target/riscv: remove 'over' brconds from vector trans

All helpers that rely on vstart >= vl are now doing early exits using
the VSTART_CHECK_EARLY_EXIT() macro. This macro will not only exit the
helper but also clear vstart.

We're still left with brconds that are skipping the helper, which is the
only place where we're clearing vstart. The pattern goes like this:

    tcg_gen_brcond_tl(TCG_COND_GEU, cpu_vstart, cpu_vl, over);
    (... calls helper that clears vstart ...)
    gen_set_label(over);
    return true;

This means that every time we jump to 'over' we're not clearing vstart,
which is an oversight that we're doing across the board.

Instead of setting vstart = 0 manually after each 'over' jump, remove
those brconds that are skipping helpers. The exception will be
trans_vmv_s_x() and trans_vfmv_s_f(): they don't use a helper and are
already clearing vstart manually in the 'over' label.

While we're at it, remove the (vl == 0) brconds from trans_rvbf16.c.inc
too since they're unneeded.

Suggested-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-ID: <20240314175704.478276-8-dbarboza@ventanamicro.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>

target/riscv/insn_trans/trans_rvbf16.c.inc

@@ -71,11 +71,8 @@ static bool trans_vfncvtbf16_f_f_w(DisasContext *ctx, arg_vfncvtbf16_f_f_w *a)
 
     if (opfv_narrow_check(ctx, a) && (ctx->sew == MO_16)) {
         uint32_t data = 0;
-        TCGLabel *over = gen_new_label();
 
         gen_set_rm_chkfrm(ctx, RISCV_FRM_DYN);
-        tcg_gen_brcondi_tl(TCG_COND_EQ, cpu_vl, 0, over);
-        tcg_gen_brcond_tl(TCG_COND_GEU, cpu_vstart, cpu_vl, over);
 
         data = FIELD_DP32(data, VDATA, VM, a->vm);
         data = FIELD_DP32(data, VDATA, LMUL, ctx->lmul);
@@ -87,7 +84,6 @@ static bool trans_vfncvtbf16_f_f_w(DisasContext *ctx, arg_vfncvtbf16_f_f_w *a)
                            ctx->cfg_ptr->vlenb, data,
                            gen_helper_vfncvtbf16_f_f_w);
         mark_vs_dirty(ctx);
-        gen_set_label(over);
         return true;
     }
     return false;
@@ -100,11 +96,8 @@ static bool trans_vfwcvtbf16_f_f_v(DisasContext *ctx, arg_vfwcvtbf16_f_f_v *a)
 
     if (opfv_widen_check(ctx, a) && (ctx->sew == MO_16)) {
         uint32_t data = 0;
-        TCGLabel *over = gen_new_label();
 
         gen_set_rm_chkfrm(ctx, RISCV_FRM_DYN);
-        tcg_gen_brcondi_tl(TCG_COND_EQ, cpu_vl, 0, over);
-        tcg_gen_brcond_tl(TCG_COND_GEU, cpu_vstart, cpu_vl, over);
 
         data = FIELD_DP32(data, VDATA, VM, a->vm);
         data = FIELD_DP32(data, VDATA, LMUL, ctx->lmul);
@@ -116,7 +109,6 @@ static bool trans_vfwcvtbf16_f_f_v(DisasContext *ctx, arg_vfwcvtbf16_f_f_v *a)
                            ctx->cfg_ptr->vlenb, data,
                            gen_helper_vfwcvtbf16_f_f_v);
         mark_vs_dirty(ctx);
-        gen_set_label(over);
         return true;
     }
     return false;
@@ -130,11 +122,8 @@ static bool trans_vfwmaccbf16_vv(DisasContext *ctx, arg_vfwmaccbf16_vv *a)
     if (require_rvv(ctx) && vext_check_isa_ill(ctx) && (ctx->sew == MO_16) &&
         vext_check_dss(ctx, a->rd, a->rs1, a->rs2, a->vm)) {
         uint32_t data = 0;
-        TCGLabel *over = gen_new_label();
 
         gen_set_rm_chkfrm(ctx, RISCV_FRM_DYN);
-        tcg_gen_brcondi_tl(TCG_COND_EQ, cpu_vl, 0, over);
-        tcg_gen_brcond_tl(TCG_COND_GEU, cpu_vstart, cpu_vl, over);
 
         data = FIELD_DP32(data, VDATA, VM, a->vm);
         data = FIELD_DP32(data, VDATA, LMUL, ctx->lmul);
@@ -147,7 +136,6 @@ static bool trans_vfwmaccbf16_vv(DisasContext *ctx, arg_vfwmaccbf16_vv *a)
                            ctx->cfg_ptr->vlenb, data,
                            gen_helper_vfwmaccbf16_vv);
         mark_vs_dirty(ctx);
-        gen_set_label(over);
         return true;
     }
     return false;