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Re: [PATCH 06/38] target/riscv: SIMD 16-bit Shift Instructions


From: LIU Zhiwei
Subject: Re: [PATCH 06/38] target/riscv: SIMD 16-bit Shift Instructions
Date: Wed, 17 Mar 2021 10:30:59 +0800
User-agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.8.0



On 2021/3/17 3:54, Alistair Francis wrote:
On Mon, Mar 15, 2021 at 10:40 PM LIU Zhiwei <zhiwei_liu@c-sky.com> wrote:


On 2021/3/16 5:25, Alistair Francis wrote:
On Fri, Feb 12, 2021 at 10:16 AM LIU Zhiwei <zhiwei_liu@c-sky.com> wrote:
Signed-off-by: LIU Zhiwei <zhiwei_liu@c-sky.com>
---
   target/riscv/helper.h                   |   9 ++
   target/riscv/insn32.decode              |  17 ++++
   target/riscv/insn_trans/trans_rvp.c.inc | 115 ++++++++++++++++++++++++
   target/riscv/packed_helper.c            | 104 +++++++++++++++++++++
   4 files changed, 245 insertions(+)

diff --git a/target/riscv/helper.h b/target/riscv/helper.h
index a69a6b4e84..20bf400ac2 100644
--- a/target/riscv/helper.h
+++ b/target/riscv/helper.h
@@ -1184,3 +1184,12 @@ DEF_HELPER_3(rsub8, tl, env, tl, tl)
   DEF_HELPER_3(ursub8, tl, env, tl, tl)
   DEF_HELPER_3(ksub8, tl, env, tl, tl)
   DEF_HELPER_3(uksub8, tl, env, tl, tl)
+
+DEF_HELPER_3(sra16, tl, env, tl, tl)
+DEF_HELPER_3(sra16_u, tl, env, tl, tl)
+DEF_HELPER_3(srl16, tl, env, tl, tl)
+DEF_HELPER_3(srl16_u, tl, env, tl, tl)
+DEF_HELPER_3(sll16, tl, env, tl, tl)
+DEF_HELPER_3(ksll16, tl, env, tl, tl)
+DEF_HELPER_3(kslra16, tl, env, tl, tl)
+DEF_HELPER_3(kslra16_u, tl, env, tl, tl)
diff --git a/target/riscv/insn32.decode b/target/riscv/insn32.decode
index 358dd1fa10..6f053bfeb7 100644
--- a/target/riscv/insn32.decode
+++ b/target/riscv/insn32.decode
@@ -23,6 +23,7 @@
   %rd        7:5

   %sh10    20:10
+%sh4    20:4
   %csr    20:12
   %rm     12:3
   %nf     29:3                     !function=ex_plus_1
@@ -59,6 +60,7 @@
   @j       ....................      ..... ....... &j      imm=%imm_j          
%rd

   @sh      ......  ...... .....  ... ..... ....... &shift  shamt=%sh10      
%rs1 %rd
+@sh4     ......  ...... .....  ... ..... ....... &shift  shamt=%sh4      %rs1 
%rd
   @csr     ............   .....  ... ..... .......               %csr     %rs1 
%rd

