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target/arm: Add FPCR.NEP to TBFLAGS

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For FEAT_AFP, we want to emit different code when FPCR.NEP is set, so
that instead of zeroing the high elements of a vector register when
we write the output of a scalar operation to it, we instead merge in
those elements from one of the source registers.  Since this affects
the generated code, we need to put FPCR.NEP into the TBFLAGS.

FPCR.NEP is treated as 0 when in streaming SVE mode and FEAT_SME_FA64
is not implemented or not enabled; we can implement this logic in
rebuild_hflags_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 16:39:18 +00:00
parent 8a5a2b943e
commit 7025fa996f
4 changed files with 13 additions and 0 deletions
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1
target/arm/cpu.h
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@ -3214,6 +3214,7 @@ FIELD(TBFLAG_A64, NV2_MEM_E20, 35, 1)
/* Set if FEAT_NV2 RAM accesses are big-endian */
FIELD(TBFLAG_A64, NV2_MEM_BE, 36, 1)
FIELD(TBFLAG_A64, AH, 37, 1) /* FPCR.AH */
FIELD(TBFLAG_A64, NEP, 38, 1) /* FPCR.NEP */
/*
* Helpers for using the above. Note that only the A64 accessors use

9
target/arm/tcg/hflags.c
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@ -407,6 +407,15 @@ static CPUARMTBFlags rebuild_hflags_a64(CPUARMState *env, int el, int fp_el,
if (env->vfp.fpcr & FPCR_AH) {
DP_TBFLAG_A64(flags, AH, 1);
}
if (env->vfp.fpcr & FPCR_NEP) {
/*
* In streaming-SVE without FA64, NEP behaves as if zero;
* compare pseudocode IsMerging()
*/
if (!(EX_TBFLAG_A64(flags, PSTATE_SM) && !sme_fa64(env, el))) {
DP_TBFLAG_A64(flags, NEP, 1);
}
}
return rebuild_hflags_common(env, fp_el, mmu_idx, flags);
}

1
target/arm/tcg/translate-a64.c
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@ -9742,6 +9742,7 @@ static void aarch64_tr_init_disas_context(DisasContextBase *dcbase,
dc->nv2_mem_e20 = EX_TBFLAG_A64(tb_flags, NV2_MEM_E20);
dc->nv2_mem_be = EX_TBFLAG_A64(tb_flags, NV2_MEM_BE);
dc->fpcr_ah = EX_TBFLAG_A64(tb_flags, AH);
dc->fpcr_nep = EX_TBFLAG_A64(tb_flags, NEP);
dc->vec_len = 0;
dc->vec_stride = 0;
dc->cp_regs = arm_cpu->cp_regs;

2
target/arm/tcg/translate.h
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@ -157,6 +157,8 @@ typedef struct DisasContext {
bool nv2_mem_be;
/* True if FPCR.AH is 1 (alternate floating point handling) */
bool fpcr_ah;
/* True if FPCR.NEP is 1 (FEAT_AFP scalar upper-element result handling) */
bool fpcr_nep;
/*
* >= 0, a copy of PSTATE.BTYPE, which will be 0 without v8.5-BTI.
* < 0, set by the current instruction.