target/arm: Introduce FPST_ZA, FPST_ZA_F16

Rather than repeatedly copying FPST_FPCR to locals
and setting default nan mode, create dedicated float_status.

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20250704142112.1018902-12-richard.henderson@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

diff --git a/target/arm/cpu.c b/target/arm/cpu.c
index ebac86f70d3cea64518178bb0c6db18d2154bd36..7b207f2620cc938be5bec67a2ca218fcc53a64d2 100644 (file)
--- a/target/arm/cpu.c
+++ b/target/arm/cpu.c
@@ -554,11 +554,15 @@ static void arm_cpu_reset_hold(Object *obj, ResetType type)
     set_flush_inputs_to_zero(1, &env->vfp.fp_status[FPST_STD]);
     set_default_nan_mode(1, &env->vfp.fp_status[FPST_STD]);
     set_default_nan_mode(1, &env->vfp.fp_status[FPST_STD_F16]);
+    set_default_nan_mode(1, &env->vfp.fp_status[FPST_ZA]);
+    set_default_nan_mode(1, &env->vfp.fp_status[FPST_ZA_F16]);
     arm_set_default_fp_behaviours(&env->vfp.fp_status[FPST_A32]);
     arm_set_default_fp_behaviours(&env->vfp.fp_status[FPST_A64]);
+    arm_set_default_fp_behaviours(&env->vfp.fp_status[FPST_ZA]);
     arm_set_default_fp_behaviours(&env->vfp.fp_status[FPST_STD]);
     arm_set_default_fp_behaviours(&env->vfp.fp_status[FPST_A32_F16]);
     arm_set_default_fp_behaviours(&env->vfp.fp_status[FPST_A64_F16]);
+    arm_set_default_fp_behaviours(&env->vfp.fp_status[FPST_ZA_F16]);
     arm_set_default_fp_behaviours(&env->vfp.fp_status[FPST_STD_F16]);
     arm_set_ah_fp_behaviours(&env->vfp.fp_status[FPST_AH]);
     set_flush_to_zero(1, &env->vfp.fp_status[FPST_AH]);

diff --git a/target/arm/cpu.h b/target/arm/cpu.h
index 96a490726654cfda6b9620f74a1937695f259080..2530aaca22ca5a2438e67d4db0240bb7c656d5cf 100644 (file)
--- a/target/arm/cpu.h
+++ b/target/arm/cpu.h
@@ -207,6 +207,8 @@ typedef struct NVICState NVICState;
  *       when FPCR.AH == 1 (bfloat16 conversions and multiplies,
  *       and the reciprocal and square root estimate/step insns);
  *       for half-precision
+ * ZA: the "streaming sve" fp status.
+ * ZA_F16: likewise for half-precision.
  *
  * Half-precision operations are governed by a separate
  * flush-to-zero control bit in FPSCR:FZ16. We pass a separate
@@ -227,6 +229,12 @@ typedef struct NVICState NVICState;
  * they ignore FPCR.RMode. But they don't ignore FPCR.FZ16,
  * which means we need an FPST_AH_F16 as well.
  *
+ * The "ZA" float_status are for Streaming SVE operations which use
+ * default-NaN and do not generate fp exceptions, which means that they
+ * do not accumulate exception bits back into FPCR.
+ * See e.g. FPAdd vs FPAdd_ZA pseudocode functions, and the setting
+ * of fpcr.DN and fpexec parameters.
+ *
  * To avoid having to transfer exception bits around, we simply
  * say that the FPSCR cumulative exception flags are the logical
  * OR of the flags in the four fp statuses. This relies on the
@@ -240,10 +248,12 @@ typedef enum ARMFPStatusFlavour {
     FPST_A64_F16,
     FPST_AH,
     FPST_AH_F16,
+    FPST_ZA,
+    FPST_ZA_F16,
     FPST_STD,
     FPST_STD_F16,
 } ARMFPStatusFlavour;
-#define FPST_COUNT  8
+#define FPST_COUNT  10
 
 typedef struct CPUArchState {
     /* Regs for current mode.  */

diff --git a/target/arm/tcg/vfp_helper.c b/target/arm/tcg/vfp_helper.c
index b1324c5c0a6a33c692232220fc8435324f3e91ad..e156e3774ad8f154e968e7bcef002e8d5c435a94 100644 (file)
--- a/target/arm/tcg/vfp_helper.c
+++ b/target/arm/tcg/vfp_helper.c
@@ -123,7 +123,7 @@ uint32_t vfp_get_fpsr_from_host(CPUARMState *env)
     a64_flags |= (get_float_exception_flags(&env->vfp.fp_status[FPST_A64_F16])
           & ~(float_flag_input_denormal_flushed | float_flag_input_denormal_used));
     /*
-     * We do not merge in flags from FPST_AH or FPST_AH_F16, because
+     * We do not merge in flags from FPST_{AH,ZA} or FPST_{AH,ZA}_F16, because
      * they are used for insns that must not set the cumulative exception bits.
      */
 
