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Re: [PATCH qemu v4 04/14] target/riscv: rvv: Add tail agnostic for vv in


From: Weiwei Li
Subject: Re: [PATCH qemu v4 04/14] target/riscv: rvv: Add tail agnostic for vv instructions
Date: Fri, 25 Mar 2022 17:10:19 +0800
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.14.0


在 2022/3/1 下午5:07, ~eopxd 写道:
From: eopXD <eop.chen@sifive.com>

This is the first commit regarding the tail agnostic behavior.
Added option 'rvv_ta_all_1s' to enable the behavior, the option
is default to false.

Signed-off-by: eop Chen <eop.chen@sifive.com>
Reviewed-by: Frank Chang <frank.chang@sifive.com>
---
  target/riscv/cpu.c                      |   1 +
  target/riscv/cpu.h                      |   2 +
  target/riscv/cpu_helper.c               |   2 +
  target/riscv/insn_trans/trans_rvv.c.inc |  10 +
  target/riscv/internals.h                |   5 +-
  target/riscv/translate.c                |   2 +
  target/riscv/vector_helper.c            | 315 ++++++++++++++----------
  7 files changed, 206 insertions(+), 131 deletions(-)

diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c
index ddda4906ff..cd4cf4b41e 100644
--- a/target/riscv/cpu.c
+++ b/target/riscv/cpu.c
@@ -810,6 +810,7 @@ static Property riscv_cpu_properties[] = {
      DEFINE_PROP_BOOL("x-aia", RISCVCPU, cfg.aia, false),
DEFINE_PROP_UINT64("resetvec", RISCVCPU, cfg.resetvec, DEFAULT_RSTVEC),
+    DEFINE_PROP_BOOL("rvv_ta_all_1s", RISCVCPU, cfg.rvv_ta_all_1s, false),
      DEFINE_PROP_END_OF_LIST(),
  };
diff --git a/target/riscv/cpu.h b/target/riscv/cpu.h
index c069fe85fa..8c4a79b5a0 100644
--- a/target/riscv/cpu.h
+++ b/target/riscv/cpu.h
@@ -369,6 +369,7 @@ struct RISCVCPUConfig {
      bool ext_zhinxmin;
      bool ext_zve32f;
      bool ext_zve64f;
+    bool rvv_ta_all_1s;
/* Vendor-specific custom extensions */
      bool ext_XVentanaCondOps;
@@ -516,6 +517,7 @@ FIELD(TB_FLAGS, XL, 20, 2)
  /* If PointerMasking should be applied */
  FIELD(TB_FLAGS, PM_MASK_ENABLED, 22, 1)
  FIELD(TB_FLAGS, PM_BASE_ENABLED, 23, 1)
+FIELD(TB_FLAGS, VTA, 24, 1)
#ifdef TARGET_RISCV32
  #define riscv_cpu_mxl(env)  ((void)(env), MXL_RV32)
diff --git a/target/riscv/cpu_helper.c b/target/riscv/cpu_helper.c
index 1c60fb2e80..2941c88c31 100644
--- a/target/riscv/cpu_helper.c
+++ b/target/riscv/cpu_helper.c
@@ -65,6 +65,8 @@ void cpu_get_tb_cpu_state(CPURISCVState *env, target_ulong 
*pc,
          flags = FIELD_DP32(flags, TB_FLAGS, LMUL,
                      FIELD_EX64(env->vtype, VTYPE, VLMUL));
          flags = FIELD_DP32(flags, TB_FLAGS, VL_EQ_VLMAX, vl_eq_vlmax);
+        flags = FIELD_DP32(flags, TB_FLAGS, VTA,
+                    FIELD_EX64(env->vtype, VTYPE, VTA));
      } else {
          flags = FIELD_DP32(flags, TB_FLAGS, VILL, 1);
      }
diff --git a/target/riscv/insn_trans/trans_rvv.c.inc 
b/target/riscv/insn_trans/trans_rvv.c.inc
index 57953923d5..166ee9df2b 100644
--- a/target/riscv/insn_trans/trans_rvv.c.inc
+++ b/target/riscv/insn_trans/trans_rvv.c.inc
@@ -1223,6 +1223,15 @@ do_opivv_gvec(DisasContext *s, arg_rmrr *a, GVecGen3Fn 
*gvec_fn,
      tcg_gen_brcond_tl(TCG_COND_GEU, cpu_vstart, cpu_vl, over);
if (a->vm && s->vl_eq_vlmax) {
+        if (s->vta && s->lmul < 0) {
+            /* tail elements may pass vlmax when lmul < 0
+             * set tail elements to 1s
+             */
+            uint32_t vlenb = s->cfg_ptr->vlen >> 3;
+            tcg_gen_gvec_ori(s->sew, vreg_ofs(s, a->rd),
+                             vreg_ofs(s, a->rd), -1,
+                             vlenb, vlenb);
+        }