   @atom_ld ..... aq:1 rl:1 ..... ........ ..... ....... &atomic rs2=0     %rs1 
%rd
@@ -635,3 +637,18 @@ rsub8      0000101  ..... ..... 000 ..... 1111111 @r
   ursub8     0010101  ..... ..... 000 ..... 1111111 @r
   ksub8      0001101  ..... ..... 000 ..... 1111111 @r
   uksub8     0011101  ..... ..... 000 ..... 1111111 @r
+
+sra16      0101000  ..... ..... 000 ..... 1111111 @r
+sra16_u    0110000  ..... ..... 000 ..... 1111111 @r
+srai16     0111000  0.... ..... 000 ..... 1111111 @sh4
+srai16_u   0111000  1.... ..... 000 ..... 1111111 @sh4
+srl16      0101001  ..... ..... 000 ..... 1111111 @r
+srl16_u    0110001  ..... ..... 000 ..... 1111111 @r
+srli16     0111001  0.... ..... 000 ..... 1111111 @sh4
+srli16_u   0111001  1.... ..... 000 ..... 1111111 @sh4
+sll16      0101010  ..... ..... 000 ..... 1111111 @r
+slli16     0111010  0.... ..... 000 ..... 1111111 @sh4
+ksll16     0110010  ..... ..... 000 ..... 1111111 @r
+kslli16    0111010  1.... ..... 000 ..... 1111111 @sh4
+kslra16    0101011  ..... ..... 000 ..... 1111111 @r
+kslra16_u  0110011  ..... ..... 000 ..... 1111111 @r
diff --git a/target/riscv/insn_trans/trans_rvp.c.inc 
b/target/riscv/insn_trans/trans_rvp.c.inc
index 109f560ec9..848edab7e5 100644
--- a/target/riscv/insn_trans/trans_rvp.c.inc
+++ b/target/riscv/insn_trans/trans_rvp.c.inc
@@ -238,3 +238,118 @@ GEN_RVP_R_OOL(rsub8);
   GEN_RVP_R_OOL(ursub8);
   GEN_RVP_R_OOL(ksub8);
   GEN_RVP_R_OOL(uksub8);
+
+/* 16-bit Shift Instructions */
+static bool rvp_shift_ool(DisasContext *ctx, arg_r *a,
+                          gen_helper_rvp_r *fn, target_ulong mask)
+{
+    TCGv src1, src2, dst;
+
+    src1 = tcg_temp_new();
+    src2 = tcg_temp_new();
+    dst = tcg_temp_new();
+
+    gen_get_gpr(src1, a->rs1);
+    gen_get_gpr(src2, a->rs2);
+    tcg_gen_andi_tl(src2, src2, mask);
+
+    fn(dst, cpu_env, src1, src2);
+    gen_set_gpr(a->rd, dst);
+
+    tcg_temp_free(src1);
+    tcg_temp_free(src2);
+    tcg_temp_free(dst);
+    return true;
+}
+
+typedef void GenGvecShift(unsigned, uint32_t, uint32_t, TCGv_i32,
+                          uint32_t, uint32_t);
+static inline bool
+rvp_shift(DisasContext *ctx, arg_r *a, uint8_t vece,
+          GenGvecShift *f64, gen_helper_rvp_r *fn,
+          uint8_t mask)
+{
+    if (!has_ext(ctx, RVP)) {
+        return false;
+    }
+
+#ifdef TARGET_RISCV64
Hmm....

I don't want to add any more #defines on the RISC-V xlen. We are
trying to make the QEMU RISC-V implementation xlen independent.
I noticed the change, but was not quite clear about the benefit of it.

Could you give a brief explanation?
Yep, there are a few reasons for it.

AFAIK every QEMU platform except RISC-V allows the 64-bit binary to
run the 32-bit guests. So for example in the ARM QEMU builds I can use
qemu-system-aarch64 to run 32-bit ARMv7 guests. This is a step towards
allowing us to do the same with RISC-V.
Get it. By explicitly specifying a 32bit CPU option in command line, qemu-system-riscv64
can run a 32-bit guest application. Is it right?

It's also a step towards allowing fixed XLEN CPUS to run. For example
4 64-bit application CPUs and a single 32-bit power management CPU can
all run together.

Also XLEN in RISC-V is configurable. A 64-bit Hypervisor can have
32-bit XLEN guests according to the spec. This is a step towards
allowing that as well.
Really interesting points.

I have not used QEMU in this way. Are these features ready now?
Can you use `riscv_cpu_is_32bit(env)` instead, here are everywhere
else you add a #define TARGET... ?
Sure, I think there are two ways.

1) Get env from the current_cpu, then call riscv_cpu_is_32bit(env).

It's some strange,  because I can't find current_cpu reference from many
archs.

I don't know whether it has side effects.