@@ -196,6 +196,8 @@ void vfp_set_fpcr_to_host(CPUARMState *env, uint32_t val, uint32_t mask)
         set_float_rounding_mode(i, &env->vfp.fp_status[FPST_A64]);
         set_float_rounding_mode(i, &env->vfp.fp_status[FPST_A32_F16]);
         set_float_rounding_mode(i, &env->vfp.fp_status[FPST_A64_F16]);
+        set_float_rounding_mode(i, &env->vfp.fp_status[FPST_ZA]);
+        set_float_rounding_mode(i, &env->vfp.fp_status[FPST_ZA_F16]);
     }
     if (changed & FPCR_FZ16) {
         bool ftz_enabled = val & FPCR_FZ16;
@@ -203,15 +205,18 @@ void vfp_set_fpcr_to_host(CPUARMState *env, uint32_t val, uint32_t mask)
         set_flush_to_zero(ftz_enabled, &env->vfp.fp_status[FPST_A64_F16]);
         set_flush_to_zero(ftz_enabled, &env->vfp.fp_status[FPST_STD_F16]);
         set_flush_to_zero(ftz_enabled, &env->vfp.fp_status[FPST_AH_F16]);
+        set_flush_to_zero(ftz_enabled, &env->vfp.fp_status[FPST_ZA_F16]);
         set_flush_inputs_to_zero(ftz_enabled, &env->vfp.fp_status[FPST_A32_F16]);
         set_flush_inputs_to_zero(ftz_enabled, &env->vfp.fp_status[FPST_A64_F16]);
         set_flush_inputs_to_zero(ftz_enabled, &env->vfp.fp_status[FPST_STD_F16]);
         set_flush_inputs_to_zero(ftz_enabled, &env->vfp.fp_status[FPST_AH_F16]);
+        set_flush_inputs_to_zero(ftz_enabled, &env->vfp.fp_status[FPST_ZA_F16]);
     }
     if (changed & FPCR_FZ) {
         bool ftz_enabled = val & FPCR_FZ;
         set_flush_to_zero(ftz_enabled, &env->vfp.fp_status[FPST_A32]);
         set_flush_to_zero(ftz_enabled, &env->vfp.fp_status[FPST_A64]);
+        set_flush_to_zero(ftz_enabled, &env->vfp.fp_status[FPST_ZA]);
         /* FIZ is A64 only so FZ always makes A32 code flush inputs to zero */
         set_flush_inputs_to_zero(ftz_enabled, &env->vfp.fp_status[FPST_A32]);
     }
@@ -223,6 +228,7 @@ void vfp_set_fpcr_to_host(CPUARMState *env, uint32_t val, uint32_t mask)
         bool fitz_enabled = (val & FPCR_FIZ) ||
             (val & (FPCR_FZ | FPCR_AH)) == FPCR_FZ;
         set_flush_inputs_to_zero(fitz_enabled, &env->vfp.fp_status[FPST_A64]);
+        set_flush_inputs_to_zero(fitz_enabled, &env->vfp.fp_status[FPST_ZA]);
     }
     if (changed & FPCR_DN) {
         bool dnan_enabled = val & FPCR_DN;
@@ -240,9 +246,13 @@ void vfp_set_fpcr_to_host(CPUARMState *env, uint32_t val, uint32_t mask)
             /* Change behaviours for A64 FP operations */
             arm_set_ah_fp_behaviours(&env->vfp.fp_status[FPST_A64]);
             arm_set_ah_fp_behaviours(&env->vfp.fp_status[FPST_A64_F16]);
+            arm_set_ah_fp_behaviours(&env->vfp.fp_status[FPST_ZA]);
+            arm_set_ah_fp_behaviours(&env->vfp.fp_status[FPST_ZA_F16]);
         } else {
             arm_set_default_fp_behaviours(&env->vfp.fp_status[FPST_A64]);
             arm_set_default_fp_behaviours(&env->vfp.fp_status[FPST_A64_F16]);
+            arm_set_default_fp_behaviours(&env->vfp.fp_status[FPST_ZA]);
+            arm_set_default_fp_behaviours(&env->vfp.fp_status[FPST_ZA_F16]);
         }
     }
     /*