          gvec_fn(s->sew, vreg_ofs(s, a->rd),
                  vreg_ofs(s, a->rs2), vreg_ofs(s, a->rs1),
                  MAXSZ(s), MAXSZ(s));
@@ -1231,6 +1240,7 @@ do_opivv_gvec(DisasContext *s, arg_rmrr *a, GVecGen3Fn 
*gvec_fn,
data = FIELD_DP32(data, VDATA, VM, a->vm);
          data = FIELD_DP32(data, VDATA, LMUL, s->lmul);
+        data = FIELD_DP32(data, VDATA, VTA, s->vta);
          tcg_gen_gvec_4_ptr(vreg_ofs(s, a->rd), vreg_ofs(s, 0),
                             vreg_ofs(s, a->rs1), vreg_ofs(s, a->rs2),
                             cpu_env, s->cfg_ptr->vlen / 8,
diff --git a/target/riscv/internals.h b/target/riscv/internals.h
index dbb322bfa7..512c6c30cf 100644
--- a/target/riscv/internals.h
+++ b/target/riscv/internals.h
@@ -24,8 +24,9 @@
  /* share data between vector helpers and decode code */
  FIELD(VDATA, VM, 0, 1)
  FIELD(VDATA, LMUL, 1, 3)
-FIELD(VDATA, NF, 4, 4)
-FIELD(VDATA, WD, 4, 1)
+FIELD(VDATA, VTA, 4, 1)
+FIELD(VDATA, NF, 5, 4)
+FIELD(VDATA, WD, 5, 1)
/* float point classify helpers */
  target_ulong fclass_h(uint64_t frs1);
diff --git a/target/riscv/translate.c b/target/riscv/translate.c
index fac998a6b5..7775dade26 100644
--- a/target/riscv/translate.c
+++ b/target/riscv/translate.c
@@ -94,6 +94,7 @@ typedef struct DisasContext {
       */
      int8_t lmul;
      uint8_t sew;
+    uint8_t vta;
      target_ulong vstart;
      bool vl_eq_vlmax;
      uint8_t ntemp;
@@ -1083,6 +1084,7 @@ static void riscv_tr_init_disas_context(DisasContextBase 
*dcbase, CPUState *cs)
      ctx->vill = FIELD_EX32(tb_flags, TB_FLAGS, VILL);
      ctx->sew = FIELD_EX32(tb_flags, TB_FLAGS, SEW);
      ctx->lmul = sextract32(FIELD_EX32(tb_flags, TB_FLAGS, LMUL), 0, 3);
+    ctx->vta = FIELD_EX32(tb_flags, TB_FLAGS, VTA) && cpu->cfg.rvv_ta_all_1s;
      ctx->vstart = env->vstart;
      ctx->vl_eq_vlmax = FIELD_EX32(tb_flags, TB_FLAGS, VL_EQ_VLMAX);
      ctx->misa_mxl_max = env->misa_mxl_max;
diff --git a/target/riscv/vector_helper.c b/target/riscv/vector_helper.c
index d0452a7756..b9976f9d77 100644
--- a/target/riscv/vector_helper.c
+++ b/target/riscv/vector_helper.c
@@ -122,6 +122,11 @@ static inline int32_t vext_lmul(uint32_t desc)
      return sextract32(FIELD_EX32(simd_data(desc), VDATA, LMUL), 0, 3);
  }
+static inline uint32_t vext_vta(uint32_t desc)
+{
+    return FIELD_EX32(simd_data(desc), VDATA, VTA);
+}
+
  /*
   * Get the maximum number of elements can be operated.
   *
@@ -140,6 +145,20 @@ static inline uint32_t vext_max_elems(uint32_t desc, 
uint32_t log2_esz)
      return scale < 0 ? vlenb >> -scale : vlenb << scale;
  }
+/*
+ * Get number of total elements, including prestart, body and tail elements.
+ * Note that when LMUL < 1, the tail includes the elements past VLMAX that
+ * are held in the same vector register.
+ */
+static inline uint32_t vext_get_total_elems(RISCVCPU *cpu, target_ulong vtype)
+{
+    uint8_t sew = FIELD_EX64(vtype, VTYPE, VSEW);
+    int8_t lmul = sextract32(FIELD_EX64(vtype, VTYPE, VLMUL), 0, 3) < 0 ?
+                  0 : sextract32(FIELD_EX64(vtype, VTYPE, VLMUL), 0, 3);
+    return cpu->cfg.vlen >> (sew + 3 - lmul);
+}
+

I have sent another patchset to  try to optimize a few point for rvv.  One of the point I haven't done is that,

for some rvv instructions, lmul field in 'desc'( or the total desc) is assigned in trans_* but not used in helper function.

This field seems can be used here. I think It may be better to use desc and esz(just like vext_max_elems) here.

Regards,

Weiwei Li




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