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target/arm: Adjust exception flag handling for AH = 1

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When FPCR.AH = 1, some of the cumulative exception flags in the FPSR
behave slightly differently for A64 operations:
 * IDC is set when a denormal input is used without flushing
 * IXC (Inexact) is set when an output denormal is flushed to zero

Update vfp_get_fpsr_from_host() to do this.

Note that because half-precision operations never set IDC, we now
need to add float_flag_input_denormal_used to the set we mask out of
fp_status_f16_a64.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
This commit is contained in:
Peter Maydell 2025-02-01 16:39:12 +00:00
parent b3d00d0a44
commit a4550b7be9
1 changed files with 14 additions and 3 deletions
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17
target/arm/vfp_helper.c
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@ -78,7 +78,7 @@ static void arm_set_ah_fp_behaviours(float_status *s)
#ifdef CONFIG_TCG
/* Convert host exception flags to vfp form. */
static inline uint32_t vfp_exceptbits_from_host(int host_bits)
static inline uint32_t vfp_exceptbits_from_host(int host_bits, bool ah)
{
uint32_t target_bits = 0;
@ -100,6 +100,16 @@ static inline uint32_t vfp_exceptbits_from_host(int host_bits)
if (host_bits & float_flag_input_denormal_flushed) {
target_bits |= FPSR_IDC;
}
/*
* With FPCR.AH, IDC is set when an input denormal is used,
* and flushing an output denormal to zero sets both IXC and UFC.
*/
if (ah && (host_bits & float_flag_input_denormal_used)) {
target_bits |= FPSR_IDC;
}
if (ah && (host_bits & float_flag_output_denormal_flushed)) {
target_bits |= FPSR_IXC;
}
return target_bits;
}
@ -117,7 +127,7 @@ static uint32_t vfp_get_fpsr_from_host(CPUARMState *env)
a64_flags |= get_float_exception_flags(&env->vfp.fp_status_a64);
a64_flags |= (get_float_exception_flags(&env->vfp.fp_status_f16_a64)
& ~float_flag_input_denormal_flushed);
& ~(float_flag_input_denormal_flushed | float_flag_input_denormal_used));
/*
* Flushing an input denormal *only* because FPCR.FIZ == 1 does
* not set FPSR.IDC; if FPCR.FZ is also set then this takes
@ -129,7 +139,8 @@ static uint32_t vfp_get_fpsr_from_host(CPUARMState *env)
if ((env->vfp.fpcr & (FPCR_FZ | FPCR_AH)) != FPCR_FZ) {
a64_flags &= ~float_flag_input_denormal_flushed;
}
return vfp_exceptbits_from_host(a32_flags | a64_flags);
return vfp_exceptbits_from_host(a64_flags, env->vfp.fpcr & FPCR_AH) |
vfp_exceptbits_from_host(a32_flags, false);
}
static void vfp_clear_float_status_exc_flags(CPUARMState *env)