2)  Add a similar function cpu_is_32bit(DisasContext *ctx).
This is probably a better option, but I'm open to either way if you
have a strong preference.
I will add a patch in this way in v2. Thanks a lot.

Zhiwei

Alistair

In this way, the type of  misa field  in struct DisasContext should be
target_ulong.
Currently, the type of misa filed is uint32_t.

Do you think which one is better? Thanks very much.

Zhiwei
Alistair

+    if (a->rd && a->rs1 && a->rs2) {
+        TCGv_i32 shift = tcg_temp_new_i32();
+        tcg_gen_extrl_i64_i32(shift, cpu_gpr[a->rs2]);
+        tcg_gen_andi_i32(shift, shift, mask);
+        f64(vece, offsetof(CPURISCVState, gpr[a->rd]),
+            offsetof(CPURISCVState, gpr[a->rs1]),
+            shift, 8, 8);
+        tcg_temp_free_i32(shift);
+        return true;
+    }
+#endif
+    return rvp_shift_ool(ctx, a, fn, mask);
+}
+
+#define GEN_RVP_SHIFT(NAME, GVEC, VECE)                     \
+static bool trans_##NAME(DisasContext *s, arg_r *a)         \
+{                                                           \
+    return rvp_shift(s, a, VECE, GVEC, gen_helper_##NAME,   \
+                     (8 << VECE) - 1);                      \
+}
+
+GEN_RVP_SHIFT(sra16, tcg_gen_gvec_sars, 1);
+GEN_RVP_SHIFT(srl16, tcg_gen_gvec_shrs, 1);
+GEN_RVP_SHIFT(sll16, tcg_gen_gvec_shls, 1);
+GEN_RVP_R_OOL(sra16_u);
+GEN_RVP_R_OOL(srl16_u);
+GEN_RVP_R_OOL(ksll16);
+GEN_RVP_R_OOL(kslra16);
+GEN_RVP_R_OOL(kslra16_u);
+
+static bool rvp_shifti_ool(DisasContext *ctx, arg_shift *a,
+                           gen_helper_rvp_r *fn)
+{
+    TCGv src1, dst, shift;
+
+    src1 = tcg_temp_new();
+    dst = tcg_temp_new();
+
+    gen_get_gpr(src1, a->rs1);
+    shift = tcg_const_tl(a->shamt);
+    fn(dst, cpu_env, src1, shift);
+    gen_set_gpr(a->rd, dst);
+
+    tcg_temp_free(src1);
+    tcg_temp_free(dst);
+    tcg_temp_free(shift);
+    return true;
+}
+
+static inline bool
+rvp_shifti(DisasContext *ctx, arg_shift *a,
+           void (* f64)(TCGv_i64, TCGv_i64, int64_t),
+           gen_helper_rvp_r *fn)
+{
+    if (!has_ext(ctx, RVP)) {
+        return false;
+    }
+
+#ifdef TARGET_RISCV64
+    if (a->rd && a->rs1 && f64) {
+        f64(cpu_gpr[a->rd], cpu_gpr[a->rs1], a->shamt);
+        return true;
+    }
+#endif
+    return rvp_shifti_ool(ctx, a, fn);
+}
+
+#define GEN_RVP_SHIFTI(NAME, OP, GVEC)                   \
+static bool trans_##NAME(DisasContext *s, arg_shift *a)  \
+{                                                        \
+    return rvp_shifti(s, a, GVEC, gen_helper_##OP);      \
+}
+
+GEN_RVP_SHIFTI(srai16, sra16, tcg_gen_vec_sar16i_i64);
+GEN_RVP_SHIFTI(srli16, srl16, tcg_gen_vec_shr16i_i64);
+GEN_RVP_SHIFTI(slli16, sll16, tcg_gen_vec_shl16i_i64);
+GEN_RVP_SHIFTI(srai16_u, sra16_u, NULL);
+GEN_RVP_SHIFTI(srli16_u, srl16_u, NULL);
+GEN_RVP_SHIFTI(kslli16, ksll16, NULL);
diff --git a/target/riscv/packed_helper.c b/target/riscv/packed_helper.c
index 62db072204..7e31c2fe46 100644
--- a/target/riscv/packed_helper.c
+++ b/target/riscv/packed_helper.c
@@ -425,3 +425,107 @@ static inline void do_uksub8(CPURISCVState *env, void 
*vd, void *va,
   }

