemu/target/arm/cpu.h

@@ -568,11 +568,13 @@ typedef struct CPUARMState {
         ARMPredicateReg preg_tmp;
 #endif
 
-        uint32_t xregs[16];
         /* We store these fpcsr fields separately for convenience.  */
+        uint32_t QEMU_ALIGNED(16, qc[4]);
         int vec_len;
         int vec_stride;
 
+        uint32_t xregs[16];
+
         /* Scratch space for aa32 neon expansion.  */
         uint32_t scratch[8];
 
@@ -1369,6 +1371,7 @@ void vfp_set_fpscr(CPUARMState *env, uint32_t val);
 #define FPCR_FZ16   (1 << 19)   /* ARMv8.2+, FP16 flush-to-zero */
 #define FPCR_FZ     (1 << 24)   /* Flush-to-zero enable bit */
 #define FPCR_DN     (1 << 25)   /* Default NaN enable bit */
+#define FPCR_QC     (1 << 27)   /* Cumulative saturation bit */
 
 static inline uint32_t vfp_get_fpsr(CPUARMState *env)
 {

qemu/target/arm/helper.c

@@ -11779,8 +11779,7 @@ static inline int vfp_exceptbits_from_host(int host_bits)
 
 uint32_t HELPER(vfp_get_fpscr)(CPUARMState *env)
 {
-    int i;
+    uint32_t i, fpscr;
-    uint32_t fpscr;
 
     fpscr = env->vfp.xregs[ARM_VFP_FPSCR]
             | (env->vfp.vec_len << 16)
@@ -11792,6 +11791,10 @@ uint32_t HELPER(vfp_get_fpscr)(CPUARMState *env)
     i |= (get_float_exception_flags(&env->vfp.fp_status_f16)
           & ~float_flag_input_denormal);
     fpscr |= vfp_exceptbits_from_host(i);
+
+    i = env->vfp.qc[0] | env->vfp.qc[1] | env->vfp.qc[2] | env->vfp.qc[3];
+    fpscr |= i ? FPCR_QC : 0;
+
     return fpscr;
 }
 
@@ -11838,10 +11841,19 @@ void HELPER(vfp_set_fpscr)(CPUARMState *env, uint32_t val)
      * (which are stored in fp_status), and the other RES0 bits
      * in between, then we clear all of the low 16 bits.
      */
-    env->vfp.xregs[ARM_VFP_FPSCR] = val & 0xffc80000;
+    env->vfp.xregs[ARM_VFP_FPSCR] = val & 0xf7c80000;
     env->vfp.vec_len = (val >> 16) & 7;
     env->vfp.vec_stride = (val >> 20) & 3;
 
+    /*
+     * The bit we set within fpscr_q is arbitrary; the register as a
+     * whole being zero/non-zero is what counts.
+     */
+    env->vfp.qc[0] = val & FPCR_QC;
+    env->vfp.qc[1] = 0;
+    env->vfp.qc[2] = 0;
+    env->vfp.qc[3] = 0;
+
     changed ^= val;
     if (changed & (3 << 22)) {
         i = (val >> 22) & 3;

qemu/target/arm/neon_helper.c

@@ -16,7 +16,7 @@
 #define SIGNBIT (uint32_t)0x80000000
 #define SIGNBIT64 ((uint64_t)1 << 63)
 
-#define SET_QC() env->vfp.xregs[ARM_VFP_FPSCR] |= CPSR_Q
+#define SET_QC() env->vfp.qc[0] = 1
 
 #define NEON_TYPE1(name, type) \
 typedef struct \

qemu/target/arm/vec_helper.c

@@ -37,7 +37,7 @@
 #define H4(x)  (x)
 #endif
 
-#define SET_QC() env->vfp.xregs[ARM_VFP_FPSCR] |= CPSR_Q
+#define SET_QC() env->vfp.qc[0] = 1
 
 static void clear_tail(void *vd, uintptr_t opr_sz, uintptr_t max_sz)
 {