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target/arm: Convert VFP fused multiply-add insns to decodetree

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Convert the VFP fused multiply-add instructions (VFNMA, VFNMS,
VFMA, VFMS) to decodetree.

Note that in the old decode structure we were implementing
these to honour the VFP vector stride/length. These instructions
were introduced in VFPv4, and in the v7A architecture they
are UNPREDICTABLE if the vector stride or length are non-zero.
In v8A they must UNDEF if stride or length are non-zero, like
all VFP instructions; we choose to UNDEF always.

Backports commit d4893b01d23060845ee3855bc96626e16aad9ab5 from qemu
This commit is contained in:
Peter Maydell 2019-06-13 18:22:48 -04:00 committed by Lioncash
parent 321bcc822b
commit 0ebb6b8b90
No known key found for this signature in database
GPG key ID: 4E3C3CC1031BA9C7
3 changed files with 133 additions and 52 deletions
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123
qemu/target/arm/translate-vfp.inc.c
View file

@ -1500,3 +1500,126 @@ static bool trans_VDIV_dp(DisasContext *s, arg_VDIV_sp *a)
{
return do_vfp_3op_dp(s, gen_helper_vfp_divd, a->vd, a->vn, a->vm, false);
}
static bool trans_VFM_sp(DisasContext *s, arg_VFM_sp *a)
{
/*
* VFNMA : fd = muladd(-fd, fn, fm)
* VFNMS : fd = muladd(-fd, -fn, fm)
* VFMA : fd = muladd( fd, fn, fm)
* VFMS : fd = muladd( fd, -fn, fm)
*
* These are fused multiply-add, and must be done as one floating
* point operation with no rounding between the multiplication and
* addition steps. NB that doing the negations here as separate
* steps is correct : an input NaN should come out with its sign
* bit flipped if it is a negated-input.
*/
TCGContext *tcg_ctx = s->uc->tcg_ctx;
TCGv_ptr fpst;
TCGv_i32 vn, vm, vd;
/*
* Present in VFPv4 only.
* In v7A, UNPREDICTABLE with non-zero vector length/stride; from
* v8A, must UNDEF. We choose to UNDEF for both v7A and v8A.
*/
if (!arm_dc_feature(s, ARM_FEATURE_VFP4) ||
(s->vec_len != 0 || s->vec_stride != 0)) {
return false;
}
if (!vfp_access_check(s)) {
return true;
}
vn = tcg_temp_new_i32(tcg_ctx);
vm = tcg_temp_new_i32(tcg_ctx);
vd = tcg_temp_new_i32(tcg_ctx);
neon_load_reg32(s, vn, a->vn);
neon_load_reg32(s, vm, a->vm);
if (a->o2) {
/* VFNMS, VFMS */
gen_helper_vfp_negs(tcg_ctx, vn, vn);
}
neon_load_reg32(s, vd, a->vd);
if (a->o1 & 1) {
/* VFNMA, VFNMS */
gen_helper_vfp_negs(tcg_ctx, vd, vd);
}
fpst = get_fpstatus_ptr(s, 0);
gen_helper_vfp_muladds(tcg_ctx, vd, vn, vm, vd, fpst);
neon_store_reg32(s, vd, a->vd);
tcg_temp_free_ptr(tcg_ctx, fpst);
tcg_temp_free_i32(tcg_ctx, vn);
tcg_temp_free_i32(tcg_ctx, vm);
tcg_temp_free_i32(tcg_ctx, vd);
return true;
}
static bool trans_VFM_dp(DisasContext *s, arg_VFM_sp *a)
{
/*
* VFNMA : fd = muladd(-fd, fn, fm)
* VFNMS : fd = muladd(-fd, -fn, fm)
* VFMA : fd = muladd( fd, fn, fm)
* VFMS : fd = muladd( fd, -fn, fm)
*
* These are fused multiply-add, and must be done as one floating
* point operation with no rounding between the multiplication and
* addition steps. NB that doing the negations here as separate
* steps is correct : an input NaN should come out with its sign
* bit flipped if it is a negated-input.
*/
TCGContext *tcg_ctx = s->uc->tcg_ctx;
TCGv_ptr fpst;
TCGv_i64 vn, vm, vd;
/*
* Present in VFPv4 only.
* In v7A, UNPREDICTABLE with non-zero vector length/stride; from
* v8A, must UNDEF. We choose to UNDEF for both v7A and v8A.
*/
if (!arm_dc_feature(s, ARM_FEATURE_VFP4) ||
(s->vec_len != 0 || s->vec_stride != 0)) {
return false;
}
/* UNDEF accesses to D16-D31 if they don't exist. */
if (!dc_isar_feature(aa32_fp_d32, s) && ((a->vd | a->vn | a->vm) & 0x10)) {
return false;
}
if (!vfp_access_check(s)) {
return true;
}
vn = tcg_temp_new_i64(tcg_ctx);
vm = tcg_temp_new_i64(tcg_ctx);
vd = tcg_temp_new_i64(tcg_ctx);
neon_load_reg64(s, vn, a->vn);
neon_load_reg64(s, vm, a->vm);
if (a->o2) {
/* VFNMS, VFMS */
gen_helper_vfp_negd(tcg_ctx, vn, vn);
}
neon_load_reg64(s, vd, a->vd);
if (a->o1 & 1) {
/* VFNMA, VFNMS */
gen_helper_vfp_negd(tcg_ctx, vd, vd);
}
fpst = get_fpstatus_ptr(s, 0);
gen_helper_vfp_muladdd(tcg_ctx, vd, vn, vm, vd, fpst);
neon_store_reg64(s, vd, a->vd);
tcg_temp_free_ptr(tcg_ctx, fpst);
tcg_temp_free_i64(tcg_ctx, vn);
tcg_temp_free_i64(tcg_ctx, vm);
tcg_temp_free_i64(tcg_ctx, vd);
return true;
}

