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target/arm: Introduce FPST_ZA, FPST_ZA_F16

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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>
This commit is contained in:
Richard Henderson 2025-07-04 08:19:34 -06:00 • committed by Peter Maydell
parent afb1bd20df
commit c994c84d38
3 changed files with 26 additions and 2 deletions
Download patch file Download diff file Expand all files Collapse all files

4
target/arm/cpu.c
View file

@ -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]);

12
target/arm/cpu.h
View file

@ -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. */

12
target/arm/tcg/vfp_helper.c
View file

@ -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]);
}
}
/*