   RVPR(uksub8, 1, 1);
+
+/* 16-bit Shift Instructions */
+static inline void do_sra16(CPURISCVState *env, void *vd, void *va,
+                            void *vb, uint8_t i)
+{
+    int16_t *d = vd, *a = va;
+    uint8_t shift = *(uint8_t *)vb & 0xf;
+    d[i] = a[i] >> shift;
+}
+
+RVPR(sra16, 1, 2);
+
+static inline void do_srl16(CPURISCVState *env, void *vd, void *va,
+                            void *vb, uint8_t i)
+{
+    uint16_t *d = vd, *a = va;
+    uint8_t shift = *(uint8_t *)vb & 0xf;
+    d[i] = a[i] >> shift;
+}
+
+RVPR(srl16, 1, 2);
+
+static inline void do_sll16(CPURISCVState *env, void *vd, void *va,
+                            void *vb, uint8_t i)
+{
+    uint16_t *d = vd, *a = va;
+    uint8_t shift = *(uint8_t *)vb & 0xf;
+    d[i] = a[i] << shift;
+}
+
+RVPR(sll16, 1, 2);
+
+static inline void do_sra16_u(CPURISCVState *env, void *vd, void *va,
+                              void *vb, uint8_t i)
+{
+    int16_t *d = vd, *a = va;
+    uint8_t shift = *(uint8_t *)vb & 0xf;
+
+    d[i] = vssra16(env, 0, a[i], shift);
+}
+
+RVPR(sra16_u, 1, 2);
+
+static inline void do_srl16_u(CPURISCVState *env, void *vd, void *va,
+                              void *vb, uint8_t i)
+{
+    uint16_t *d = vd, *a = va;
+    uint8_t shift = *(uint8_t *)vb & 0xf;
+
+    d[i] = vssrl16(env, 0, a[i], shift);
+}
+
+RVPR(srl16_u, 1, 2);
+
+static inline void do_ksll16(CPURISCVState *env, void *vd, void *va,
+                             void *vb, uint8_t i)
+{
+    int16_t *d = vd, *a = va, result;
+    uint8_t shift = *(uint8_t *)vb & 0xf;
+
+    result = a[i] << shift;
+    if (shift > (clrsb32(a[i]) - 16)) {
+        env->vxsat = 0x1;
+        d[i] = (a[i] & INT16_MIN) ? INT16_MIN : INT16_MAX;
+    } else {
+        d[i] = result;
+    }
+}
+
+RVPR(ksll16, 1, 2);
+
+static inline void do_kslra16(CPURISCVState *env, void *vd, void *va,
+                              void *vb, uint8_t i)
+{
+    int16_t *d = vd, *a = va;
+    int32_t shift = sextract32((*(target_ulong *)vb), 0, 5);
+
+    if (shift >= 0) {
+        do_ksll16(env, vd, va, vb, i);
+    } else {
+        shift = -shift;
+        shift = (shift == 16) ? 15 : shift;
+        d[i] = a[i] >> shift;
+    }
+}
+
+RVPR(kslra16, 1, 2);
+
+static inline void do_kslra16_u(CPURISCVState *env, void *vd, void *va,
+                                void *vb, uint8_t i)
+{
+    int16_t *d = vd, *a = va;
+    int32_t shift = sextract32((*(uint32_t *)vb), 0, 5);
+
+    if (shift >= 0) {
+        do_ksll16(env, vd, va, vb, i);
+    } else {
+        shift = -shift;
+        shift = (shift == 16) ? 15 : shift;
+        d[i] = vssra16(env, 0, a[i], shift);
+    }
+}
+
+RVPR(kslra16_u, 1, 2);
--
2.17.1





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