53
qemu/target/arm/translate.c
View file

@ -3194,7 +3194,7 @@ static int disas_vfp_insn(DisasContext *s, uint32_t insn)
rn = VFP_SREG_N(insn);
switch (op) {
case 0 ... 8:
case 0 ... 13:
/* Already handled by decodetree */
return 1;
default:
@ -3380,57 +3380,6 @@ static int disas_vfp_insn(DisasContext *s, uint32_t insn)
for (;;) {
/* Perform the calculation. */
switch (op) {
case 10: /* VFNMA : fd = muladd(-fd, fn, fm) */
case 11: /* VFNMS : fd = muladd(-fd, -fn, fm) */
case 12: /* VFMA : fd = muladd( fd, fn, fm) */
case 13: /* VFMS : fd = muladd( fd, -fn, fm) */
/* These are fused multiply-add, and must be done as one
* floating point operation with no rounding between the
* multiplication and addition steps.
* NB that doing the negations here as separate steps is
* correct : an input NaN should come out with its sign bit
* flipped if it is a negated-input.
*/
if (!arm_dc_feature(s, ARM_FEATURE_VFP4)) {
return 1;
}
if (dp) {
TCGv_ptr fpst;
TCGv_i64 frd;
if (op & 1) {
/* VFNMS, VFMS */
gen_helper_vfp_negd(tcg_ctx, s->F0d, s->F0d);
}
frd = tcg_temp_new_i64(tcg_ctx);
tcg_gen_ld_f64(tcg_ctx, frd, tcg_ctx->cpu_env, vfp_reg_offset(dp, rd));
if (op & 2) {
/* VFNMA, VFNMS */
gen_helper_vfp_negd(tcg_ctx, frd, frd);
}
fpst = get_fpstatus_ptr(s, 0);
gen_helper_vfp_muladdd(tcg_ctx, s->F0d, s->F0d,
s->F1d, frd, fpst);
tcg_temp_free_ptr(tcg_ctx, fpst);
tcg_temp_free_i64(tcg_ctx, frd);
} else {
TCGv_ptr fpst;
TCGv_i32 frd;
if (op & 1) {
/* VFNMS, VFMS */
gen_helper_vfp_negs(tcg_ctx, s->F0s, s->F0s);
}
frd = tcg_temp_new_i32(tcg_ctx);
tcg_gen_ld_f32(tcg_ctx, frd, tcg_ctx->cpu_env, vfp_reg_offset(dp, rd));
if (op & 2) {
gen_helper_vfp_negs(tcg_ctx, frd, frd);
}
fpst = get_fpstatus_ptr(s, 0);
gen_helper_vfp_muladds(tcg_ctx, s->F0s, s->F0s,
s->F1s, frd, fpst);
tcg_temp_free_ptr(tcg_ctx, fpst);
tcg_temp_free_i32(tcg_ctx, frd);
}
break;
case 14: /* fconst */
if (!arm_dc_feature(s, ARM_FEATURE_VFP3)) {
return 1;

9
qemu/target/arm/vfp.decode
View file

@ -142,3 +142,12 @@ VDIV_sp ---- 1110 1.00 .... .... 1010 .0.0 .... \
vm=%vm_sp vn=%vn_sp vd=%vd_sp
VDIV_dp ---- 1110 1.00 .... .... 1011 .0.0 .... \
vm=%vm_dp vn=%vn_dp vd=%vd_dp
VFM_sp ---- 1110 1.01 .... .... 1010 . o2:1 . 0 .... \
vm=%vm_sp vn=%vn_sp vd=%vd_sp o1=1
VFM_dp ---- 1110 1.01 .... .... 1011 . o2:1 . 0 .... \
vm=%vm_dp vn=%vn_dp vd=%vd_dp o1=1
VFM_sp ---- 1110 1.10 .... .... 1010 . o2:1 . 0 .... \
vm=%vm_sp vn=%vn_sp vd=%vd_sp o1=2
VFM_dp ---- 1110 1.10 .... .... 1011 . o2:1 . 0 .... \
vm=%vm_dp vn=%vn_dp vd=%vd_dp o1=2